2 phase 230 volt elevator

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david

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I did an inspection upgrade from 120/240 Single phase to 120/208 3 phase.
Elevator is supplied through a transformer 230/230 the elevator motor is 230 2 phase.
The electrician asked me how can he reefed the elevator motor from the 120/208 3 phase.
One solution I would have is install a 100 amp 120/240 single phase service, and just re-feed the elevator. I am not sure why they went to three phase when this is just a furniture store with a cargo elevator.

Is there a better solution?
 
Do you really mean that the elevator is two phase (90 degree phase shift)?
If so it will have to be fed using a Scott-T transformer from a single phase source.
Conversion to direct use of three phase for the elevator would require replacing the motor.
Adding in a boost transformer to allow the existing Scott-T to run off a single phase of the 120 or 208 would be possible, but would be a major intermittent unbalanced load on the three phase service.
Will POCO allow an additional single phase service at this location?

Tapatalk!
 
Thanks for the reply
The original single phase service has not been disconnected yet. It will be removed once the cut in card goes in to energize the new 120/ 208 3 phase.
The electrician states that the elevator motor is 2 phase. You have too go to the roof then enter a room from there. I did not go to the roof.
The service is a old switch board open fusible knife switches, Switched neutrals
There is an old transformer some of the name plate data missing it says 230 / 230 this is what the elevator motor is being feed through. There are five leads exposed wiring one lead taped off no connection. None of the leads are identified in any way. One lead smaller size than the rest.

Because the motor says 2 phase 230 volt and the transformer feeding the elevator is 230 volt single phase I say I think so!!!
 
The transformer could be a multiple core Scott-T transformer inside a single enclosure. But that would actually require three phase input, not single. I suppose it could also be a phase shift network, using capacitors and ferro-resonsnce.
But it seems far more likely that the motor is not really two phase.
In your area how much of the work will require bringing in a licensed elevator technician?

Tapatalk!
 
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I vote; the existing transformer is a 3-phase Scott-T unit to derive 2-Phase 240V from a 3-phase 240V supply.

Your choices are:
Boost your new 208V up to 240V and refeed the existing equipment.
Replace the existing Scott-T with a 208Vto 240V unit.
Replace your 2-phase motor with a new 3-phase one.
 
The elevator is grandfathered in if he touches it will never pass the state certification he will have to take it out of service.
called the electrician back he is sure the existing service is single phase.
The transformer is the green Box to the left of the picture.
 
You cannot get 2-phase directly from 1-phase.
If the original service was single-phase there is other equipment not shown in the picture.

Boost your voltage from 208V to approx 228V or 236 (these are common step up amounts) then refeed your existing transformer.
 
jim dungar said:
You cannot get 2-phase directly from 1-phase.
If the original service was single-phase there is other equipment not shown in the picture.

Boost your voltage from 208V to approx 228V or 236 (these are common step up amounts) then refeed your existing transformer.
Click to expand...

There may be more equipment in the room above the roof. I am not that knowledgeable when it comes to 2 phase systems . I'll let the electrician know. Kicked it around here in the office thought maybe two single phase coils wrapped in opposite directions might cause a phase shift. But like I said I am a novice when it comes 2 phase equipment.
 
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david said:
There may be more equipment in the room above the roof. I am not that knowledgeable when it comes to 2 phase systems . I'll let the electrician know. Kicked it around here in the office thought maybe two single phase coils wrapped in opposite directions might cause a phase shift. But like I said I am a novice when it comes 2 phase equipment.
Click to expand...

Two single phase coils wrapped in opposite directions will produce a phase shift, but only of 180 degrees. Unfortunately there is no way to make use of that to generate a phase at any different angle, so we call that a single phase system. The term "split phase" is also sometimes used when there is a neutral between the two phase wires, but that term is so potentially misleading that its use is discouraged around here.
<lecture mode>
Once you have a phase angle of other than 0 and 180, you can then generate any phase angle you want with a complicated enough transformer system.
(On the math side of things, we would say that any two non-collinear vectors in a two dimensional space form a basis for that space from which any other vector can be generated by an appropriate combination of multiplication (transformer) and addition (series circuit.) )</lecture mode>
The Scott-T circuit is just a very efficient and standardized method of doing that for a conversion between three phase and two phase.

PS: There is an off chance that you can find out more about the transformer by contacting VA Tech, the successor company to Packard Electric. See https://en.wikipedia.org/wiki/Ferranti-Packard
 
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Was it working before ? If yes and you only have single phase feeding it, you already have what you need for converting to 2 phase if it is 2 phase, just step up voltage. A 2 phase motors uses 4 or 8 wires if I remember right. If its real old it might just be 2 phase.
 
just the cowboy said:
Was it working before ? If yes and you only have single phase feeding it, you already have what you need for converting to 2 phase if it is 2 phase, just step up voltage. A 2 phase motors uses 4 or 8 wires if I remember right. If its real old it might just be 2 phase.
Click to expand...

I agree if it was already working there must be conversion equipment already there, you may need to boost the voltage to get proper voltage.

You may also be able to operate a two phase motor directly from a three phase source, but keep in mind it will not be the same as running from a two phase source. You will have a 120 degree shift between phases instead of 90 degrees, and you will get rotation if you connect one phase of the motor between A and B of the source and the other phase of the motor between B and C (or other scenarios that put each winding between different phases. I don't know that I could be enough help to determine if it would be a good choice to set it up that way or exactly what to consider to get within desired operating values. I imagine you could use some capacitors or inductors to tweak the phase shift though.
 
Since the phase spacing of the voltage peaks will not match the rotational spacing of the windings/poles, the motor will not be running efficiently.
It would be similar to leaving the start winding of an capacitor start motor connected or having the wrong size capacitor in a capacitor run motor. And if the motor is wired as a four leg wye with the center point connected internally you could not duplicate that from three phase supply.

Tapatalk!
 
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