240v Motor in 480V System

[jimmycash]

Hi,

I have an old industrial thermal shock chamber that runs on 3 phase 480 volts. One of it's condensor cooling fan motors went bad and the exact motor is obsolete so I can't find an exact replacement.

Nameplate Info:
Magnetek Model DA2G097N
2 phase 480 volts, .9amps, 1550 RPM, 1/15HP, 60hz
Frame 42Y 5" O.D. , shaded pole, 3 wire phase, phase and ground.

I can find motors by other manufacturers that are close enough to most of the critical specs (rpm, hp, 5" OD)
but they are all either 115/120 or 230/240 volts.

I could install a step down transformer to make any of them work but I would like to avoid that extra $100 to $150
dollar expense so my question is;
- can I use the motor that is spec'd at only 240 volts and wire it to one phase and ground?
- does it matter if it's a shaded pole or PSC motor?

Thanks,

Jim

 

[wayne440]

can I use the motor that is spec'd at only 240 volts and wire it to one phase and ground?

No, for a number of reasons, some of which should be obvious. The first, "ground" is never used to carry current under normal conditions.

 

[DRWeig]

Wayne is correct. Also, the voltage to ground (or neutral) for a 480/3-phase system is 277V not 240V.

Plunk down on the transformer. Then get a licensed electrician to wire it up for you according to code, so that it's safe.

Best to you,

Goober Dave

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[LiteYear]

'ang on, 'ang on... you say the chamber "runs on 3 phase 480 volts" yet the motor specs you list are (3 wire) 2 phase 480 volts. 3 phase and 2 phase are very different things. If your supply is 3 phase and your motor is 2 phase, you must already have something sitting in between (likely a Scott-T transformer). In that case, are you sure the 3 phase primary is the same voltage as the 2 phase secondary? It certainly could be, but doesn't have to be.

Anyway, these other motors you've found - are they single phase, 2 phase or 3 phase? Makes a big difference.

So if you connect before the Scott-T transformer you'll have 3 phase at the primary voltage (say 480V). As DRWeig, the single phase to neutral (if it exists) voltage is then 277V. On the secondary side of the Scott-T transformer you'll have 2 phase, 90 degrees apart at 480V. The wire common to the two phases could be grounded, but each phase is 480V relative to that so there's still no 240V available.

The other bit I don't quite get is that it's a 1/15HP motor running on 480V. If it really is a 50W motor, then it's probably no wonder you can only find lower voltage motors - at 480V the terminals would just about be bigger than the motor!

I'd double check what you have available and what you need. You may or may not get away without an additional transformer.