3 phase motor star delta staring controls

[Chrisday1990]

How about helping the guy out and building his confidence instead of always putting ppl down, telling them they are out of their depth. Have you never come across something that you were unsure about and tried to seek advice from someone?? Sometimes you only learn by taking on such jobs and getting hands on experience. If you turn up to every difficult job and said 'oh I've never done this before I better leave it to someone else' you would never learn!! Rant over.

Thanks dark wood I share the same philosophy and that's exactly what we are doing, very kind/encouraging words.

 

[PEG]

Darkwoods cautionary message is not without worth...a client of mine decided to do some "real-time" learning on a large 3 PH screw compressor panel,and manually engaged the star and delta contactors simultaneously with alarming consequences. At least he can see now,even if he wanted another go...which he does not! The bill for full rectification was another reminder...

 

[Chrisday1990]

WOW, I would hate to have been that guy he must have felt crap. Yet such an easy and unforgiving mistake to make.

 

[ipf]

Darkwoods cautionary message is not without worth...a client of mine decided to do some "real-time" learning on a large 3 PH screw compressor panel,and manually engaged the star and delta contactors simultaneously with alarming consequences. At least he can see now,even if he wanted another go...which he does not! The bill for full rectification was another reminder...

I can imagine...can be bad enough getting the direction wrong on a 'screw'

 

[Knobhead]

We only had two Y∆ starters on plant. High pressure water pumps bought as a turnkey project.

One of the idiots (management) decided they should be like the rest of the plant where the PLC took control of all drives. So I got lumbered with altering the program. The contractor installing the drives seemed a bit bemused when I told him to rip all the control wiring out other that the power side. All he had to do was connect a 19 core to the various parts and in to one of the I/O racks. I’d had to install yet another volt free 16 way O/P card.

OK so far.
Enter Tony with a thumping hangover, things went badly wrong from then on.
First off, allocate the new cards location, smartarse here though he could do it on the fly. The plant shut down.
I’m not popular at this point

Get the plant up and running.
Start again with the program.
Both pumps were fed off a small CFS sub board with a 600A incomer. So the pumps had to start in sequence. Forgot all about that bit.
Any though of scan sequence went from my mind and I managed to get two networks cutting each others throats, couldn’t see this on the PC so carried blithely on.
So, power up the pumps and toddle off to the control panel.
Press sequence start everything went fine until the pumps started, the lights dimmed. At that point I remember they shouldn’t start together. The supply was holding so let them carry on.
Come the transition point all the lights started pulsing on and off. The Y∆ contactors were going in and out with the PLC scan rate.
I’m even more unpopular

I’m sobering up by now, quick re-gig of the program.
Try again.
Pump 1 tries to start.
It’s gone dark in here!
I’m definitely not popular by now.
The 600A fused supply to the sub board had held. One of the 1200A plant feeder ACB’s had tripped.
Both the Y∆ contactors had just about melted.
Ooopps.

The upshot was.
The contractor got rather a large bill for the repairs.

OK I’m a barsteward, I shifted the blame on to the contractor. The plant worked perfectly after the repairs so it must have been his fault…………..

 

[ipf]

Some nasty individuals in industry