When we assemble AC and DC power circuits and connect the power supply, we often encounter no response. In this case, we need to check and reconfigure the composition and components of the circuit, but we cannot find the cause of the failure. What is suspicious in this case?

 

500kW load bank
 

Ac power supply and DC power supply digital I/O, timer and counter suspicious:

Digital I/O is embedded in AC and DC power supplies to test the system. I used it for the open collector output, but it was actually the culprit that caused the failure.

It was not realized that there are two devices that can be used to fill and pull currents as output circuits for digital I/O, timers, and counters that must be used as collector open-circuit outputs or fill currents.

That is, in the past, I thought of the open collector outputs of AC and DC power sources as the emitter and collector outputs separately, forming a circuit that could be connected.

For, in the past, AC and DC power supplies were specified as examples of outputs that could be used for both filling and pulling currents, and were used directly as open collector outputs.

It is assumed that the circuit that can be used for both filling and pulling currents depends on the method of connecting the load. For AC and DC power loads, it can fill current or pull current. Therefore, with this output method, it is very flexible (correct for incorrect usage).

On the other hand, assuming the open collector output mode of AC and DC power supplies, the current flow is consistent with the NPN transistor, that is, the fill current. In the case of open collector output, the internal circuit is grounded at the emitter and can only be connected to the collector side. Because only the current is filled, NPN transistors cannot be used to drive the circuit.