How to use a multimeter to measure the quality of the inverter, it needs to be noted that for personal safety, it is necessary to ensure that the machine is powered off, and remove the inverter input power line R, S, T and output line U, V, W before operation! First, the multimeter is put into the "secondary tube" file, and then the red and black pen of the multimeter are detected according to the following steps:
The black pen touches the negative pole P(+) of the DC bus, and the red pen touches R, S, and T in turn, recording the displayed value on the multimeter. Then touch the red pen to N (-) and the black pen to R , S and T in order to record the display value of the multimeter. If the six-time display value is fundamentally balanced, it indicates that there is no problem with the rectifier or soft-start resistance of the inverter diode, on the contrary, the rectifier module or soft-start resistor in the corresponding direction is damaged, and the phenomenon: no appearance.
The red pen touches the negative pole P(+) of the DC bus, and the black pen touches U, V, and W in turn, recording the display value on the multimeter. Then touch the black pen to N(-), and the red pen to touch U, V, and W in order to record the display value of the multimeter. If the six display values are fundamentally balanced, it indicates that there is no problem with the IGBT inverter module of the inverter, on the contrary, the IGBT inverter module in the corresponding direction is damaged, and the phenomenon is no output or fault.
Use the inverter to drag a power-matched asynchronous motor to run no-load on the spot, adjust the frequency f, and start from 50Hz to the lowest frequency.
In this process, the no-load current of the motor is detected with an ammeter, if the no-load current is very stable in the process of frequency drop, and it can persist at all, it is a good inverter.
The lowest Z frequency can be calculated in this way, (synchronous speed - extra speed) × pole pair p÷60. For example, a 4-pole motor, the extra speed is 1470 rpm, Z low frequency = (1500-1470)× 2÷60 = 1Hz.
There is no problem with the soft start resistor, on the contrary, the rectifier module or soft start resistor in the corresponding direction is damaged, and the phenomenon: no appearance.
The red pen touches the negative pole P(+) of the DC bus, and the black pen touches U, V, and W in turn, recording the display value on the multimeter. Then touch the black pen to N(-), and the red pen to touch U, V, and W in order to record the display value of the multimeter. If the six display values are fundamentally balanced, it indicates that there is no problem with the IGBT inverter module of the inverter, on the contrary, the IGBT inverter module in the corresponding direction is damaged, and the phenomenon is no output or fault.
Use the inverter to drag a power-matched asynchronous motor to run no-load on the spot, adjust the frequency f, and start from 50Hz to the lowest frequency.
In this process, the no-load current of the motor is detected with an ammeter, if the no-load current is very stable in the process of frequency drop, and it can persist at all, it is a good inverter.
The lowest Z frequency can be calculated in this way, (synchronous speed - extra speed) × pole pair p÷60. For example, a 4-pole motor, the extra speed is 1470 rpm, Z low frequency = (1500-1470)× 2÷60 = 1Hz.
Identification of AC and DC solid state relays: Generally, next to the input and output terminals of the DC solid state relay shell, they are marked with "+" and "-" symbols, and the words "DC input" and "DC output" are noted. The communication solid state relay can only mark the "+" and "-" symbols on the input, and there is no positive or negative difference at the output.
Identification of input and output: Solid state relay without identification, multimeter R×10k file, by measuring the forward and reverse resistance values of each pin to distinguish the input and output terminals. When the forward resistance of one of the two pins is small and the reverse resistance is infinity, the two pins are the input and the other two pins are the output. In a measurement with a small resistance, the black pen is connected to the positive input end, and the red watch pen is connected to the negative input end.
If the forward and reverse resistance of both pins is measured to be 0, it means that the solid state relay has broken down. If the forward and reverse resistance values of each pin of the solid state relay are measured to be infinite, it means that the solid state relay has been damaged by an open circuit.
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