Variable Frequency Drive Protection Functions on Motor
Mon, Nov 18 by ATO.com
The variable frequency drive has the following ten protections on the motor:
- Over-voltage protection
The variable frequency drive output has automatic voltage regulator function to control the external overtop power input to be not exceed the motor rated voltage.
- Under-voltage protection
When the motor voltage is lower than 90% of normal, VFD will enter the protection mode and reduces the output frequency. When the motor voltage is lower than 65.2% of normal, it will be shut down.
- Over-current protection
When the motor current exceeds a certain range of rated value, VFD will reduce the output frequency or shut down for protection.
- Phase-loss protection
VFD can monitor the output voltage, and when the output phase is loss, the variable frequency drive will alarm and shut it down after a period of time to protect the motor.
- Reverse-phase protection
VFD can make the motor rotates only in one direction and unable to be set unless the user changes the phase sequence of the motors A, B, and C wiring, otherwise there is no possibility of reversal.
- Overload protection
When the motor current exceeds the rated, the variable frequency drive will protect the motor by stopping it when the motor current exceeds 2 times of the rated and lasts for 1 minute.
- Grounding protection
This function is offered by the ground protection transformer and relay. When one phase or two phases is grounded, the variable frequency drive will alarm. Of course, it can also be designed to immediately shutdown when grounded if the user required.
- Short circuit protection
When VFD output short circuit, it will inevitably lead to over current. In this case, VFD is able to shut down the motor in 10 microseconds for protection.
- Over clocking protection
VFD has the maximum and minimum frequency limiting function, so that the output frequency can only be within the specified range, thus realizing the over clocking protection function.
- Stall protection
Stall protection is generally for synchronous motors. For induction motors, the stall during acceleration is necessarily over current, and VFD can protect the motor by over current and overload protection. Stall during deceleration can be avoided by setting a safe deceleration time during commissioning.