This has probably be discussed ad nausium, but I was unable to find any information on it. I have 4 spare motors that are single voltage, 6 wire, 2 speed 460v, from 10hp to 50hp. I was wanting to create a RPC from one of the motors, but they can't be rewired to 240. Will any of these motors work on 240 single phase, and if so, what's the de-rating?
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240v RPC using 460V motor
- Thread starter wetoddid
- Start date
- Replies 12
- Views 1,886
johansen
Stainless
- Joined
- Aug 16, 2014
- Location
- silverdale wa
If you can rewire them for 277 delta that would be better than 480 y.
As far as derating, a 480v motor run on 240 will develope 25% of the torque at the shaft. However the motor will be more efficient at such a load than a motor of 1/4th the size run at nameplate volts and full load.
So its use as an rpc you run into the same fundamental limit: voltage drop under load. And heat in the coils. Dont exceed nameplate amps through any single coil unless the other coils offset the extra heat
As far as derating, a 480v motor run on 240 will develope 25% of the torque at the shaft. However the motor will be more efficient at such a load than a motor of 1/4th the size run at nameplate volts and full load.
So its use as an rpc you run into the same fundamental limit: voltage drop under load. And heat in the coils. Dont exceed nameplate amps through any single coil unless the other coils offset the extra heat
I assume you mean to rewire the motors in the machines I intend on running? Not sure how I can rewire these single voltage motors to 277 Delta....not even sure how to wire any motor to 277 delta. I figured 277 was a product of the wye configuration.
Is my ignorance showing yet?
My thought process was to brute force a 10hp 240 RPC with a 50hp 460V motor, since I bought it unused for $30. Feel free to tell me I'm pursuing this the most impractical way possible
A motor rated 489V and set up as "wye", will have a coil rating of 277VAC.
With the wye coils reconnected for delta, it will be set up to run from 277VAC 3 phase..... Of course that does not exist,, but it is much closer to 240VAC than 480VAC is. So the motor should work reasonably well at 240VAC as an RPC idler,
Over-sizing it considerably vs the load is a good plan when the motor is really for a higher voltage than what you have, as in the case of a 277VAC motor run at 240VAC.
With the wye coils reconnected for delta, it will be set up to run from 277VAC 3 phase..... Of course that does not exist,, but it is much closer to 240VAC than 480VAC is. So the motor should work reasonably well at 240VAC as an RPC idler,
Over-sizing it considerably vs the load is a good plan when the motor is really for a higher voltage than what you have, as in the case of a 277VAC motor run at 240VAC.
Last edited:
johansen
Stainless
- Joined
- Aug 16, 2014
- Location
- silverdale wa
I assume you mean to rewire the motors in the machines I intend on running? Not sure how I can rewire these single voltage motors to 277 Delta....not even sure how to wire any motor to 277 delta. I figured 277 was a product of the wye configuration.
Is my ignorance showing yet?
My thought process was to brute force a 10hp 240 RPC with a 50hp 460V motor, since I bought it unused for $30. Feel free to tell me I'm pursuing this the most impractical way possible
a 40 hp 480v RPC run as a 240v system is electrically similar to a 10hp 240v RPC.
The deeper I dig, the more confused I'm getting here.
I'm interested in the wye configuration, but can't figure out how to do that with a 6 wire motor. Data plate is wholly lacking information and there is no wiring schematic on the motor or inside the junction box.
I assumed that 3 of the wires were for low speed and 3 were for high speed. Anybody have a clue as to how to wire it up for wye?
I'm interested in the wye configuration, but can't figure out how to do that with a 6 wire motor. Data plate is wholly lacking information and there is no wiring schematic on the motor or inside the junction box.
I assumed that 3 of the wires were for low speed and 3 were for high speed. Anybody have a clue as to how to wire it up for wye?
thermite
Diamond
- Joined
- Sep 21, 2011
Feel free to tell me I'm pursuing this the most impractical way possible
Consider yourself so told. They are HIGHLY "non-linear' creatures.
Do this only if you WANT an electrically-heated shop and are unable to afford radiant baseboard heaters.
But you will still need an RPC idler.
Illinoyance
Stainless
- Joined
- Aug 24, 2015
Three of the terminals are used for low speed. The other three are for high speed.
johansen
Stainless
- Joined
- Aug 16, 2014
- Location
- silverdale wa
Two speed motors are lower powerfactor due to the short pitched windings. No experience using one, so still worth the experiment.
Looks like a Brook Crompton Parkinson Motor, a special at that. Two separate windings in one shell.
D200L - IEC metric frame size, about the size of a 50HP standard motor.
B449274 - Part number,not a current model, it's a special.
7.5/7.5 - HP rating of each winding.
1760/870 - RPM of each winding, synchronous speed 1800/900, 4pole/8pole.
460 - single voltage, both windings.
13/16 - Full load amperage of each winding.
60/3 - 60Hz, 3Φ
MCR - ?
B - Design B
Summary, 7.5HP metric motor, 2 Spd, designed to US NEMA specifications, about the size of a 50HP.
You would be better of to cash it in at the scrap yard, for a more suitable RPC idler.
SAF Ω
D200L - IEC metric frame size, about the size of a 50HP standard motor.
B449274 - Part number,not a current model, it's a special.
7.5/7.5 - HP rating of each winding.
1760/870 - RPM of each winding, synchronous speed 1800/900, 4pole/8pole.
460 - single voltage, both windings.
13/16 - Full load amperage of each winding.
60/3 - 60Hz, 3Φ
MCR - ?
B - Design B
Summary, 7.5HP metric motor, 2 Spd, designed to US NEMA specifications, about the size of a 50HP.
You would be better of to cash it in at the scrap yard, for a more suitable RPC idler.
SAF Ω