Basic methods and steps for inverter commissioning:
I. No-load power-on test of the frequency converter
1. Ground the inverter's grounding terminal.
2. Connect the power input terminal of the frequency converter to the power supply via a leakage protection switch.
3. Check if the inverter display window is normal at the factory. If it is incorrect, it should be reset; otherwise, it should be returned or replaced.
4. Familiarize yourself with the inverter 's operation keys. Most inverters have six keys: RUN, STOP, PROG, DATAPENTER, UP, ▲, and DOWN. The definitions of these keys are generally the same across different inverters. In addition, some inverters may have function keys such as MONITOR PISPLAY, RESET, JOG, and SHIFT.
II. Variable frequency drive with motor running under no-load
1. When setting the motor's power and number of poles, the inverter's operating current must be taken into account.
2. Set the inverter 's maximum output frequency, base frequency, and torque characteristics. General-purpose inverters offer multiple VPf curves for users to choose from. Users should select the appropriate VPf curve based on the nature of the load. For fan and pump loads, the inverter's torque operation code should be set to variable torque and reduced torque operation characteristics. To improve the inverter's low-speed performance during startup and ensure the motor's output torque meets the startup requirements of the production load, the starting torque needs to be adjusted. Torque control is more complex in asynchronous motor variable frequency speed control systems. In the low-frequency range, the effects of resistance and leakage reactance are not negligible. If VPf is kept constant, the magnetic flux will decrease, thus reducing the motor's output torque. Therefore, appropriate voltage compensation is needed in the low-frequency range to increase torque. Generally, inverter compensation is manually set by the user.
3. Set the frequency converter to its built-in keyboard operation mode, press the run button and stop button, and observe whether the motor can start and stop normally.
4. Familiarize yourself with the protection codes when the frequency converter malfunctions, observe the factory default values of the thermal protection relay, and observe the overload protection settings; you can modify them if necessary. The frequency converter operator can set the electronic thermal relay function according to the frequency converter's instruction manual. When the frequency converter's output current exceeds its allowable current, the overcurrent protection will cut off the frequency converter's output. Therefore, the maximum threshold value of the frequency converter's electronic thermal relay should not exceed the frequency converter's maximum allowable output current.
III. Load-bearing trial operation
1. Manually operate the run/stop button on the inverter panel, observe the motor running and stopping process and the inverter's display window, and check for any abnormal phenomena.
2. If the inverter trips its overcurrent protection during the start-up and stop of the motor, the acceleration/deceleration time should be reset. The motor's acceleration during acceleration and deceleration depends on the acceleration torque, while the inverter's frequency change rate during start-up and braking is set by the user. If the motor's moment of inertia or load changes, insufficient acceleration torque may occur when accelerating or decelerating according to the preset frequency change rate, leading to motor stall. This means the motor speed and the inverter's output frequency are not synchronized, resulting in overcurrent or overvoltage. Therefore, the acceleration and deceleration times need to be set appropriately based on the motor's moment of inertia and load to ensure that the inverter's frequency change rate matches the motor's speed change rate.
