Application of PFA rectifier feedback device in power dynamometer

Electric dynamometer is a comprehensive testing equipment for performance testing of various power machinery. It is mainly used for testing the input power of fans, water pumps, hydraulic or gear transmissions, and can also be used for testing the output power of engines. It is a fully functional (with both electric and power generation conditions), high-performance and important testing equipment. It is coaxially connected to the tested motor through a shaft connector, used to simulate and control the load of the tested motor, to measure parameters such as torque, speed, current, voltage, power, efficiency, etc. of the motor. And other special power testing projects, such as safety testing, dynamic balance testing experiments, etc.

Application case of PFA rectifier feedback device in the dynamometer industry

Analysis of the current dynamometer control system scheme:

The first option:

Use ABB and Siemens variable frequency feedback integrated machine (four quadrant frequency converter) to meet the operational requirements of the dynamometer. This type of solution has a high price, good torque accuracy, and stable speed accuracy.

The second option:

Using ABB and Siemens ordinary vector frequency converters with PFA rectification feedback device scheme to meet the operational requirements of the dynamometer. This type of solution integrates the universal advantages of ABB and Siemens frequency converter vector algorithms, and the torque accuracy and constant speed accuracy fully meet the accuracy requirements of the dynamometer. On the other hand, using PFA rectifier feedback device has a higher cost-effectiveness, and it stably feeds back the energy of the accompanying test motor in the power generation state to the grid, with current harmonics<5% and voltage harmonics<1%.

The third option:

Domestic four quadrant frequency converters have similar prices to the second solution, but the vector algorithm of domestic frequency converters is limited, especially in controlling the stability accuracy and torque accuracy that affect the performance of the dynamometer.

Core Technology Description of PFA Rectification Feedback Device:

â‘´ Adopting high-speed DSP central processing unit:

Upgrade the new generation rectification feedback control software, with accurate control accuracy, good stability, less harmonics, and strong anti-interference ability;

⑵ Adopting the latest SVPWM modulation technology in the industry:

Upgrade the new generation SVPWM vector control technology to meet the requirements of rectification feedback national standards for current harmonics;

⑶ Standard RS485 communication and feedback power display:

The product comes standard with RS485 communication and keyboard communication display, and all software control parameters are open for display and debugging, making product monitoring convenient;

â‘· Prevent islanding effect:

The software monitors the status of the air power grid in real-time, and immediately stops the feedback of electrical energy to the grid when the grid is cut off, to prevent islanding effects;

⑸ Adopting LC filtering technology:

Optimize LC filtering to effectively suppress harmonics and electromagnetic interference, with voltage and current THD<5%, ensuring feedback of clean electrical energy;

Adopting automatic phase sequence discrimination technology:

Upgrade the automatic phase sequence discrimination technology, allowing the phase sequence of the three-phase power grid to be freely connected without the need for manual differentiation;

Upgrade hardware design beyond the national standard requirements for voltage resistance:

The newly upgraded hardware design meets the requirement of a 1-minute withstand voltage of 2500 volts AC, with a leakage current of less than 2mA, far below the national standard of 30mA;

â‘» Improve the rectification feedback current level of the machine:

Newly upgraded hardware and control software, reducing the product's machine volume by over 31% and increasing current by 34%;

Configure fuses:

Configure DC and three-phase AC fuses, ensure short-circuit protection is in place, and guarantee the safe operation of the inverter;

⑽ Built in input filtering device, full process noise filtering, interference to the power grid is 1/4 of that of ordinary commercial frequency converters;

⑾ Built in rectifier feedback active front-end, which can feedback regenerated electrical energy to the grid. Built in reactor and filter, can be directly connected to the power grid, with an energy feedback efficiency of up to 97%. Energy saving by 20% to 50% more than general frequency converters, with heat loss below 3% of resistance braking, reducing heat sources, and increasing safety factor;

12. Built in rectifier feedback active front-end, using IGBT rectification, can reduce 15% to 25% of the power grid capacity compared to using a general frequency converter rectifier bridge rectification;

â’€ Built in rectifier feedback active front-end, power factor up to 0.99;

Built in rectifier feedback active front-end, during rated operation, the THD distortion of grid voltage is less than 5%, and the THD distortion of grid current is less than 5%, meeting the quality requirements of the grid;

All round drive, compatible with permanent magnet synchronous motor and asynchronous motor controllers;

485 communication function, supporting mainstream 485 communication protocol in RTU mode;

â’„ It has multiple protection functions such as overcurrent, overload, short circuit, overvoltage, hardware overvoltage, undervoltage, power grid phase loss, power grid amplitude, overheating, external fault input, etc., to ensure safer and more reliable system operation;

Easy to install, debug, and operate, with convenient maintenance and upkeep;

Application case analysis of dynamometer rectifier feedback device:

Tianjin Keda Power Testing Technology Co., Ltd. is mainly dedicated to the testing of motorcycles, automobiles, engines and their key components, with a development history of over 20 years. Since 2008, it has been using the Siemens universal vector frequency converter and our PFA rectifier feedback device solution.

Taking the ACD-11 AC electric dynamometer, which is a specialized testing equipment for small general-purpose gasoline engine test stands, as an example, the system adopts AC motor and frequency conversion control technology, as well as computer technology and testing software, to meet the testing requirements of small general-purpose gasoline engines.

2、 Main functions:

1. This system mainly consists of the following parts:

(1) Host: AC power dynamometer;

(2) Dynamometer control: SIEMENS AC variable frequency speed regulation device, using manual knob to adjust the operating condition point;

(3) Detection and data processing part: using industrial control computers to detect and display various detection parameters, manage data, print test reports, and draw engine characteristic curves;

2. Adopting SIEMENS fully digital control device, the AC electric dynamometer has two operating states: electric and dynamometer. When electric, it can drive the engine to automatically operate, and when dynamometer is used, it applies load to the engine, with fast and stable control characteristics;

3. During dynamometer operation, the mechanical energy of the engine is fed back to the power grid through a PFA rectifier feedback device. When the dynamometer operates below the rated speed of the variable frequency motor, it can reach the rated torque capacity of the dynamometer. When the dynamometer operates above the rated speed of the variable frequency motor, it can reach the rated power of the dynamometer;

4. The dynamometer adopts constant speed control or constant torque control mode;

The system testing accuracy maintains the control accuracy of Siemens universal vector frequency converter

(1) Speed: ± 0.2% ± 1r/min;

(2) Torque: ± 1%;