How to use a multimeter to measure the quality of the inverter

The frequency converter is a commonly used electric energy control instrument, which is widely used in many industries such as industry, chemical industry, shipbuilding, electronics, electricity, aviation, machine tools, etc. How can users determine the quality of the frequency converter when using it ? In fact, a multimeter can be used to measure the quality of the frequency converter, so what is the specific measurement method? The following editor will introduce the method of using a multimeter to measure the quality of the frequency converter.

1. Touch the negative pole p(+) of the DC bus with the black test lead, touch r, s, t with the red test lead in turn, and record the displayed value on the multimeter; then touch n(-) with the red test lead, touch r, s, t with the black test lead in turn, and record the displayed value on the multimeter; if the six displayed values ​​are basically balanced, it means that there is no problem with the inverter diode rectification or soft-start resistor. Otherwise, the rectifier module or soft-start resistor at the corresponding position is damaged, and the phenomenon is: no display.

2. Touch the negative pole P (+) of the DC bus with the red test lead, touch U, V, and W with the black test lead in turn, and record the displayed values ​​on the multimeter; then touch the black test lead to N (-), and touch the red test lead to U, V, and W in turn, and record the displayed values ​​on the multimeter; if the six displayed values ​​are basically balanced, it indicates that there is no problem with the IGBT inverter module of the inverter. Otherwise, the IGBT inverter module at the corresponding position is damaged, and the phenomenon is: no output or fault is reported.

1) Use the inverter to drive an asynchronous motor with matching power to run at no-load, and adjust the frequency f from 50 Hz to the lowest frequency;

2) Use an ammeter to detect the no-load current of the motor during this process. If the no-load current is very stable and remains basically unchanged during the frequency reduction process, it is a good inverter;

3) The minimum frequency can be calculated as follows: (synchronous speed - rated speed) × number of pole pairs p ÷ 60. For example, a 4-pole motor with a rated speed of 1470 rpm has a minimum frequency = (1500-1470) × 2 ÷ 60 = 1 Hz;

(1) Distinguishing between AC and DC solid-state relays : Usually, there are two labels next to the input and output terminals of the DC solid-state relay housing .

The "+" and "-" symbols are marked with the words "DC input" and "DC output". However, the AC solid-state relay can only mark the "+" and "-" symbols on the input end, and the output end has no positive or negative distinction.

(2) Identification of input and output terminals: For unmarked solid-state relays, use a multimeter at the r×10 k position to identify the input and output terminals by measuring the forward and reverse resistance values ​​of each pin. When the forward resistance of two pins is small and the reverse resistance is infinite, these two pins are the input terminals, and the remaining two pins are the output terminals. In a measurement with a small resistance value, the black test lead is connected to the positive input terminal, and the red test lead is connected to the negative input terminal.

If the forward and reverse resistances of two pins are both 0, it means that the solid-state relay has been broken down. If the forward and reverse resistances of each pin of the solid-state relay are infinite, it means that the solid-state relay has been open-circuited and damaged.