Hello everyone,

I'd like to know how "test position" is implemented on electric drives. I know that when engineering motor drives such as fans, pumps and similar, to test control and protection logic, many put the motor in test position first, which means that there is indication that motor is ready to be started and similar, while it is not starting in reality. Basicaly, the DCS system sees that pump is ready and it can be started (not in reality), all protections are tested, and then, motor is started in reality and there is the real test.

I wonder if you heard of this and especially how this is implemented. These test positions exist mainly with motors of high power (6 kV voltage or more).

Can you suggest links to learn more?

Thanks.

 

Mikas,
It is not the motor that is put into the test position, it is the switchgear. There are some differences depending on the drive type, but in general the disconnect switches for the contactors are opened (sometimes the contactors are racked out). That causes the switchgear to loose control power.

That is why there is the test switch in the switchgear, which when in test position, allows you to supply control power from another source. Now you can close the contactors and play with the system. Sometimes the drive will provide simulated signals (voltage and frequency) to make it look like the motor is running.

Hugo

 

Hugo, thank you for your reply,

Yes you're right, I had an opportunity to see for myself. It's all about switchgear. There are high voltage cell that is practically racked out on the rails so there is no physical connection and hence drive cannot start. On the other hand there are switches that can be pushed manually and special cables with connectors that can be plugged into a cell although it is racked out. In that case DCS thinks drive is ready and when there is start command, drive starts in DCS but not in reality. This is very usefull when someone wants to test protection and interlocking logic without risk of damaging the drive...