As everyone knows, the frequency converter has many protection functions, such as overcurrent, overvoltage, overload protection and so on. With the continuous improvement of industrial automation, the frequency converter has also been widely used.
In the design process of electronic circuits, engineers inevitably need to measure some measuring instruments with a multimeter. Engineers know that a multimeter can measure DC current, communication voltage, and DC voltage. The inverter is a device that controls the communication motor by modifying the working power frequency of the motor. This article will explain to you how to use a multimeter to measure the quality of the inverter.
The requirement is that for personal safety, it is necessary to ensure that the machine is powered off and remove the inverter input power lines R, S, T and output lines U, V, W. First, hit the multimeter to the “secondary tube” file, then check the following steps with the multimeter’s red and black test leads:
The black test lead touches the negative pole P(+) of the DC bus, and the red test lead sequentially touches R, S, and T to record the appearance value on the multimeter. Then touch the red pen to touch N(-), and the black pen touches R, S, and T in sequence to record the appearance value of the multimeter. If the six-time appearance value is fundamentally balanced, it indicates that there is no problem with the inverter diode rectification or soft-start resistance, and vice versa, the rectification module or soft-start resistor of the corresponding orientation is damaged, and the scene: no appearance.
The red pen touches the negative pole P(+) of the DC bus, and the black tester sequentially touches U, V, and W to record the appearance value on the multimeter. Then touch the black test pen N(-), and the red test pen touches U, V, W in sequence to record the appearance value of the multimeter. If the six-time appearance value is fundamentally balanced, it indicates that there is no problem with the inverter IGBT inverter module, and vice versa, the IGBT inverter module of the corresponding orientation is damaged. The scene: no output or reported fault.
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 check the no-load current of the motor. If the no-load current is stable during the frequency reduction process, it can be kept unchanged, that is, a good inverter.
The lowest frequency can be accounted for this, (synchronous speed – extra speed) & times; pole pairs p ÷ 60. For example, a 4-pole motor with an additional speed of 1470 rpm and a minimum frequency = (1500-1470) x 2 ÷ 60 = 1 Hz.
There is no problem with the soft start resistor, and the rectifier module or soft start resistor of the corresponding orientation is damaged. The scene: no display.
The red pen touches the negative pole P(+) of the DC bus, and the black tester sequentially touches U, V, and W to record the appearance value on the multimeter. Then touch the black test pen N(-), and the red test pen touches U, V, W in sequence to record the appearance value of the multimeter. If the six-time appearance value is fundamentally balanced, it indicates that there is no problem with the inverter IGBT inverter module, and vice versa, the IGBT inverter module of the corresponding orientation is damaged. The scene: no output or reported fault.
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 check the no-load current of the motor. If the no-load current is stable during the frequency reduction process, it can be kept unchanged, that is, a good inverter.
The lowest frequency can be calculated as such (synchronous speed – extra speed) × pole pair p ÷ 60. For example, a 4-pole motor with an additional speed of 1470 rpm and a minimum frequency = (1500-1470) x 2 ÷ 60 = 1 Hz.
The distinction between AC and DC solid-state relays: Generally, the input and output ends of the DC solid-state relay housing are marked with the “+” and “-” symbols, and the words “Dc input” and “DC output” are marked. The communication solid state relay can only mark the “+” and “-” symbols on the input end, and the output end has no positive or negative points.
The distinction between input and output: solid-state relay without identification, multimeter R × 10k file, after measuring the positive and negative resistance values of each pin to distinguish between input and output. When the forward resistance of a pair of pins is small and the reverse resistance is infinite, the two pins are the input terminals, and the other two pins are the output terminals. In a measurement with a small resistance, the black pen is connected to the positive input, and the red pen is connected to the negative input.
If the positive and negative resistances of a certain two pins are both 0, it is clarified that the solid state relay has broken through. If the positive and negative resistance values of the pins of the solid state relay are measured to be infinite, it is clarified that the solid state relay is open circuit damaged.
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