From what aspects does the inverter protect the motor?
The frequency converter is widely used in various industries, mainly because its energy-saving and variable frequency speed control functions are applied in equipment and working condition systems. Then, from what aspects does the inverter protect the motor? Below we will analyze and answer this question.
The protection of the inverter to the motor mainly includes the following aspects: over voltage protection, under voltage protection, over current protection, phase loss protection, reverse phase protection, overload protection, ground protection, short circuit protection, over frequency protection and stall protection. The following is a brief introduction to the protection methods of these types of inverters.
1. Overvoltage protection:
The output of the inverter has a voltage detection function, and the inverter can automatically adjust the output voltage so that the motor does not withstand overvoltage. Even when the output voltage adjustment fails and the output voltage exceeds 110% of the normal voltage, the inverter protects the motor by stopping the machine.
2. Undervoltage protection:
When the voltage of the motor is lower than 90% of the normal voltage, the inverter protection stops.
3. Overcurrent protection:
When the current of the motor exceeds 150%/3 seconds of the rated value, or 200%/10 microseconds of the rated current, the inverter protects the motor by stopping.
4. Phase loss protection:
The output voltage is monitored. When the output is out of phase, the inverter will alarm. After a period of time, the inverter will stop the motor to protect the motor.
5. Reverse protection:
The inverter allows the motor to rotate in only one direction. The direction of rotation cannot be set. Unless the user changes the phase sequence of the motor A, B, and C wiring, there is no possibility of inversion.
6. Overload protection:
The inverter monitors the motor current. When the motor current exceeds 120%/1 minute of the rated current, the inverter protects the motor by stopping.
7. Ground protection:
The frequency converter 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 inverter alarms. Of course, if the user requests, we can also design to protect the shutdown immediately after grounding.
8. Short circuit protection:
After the inverter output is short-circuited, it will inevitably cause over-current. The inverter will stop the motor to protect the motor within 10 microseconds.
9. Overclocking protection:
The inverter has maximum and minimum frequency limit functions, so that the output frequency can only be within the specified range, thus achieving overclock protection.
10. Stall protection:
Stall protection is generally for synchronous motors. For asynchronous motors, the stall in the acceleration process must be manifested as overcurrent, and the inverter achieves this protection function through overcurrent and overload protection. Stall during deceleration can be avoided by setting a safe deceleration time during commissioning.
