Contactor / Motor Starter coil voltage question. 4

[itsmoked]

A super heavy grinding machine I'm looking at is to be supplied 220V 3ph (About 115A). Looking into one of its control bays I see every coil for every motor starter and relay are clearly labeled 110 or 120V 60Hz.

There is NO control transformer and all control power is derived from direct connections between the three phases.

How are these coils not toasting? What am I missing? Are the overloads somehow dropping 120V?

Here's the general look:

It's all Allen Bradly stuff from wayyYYYYYYY back.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

I think there must be something hidden somewhere.

Those wires don't look like they were designed to carry 115 A. More like 10-ish A.

Did you measure coil voltage?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

The part of the overload relays that the coils see is a normally closed switch. There is probably less than one Volt drop across the switch contacts. Check to see if the machine was connected with a neutral conductor. That machine looks older than Gunnar and I. They may have used the ground connection for a neutral source.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Gunnar; Those are all the ancillary motor starters. The 30HP motor starter is inside the machine behind this panel. It has the #2 wires running to it. It also has a 120V coil.

See the bottom wire with the tape label on it that states "Y" on it? Notice how it goes from coil to coil to coil? I believe it's the 'return' for all of them. It's common to the center lug on the power disconnect.. (pictured below)

As for measuring the voltage? This machine was bought in Seattle running. Brought to Silicon Valley and installed. The numb nutz who installed it hooked it right up on up to 480V (which I'm measuring as 498V) and threw the switch. Smoke ensued in great gouts out of the bottom center starter in the above picture. Someone purchased and installed a replacement coil.

I was called and asked to solve the riddles and make it run again. They provided a 480 to 208V 30kva transformer 'in case I wanted to use it'. Ha! This thing needs probably a 45kva transformer to be happy. We haven't found one and so I have no way to power it up safely yet. And I certainly don't want to let more smoke out of it discovering that now all the coils are getting 2x the voltage they should have instead of 4X. So I'm real leery of applying any power without understanding how this could ever work.

Bill; There is no provision anywhere in the main disconnect for a neutral that I can find.

Here tizscale is hard to tell from this picture but this box is about 2 feet tall)

That said there are newer additions like an unpolarized zip-cord hanging out a vent that has one side screwed to the chassis and the other wire-nutted onto a mystery cable that goes nowhere near the 'field of contactors'.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

It smoked! How appropriate...

Sorry.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[LionelHutz]

It had to be either powered with a 208V/120V wye service or a 240V delta with one of the delta legs center tapped to also provide 120V:120V. I can't see the picture of the machine at work.

The zip cord tied to the chassis would suggest they used the ground as the neutral.

 

[flexoprinting]

Jeeze Keith, I would tell the customer you need to bring it up to date and start from the motor back and install new control system. What a challenge otherwise!, I hope the motor has a Data plate you can actually read.

 

[ScottyUK]

Given the age of it, is it possible that someone has done something naughty and connected the control power from one phase down to the frame earth? It would work, although it would be a code violation just about anywhere on the planet.

 

[John2025]

Scotty's theory would explain why it "worked" on 220 and smoked on 480. Seems like it would be easy to check continuity between the return side of the contactors and the frame. Scary thought, though.

 

[jraef]

Keith,
The fact that the "Y" wire is common to all of them, then connected to the center pole of the disconnect, may mean that this was a 240/120 3 phase 4 wire center tapped open delta service, where one of the windings between two of the phases is center tapped, so A or B to Neutral would be 120V. That's a really old connection pattern, but this is a really old system. Those are A-B 709 starters, they stopped shipping those in 1979. At that time and in your neck of the woods, I would not doubt that PG&E would use that setup, it gives someone 3 phase 240V for machines, plus 120V for lights and receptacles, but only needs two transformers.

"Will work for (the memory of) salami"

 

[davidbeach]

Sorry Jeff, interesting idea, but that open delta still brings in three phase conductors plus a neutral. Looking at the connections at the customer equipment you can't tell an open delta service from a closed delta service. It would be interesting to see the remnants of the Seattle installation if it still exists.

That disconnect in the second picture; how sure are you that the center blade is a phase conductor and not a neutral from a center tap? On one hand it looks like bigger wires have been chopped off from the top lugs that might have been larger enough to supply the stated load, but you also say it ran (or was at least powered up) presumably without those wires.

 

[itsmoked]

For your edutainment.
This thing is a massive iron casting. People who 'know' like them because they are so freaking rigid they hold close tolerances.

Thanks Jeff for dating those ABs for us. I'm guessing this thing is from the mid 60s.

Well if this was the center-tapped crazy open delta scheme, as I'm coming to believe, I really have my work cut out isolating the control out so I can use a control transformer.

Look at what I'm facing. There is a porthole on the back of the machine I can just get my shoulders thru.
I'd sure hate to have to change out a motor from in there. HAHAHAHA.


The big contactor and here you can see the killer zip cord coming up from the lower right. Notice how one is screwed to the box and the other is nutted to an S.O. cord with about 5 wires in it and 4 of them are grounded!? Man-o-man.

Feed control.

Osculating and rotating motors.

Anyone have suggestions for where we should look to get the 480->240V 45kVA transformer? I used to get catalogs from some central plains surplus place but I can't find any of them. I wonder if they still exist.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davidbeach]

Eaton # V48M22T45EE was the result of a quick search. It's a common catalog configuration, perhaps not a commonly stocked product.

 

[Skogsgurra]

Smoked, the first picture you show us (19 Sep 14 7:28 ) has a wire that seems to need a 10 fuse connected to the B phase of that mighty breaker. Please, put a fuse there - or you may need to put out a fire anytime soon.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[jraef]

Keith,
To make matters possible a little worse, or better depending on how you approach it, is that those motor starters no longer meet code, so although "grandfather clauses" are such that people cannot be forced to remove replace them on existing installations, the way they get compliance is to not allow any changes or re-installations. The 709 series starters only had 2 overload heaters in them, as you can see in your photos. The code changed in 1975 (I think) to require that each phase must have overload protection now. That's why A-B had to re-design, as did everyone else at that time. If the project is not going to be permitted and inspected, i suppose your customer could get away with it but should anything go wrong, a fire or insurance investigator may pick up on that little detail and it could be trouble for all involved. You might want to leverage this issue into convincing them that they have to modernize. At 50 years old, the mechanical components are going to be on their last legs, and new parts for those have not been available for 30 years or so, which means you replace old parts with other old parts, or at best, "NOS" parts from surplus houses.

"Will work for (the memory of) salami"

 

[itsmoked]

davidbeach
Thanks a million for that tip! Those look really popular and are everywhere for reasonable $$.

Gunnar; That smaller white wire? That is odd. It's a scabbed on wire that is wire-nutted onto a single 14AWG wire that runs off away from all the 'controls'. It's one I'll have to get to the bottom of too. There are little non-factory fused disconnect boxes stuck here and there. If that wire proves necessary I'll probably move it to one of them.

Jeff; Thanks for the heads-up on that.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Yes, that white one.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

Hi Keith.
Before installing a transformer I would consult a motor shop on the feasibility and cost of converting the motor to a nine lead motor. (230/460 Volt) or just reconnecting for 460V (480) Volts.
As for delta or open delta and wye connections:
Regardless of the supply, all of the above systems will look the same in the panel or disconnect switch.
There will be three hot connections.
There should be a ground connection and there may be a neutral connection. (Ground and neutral should be connected together at the service location.)
The difference will be the voltages measured from the hot lines to ground or neutral.
If that machine was working then either;
1> There was a control transformer that has been robbed and the wire connected to something confusing.
2> There was no control transformer and either a neutral connection or an illegal connection to ground was used to supply 120 Volts for the controls.
Another option:
An auto transformer solution;
You need 120 Amps. With an auto transformer connection each winding will supply 50% of the current. 60 Amps x 240 Volts = 14.4 KVA.
A pair of 15 KVA boost rated transformers transformers at 240:240 Volts should do the trick. You will probably find a 120/240:240/480 Volt transformer that can be connected as 240:240 Volts.
I would strongly suggest installing a three pole overload relay on at least the main motor.
When three pole O/Ls were mandated, a third identical single pole O/L relay was added beside on of the original O/Ls. (One on one side, two on the other side.)
For every three pole O/L relay you instal on a small contactor, you will remove two single pole O/Ls which can be used to retrofit two other small starters.
While this may not be code compliant, it will provide functional compliance with the intent of the code. That is, each phase will be overload protected.
It will be between you and the customer to classify this as a new installation or repairs to an existing installation.




Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Thanks Bill for more input.

While most the motors appear to be 220V/440V with all the weird stuff going on, and ZERO documentation, I'd not be comfortable trying the switch. Not to mention, you see where I'd have to crawl!! LOL

I'd love to go with the autotransformer option but that solution is actually in an anti-sweet-spot place. Above about 5kVA BB's become a much rarer. A couple of 15kVA buck/boosts look to cost considerably more than one VM48 and look to be way harder to get. Rather than just sitting on the floor they also require some way to hang hundreds of pounds somewhere somehow making the whole solution pricey-er and logistically more challenging.

Since this machine was designed for the 220V world is there any reason I can't use a V48M22T45EE (480/208) and just 'tap' it up to 220V? (has 7 taps)

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

That transformer (V48M22T45EE) has a 4 wire delta secondary. You will have the recommended 240/120 Volts with a 480 Volt primary.
At 498 Volts your incoming looks to be 3.75% high. I would try to check the voltage during the peak loading times on your distribution feeder. There may be a reason why the voltage is a few percent high and later in the day it may go low.
I would tend to leave the feed as is and use the 100% taps.
Most disconnect switch manufacturers offer a neutral terminal that may be ordered with the switch or may be purchased separately later for field installation.
Good call on the transformer DavidBeach.
I did a comparison on the transformers Keith. NOT sweet spot is right. Just a little more total weight and a higher price for two transformers suitable for an auto transformer connection.

Bill
--------------------
"Why not the best?"
Jimmy Carter