From what aspects does VFD (Variable-frequency Drive) protect the motor?

From what aspects does VFD (Variable-frequency Drive) protect the motor?

VFD (Variable-frequency Drive) is widely used in various industries, mainly because its energy-saving and frequency conversion speed regulation functions are applied in equipment and working condition systems, so from what aspects does VFD (Variable-frequency Drive) play a role in the motor? What about protection? Below we will analyze and answer this question.

VFD (Variable-frequency Drive) protects the motor mainly in the following aspects: overvoltage protection, undervoltage protection, overcurrent protection, phase loss protection, reverse phase protection, overload protection, grounding protection, short circuit protection, overfrequency protection and stall protection. The following is a brief introduction to the protection methods of these types of VFD (Variable-frequency Drive) for the motor.

1. Overvoltage protection:

The output of VFD (Variable-frequency Drive) has a voltage detection function, and VFD (Variable-frequency Drive) can automatically adjust the output voltage to prevent the motor from overvoltage. Even when the output voltage adjustment fails and the output voltage exceeds 110% of the normal voltage, the VFD (Variable-frequency Drive) will protect the motor by shutting down.

2. Undervoltage protection:

When the voltage of the motor is lower than 90% of the normal voltage, the VFD (Variable-frequency Drive) protection stops.

3. Overcurrent protection:

When the motor current exceeds 150% of the rated value for 3 seconds, or 200% of the rated current for 10 microseconds, VFD (Variable-frequency Drive) protects the motor by shutting down.

4. Phase loss protection:

Monitor the output voltage. When the output phase is missing, the VFD (Variable-frequency Drive) will alarm. After a period of time, the VFD (Variable-frequency Drive) will stop to protect the motor.

5. Reverse protection:

VFD (Variable-frequency Drive) allows the motor to rotate in only one direction, and the direction of rotation cannot be set. Unless the user changes the phase sequence of the motor A, B, and C connections, there is no possibility of phase reversal.

6. Overload protection:

VFD (Variable-frequency Drive) monitors the motor current. When the motor current exceeds 120% of the rated current/1 minute, VFD (Variable-frequency Drive) protects the motor by shutting down.

7. Ground protection:

VFD (Variable-frequency Drive) is equipped with a special grounding protection circuit, which is generally composed of a grounding protection transformer and a relay. When one or two phases are grounded, the VFD (Variable-frequency Drive) will alarm. Of course, if the user requires, we can also design it to protect and stop immediately after grounding.

8. Short circuit protection:

After the VFD (Variable-frequency Drive) output is short-circuited, it will inevitably cause overcurrent, and the VFD (Variable-frequency Drive) will stop to protect the motor within 10 microseconds.

9. Overclocking Protection:

VFD (Variable-frequency Drive) has maximum and minimum frequency limiting functions, so that the output frequency can only be within the specified range, thereby realizing the overfrequency protection function.

10. Stall protection:

Stall protection is generally for synchronous motors. For asynchronous motors, the stall during acceleration will inevitably manifest as overcurrent, and VFD (Variable-frequency Drive) realizes this protection function through overcurrent and overload protection. Stall during deceleration can be avoided by setting a safe deceleration time during commissioning.