Why does the frequency converter of Hengli Motor cause the motor to burn out?
Why does the frequency converter burn out the motor?
The heat dissipation of ordinary asynchronous motors relies on the fan behind the motor's rear to blow air and dissipate heat. If the motor runs at low frequency for a long time (i.e. running below the rated frequency of the motor for a long time). When the motor speed is low, the fan blows less air, which leads to poor heat dissipation of the motor. If it is too hot, it will burn out the motor. If there is a problem with the motor, the motor current will increase. If the maximum current of the frequency converter is exceeded, the frequency converter will implement protection to stop output and report a fault code to the user.
The frequency converter displays OC, which means overcurrent. The solution is to replace the motor with a dedicated variable frequency motor or install a cooling fan on the motor. Or replace it with a more powerful motor.
What are the reasons for motor burnout caused by frequency converters
The faults of the motor are not actually caused by the motor itself, but mostly due to non-standard debugging of the frequency converter or the use of non variable frequency motors as variable frequency motors. There are mainly the following situations:
1. Use ordinary motors as variable frequency motors.
Due to the connection between the ordinary motor cooling fan and the shaft, when using a frequency converter for speed regulation, the speed is unstable and cannot reach the rated speed of the motor. The cooling fan cannot function properly, causing poor heat dissipation of the motor; In addition, ordinary motors are not designed according to frequency conversion requirements, which can cause the motor to heat up or burn out.
2. Variable frequency motors and frequency converters are directly connected for use without debugging.
The two most commonly used methods for controlling motors with frequency converters are vector control and V/F curve control. Each control method must first set the type of motor (synchronous, asynchronous, with or without an encoder), rated power, rated voltage, rated current, speed or number of poles, rated frequency, maximum operating frequency, acceleration and deceleration time for motor start and stop, protection mode and protection ratio factor, carrier frequency, etc., all of which are indispensable. After setting these parameters, choose whether to use vector control or V/F control. When choosing vector control, the motor should be paired with a frequency converter for dynamic self-learning under no-load or static self-learning with load. Only after self-learning can the motor be matched with the frequency converter to achieve the accuracy of vector control; When choosing V/F control, there is no need for self-learning, and the parameters can be adjusted and directly powered on for operation.
3. The direction of operation of the variable frequency motor fan is not consistent with the rotation direction indicated on the fan, and the fan cannot function, causing the motor's heat dissipation to deteriorate. The heat generated by the motor cannot be dissipated, resulting in the motor overheating or burning out.
4. 2 and 3 of the above three situations occur the most frequently
When the motor current in the frequency converter is set too high, the motor protection parameters are set too high, and the motor is overloaded, the frequency converter cannot protect the motor according to the actual current of the motor, causing the motor to overheat or burn out due to overload; When the motor speed is set incorrectly, if the set speed exceeds the rated speed of the motor, the motor will operate at a higher speed in the constant power range at the rated frequency point. The higher the speed, the smaller the output torque, which can cause excessive motor current, heat generation, or motor burnout; If the acceleration and deceleration time of the motor is too short, the frequency converter will report an overcurrent fault and provide protection; The frequency converter adopts vector control, but the motor is not paired with the frequency converter for self-learning, which causes the parameters of the motor controlled by the frequency converter to not match the actual values of the motor, resulting in poor control accuracy, motor heating or burning out; When the carrier frequency is set relatively high, the switching rate of the inverter switch tube is relatively high, and the heat generation increases. At this time, the ability of the inverter to resist changes in load current decreases. When the load current increases, the inverter may trip due to overcurrent, which is reflected on the surface as a problem with the motor; The motor protection current is not set, and most frequency converters default to a protection current of 150% of the rated output current of the frequency converter. The frequency converter will only protect when the motor current reaches this value; The output current of the frequency converter should be greater than the rated current of the motor. When the current of the motor reaches the protection current of the frequency converter, the motor is actually overloaded by more than 150%. The motor heats up severely and burns out. The phenomenon that customers see is that the frequency converter is not a problem, but the quality of the motor is unreliable.
5. In response to the above situation, it is recommended that customers choose frequency converters to control motors. They should choose frequency converters from manufacturers with good quality. Although the initial investment is a bit higher, the quality is guaranteed, the fault free operation time is long, and it is not easy to cause production stoppages due to motor or frequency converter failures. In addition, high-quality frequency converters have guaranteed after-sales service and fast response time
