故障查找

1、疑似模擬量輸出板卡問題，用萬用表測量4-20mA輸出信號，信號是正常的!

2、開始懷疑是變頻器控制信號輸入端有了問題，換了一臺同型號變頻器，問題仍然如此。

3、用一臺手持式信號發(fā)射器做4-20mA輸出信號源，輸出標(biāo)準(zhǔn)電流信號至變頻器，這下變頻器啟動了，因而我們排除了模擬量輸出板卡和變頻器的故障。

4、由此推測是變頻器的干擾信號傳導(dǎo)至模擬量通道所致。

5、為了驗證，在PLC模擬量4-20mA輸出通道中加裝了一臺信號隔離模塊TA3012，TA3012的輸入端子5、6接模擬量輸出模塊，輸出端子1、2端子接變頻器，3、4端子接外部24VDC供電電源，變頻器正常啟動了。

6、據(jù)此斷定，問題的根源在于變頻器干擾模擬量通道所致。

Fault finding

1. Suspected analog output board issue, measure the 4-20mA output signal with a multimeter, and the signal is normal!

2. I began to suspect that there was a problem with the control signal input of the frequency converter. I replaced it with a frequency converter of the same model, but the problem still persists.

3. We used a handheld signal transmitter as a 4-20mA output signal source, outputting a standard current signal to the frequency converter. As a result, the frequency converter started, and we ruled out faults with the analog output board and frequency converter.

4. It can be inferred that the interference signal from the frequency converter is transmitted to the analog channel.

5. To verify, a signal isolation module TA3012 was installed in the 4-20mA output channel of the PLC analog signal. Input terminals 5 and 6 of TA3012 were connected to the analog output module, output terminals 1 and 2 were connected to the frequency converter, and terminals 3 and 4 were connected to an external 24VDC power supply. The frequency converter started normally.

6. Based on this, it can be concluded that the root cause of the problem lies in the interference of the frequency converter with the analog channel.