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How to judge the quality of the inverter

        It should be noted that for personal safety, it is necessary to ensure that the machine is powered off, and the inverter input power lines R, S, T and output lines U, V, W can be removed to operate! First, hit the multimeter into the "secondary tube" file, and then use the red test pen and black test pen of the multimeter to check the following steps:

        The black test lead contacts the negative pole P(+) of the DC bus, and the red test lead contacts R, S, and T in sequence to record the displayed value on the multimeter. Then touch the red test lead to N(-), and the black test lead touches R, S, and T in turn to record the display value of the multimeter. If the six display values are basically balanced, it indicates that there is no problem with the inverter diode rectification or soft-start resistance, otherwise the rectifier module or soft-start resistor at the corresponding position is damaged. Phenomenon: No display.

        The red test lead contacts the negative pole P(+) of the DC bus, and the black test lead contacts U, V, and W in sequence to record the displayed value on the multimeter. Then touch the black test lead to N(-), and the red test lead touches U, V, and W in turn to record the display value of the multimeter. If the display value of the six times is basically balanced, it indicates that there is no problem with the IGBT inverter module of the inverter, and vice versa, the IGBT inverter module of the corresponding position is damaged. Phenomenon: no output or failure.

Use the inverter to drag a power-matched asynchronous motor to run at no load, and adjust the frequency f from 50 Hz to the lowest frequency.

        In this process, the current meter is used to detect the no-load current of the motor. If the no-load current is stable during the frequency drop and can be kept basically unchanged, it is a good inverter.

The lowest frequency can be calculated in this way (synchronous speed - rated speed) × pole pair p ÷ 60. For example, a 4-pole motor with a rated speed of 1470 rpm and a minimum frequency = (1500-1470) x 2 ÷ 60 = 1 Hz.