21 problems that should be paid attention to when using air compressor inverter

21 problems that should be paid attention to when using air compressor inverter

Improper use of the inverter will not only fail to give full play to its excellent functions, but may also damage the inverter and its equipment, or cause interference, etc. Therefore, the following matters should be noted during use:

　　 1. The inverter must be selected correctly.

　　2. Read the product manual carefully, and connect, install and use in accordance with the requirements of the manual.

　　3. The inverter device should be grounded reliably, and radio frequency interference should be suppressed to prevent the inverter from causing electric shock due to electric leakage.

4. When the frequency converter is used to control the motor speed, the temperature rise and noise of the motor will be higher than when the network power (power frequency) is used; at low speeds, due to the low speed of the motor blades, attention should be paid to ventilation and cooling and the load should be appropriately reduced to avoid The motor temperature rise exceeds the allowable value.

　　 5. The impedance of the power supply line cannot be too small. When the inverter is connected to the voltage grid, when the capacity of the distribution transformer is greater than 500KVA or the capacity of the distribution transformer is greater than 10 times the capacity of the inverter, or the inverter is connected very close to the distribution transformer, due to the loop impedance If the input is small, it will cause a big surge to the inverter at the moment of input, which will damage the rectifier components of the inverter. When the line impedance is too small, an AC reactor should be installed between the power grid and the inverter.

　　6. ​​When the three-phase voltage unbalance rate of the power grid is greater than 3%, the peak value of the inverter input current will be very large, which will cause the inverter and its connection to overheat or damage the electronic components. At this time, an AC reactor is also required. Especially when the transformer is V-shaped connection method, it is more serious. In addition to installing a reactor on the AC side, it is also necessary to install a DC reactor on the DC side.

　　7. Do not install an oversized capacitor on the incoming line side to improve the power factor, nor install a capacitor between the motor and the inverter, otherwise the line impedance will decrease, overcurrent will occur and the inverter will be damaged.

　　 8. Compensation capacitors cannot be connected in parallel on the outlet side of the inverter, and capacitors cannot be connected in parallel to reduce the higher harmonics of the inverter output voltage, otherwise the inverter may be damaged in order to reduce harmonics. Reactors can be connected in series.

　　9. The starting and stopping of the motor speed-regulated by the frequency converter cannot be directly operated by circuit breakers and contactors, but the control terminals of the frequency converter should be used for operation, otherwise the frequency converter will be out of control and may cause serious consequences

　　 10. It is generally not advisable to install an AC contactor between the frequency converter and the motor, so as to avoid over-voltage during the interruption and damage to the inverter. If additional installation is required, the output contactor should be closed before the inverter runs.

　　11. For the occasion that the frequency converter drives the ordinary motor for constant torque operation, the long-term low-speed operation should be avoided as much as possible, otherwise the heat dissipation effect of the motor will be poor and the heat will be serious. If you need to run at low speed and constant torque for a long time, you must choose a variable frequency motor.

　　12. For the occasions of lifting load and frequent start and stop, torque will be generated. It is necessary to select an appropriate braking resistor, otherwise the inverter will often trip due to overcurrent or overvoltage faults.

　　 13. When the motor has another brake, the inverter should work in free stop mode, and the braking action signal will be sent out after the inverter sends a stop command.

　　14. The resistance of the external braking resistor of the inverter cannot be less than the requirement of the braking resistor allowed by the inverter. On the premise of meeting the braking requirements, the braking resistance should be larger. Never directly short-circuit the terminal that should be connected to the braking resistor, otherwise, a short-circuit accident may occur through the switch tube during braking.

　　 15. When the inverter 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. Correctly handle the speed increase and deceleration problems. If the acceleration and deceleration time set by the inverter is too short, it is easy to be "electric shock" and may damage the inverter. Therefore, when the inverter is used, the acceleration and deceleration time should be extended as far as possible if the load equipment allows.

　　 If the load is heavy, the acceleration and deceleration time should be increased; otherwise, the acceleration and deceleration time can be appropriately reduced.

　　 If the load equipment needs to accelerate and decelerate in a short time, you must consider increasing the capacity of the inverter to avoid excessive current that exceeds the rated current of the inverter.

　　 If the load equipment requires a short acceleration and deceleration time (such as within 1S), you should consider using a brake system on the inverter. Generally larger capacity inverters are equipped with brake systems.

　　 17. Avoid the mechanical resonance point of the load equipment. Because the motor is within a certain frequency range, it may encounter the mechanical resonance point of the equipment, produce mechanical resonance, and affect the operation of the system. For this reason, it is necessary to set a jump frequency (or avoidance frequency) for the inverter, and jump over (avoid) the frequency to avoid the resonance point.

　　 18. Before using the motor for the first time or connecting it to the inverter after being placed for a long time, the insulation resistance of the motor must be measured (using a 500V or 1000V megger, the measured value should not be less than 5M ohms). If the insulation resistance is too low, the inverter will be damaged.

　　19. The inverter should be installed vertically, with ventilation space reserved, and the ambient temperature should not exceed 40°C.

　　 20. Anti-interference measures must be taken to prevent the inverter from being disturbed and affecting its normal operation, or the higher harmonics generated by the inverter will interfere with the normal operation of other electronic equipment.

　　 21. Pay attention to the thermal protection of the motor. If the motor is adapted to the capacity of the frequency converter, the thermal protection inside the frequency converter can effectively protect the motor. If the two capacities do not match, the protection value must be adjusted or other protective measures must be taken 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%-105% of the rated current of the inverter.