Dear All of You

here I have problem in which some of signals in PCS7 showed bad quality during 6.6KV motor start.

the plant has good ground resistance as below 2ohms.

I know inrush current will happen during big motor start but other control system doesn't showed BQ at the same time. does anyone have same experience and sulution, I'm appreciate if you share your experience

Michael

 

Check the following:

1. Are the signal cables of the signals going faulty copper type (i.e. not fibre optic)?

2. Are these running in parallel and close to the motor supply cable or the motor chassis?

3. Are the signal cables shielded or non-shielded type?

4. If the signal cables are of the shielded type, are the shields properly connected to ground at one end only?

It seems that the problem you have is electrical noise induced in the control signals by the motor starting current. The source could be either the motor supply cable or the motor itself. look in that direction.

 

I once got a call to find out why a Modicon PLC was dropping out with a motor start. It turned out the power supply was missing some jumpers and so was operating on 120 VAC with the tap set for 240 VAC. You could also try adding a power conditioner to the AC supply.

Hope this helps,
Roy

 

Responding to Riolyn's 30-Oct-08 (18:24) query... Look at Control.com's:

http://control.com/thread/1026157812

Regards, Phil Corso ([email protected])

 

Responding to Michael's 15-Nov-08 (23:50) query... search the Control List Archives for the following threads:

o http://control.com/thread/1026157812

o http://control.com/thread/1026209342

o http://control.com/thread/1026211569

o http://control.com/thread/1026245378

Regards, Phil Corso ([email protected])