Star Delta Starter with Timer Relay or with PLC Timer

A mechanical star delta time has a small time delay between the Star-delta changeover also use mechanically interlocked contractors for Star delta
 
Timer relay - anyone can change the time delay without the need for software or interface cables.
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The transition time is more of an art than science, because the load on the motor makes a difference. You want that to be easy.

And as said earlier, there are really TWO time delays involved in a Star-Delta transition timer. Electro-mechanical timers do it via contact operating times, electronic S-D timers have to emulate that, which is not a simple thing in a PLC. Not impossible, but you have to fully and deeply understand the process. Not enough or too much of an open transition time can cause severe damage, both electrically and physically. I've seen open transition problems cause a 500HP motor shaft to shear off.

That's also why I never use S-D any more, I use RVSS starters.
 
Plc timer every time
Use mechanical interlocks and inputs from the n/c of star and delta.

It's not often a timer needs adjusting once set correctly.
 
Thanks all, I think I like the idea of a PLC timer with mechanically interlocked contacts best, but in the end it is probably not priority 1 at the moment to evangelise either way.

Agree with RVSS for higher kW applications.

My new years resolution is to phase out imperial measurements, especially the mile, which I will be replacing with 1.852km, unless the person specifically tells me they are working with the international mile.

I am also going to assume metric horsepower, ie. the power to raise 75kg by 1m in 1 second under 9.80665 N/kg of gravity.
 
I would agree with jraef for sure regarding RV starters over S - D. I worked for a large water utility for 10 years out west, and we had mostly 5kv motors with RVAT starters. The transition, incomplete sequence, etc. used relays. A-B made a good one. We re-wired a lot of them to transition on current using a GE Multilin 469 MPR. It has a lot of capabilities that certainly surpass relay logic, but it is quite expensive.
 
Thanks all, I think I like the idea of a PLC timer with mechanically interlocked contacts best, but in the end it is probably not priority 1 at the moment to evangelise either way.

Agree with RVSS for higher kW applications.

My new years resolution is to phase out imperial measurements, especially the mile, which I will be replacing with 1.852km, unless the person specifically tells me they are working with the international mile.

I am also going to assume metric horsepower, ie. the power to raise 75kg by 1m in 1 second under 9.80665 N/kg of gravity.

What is this wicked metric heresy speak.....LOL 🍻
 

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