Transformer Serving an Elevator

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stuartdmc

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Newport Beach, Irvine, CA
What type of transformer is best to serve the needs of an Elevator?

My project requires that I design a step down transformer to convert 240 3 phase delta power to 120/208v 3 phase to power the elevator motor. I have spcifyed a 75 KVA rated transformer with K-factor-1, Nema TP-1, 150c aluminum windings, imp. 5.67%.

Can I get someone to comment on if this type is sufficient r is there a specific isolation needed?.

FYI;
elevator motor 25hp. @ 208v/3 phase/
 
masterinbama said:
I would use buck and boost for the motor and use a separate 240V to 120 volt for the cab lights and pit receptacle. It would be much cheaper than the single 75 KVA.
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I don't know if they make a buck transformer large enough to handle the max peak running load of 114-225amps? Plus that seems messy to me, having 3 transformers mounted on the wall for the motor plus the disconnect, and another xfmer for a 120v panel. all in the elevator equipment room? I don't like it.
 
stuartdmc said:
I don't know if they make a buck transformer large enough to handle the max peak running load of 114-225amps? Plus that seems messy to me, having 3 transformers mounted on the wall for the motor plus the disconnect, and another xfmer for a 120v panel. all in the elevator equipment room? I don't like it.
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Your buck and boost only has to handle the difference between 240 and 208
or roughly 10 KVA
 
masterinbama said:
Your buck and boost only has to handle the difference between 240 and 208
or roughly 10 KVA
Click to expand...

If you were stepping up/down 208/240 for a motor you can do this. If you must go from say 240 corner ground to 208Y/120, you can't use an auto-transformer to change the grounding reference.


i.e. to use European spec equipment safely in the US homes, you'll need a 240:240 transformer, because EU is 415Y/240 with 240 between N-L. US is 240v L-L. The Eu layout is similar 277v from our 480Y/277v.

So, 240:240 isolation transformer is needed, so you can make the load side properly ground referenced for single pole switch/relays used within the equipment.
 
Electric-Light said:
If you were stepping up/down 208/240 for a motor you can do this. If you must go from say 240 corner ground to 208Y/120, you can't use an auto-transformer to change the grounding reference.


i.e. to use European spec equipment safely in the US homes, you'll need a 240:240 transformer, because EU is 415Y/240 with 240 between N-L. US is 240v L-L. The Eu layout is similar 277v from our 480Y/277v.

So, 240:240 isolation transformer is needed, so you can make the load side properly ground referenced for single pole switch/relays used within the equipment.
Click to expand...
But as masterinbama suggested, it is still going to be cheaper and easier to just get a separate small 240-120V single phase transformer for the lights and controls and use the 10kVA bucking autotransformers for the motor power.

Or if it is temporary, just forgo the motor power issue and separate the lights / controls onto a separate 1PH xfmr, then let the motor(s) run on 240V. Chances are the motor(s) will be OK with that, you can easily check with the mfr.

I don't know what all the EU stuff is about, the OP is in Southern California and I don't know of any elevator mfrs that make equipment that is not designed for the market it serves.
 
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Jraef said:
But as masterinbama suggested, it is still going to be cheaper and easier to just get a separate small 240-120V single phase transformer for the lights and controls and use the 10kVA bucking autotransformers for the motor power.

Or if it is temporary, just forgo the motor power issue and separate the lights / controls onto a separate 1PH xfmr, then let the motor(s) run on 240V. Chances are the motor(s) will be OK with that, you can easily check with the mfr.

I don't know what all the EU stuff is about, the OP is in Southern California and I don't know of any elevator mfrs that make equipment that is not designed for the market it serves.
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controls might not be rated to be floating 240v with respect to ground if it calls for 208Y/120v
 
Electric-Light said:
controls might not be rated to be floating 240v with respect to ground if it calls for 208Y/120v
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The manufacture said that the motor and controls would not run on 240v if we ordered a 208v motor, and that we will need to convert to the power to the required 208v.
I do get it about the auto-transformer, it would be cheaper, so I'll need to look into that possibility.
 
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