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Fault phenomenon: After the inverter is powered on, start the inverter, and connect the positive rotation terminal to the common terminal! The inverter RUN light is on! After the user sets the operating frequency to the inverter through the man-machine interface for many times, the inverter does not respond and the frequency is always zero!
The frequency of the inverter has been set and given by external terminals! This frequency converter is used to control the motor of the traction machine, because our factory produces pipes, and a motor is required to produce pipes! The combination of frequency converter and motor we call it traction machine! The inverter is to drive the two motors.
The frequency of the inverter is written into the PLC by the user through the man-machine interface (this PLC is Siemens S7-200)
Then the frequency is given to the inverter by the PLC! The traction speed and setting on the man-machine interface are the frequency for this inverter!
When the user writes the required speed into the PLC through the man-machine interface, then the expansion module EM232 (analog output module) of the PLC outputs a voltage from 0V to 10V to realize frequency setting for our inverter! EM232 module picture)
EM232 module is an analog output module! The terminals are marked with M0, V0, I0, M1, V1, and I1, which are the terminals for analog output. If the output you want is a voltage signal, connect M0, V0, and M1, V1, and connect the current signal to M0. , I0, and M1, I1. M is the common terminal, V represents the voltage, I represents the current, and the following 0,1 represents the channel number.
Look at the functions of each terminal of the inverter
Inverter terminal (AI1) AI is the abbreviation of Analog input, 1 means channel 1! So how is the EM232 module connected to the inverter? I drew the circuit diagram for you.
According to the speed set by the user, the EM232 module will output a voltage of 0V to 10V from its terminals M0 and V0, which will be transmitted to the analog input terminals GND and AI1 of the inverter. The inverter obtains the voltage on the terminals GND, AI1 and Come to change frequency and set frequency!
After setting the speed on the man-machine interface, I use a multimeter to measure whether there is DC voltage at the terminals of the inverter, GND, AI1. The measured multimeter shows zero, no voltage! At first, I thought it might be that the wires from terminal (EM232 module) M0 to (inverter terminal) GND and (EM232 module) V0 to (inverter terminal) AI1 were broken, resulting in no voltage!
In order to eliminate the possibility of broken wires, after setting the speed on the man-machine interface, I use a multimeter to measure whether there is a voltage output on the terminals M0 and V0 of the EM232 module! As a result, the measured voltage was 0V, which also ruled out the possibility of a broken line! (Because the lighting problem of the photo was not clear at the time, I can only simulate it for everyone)
Since there is no problem with the circuit, I suspected that the EM232 analog output module was broken, so I removed the module. Then I removed a good EM232 module from another machine and installed it! After installing it, test the machine, and it is measured that the inverter terminals GND and AI1 have voltage! Prove that the EM232 module has a voltage output! At this time, there is frequency on the frequency converter and the traction motor has turned up!
After replacing the EM232 module, the fault is eliminated and the device operates normally! The main reason for this equipment failure is that the EM232 module is damaged and there is no voltage output!