RELAYS & TYPICAL APPLICATION GUIDE

(Fuse Applications In EV, Solar?PV, ESS, Industrial Automation, Home Appliances?etc.)

I. About Relay & Classification

It has been nearly two hundred years since the invention of relays - as early as 1831, American physicist and scientist Joseph Henry, who was famous for his inductance unit, invented the relay by utilizing electromagnetic induction in his research on circuit control.

Relays?are kinds of?switching device and electrical control devices that play an important role in electrical control systems. It achieves the operation and protection of various electrical equipment by controlling the on-off of the circuit.

?By?different working principles and application fields, relays can be divided into:

(1) Electromagnetic Relay: The most common and widely used type of relay in daily life and work. It uses electromagnetic attraction to make and break contacts, achieving circuit switching control. Electromagnetic relays are widely used in fields such as household appliances, industrial automation, and mechanical control.

?(2) Solid State Relay?- SSR:?Due to the use of semiconductor devices (such as transistors, thyristors etc.) instead of traditional electromagnetic coils and contact structures, SSR?have advantages such as fast response, long lifespan, and vibration resistance. SSR?are mainly used in fields such as high-frequency switches, precision instruments, and photovoltaic power generation systems.

?(3) Safety Relay:?It is composed of several relays and circuits, in order to complement each other's abnormal defects and achieve the complete function of correct and low malfunction relays. The lower the error and failure values, the higher the safety factor. Therefore, multiple safety relays need to be designed to protect different levels of machinery, with the main goal of protecting mechanical operators exposed to different levels of danger. A "safety relay" is not a "fault free relay", but rather a regular action when a fault occurs. It has a forced guided contact structure, which can ensure safety even in the event of contact melting, which is completely different from ordinary relays.

?(4) Time Relay: A time relay is a relay that can make and break contacts according to a preset time delay. Time relays are widely used in fields such as timing control, cycle control, and timing control, such as lighting control and automated production lines.

?We here?briefly listed?several common types of relays?above. In fact there are more, including voltage relay, thermal relay, signal relay, speed relay, temperature relay, protection relay, DC contactor?etc.?- they have different functions?in different?application ranges.

?It is crucial to fully understand practical applications and match?&?select appropriate relays, which is also important to guarantee the reliability and safety of equipment control circuits. Therefore, we?next?will explore the specific applications of relays, and also attached?guidelines and precautions for how to select different relays?by following chapters.

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II. Relays in Key Application Fields

The application of relays is very wide, which can be seen in many fields such as automobiles, charging facilities and equipment, wind and solar energy storage, household appliances, communication, power systems, industrial automation, security monitoring, smart homes, IoT control.

2.1 Automotive Application

?Automotive relays are mainly used to control the switching of automotive electrical equipment and the conversion of control signals. They have the characteristics of high switching load power (passenger car coil voltage 12V, 24V?for commercial vehicle), wide temperature resistance range (-40 ℃~125 ℃), high impact and vibration resistance. Due to different configurations of vehicles, the number of relays used in a single car also varies. In the past, the number of relays used in each passenger car ranged from 20 to 40?pieces. With the development of smart automobile?and the increasing demand for safety, comfort, and entertainment from consumers, the current number of relays in each (especially high-end)?vehicle can reach over 70?pieces. The following are specific scenarios where relays are commonly used in automobiles:

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(1) Electric Seat Control:?The function of a relay is to control the current direction of a bidirectional electric motors (BLDC motors), motors including front and rear, left and right, up and down, folding of the rear seats, heating control of the seats?etc. When the corresponding switch is operated for commutation, the relay causes the electric motor to rotate in different directions, thereby achieving the goal of moving the electric seat in different directions.

Reference of relays:

102-1AH-C、102-1AH-V、102-1AH-S、102-1CH-C、102-1CH-V、102-1CH-S.

103-1AH-C、103-1AH-V、103-1AH-S、103T-1AH-C、103T-1AH-V、103T-1AH-S、103-1CH-C、103-1CH-V、103-1CH-S、103T-1CH-C、103T-1CH-V、103T-1CH-S

812H-1C-C、812H-1C-V、812H-1C-S、812H-1C-C F、812H-1C-V F、812H-1C-S F、812H-1A-C、812H-1A-V、812H-1A-S、812H-1A-C F、812H-1A-V F、812H-1A-S F、812H-1B-C、812H-1B-V、812H-1B-S、812H-1B-C F、812H-1B-V F、812H-1B-S F

?Standard Types: 822E-1A、822E-1A-C、822E-1A-V、822E-1A-S、822E-1B、822E-1B-C、822E-1B-V、822E-1B-S、822E-1C、822E-1C-C、822E-1C-V、822E-1C-S、822U-1A、822U-1A-C、822U-1A-V、822U-1A-S、822U-1B、822U-1B-C、822U-1B-V、822U-1B-S、822U-1C、822U-1C-C、822U-1C-V、822U-1C-S、822UA-1A-C、822UA-1A-V、822UA-1A-S、822UA-1B-C、822UA-1B-V、822UA-1B-S、822UA-1C-C、822UA-1C-V、822UA-1C-S

Hi-Sensitivity Types: 822EN-1A、822EN-1A-C、822EN-1A-V、822EN-1A-S、822EN-1B、822EN-1B-C、822EN-1B-V、822EN-1B-S、822EN-1C、822EN-1C-C、822EN-1C-V、822EN-1C-S、822UN-1A、822UN-1A-C、822UN-1A-V、822UN-1A-S、822UN-1B、822UN-1B-C、822UN-1B-V、822UN-1B-S、822UN-1C、822UN-1C-C、822UN-1C-V、822UN-1C-S、822UAN-1A-C、822UAN-1A-V、822UAN-1A-S、822UAN-1B-C、822UAN-1B-V、822UAN-1B-S、822UAN-1C-C、822UAN-1C-V、822UAN-1C-S

895-1A-C、895-1A-V、895-1A-S、895-1A-C-H、895-1A-V-H、895-1A-S-H、895-1C-C、895-1C-V、895-1C-S、895-1C-C-H、895-1C-V-H、895-1C-S-H、895-2A-C、895-2A-V、895-2A-S

?(2) Window Control:?Control the lifting and lowering of the vehicle?window glass,?control the?opening and closing of the car?sunroof. When press window button,?the?relay will activate to control the rise or fall of the window glass.

Reference of relays:

?(3) Lamp control: Control of vehicle headlights, turn signals, interior illumination, ambient lighting, fog lights?etc..

Reference of relays:

301-1A-D、301-1A-C、301-1A-S、301-1A-D-R1、301-1A-C-R1、301-1A-S-R1、301-1A-D-D1、301-1A-C-D1、301-1A-S-D1、301-1C-D、301-1C-C、301-1C-S、301-1C-D-R1、301-1C-C-R1、301-1C-S-R1、301-1C-D-D1、301-1C-C-D1、301-1C-S-D1

303-1AH-C、303-1AH-S、303-1AH-C-R1、303-1AH-S-R1、303-1AH-C-D1、303-1AH-S-D1

896-1AH-D、896-1AH-C、896-1AH-S、896H-1AH-D、896H-1AH-C、896H-1AH-S、896-1CH-D、896-1CH-C、896-1CH-S、896H-1CH-D、896H-1CH-C、896H-1CH-S、896-2AH-D、896-2AH-C、896-2AH-S、896H-2AH-D、896H-2AH-C、896H-2AH-S、896P-2AH-D、896P-2AH-C、896P-2AH-S、896HP-2AH-D、896HP-2AH-C、896HP-2AH-S、896-2AH-D1、896-2AH-C1、896H-2AH-D1、896H-2AH-C1、896H-2AH-D1S、896H-2AH-C1S、896H-1CH-D1SF-R1、896H-1CH-D1SW-R1......

905-1AH-C、905-1AH-V、905-1AH-S、905-1CH-C、905-1CH-V、905-1CH-S.

(4) Rear-view Mirror Control: automatic folding control of the rear-view mirror, heating, deicing, demist control of the mirror glass and windshield.

Reference of relays:

(5) Windshield Wiper Control: Controlling front windshield wiper?and SUV rear windshield wiper - By measuring the signal of the wiper switch, the relay switch is controlled to adjust the wiper speed.

?(6) Vehicle Body &?Door Control: Relays in vehicle body control module, for unlocking and opening of doors, achieve the function?of perceptive automatic opening of car trunk?etc..

??(7) Air Conditioning System:?The compressor in the vehicle air conditioning system requires relays as switch controls.

871-1A-D、871-1A-DF、871-1A-C、871-1A-D-R1、871-1A-DF-R1、871-1A-C-R1、871-1A-D-D1、871-1A-DF-D1、871-1A-C-D1、871-1C-D、871-1C-DF、871-1C-C、871-1C-D-R1、871-1C-DF-R1、871-1C-C-R1、871-1C-D-D1、871-1C-DF-D1、871-1C-C-D1

898-1AH-D、898-1AH-C、898-1AH-S、898H-1AH-D、898H-1AH-C、898H-1AH-S、 898-1CH-D、898-1CH-C、898-1CH-S、898H-1CH-D、898H-1CH-C、898H-1CH-S、898-1AH-D1、898-1AH-C1、898H-1AH-D1、898H-1AH-C1、898H-1CH-D1、898H-1CH-C1、898H-1CH-D1SF-R1、898H-1CH-D1SW-R1......

(8) Relays in Other?Applications: The vehicle's power steering wheel, braking system, ignition system, clutch, starter, oil pump, battery, horn, charging indicator, fan, relay box, junction box, and other parts?also require relays for control.

?*# 102、103、301、303、822、871、896H?Series

897-1AH-D、897-1AH-C、897-1AH-S、897-1AH-D-R1、897-1AH-C-R1、897-1AH-S-R1、 897P-1AH-D、897P-1AH-C、897P-1AH-S、897P-1AH-D-R1、897P-1AH-C-R1、897P-1AH-S-R1、897-1AH-D1-R1、897-1AH-C1-R1、897-1AH-D1S-R1、897-1AH-C1S-R1、897-1AH-D1SF-R1、897-1AH-D1SW-R1......

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2.2 Application of EV Charging Station & Equipment

?As an important component of the electric vehicle charging station, relays can achieve circuit switching, over-current protection, over-voltage protection, and fast switching functions. In the application of charging stations/charging piles, electricity?flows from the power grid into the interior of the charging station, and is transmitted to electric vehicles for charging through the control of relays. After the battery is fully charged, the relay cuts off the circuit to prevent overcharging and ensure the safe use of the charging station. When a fault occurs during the use of the charging station, resulting in excessive current or voltage, or when the charging station experiences current overload or over-voltage, the relay will automatically cut off the circuit to avoid charging station faults or damage caused by over-current and a series of safety issues. In addition, when the charging station needs to switch circuits, the relay can quickly switch circuits and still ensure the efficient and stable operation of the charging station in daily applications with frequent circuit switching.

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2.2.1 Relays?in DC Charging Station

?The relay mainly achieves three functions in the direct current?charging station:

?(1) Control?Power: The charging station relay can serve as a control power switch. When the charging station is activated, the relay is activated for turning on the control power. After the charging is completed, the relay is activated again for?disconnecting the?control power.

?(2) Circuit Switch: The charging station relay can achieve circuit switching. When the charging station uses different charging methods, the relay can achieve circuit switching. For example, when the charging station switches from AC charging to DC charging, the relay can undertake and complete frequent switching tasks.

?(3) Status Indication: The charging station relay can also achieve the function of charging status indication. When an electric vehicle is charging, the relay can control the indicator light of the charging station to indicate the charging status of the electric vehicle.

Reference of relays:

Features: Using silver alloy contacts, high-quality copper materials and components and materials that comply with RoHS standards, high sensitivity, long service life, contact conversion can provide 1 group (15A) or 2 groups/3 groups/4 groups (12A); Installation options?of PCB/socket?& rail/flange; Certifications including CCC, CQC, CE, TUV, and UL.

Reference?of Dimension?& Installation

Basic parameters:?load current 12A, load voltage 300V, dielectric withstand voltage between different pole contacts 2500V/S (between contacts of the same coil), overall insertion and extraction force ≤ 70N, connecting wire AWG20-14 (0.5~2.5mm 2）。

Features: Used for pre-charge control of DC charging stations, unique magnetic arc extinguishing design, with 1,000VDC cut-off function, higher surge resistance and current tolerance, with no polarity in load and coil. The current of 20/40A/60A/80A/100A are optional.

Features:?Load voltage 1,000V DC?or 1,500VDC, coil voltage 12VDC?or 24VDC, contact material made of silver copper alloy, current 150A/200A/250A/300A optional, normally open or normally closed optional, auxiliary contact polarity free.

Overall, relays, like fuses,?are important components of the new energy vehicle charging station (especially DC charging station). The matching, linkage, and collaborative work of these components ensure the overall safety, stability, reliability, and service life of the charging station. In practical design and application, it is necessary to select appropriate relay based on specific requirements such as the current load of the charging station, the protection level of the charging environment, and reference to the selected fuses.

2.2.2?Relays?in AC Charging Station/Piles

Comparing with DC charging station, the design of AC charging station / charging pile for new energy vehicles is much simpler, and the relay models used are relatively single. The control PCB board of typical?AC charging pile which contain relays?just like below:

?Reference of relays:

Features: Using high-quality silver alloy contacts, using high-quality copper materials and RoHS compliant components and materials, small size, light weight, strong seismic resistance, high capacity contacts (30A/40A), strong sensitivity, good durability, internal waterproof and dust-proof, long service life, and can be directly welded to PCB boards; The product has certifications including CQC, CE, TUV, and UL.

*67E 1D (4-hole or 5-hole, normally closed contact - international code B);

*67E 1H (4-hole or 5-hole, normally open contact - international code A);

*67E 1Z (5-hole or 6-hole, conversion type contact - international code C).

Features:?Silver alloy contacts, switching voltage 250VDC/30VDC, coil power DC0.53W/AC1.1VA, electrical life ≥ 100,000 times, PCB board installation.

?In addition, 20A or 32A relays are?used in the on-board charger (OBC); The electric vehicle portable charging gun (IC-CPD) also use relays?to control the charging switch.

??2.2.3 Relays in?Charging System of E-Scooters?

Taking the public charging station for electric?scooter?(2-wheels/3-wheels vehicles)?as an example, one station can connect and control multiple vehicles to charge and monitor their status simultaneously. The following picture?shows a master control PCB board that can support the charging of 5 electric scooters:

?Reference of part numbers:

Features: High capacity contacts (10A/15A), with certificates including CQC, CE?& TUV.

2.3 Relays in Solar Photovoltaic Systems

(1) Input Protection: The photovoltaic?(solar PV)?inverter needs to provide input protection for the direct current output from the solar panel to prevent damage to the inverter due to short circuit or over-voltage conditions. At this time, a relay is used as the protection switch for the input end.

?(2) Output Protection: The output of the photovoltaic inverter needs to be connected to the power grid, and the output current needs to be filtered through a filtering circuit to ensure the stability and purity of the output current. At this time, a relay is used as the protection switch at the output end.

?(3) Power Outage Recovery: When the photovoltaic inverter is powered off, it is necessary to restart the inverter after the power is restored. At this time, a relay is used as a power outage recovery device.

?(4) Isolation Control:?The photovoltaic inverter needs to isolate the direct current output from the battery panel and the alternating current from the power grid to avoid interference from the battery panel to the power grid. At this time, a relay is used as an isolation switch.

Features: High capacity contacts (30A/40A), strong sensitivity, good durability, internal waterproof and dust-proof, long service life, PCB?mounted; Certified by CQC, CE, TUV?& UL.

Features:?Used for pre-charging/discharging control of photovoltaic energy storage end, unique magnetic arc extinguishing design, with 1,000VDC cut-off function, higher surge resistance and current tolerance, and no polarity in load and coil.

In addition, there are relays used as DC switches and AC switches in the photovoltaic inverter.

2.4?Relays in Wind Power Generation?System?

(1) Control &?Protection of Wind Turbines:?In wind turbines, as important electrical components, relays mainly play a role in controlling and protecting various equipment such as wind turbine blades and oil pumps, achieving monitoring and control of the entire system.

?(2) Control &?Protection of Wind Fields: In wind?fields, relays can be used to control and protect power systems, substations, transmission lines?etc.. Relays play a role in freeing the power system from various faults.

?(3) Control &?Signal Transmission of Wind Power Generation Monitoring Systems:?Relays can also be applied in wind power generation monitoring systems to achieve monitoring and control of generator sets and power systems. By transmitting signals through relays, it is possible to promptly detect abnormalities in the unit, providing strong support for equipment protection and maintenance.

Features: Small PCB board mounted electromagnetic relay, assembled with dust-free workshop processing technology and fully automated production line, with internal dust prevention, long service life (≥100,000 times), multiple choices of contact forms, contact load of 16A, and switching voltage of 250VAC/30VDC.

Features:?PCB board mounted electromagnetic relay, contact load 8A 1/3HP, switching voltage 277VAC/30VDC. The product has CQC, CE, and UL certificates.

Features: The product only has a thickness of 6mm, which can effectively save 70% of installation space, is compatible with international standard installation methods, has high switching frequency, and long service life. Can be matched and selected with intermediate relays or solid-state relays.

?The appearance and wiring diagram of the ultra-thin solid-state relay are as follows:

The socket integrated protection circuit effectively protects the relay against phase reversal and over-voltage. The socket appearance, installation dimensions, and internal wiring diagram of terminal configuration are as follows:

2.5 Relays in ESS - Energy Storage Systems

2.5.1 Safety Cutoff on The AC Side of ESS

To avoid affecting the commercial power supply while protecting the power system, when?ESS (energy storage system)?generates abnormal current, the power relay is used for safe disconnection on the grid side.

Features: Contact conversion can provide 1set(15A) or 2/3/4sets(12A), PCB welding/socket /flange installation options, and product certifications include CCC, CQC, CE, TUV & UL.

Specific models: 68A-1Z, 68A-1H, 68A-1D.

The following is solder joint of PCB type:

Features: Contact conversion can be provided with 2 sets (6.5A/10A) or 4 sets (5A), PCB board welding/base mounting options, optional LED indicator lights and resistors, and certifications including CCC, CQC, CE, TUV?and?UL.

Features: High capacity contacts (30A/40A), strong sensitivity, good durability, internal waterproof and dust-proof, long service life, PCB?mounted; Certified by CQC, CE, TUV?& UL.

Specific models: 67E 1D, 67E 1H, 67E 1Z etc.

2.5.2 Safety Cutoff on?DC side?of ESS

When the battery or energy storage system fails, the power relay is used for safety cutoff on the DC grid side of the energy storage system.

Features: Maximum allowable voltage 1,500V DC, current 20A~1,000A optional, NO/NC, auxiliary contact optional; The product meets RoHS environmental standards; Unique magnetic arc extinguishing design with higher surge resistance and current tolerance; Load connected non polarity, 12VDC/24VDC energy-saving coil optional; Short circuit resistant structural design, with a short circuit resistance capacity of up to 8,000A and a withstand voltage of over 4,000V between high and low voltages.

2.5.3 Pre-Charging Circuit Management

When the energy storage device is started, the pre-charging relay is turned on to prevent current surges during charging; After charging completed, the relay will disconnect the electricity power.

Features:?Used for pre-charging/discharging control of ESS, unique magnetic arc extinguishing design, with 1,000VDC cut-off function, higher surge resistance and current tolerance, and no polarity in load and coil.

2.5.4 Relays in Household Storage?Systems

Mainly use?relays for power distribution and output loop control of bridge circuits?in household or residential energy storage systems.

Features: Load voltage 750VDC or 450VDC optional, main contact normally open, contact material T-AgNi; S-AgSnQ2+In2O3, optional auxiliary contacts, 12VDC/24VDC coil polarity free, UL certified for safety.

Moreover, relays are also could be easily found on the control boards of many key parts of outdoor portable power stations (power banks), residential or household energy storage systems, commercial/industrial or containerized energy storage systems etc..

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2.6?Relays in Industrial Automation?&?Smart?Control

Relays are used?in?various fields?of industrial automation, including frequency converters VFD-Variable Frequency Drive, servo controllers, switch?gear control cabinets, industrial programmable logic controllers PLC (used for input and output signal transmission and switching), industrial robots and AGV logistics equipment, smart homes and intelligent IoT, power control, relay control, detection equipment, instruments and meters (used for signal transmission, switching and collection), safety control, and more.

Features: Contact conversion can be provided with 2 sets (6.5A/10A) or 4 sets (5A), PCB board welding/base mounting options, optional LED indicator lights and resistors, and certifications including CCC, CQC, CE, TUV?and?UL.(See previous chapter for other models and matching optional installation sockets.)

Features: The product only has a thickness of 6mm, which can effectively save 70% of installation space, is compatible with international standard installation methods, has high switching frequency, and long service life. Can be matched and selected with intermediate relays or solid-state relays.

Features:?The relay contact material is silver alloy, the driving method is NPN/PNP bipolar compatible, with status indicator light, rated voltage of 12VDC/24VDC/220VAC, action time ≤ 15ms, multiple contact types of NO/NC are available, mechanical life 10 ^ 7 times, with input protection and multiple output protection types.

Scope of Application: Suitable for CNC systems such as Fanuc, Mitsubishi, Siemens, as well as various industrial and agricultural machinery and equipment such as automation equipment, processing machinery and welding equipment.

Features: High capacity contacts (30A/40A), strong sensitivity, good durability, internal waterproof and dust-proof, long service life, PCB?mounted; Certified by CQC, CE, TUV?& UL.

Features:?Small PCB board mounted electromagnetic relay, assembled with dust-free workshop processing technology and fully automated production line, with internal dust prevention, long service life (≥100,000 times), multiple choices of contact forms, contact load of 16A, and switching voltage of 250VAC/30VDC.

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2.7 Relays in Home Appliances

In our daily life, relays also play an important?role in various household appliances around us, such as?air conditioners?and smart ventilation systems, refrigerators, washing machines, microwave ovens, televisions, water heaters, electric steam ovens, electric cookers, automatic dishwashers, disinfection cabinets, soybean milk machines,?juicers, steam boilers?etc..

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The following pictures are relay application reference for the main control board of the variable frequency air conditioner (the left) and board of the air conditioner’s external unit (the right):

These are relay application reference for the control board of electric water heater (left) and the control board of kitchen ventilator (right).

These are relay application in the control board of refrigeration equipment/ice making equipment/snow making equipment:

Features: The product only has a thickness of 6mm, which can effectively save 70% of installation space, is compatible with international standard installation methods, has high switching frequency, and long service life. Can be matched and selected with intermediate relays or solid-state relays.

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2.8?Other Applications Brief

As a switch control device for circuit on-off, relays are also common and critical electronic components in facilities such as intelligent parking equipment, electric door control systems, elevator or lift control, treadmills/electronic fitness equipment, massage chairs, fully automatic mahjong tables, automatic lifting tables and chairs etc.

These are relay application in the control board of the electric door control/access control system (left), entrance management systems of residential areas/subway entrances/scenic ticket entrance (right):

These are relays in intelligent parking equipment (left) and smart device controls (right).

Relays in control boards of elevator (left) and elevator VFD (right).

Relays in fitness treadmill (left) and smart massage chair/devices (right).

Relays in smart lifting adjustable desk (left) and automatic mahjong table (right).

In addition, there are also application scenarios for relays in communication network equipment and medical fields. In medical instruments and equipment such as ultrasound medical equipment, blood analysis instruments, multifunctional detectors, intelligent operating tables, multifunctional hospital beds, and automatic disinfection equipment, relays also play a role in power switching, circuit switching, communication, and motor control.

III. Guideline & Precautions of Relays

What specific factors should be taken into consideration?for the matching and selection of relays in the various applications mentioned above? Let’s briefly discuss common electromagnetic relays, solid-state relays?and intermediate relays next.

3.1 Electromagnetic Relays

When selecting and matching electromagnetic relays, it is necessary to consider the rated working voltage and current, coil voltage and current, load properties, working system, and environmental factors in practical applications. The key parameter items to be focused?on?including:

(1) Contact?Load: Determine whether the relay can withstand the application load requirements, including AC, DC, and size (inductive or resistive?etc.).

(2) Contact Form: Determine whether a NO-normally open, NC-normally closed?or conversion type,?unit contact pairs.

(3) Contact Material: Even for the same relay, different contact materials can meet different types and ranges of loads. The usual contact materials include AgNi, which is the standard material for most relay contacts and has high ablation resistance;AgNi+gold plating with good corrosion resistance, conductivity and thermal conductivity; AgPd with good consistency, strong vulcanization resistance but expensive price; AgCdO and AgSnO2 with good adhesion resistance, etc.

(4) Relay Coil:?including DC/AC voltage?level, resistance input power consumption, action voltage, release voltage, maximum allowable voltage, coil temperature rise/insulation level?etc..

(5) Performance Aspects:?packaging methods such as normally open?type/dust cover/anti solder/plastic sealing, dielectric withstand voltage, insulation resistance, vibration resistance, impact resistance?etc..

(6) Application Environment:?temperature range, duration, humidity, presence of special or harmful gases?etc.

(7) Installation Method: including the form of the lead out end, such as PCB/QC/DIP insertion/screw fixation, manual welding/wave soldering/reflow soldering, and other welding methods, as well as whether to tightly adhere to the board end or leave gaps during installation.

(8) Certification Requirements:?Applicable to CCC in China, UL and CUL in North America, VDE/TUV in Europe, and CQC in different regions.?Find more details in?"Appendix II: Relay Standards & Safety Certification".

For more detailed explanation?about relay terminologies, please refer to "Appendix I: Terminologies of Relay".

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3.2 Solid?State Relays (SSR)

In the process of selecting solid-state relays, attention should be paid to the size of load surges, temperature and time factors of the operating environment, and heat dissipation conditions of the installation environment. Detailed selection method is as follows:

(1) Determine electrical performance parameters, such as input voltage or current, output voltage or current, overload current, and dv/dt, whether they match or match the actual required technical indicators, and whether the external circuit or load matches.

?(2) Select AC or DC solid state?relay by checking?the load properties, DC controlled DC (DC-DC) or DC controlled AC (DC-AC).

?(3) Select single-phase or three-phase RRS?based on the type of load need to be controlled.

?(4) Choose different specifications of inductive load, capacitive load, or resistive load based on the type of load to determine voltage and current parameters.

?(5) Generally, the relay we choose should be greater than one-third of the load. It is recommended to control the motor by 5-7 times, and for DC motors or inductive loads by 6 times or more to prevent the reverse electromotive force from being too high and breaking down the solid-state relay.

?(6) The load capacity of solid-state relays is greatly affected by environmental temperature and their own temperature rise. During installation and use, it should be ensured that they have good heat dissipation conditions. Products with a rated working current of 10A or above should be equipped with heat sinks, and products with a rated working current of 25A or above should be equipped with heat sinks and forced cooling fans. During installation, attention should be paid to good contact between the bottom of the relay and the radiator, and an appropriate amount of thermal conductive silicone grease should be applied to achieve the best heat dissipation effect. If the surface antigen of a SSR?is coated with thermal conductive silicone grease.

?(7) When using SSR, short circuit breakdown caused by over-current and resistive loads or permanent damage to the internal output thyristor of the SSR generally requires the installation of RC circuits or varistors to protect the SSR. The selection principle is to use 500V-600V varistors for 220V, and 800V-900V varistors can be used for 380V.

?(8) When selecting?SSR for use with low current specification printed circuit boards, as the lead terminals are made of high thermal conductivity materials, welding should be carried out under conditions of temperature less than 250℃ and time less than 10S. If necessary, considering the surrounding temperature, derating can be considered. Generally, the load current should be controlled within 1/2 of the rated value for use, and the inductive load should be used within 1/3, and frequent starts or harsh environmental conditions, it should be used at a reduced rate.

?(9) The controlled load will generate a large surge current at the moment of connection. Due to the lack of time to dissipate heat, it is likely to damage the internal thyristor of the SSR. Therefore, when selecting a relay, users should analyze the surge characteristics of the controlled load before selecting the relay. Enable the relay to withstand this surge current while ensuring steady-state operation.

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3.3 Intermediate Relays

In the selection and selection of intermediate relays in applications, the following three key factors need to be comprehensively considered:

(1) The task of intermediate relays is to transmit and amplify switching signals, so the number of "contact pairs" of intermediate relays is very important.

(2) The so-called "contact pair" refers to a normally open and normally closed contact composed of a moving contact. A typical intermediate relay should have at least 2 pairs of contact pairs, with a maximum of 4 pairs of contact pairs.

(3) It is necessary to consider the pull-in current and release voltage of the intermediate relay. The pull-in current involves the total current of the control circuit power supply, while the release voltage is related to the stability of the control circuit voltage.

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Appendix I: Terminologies of Relay

?·Contact Form: Including 3 contact forms - ① Dynamic closing or normally open. When the coil is not powered on, the two contacts are disconnected, and when powered on, the two contacts are closed with the code H/A/NO (H in China, A or NO in other areas). ② Dynamic break or normally closed, when the coil is not powered on, the two contacts are closed, and after being powered on, the two contacts are opened, code?named D/B/NC Conversion type, contact group type, code name Z/C/CO. The conversion type contact group has three contacts, with a moving contact in the middle and a static contact in the upper and lower parts. When the coil is not energized, the moving contact and one of the stationary contacts open while the other closes; After the coil is powered on, the moving contact moves to make the originally opened state closed, and the originally closed state opens to achieve the purpose of conversion - such a contact group is called a conversion contact.

?·Contact Resistance: refers to the total resistance of the resistance between the contact points and the resistance of the conductor connected to the contact point and the lead out end. Generally represented by "m". Unless otherwise specified in the manual, relays with contact loads less than 1A are generally used with 6V DC. Measure the contact resistance with 0.1A, and use 6vd for relays with contact loads greater than 1AC. Measure the contact resistance at 1A. If there are differences, the maximum allowable voltage and current shall be used for testing according to the corresponding load type specified in IEC61810-7.

·Contact Voltage Drop:?Generally refers to the total voltage drop between the contacts in the load circuit of a relay, as well as on the tabs and leads connected to the contacts. Generally expressed as the voltage drop value under the specified current, such as 50mv (measured at 10A).

·Contact Material:?The material used for relay contacts, usually represented by a chemical formula, such as AgNi for silver brocade alloy contacts.

·Contact Rated Load: generally refers to the load that the contact can reliably switch under certain specified conditions, usually expressed as a combination of voltage and current. Unless otherwise specified, the loads listed in the manual are generally resistive loads.

·Maximum Switching Voltage: The maximum load voltage that a relay contact can switch. Do not exceed this value during general use, otherwise the lifespan of the relay will be reduced.

·Maximum Switching Current: The maximum load current that a relay contact can switch. Do not exceed this value during general use, otherwise the lifespan of the relay will be reduced.

·Maximum Switching Power: The maximum load that a relay contact can reliably switch, usually represented by "vA" for AC and "W" for DC.

·Mechanical Durability:?Refers to the number of times a relay can switch normally at a specified frequency under the condition that no load is applied to the contact or monitoring current and voltage are applied that will not cause mechanical durability failure of the relay. It is generally expressed as "number of times" when the rated voltage is applied to the coil.

·Electrical Durability:?Generally refers to the number of times a relay can switch normally when a specified load ratio is applied to the contacts and rated voltage is applied to the coil under certain specified environmental conditions, usually expressed as "number of times".

·Surge Current: Generally refers to the instantaneous maximum current that a relay contact can withstand for a specific type of load.

·Minimum?Applicable?Load: generally refers to the reference value of the minimum load that the relay contacts can switch. The reference value will vary depending on the on/off frequency, environmental conditions, expected contact resistance, and reliability. Therefore, please confirm the test with actual load before use.

·Insulation Resistance:?refers to the impedance presented when a specified voltage is applied between disconnected conductive parts, usually expressed in "MΩ". The voltage specified above is generally 500V DC?(or 250V DC.).

·Dielectric Withstand Voltage: refers to the voltage value at which the leakage current is less than the specified value when a certain voltage is applied between disconnected conductive parts within a specified time. The above voltage is generally the effective value of AC voltage, and unless otherwise specified, the leakage current is generally specified to be less than 1mA.

·Action Time:?refers to the time (excluding the action rebound time) of a relay in the released state, from the moment when the rated voltage of the step is applied to the coil to the moment when the normally open contact of the relay is closed, generally expressed in "ms". For magnetic retention relays, it refers to the time from the moment when a step rated voltage is applied to the coil to the moment when the normally open contact of the relay is closed in a reset state.

·Release Time: Refers to the time (excluding the release rebound time) that a relay is in an operating state, from the moment the rated voltage applied to the coil is disconnected to the moment the normally closed contact of the relay is closed, usually expressed in "ms".

·Reset Time: For magnetic holding relays only, it refers to the time from the moment when the rated voltage is applied to the reset coil to the moment when the normally closed contact of the relay is closed when the relay is in an operating state.

·Bounce?Time:?generally refers to the time from the moment of contact closure to stable closure, usually expressed in "ms".

·Switching Frequency: refers to the number of cycles of relay action and release per unit time.

·Environmental Temperature: The ambient temperature at which a relay can function normally, usually expressed in the temperature range.

·Coil Temperature Rise:?generally refers to the temperature rise of the coil when a specified voltage is applied to the coil and a rated load is applied to the contacts at the highest applicable ambient temperature. After the temperature stabilizes, the maximum value is generally given, represented by "K".

·Impact: divided into two indicators: impact stability and impact strength.

·Impact Stability: Refers to the impact value that a relay can withstand when the time for the closed contact to open and the time for the open contact to close are within the specified time. It’s generally expressed as a combination of acceleration value "m/s2" (9.8m/s2=1g) &?duration "ms".

·Impact Strength:?refers to the impact value that a relay can withstand without damage to its structure, usually expressed as a combination of acceleration value "m/s2" and duration "ms".

·Vibration:?divided into two indicators: vibration stability and vibration intensity.

·Vibration Stability: refers to the vibration value that a relay can withstand when the time of opening the closed contact and the time of closing the open contact are within the specified time, generally expressed as a combination of vibration amplitude "mm" and vibration frequency "Hz".

·Vibration Intensity: refers to the vibration value that a relay can withstand without damage to its structure, usually expressed as a combination of vibration amplitude "mm" and vibration frequency "Hz".

·Humidity: Refers to the recommended humidity requirement for reliable operation of relays, generally expressed as relative humidity "% RH".

·Lead Out Terminal Form: The form of the relay lead out terminal also shows the applicable field. The general forms of lead out terminals include PCB (printed circuit board) direct insertion (THT), surface mount (SMT), plug-in, QC (quick connect), and their combination.

·Packaging Method:?refers to the protection method for the relay body. It is generally divided into open type, dust cover type, solder proof type, plastic sealed type, and sealed type.

·Rated Coil Power: refers to the power consumed by the coil when the rated voltage is applied to the coil. Generally, DC relays are represented by "W" and AC relays are represented by "VA".

·Rated Voltage: refers to the voltage that needs to be applied to the coil in order to ensure the normal operation of the relay, usually represented by "V". For polarized relays, attention should be paid to the directionality of the applied voltage.

·Action Voltage: Refers to the voltage on the coil of a relay in a released state (reset state for magnetic holding relays), gradually increasing the voltage when the normally open contact is closed, usually represented by "V". The general manual provides a maximum value of approximately 80% of the rated voltage, which may vary with the use of the relay.

·Release Voltage: Refers to the voltage on the coil of a relay that is in an operating state, gradually decreasing from the rated voltage. The voltage when the normally closed contact is closed is generally represented by "V". The general manual provides a minimum value of approximately 10% of the rated voltage, which may vary with the use of the relay.

·Reset voltage:?Refers to the voltage on the reset coil of a magnetic holding relay that is in an operating state. The voltage when the normally closed contact is closed is usually represented by "V". The general instruction manual provides a maximum value of approximately 80% of the rated voltage

·Coil Resistance:?Generally refers to the DC resistance of the coil, usually expressed in "Ω". The general instructions provide a combination of nominal values and tolerances.

·Maximum Voltage: refers to the maximum voltage that a coil can withstand in a short period of time, usually represented by "V".

·Maximum Switching Power Curve:?displays the load that the relay can carry.

·Electrical Durability Curve: The electrical durability curve displays the typical number of life cycles under a specified load, and the data on the curve is not the guaranteed minimum number of life cycles.

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Appendix II: Relay Standards & Safety Certification

The International Electrotechnical Commission (IEC) was established in 1906 and is the world's earliest non-governmental international electrotechnical standardization organization. It is a Grade A consulting organization of the United Nations Economic and Social Council (ECOSOC) responsible for international standardization work in the fields of electrical and electronic engineering (ISO is responsible for other fields), including electrical technology in power, electronics, telecommunications, and atomic energy. The purpose of IEC is to promote international unification of electrical standards, standardization and related international cooperation in the field of electrical and electronic engineering. IEC member countries include the vast majority of industrial developed countries and some developing countries. These countries have 97% of the world's population, producing and consuming 95% of the world's electricity, and manufacturing and using 90% of the world's electrical and electronic products.

RoHS is a mandatory standard established by EU legislation, and its full name is the "Restriction of Hazardous Substances". This standard has been officially implemented since July 1, 2006, mainly used to standardize the materials and process standards of electronic and electrical products, making them more conducive to human health and environmental protection. The purpose of this standard is to eliminate six substances, including lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls, and PBDE polybrominated diphenyl ethers, in electrical and electronic products, with a focus on specifying that the content of cadmium cannot exceed 0.01%.

The "CE" mark is a safety certification mark that is considered as a passport for manufacturers to open and enter the European market. CE stands for Unification of Europe. In the EU market, the "CE" mark is a mandatory certification mark. Whether it is a product produced by internal enterprises in the EU or products produced by other countries, in order to circulate freely in the EU market, it is necessary to add the "CE" mark to indicate that the product meets the basic requirements of the EU's "New Methods for Technical Coordination and Standardization" directive. This is a mandatory requirement for products under EU law.

TUV is an abbreviation of Technische überwachungs Vereine?(means?Technical Inspection Association). The German Steam Boiler Supervision Association, established in 1871, was the predecessor of TUV?which have the same authority?like VDE, is one of the authoritative institutions in the field of electrical equipment in Germany. Electrical products certified by this agency will be recognized under German law.

VDE is the abbreviation of the Verband Deutsche Elektrotechniker, and is one of the authoritative institutions in Germany in the field of electrical equipment and components. Electrical products certified by this agency will be recognized under German law.

UL is an abbreviation for?Underwriters Laboratories Inc., a non-profit organization established in 1984. Electronic products certified by the agency can be freely sold in the US market, while electronic products without such certification are subject to restrictions when sold in most states of the United States. Due to the authority of UL, products that have obtained UL certification are recognized by many countries.

Certified to both American and Canadian standards, commonly used in North America.

CSA is the abbreviation of the Canadian Standards Association?and is Canada's authoritative certification body for electronic and electrical products. Electrical products certified by this organization can be freely sold in the market?of Canada. CSA certified products can only be sold in the Canadian market, and to enter the US market, products must also obtain UL certification from the US.

The full name of 3C certification is "China Compulsory Certification", abbreviated as CCC. It is a product conformity assessment system implemented by the government?of China?in accordance with laws and regulations to protect the personal and national safety of consumers, strengthen product quality management?and implementation.

CQC, China Quality Certification, is the most authoritative certification agency in China. Products that are not listed in the 3C certification catalog can be CQC certified by the China Quality Certification Center.

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We have already discussed and shared the relevantly typical?application fields of relays. The product models and parameters listed in the article are only part of the general?series for reference. The technical matching and selection of relay products need to be done by actual application and requirements. Please contact SCHEARO?Technologies?for more product solutions and application details! Hotline:+86 13661966568; Email: [email protected] ; Website: www.schearo.com

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