1. No-load power-on test of the inverter
1 Ground the ground terminal of the inverter.
2 Connect the power input terminal of the inverter to the power supply through the leakage protection switch.
3 Check whether the factory display of the inverter display window is normal. If it is not correct, reset it, otherwise request replacement.
4 Be familiar with the operation keys of the inverter. General inverters have 6 keys: run (RUN), stop (STOP), programming (PROG), data P confirmation (DATAPENTER), increase (UP, ▲), decrease (DOWN, “), etc., different inverter operations The definitions of the keys are basically the same. In addition, some inverters have function keys such as monitor (MONITORPDISPLAY), reset (RESET), inching (JOG), and shift (SHIFT).
2. Inverter with motor running without load
1. To set the power and number of poles of the motor, the working current of the inverter must be considered comprehensively.
2. Set the maximum output frequency, fundamental frequency, and torque characteristics of the inverter. General inverters are equipped with multiple VPf curves for users to choose, and users should choose the appropriate VPf curve according to the nature of the load. If it is a fan and pump load, set the torque operation code of the inverter to variable torque and reduced torque operation characteristics. In order to improve the low-speed performance of the inverter when starting, and to make the torque output by the motor meet the requirements of starting the production load, the starting torque should be adjusted. In the variable frequency speed regulation system of asynchronous motor, the torque control is more complicated. In the low frequency band, the influence of resistance and leakage reactance cannot be ignored. If VPf is kept constant, the magnetic flux will be reduced, thereby reducing the output torque of the motor. For this reason, the voltage must be properly compensated in the low frequency band to increase the torque. Generally, the inverter is manually set and compensated by the user.
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3. Set the inverter to its own keyboard operation mode, press the run key and stop key, and observe whether the motor can start and stop normally.
4. Familiar with the protection code when the inverter is running faulty, observe the factory value of the thermal protection relay, observe the set value of the overload protection, and modify it if necessary. The user of the inverter can set the electronic thermal relay function of the inverter according to the instruction manual of the inverter. When the inverter’s output current exceeds its allowable current, the inverter’s overcurrent protection will cut off the inverter’s output. Therefore, the maximum threshold value of the electronic thermal relay of the inverter does not exceed the maximum allowable output current of the inverter.
3. Test run with load
1. Manually operate the run stop button on the panel of the inverter, observe the motor stop process and the display window of the inverter to see if there is any abnormality.
2. If the inverter has an over-current protection action during the process of starting P and stopping the motor, reset the acceleration and P deceleration time. The acceleration of the motor during acceleration and deceleration depends on the acceleration torque, and the frequency change rate of the inverter during the start and braking process is set by the user. If the moment of inertia of the motor or the load of the motor changes, the acceleration torque may be insufficient when the speed is increased or decelerated according to the preset frequency change rate, which may cause the motor to stall, that is, the motor speed and the output frequency of the inverter are not coordinated, resulting in excessive Current or overvoltage. Therefore, it is necessary to reasonably set the acceleration and deceleration time according to the motor’s moment of inertia and load, so that the frequency change rate of the inverter can be coordinated with the change rate of the motor speed.
The method to check whether this setting is reasonable is to first select the acceleration and deceleration time according to experience and set it. If overcurrent occurs during the starting process, the acceleration time can be appropriately extended; if overcurrent occurs during braking, then Properly extend the deceleration time. On the other hand, the acceleration and deceleration time should not be set too long, too long will affect the production efficiency, especially when frequently starting and braking.
3. If the inverter still protects within a limited time, the running curve of start P stop should be changed from straight line to S-shaped, U-shaped line or S-shaped, reverse U-shaped line. When the inertia of the motor load is large, a longer start and stop time should be used, and the operating curve type should be set according to its load characteristics.
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4. If the inverter still has a running fault, try to increase the protection value of the maximum current, but the protection cannot be cancelled, and a protection margin of at least 10%～20% should be left.
5. If the inverter operation failure still occurs, replace the inverter with a higher power
6. If the frequency converter drives the motor to fail to reach the preset speed during startup, there may be two situations:
(1) Electromechanical resonance occurs in the system, which can be judged from the sound of the motor running.
The method of setting the frequency jump value can avoid the resonance point. Generally, the inverter can set three-level jump points. When the inverter controlled by VPf drives an asynchronous motor, the current and speed of the motor will oscillate in certain frequency ranges. In severe cases, the system cannot run, and even overcurrent protection occurs during acceleration, which prevents the motor from starting normally. Or it is more serious when the moment of inertia is small. Ordinary inverters are equipped with frequency jump function. Users can set the jump point and jump width on the VPf curve according to the frequency point where the system oscillates. When the motor accelerates, these frequency bands can be skipped automatically to ensure the normal operation of the system.
(2) The torque output capacity of the motor is not enough, the factory parameter settings of different brands of inverters are different, and the load capacity is different under the same conditions, or the load capacity of the motor may be different due to the different control methods of the inverter; or Due to the different output efficiency of the system, the load capacity will be different. In this case, you can increase the value of the torque boost. If it cannot be achieved, the manual torque boost function can be used. Do not set too large, the temperature rise of the motor will increase at this time. If it still does not work, you should switch to a new control method. For example, Hitachi inverters use a constant VPf ratio method. When the startup fails to meet the requirements, switch to a speed sensorless space vector control method, which has a greater torque output capacity. For loads such as fans and pumps, the curve value of torque reduction should be reduced