Inverter use precautions - Solutions - Huaqiang Electronic Network

Improper use of the inverter, not only can not play its excellent functions well, but also may damage the inverter and its equipment, or cause interference, etc., so pay attention to the following precautions in use:

1. The inverter must be selected correctly. 2. Carefully read the product instruction manual and wire, install and use it according to the requirements of the manual. 3. The inverter device should be grounded reliably to suppress RF interference and prevent electric shock caused by leakage in the inverter. 4. When the inverter is used to control the motor speed, the temperature rise and noise of the motor will be higher than when using the grid (power frequency). When the motor speed is low, the fan should be cooled or the load should be reduced properly. The motor temperature rise exceeds the allowable value. 5. The impedance of the power supply line should not be too small. When the frequency converter is connected to the low-voltage power grid, when the capacity of the distribution transformer exceeds 500KVA, or the capacity of the distribution transformer is greater than 10 times of the inverter capacity, or when the inverter is connected close to the distribution transformer, the input impedance is small due to the small loop impedance. A large inrush current to the inverter can damage the rectifying components of the inverter. When the line impedance is good, an AC reactor is installed between the transformer and the inverter. 6. When the three-phase voltage unbalance of the power grid is greater than 3%, the peak value of the input current of the inverter is very large, which will cause the inverter and the connecting line to overheat or damage the electronic components. At this time, an AC reactor is also required. Especially when the transformer is V-shaped, it is more serious. In addition to installing a reactor on the AC side, it is necessary to install a DC reactor on the DC side. 7. It is not possible to install an oversized capacitor on the incoming side because of increasing the power factor, nor can it install a capacitor between the motor and the inverter. Otherwise, the line impedance will drop and overcurrent will be generated to damage the inverter. 8. The output side of the inverter cannot be shunted in parallel. It is also not possible to parallel capacitors in order to reduce the higher harmonics of the output voltage of the inverter. Otherwise, the inverter may be damaged. In order to reduce harmonics, a reactor can be connected in series. 9. Start and stop with frequency converter speed regulation, can not directly operate with circuit breaker and contactor, and use the control terminal of the inverter to operate, otherwise it will cause the inverter to run out of control and may cause severe punishment. 10. It is generally not advisable to install an AC contactor between the inverter and the motor to avoid over-voltage and instantaneous damage to the inverter. If it needs to be installed, the output contactor should be closed before the inverter runs; before the disconnection, the inverter should stop output first. 11. For the case where the inverter drives the ordinary motor to do constant torque operation, it should try to avoid long-term low-speed operation, otherwise the heat dissipation effect of the motor will be worse and the heat will be severe. If you need to run at low speed and constant torque for a long time, you must use a variable frequency motor. 12. For the case of lifting load and frequent start and stop, there will be negative torque generation, and the braking resistor with appropriate parameters is needed. Otherwise, the inverter will trip due to overcurrent or overvoltage fault. 13. When the motor has another brake, the inverter should work in the free stop mode, and the braking action signal should be sent after the inverter sends a stop command. 14. The resistance of the external braking resistor of the inverter should not be less than the requirement of the braking resistor allowed by the inverter. The braking resistor should be larger if the braking requirements are met. Do not short-circuit the terminal that should be connected to the braking resistor. Otherwise, a short-circuit accident will occur through the switch when braking. 15. When the inverter is connected to the motor, it is not allowed to measure the insulation resistance of the motor with a megger. Otherwise, the high voltage output from the megohmmeter will damage the inverter. 16. Correctly handle the problems of speed increase and deceleration. The acceleration and deceleration time set by the inverter is too short, and it is easy to be damaged by the “electric shock”. Therefore, when using the inverter, the acceleration and deceleration time should be extended as much as possible under the premise of the load device. (1) If the load is heavy, the acceleration and deceleration time should be increased; otherwise, the acceleration and deceleration time can be appropriately reduced; (2) If the load equipment needs to be added or decelerated in a short time, it must be considered to increase the capacity of the inverter to avoid Excessive current occurs, exceeding the rated current of the inverter; (3) If the load equipment requires a short acceleration and deceleration time (such as within 1 s), then the brake system should be considered on the inverter. Generally, larger inverters are equipped with a brake system. 17. Avoid the mechanical resonance point of the load device. Because the motor is in a certain frequency range, it may encounter the mechanical resonance point of the load device, causing mechanical resonance and affecting the operation of the system. To do this, set the hopping frequency (or avoidance frequency) to the frequency converter and jump over it (avoid it) to avoid the resonance point. 18. Before the motor is used for the first time or after being placed for a long time before being connected to the inverter, the insulation resistance measurement must be performed on the motor (using a 500V or 1000V megohmmeter, the measured value should not be less than 5MΩ. If the insulation resistance is too low, the inverter will be damaged. 19. The inverter should be installed vertically, leaving room for ventilation, and the ambient temperature should not exceed 40 ° C. 20. Anti-interference measures must be taken to avoid the inverter being affected by interference and affecting its normal operation, or the high frequency generated by the inverter. Harmonics interfere with the normal operation of other electronic equipment. 21. Pay attention to the thermal protection of the motor. If the motor matches the inverter capacity, the thermal protection inside the inverter can effectively protect the motor. If the capacity of the two does not match, the protection value must be adjusted. Or take other protective measures to ensure the safe operation of the motor. The electronic thermal protection value of the inverter (motor overload detection) can be set within the range of 25% to 105% of the rated current of the inverter.