Suppliers of frequency converter supporting equipment remind you that improper use of frequency converters not only fails to fully utilize their excellent functions, but may also damage the frequency converter and its equipment, or cause interference effects. Therefore, the following precautions should be taken during use:
1. The frequency converter must be selected correctly.
2. Carefully read the product manual and follow the instructions for wiring, installation, and use.
3. The frequency converter device should be reliably grounded to suppress radio frequency interference and prevent electric shock caused by leakage of the frequency converter.
4. When using a frequency converter to control the speed of an electric motor, the temperature rise and noise of the motor will be higher than when using grid electricity (power frequency); When operating at low speeds, due to the low speed of the motor fan blades, attention should be paid to ventilation and cooling, as well as appropriately reducing the load, to prevent the temperature rise of the motor from exceeding the allowable value.
5. The impedance of the power supply line cannot be too small. When the frequency converter is connected to the voltage grid, if the capacity of the distribution transformer is greater than 500KVA, or if the capacity of the distribution transformer is greater than 10 times that of the frequency converter, or if the frequency converter is connected very close to the distribution transformer, due to the small circuit impedance, a large surge will be generated on the frequency converter at the moment of input, which will damage the rectifier components of the frequency converter. When the impedance of the line is too low, an AC reactor should be installed between the power grid and the frequency converter.
6. When the three-phase voltage imbalance rate of the power grid is greater than 3%, the peak value of the input current of the frequency converter will be very large, which can cause overheating of the frequency converter and its connections or damage to electronic components. At this time, it is also necessary to install AC reactors. Especially when the transformer is connected in a V-shape, it is more serious. In addition to installing a reactor on the AC side, a DC reactor also needs to be installed on the DC side.
7. Excessive capacitors should not be installed on the incoming side to improve the power factor, nor should capacitors be installed between the motor and the frequency converter, otherwise it will cause a decrease in line impedance, resulting in overcurrent and damage to the frequency converter.
8. Compensation capacitors cannot be connected in parallel on the output side of the frequency converter, nor can capacitors be connected in parallel to reduce high-order harmonics of the output voltage of the frequency converter, otherwise it may damage the frequency converter. In order to reduce harmonics. Can be connected in series with reactors.
9. The starting and stopping of motors regulated by frequency converters should not be directly operated by circuit breakers or contactors, but should be done using the control terminals of the frequency converter. Otherwise, it may cause the frequency converter to lose control and potentially lead to serious consequences.
10. It is generally not advisable to install AC contactors between the frequency converter and the motor to avoid overvoltage during the interruption period and damage to the inverter. If installation is required, the output contactor should be closed before the frequency converter runs.
11. For situations where a frequency converter drives a regular electric motor for constant torque operation, long-term low-speed operation should be avoided as much as possible, otherwise the motor's heat dissipation effect will deteriorate and the heating will be severe. If it is necessary to operate at low speed and constant torque for a long time, a variable frequency motor must be selected.
12. For situations where the load is increased and there is frequent start stop, there will be torque generated, and appropriate braking resistors need to be selected, otherwise the frequency converter will often trip due to overcurrent or overvoltage faults.
13. When the motor has a brake, the frequency converter should operate in a free stop mode, and the braking action signal should only be issued after the frequency converter issues a stop command.
14. The blocking of the external braking resistor of the frequency converter cannot be less than the requirement of the braking resistor allowed by the frequency converter. On the premise of meeting the braking requirements, the braking resistor should be larger. Never short-circuit the terminal that should be connected to the braking resistor directly, otherwise a short circuit accident may occur through the switch tube during braking.
15. When the frequency converter is connected to the motor, it is not allowed to use a megohmmeter to measure the insulation resistance of the motor, otherwise the high voltage output by the megohmmeter will damage the inverter.
16. Properly handle the issues of acceleration and deceleration. The acceleration and deceleration time set for the frequency converter is too short, which may cause damage to the frequency converter due to electrical shock. Therefore, when using a frequency converter, if the load equipment allows, the acceleration and deceleration time should be extended as much as possible.
① If the load is heavy, the acceleration and deceleration time should be increased; On the contrary, the acceleration and deceleration time can be appropriately reduced.
② If the load equipment needs to accelerate or decelerate in a short period of time, it is necessary to consider increasing the capacity of the frequency converter to avoid excessive current exceeding the rated current of the frequency converter.
③ If the load equipment requires a short acceleration and deceleration time (such as within 1 second), a braking system should be considered on the frequency converter. Generally, larger capacity frequency converters are equipped with braking systems.
17. Avoid mechanical resonance points of load devices. Because electric motors may encounter mechanical resonance points of equipment within a certain frequency range, resulting in mechanical resonance and affecting the operation of the system. For this purpose, it is necessary to set a jumping frequency (or avoidance frequency) for the frequency converter, and jump over (avoid) this frequency to avoid resonance points.
18. Before using the motor for the first time or for a long time before connecting it to the frequency converter, the insulation resistance of the motor must be measured (using a 500V or 1000V megohmmeter, the measured value should not be less than 5M ohms). If the insulation resistance is too low, it will damage the frequency converter.
19. The frequency converter should be installed vertically, with ventilation space left, and the ambient temperature should be controlled not to exceed 40 ℃.
20. Anti interference measures must be taken to prevent the frequency converter from being affected by interference and affecting its normal operation, or the high-order harmonics generated by the frequency converter from interfering with the normal operation of other electronic devices.
21. Pay attention to the thermal protection of the electric motor. If the capacity of the motor is compatible with that of the frequency converter, the thermal protection inside the frequency converter can effectively protect the motor. If the capacities of the two do not match, their protection values must be adjusted or other protective measures taken to ensure the safe operation of the motor.
The electronic thermal protection value of the frequency converter (motor overload detection) can be set within the range of 25% -105% of the rated current of the frequency converter.