Improper use of an AC drive can not only prevent it from functioning optimally but may also damage the drive and connected equipment or cause interference issues. Therefore, the following precautions should be observed during use:
1. The AC drive must be selected correctly.
2. Read the product manual carefully and follow its instructions for wiring, installation, and operation.
3. The AC drive unit should be reliably grounded to suppress radio frequency interference and prevent electric shock due to leakage current.
4. When controlling motor speed with an AC drive, the motor's temperature rise and noise will be higher compared to operation on mains power (utility frequency). During low-speed operation, due to the reduced speed of the motor's cooling fan, pay attention to ventilation cooling and consider appropriately reducing the load to prevent the motor temperature from exceeding its allowable limit.
5. The impedance of the power supply line should not be too low. When an AC drive is connected to a low-voltage grid—if the distribution transformer capacity exceeds 500 kVA or is more than 10 times the AC drive's capacity, or if the AC drive is installed very close to the distribution transformer—the low circuit impedance can cause a large inrush current at switch-on, damaging the drive's rectifier components. If the line impedance is too low, install an AC line reactor between the power grid and the AC drive.
6. When the three-phase grid voltage unbalance exceeds 3%, the peak input current of the AC drive becomes very high, which can cause overheating or damage to the drive and its connections. In this case, an AC line reactor is also required. This is particularly severe when the transformer has a V-connection. Besides adding a reactor on the AC side, a DC choke may also be necessary on the DC side.
7. Do not install excessively large capacitors on the input side solely to improve power factor, and do not install capacitors between the motor and the AC drive. This can reduce line impedance and cause overcurrent, damaging the AC drive.
8. Do not connect power factor correction capacitors in parallel on the output side of the AC drive, nor install capacitors in parallel to reduce higher harmonics in the output voltage, as this may damage the drive. To reduce harmonics, series reactors can be used.
9. For starting and stopping a motor controlled by an AC drive, do not use circuit breakers or contactors directly. Instead, use the AC drive's control terminals. Otherwise, it may lead to loss of control and potentially serious consequences.
10. Generally, avoid installing AC contactors between the AC drive and the motor to prevent overvoltage damage to the inverter section caused by current interruption. If one must be installed, ensure the output contactor is closed before starting the AC drive.
11. For applications where an AC drive operates a standard motor under constant torque, avoid prolonged low-speed operation, as motor cooling becomes less effective, leading to severe heating. If long-term, constant-torque, low-speed operation is required, a motor specifically designed for inverter duty (inverter-duty motor) must be selected.
12. For lifting loads or applications with frequent starts/stops, regenerative (braking) torque will be generated. It is necessary to select and connect a suitable braking resistor; otherwise, the AC drive may frequently trip due to overcurrent or overvoltage faults.
13. When the motor has an external mechanical brake, the AC drive should be set to operate in a free-stop mode, and the brake actuation signal should be issued only after the AC drive has issued the stop command.
14. The resistance of an externally connected braking resistor must not be less than the minimum value allowed by the AC drive's specifications. While meeting braking requirements, it is advisable to use a larger resistance value. Never directly short-circuit the terminals meant for the braking resistor, as this can cause a short-circuit through the switching devices during braking, leading to an accident.
15. When the AC drive is connected to the motor, do not use a megger (insulation resistance tester) to measure the motor's insulation resistance. The high voltage output by the megger can damage the inverter section.
16. Properly handle acceleration and deceleration issues. If the acceleration/deceleration times set in the AC drive are too short, it can be subjected to severe "current shocks," potentially damaging the drive. Therefore, within the limits allowed by the driven equipment, try to extend the acceleration and deceleration times as much as possible.
① If the load is heavy, increase the acceleration/deceleration times; conversely, they can be appropriately reduced for lighter loads.
② If the driven equipment requires very short acceleration/deceleration times, consider using a higher capacity AC drive to avoid excessive current exceeding the drive's rated current.
③ If the driven equipment requires extremely short acceleration/deceleration times (e.g., within 1 second), consider installing a braking unit on the AC drive. Generally, larger capacity AC drives come equipped with braking systems.
17. Avoid the mechanical resonance point of the driven equipment. Within certain frequency ranges, the motor may encounter the mechanical resonance point of the equipment, causing mechanical oscillation that affects system operation. To address this, use the AC drive's frequency jump (or skip frequency) function to skip over (avoid) that specific frequency and prevent resonance.
18. Before connecting a motor to an AC drive for the first time or after prolonged storage, it is essential to measure its insulation resistance (using a 500V or 1000V megger; the reading should be no less than 5 MΩ). If the insulation resistance is too low, it can damage the AC drive.
19. The AC drive should be mounted vertically with adequate ventilation space around it, and the ambient temperature should be controlled not to exceed 40°C.
20. Necessary anti-interference measures must be taken to prevent the AC drive from being affected by interference, which could disrupt its normal operation, or to prevent the higher harmonics generated by the AC drive from interfering with other electronic equipment.
21. Pay attention to the motor's thermal protection. If the motor and AC drive capacities are properly matched, the internal thermal protection of the AC drive can effectively protect the motor. If the capacities do not match, adjust the protection settings or adopt other protective measures to ensure safe motor operation. The electronic thermal protection value (motor overload detection) in the AC drive can typically be set within a range of 25% to 105% of the AC drive's rated current.
