Help with a 440 volt motor?

[Barncat]

I have what I believe to be a 440v 3 phase motor that cannot be rewired for 230v. There is no data plate to consult. There are only three leads coming out of the motor, and the motor starter has a 440v coil. My questions-am I right this seems to be a strictly 440v motor? Any way to internally rewire? Any way to test if it is 230 or 440v? If I apply 230v to it(bypass the starter for now) to test it, will that damage it? I have a transformer that I could back feed to get 440v, so I could do that, but if it isn’t a 440v motor, will that damage it? Also, I think my transformer is a little too small. I believe the motor to be 5hp.

 

[Technical Ted]

I would guess that it is a 440 motor from that coil. A start would be too look up the number on the heaters in that starter and you can see how many amps the heaters are rated for and then based on a 440 motor what the HP actually is.

I bought a machine that had a 440 only motor on it. For my situation and use, I replaced the motor with a single phase 220 motor. VFDs aren't available for 220 in 440 out and it would take a fairly good size transformer to setup the voltage for the required amperage. Do you have 230 3 phase in your shop (native)? You can't feed a transformer from a VFD and would need to use a converter (rotary or static) to feed the transformer if you don't have native 3 phase.

Food for thought,
Ted

 

[catsparadise]

You can rewire a 440V star connected 3 phase motor to a delta configuration - I've done it to two motors, but likewise I've resisted doing it to the 2 motors on my mill as there's a risk of messing things up.

You need to find the star point on the stator windings, unpick it to separate the three winding ends and connect them to the winding starts to connect the three windings in a ring. Any connections inside the motor need to be made with wire suitable for the temperature the motor runs at and protecting the joints from shorting and vibration has to be considered too. In the course of this, if you break the wires in the wrong place it could be time for a professional rewire.

If you're not familiar with the terms above and aren't sure what you'd be doing, I'd shy away from trying.

The transformer looks like it could happily be driven 240V to 440V. The one thing you'd have to be careful of is the rating of the motor. You don't show the motor plate, but if it's under 3HP I would have thought it would be ok as long as you're not running it to it's max capacity for long periods - the transformer says 3kVA.

The motor will run on 240V 3 phase anyway - my mill has 2 440V 3ph motors run off of 220V VFDs. You'll get less power output.

Rob

 

[Beckerkumm]

That is an old AB 709 and the N30 heaters are rated for 9.35 amps. That would imply a 5-7.5 motor. Is that a direct drive table saw? Most of those were 4-5 hp, depending on age. A few came with 7.5 but they are rare. The transformer looks to be an autotransformer so you should be able to use it. If it will start the blade and get up to speed, you might never need full hp. A 7.5 kva would be more appropriate long term. Tell me about the saw. I've rehabbed Whitney, Robinson, and Wadkin DD saws.

N Heaters often fail if tripped more than once but you can modify the starter to accept newer W heaters which are a better design. I've never had to do that but it is possible. Dave

 

[Barncat]

I would guess that it is a 440 motor from that coil. A start would be too look up the number on the heaters in that starter and you can see how many amps the heaters are rated for and then based on a 440 motor what the HP actually is.

I bought a machine that had a 440 only motor on it. For my situation and use, I replaced the motor with a single phase 220 motor. VFDs aren't available for 220 in 440 out and it would take a fairly good size transformer to setup the voltage for the required amperage. Do you have 230 3 phase in your shop (native)? You can't feed a transformer from a VFD and would need to use a converter (rotary or static) to feed the transformer if you don't have native 3 phase.

Food for thought,
Ted

Thanks for the replies everyone, I'll try and address them. I have a rotary to feed a transformer, and looking up the heaters is a good idea.

 

[Barncat]

You can rewire a 440V star connected 3 phase motor to a delta configuration - I've done it to two motors, but likewise I've resisted doing it to the 2 motors on my mill as there's a risk of messing things up.

You need to find the star point on the stator windings, unpick it to separate the three winding ends and connect them to the winding starts to connect the three windings in a ring. Any connections inside the motor need to be made with wire suitable for the temperature the motor runs at and protecting the joints from shorting and vibration has to be considered too. In the course of this, if you break the wires in the wrong place it could be time for a professional rewire.

If you're not familiar with the terms above and aren't sure what you'd be doing, I'd shy away from trying.

The transformer looks like it could happily be driven 240V to 440V. The one thing you'd have to be careful of is the rating of the motor. You don't show the motor plate, but if it's under 3HP I would have thought it would be ok as long as you're not running it to it's max capacity for long periods - the transformer says 3kVA.

The motor will run on 240V 3 phase anyway - my mill has 2 440V 3ph motors run off of 220V VFDs. You'll get less power output.

Rob

I understand the terms and have a general picture in mind of what you are saying, but would probably be too scared to try it. This motor couldn't easily be replaced if I messed it up. Does running on the lower voltage increase heat or mess anything up?

 

[Barncat]

That is an old AB 709 and the N30 heaters are rated for 9.35 amps. That would imply a 5-7.5 motor. Is that a direct drive table saw? Most of those were 4-5 hp, depending on age. A few came with 7.5 but they are rare. The transformer looks to be an autotransformer so you should be able to use it. If it will start the blade and get up to speed, you might never need full hp. A 7.5 kva would be more appropriate long term. Tell me about the saw. I've rehabbed Whitney, Robinson, and Wadkin DD saws.

N Heaters often fail if tripped more than once but you can modify the starter to accept newer W heaters which are a better design. I've never had to do that but it is possible. Dave

Thanks for looking up the heaters. That was my guess was a 5hp, but it could be 7.5. It is a Delta/Rockwell radial arm saw. 50-C is the model, but I can't find too much Info on it. Currently has a 16" blade, believe it can take a 20" blade.

 

[Beckerkumm]

I would not run that motor on 240 as a long term answer. you will find that the power is not adequate and starving voltage isn't good for those old wires and insulation. Old large frame fat bodied motors are good candidates for rewinding if the cost of a transformer and high voltage are things you want to avoid. My motor guy charged me about 400-500 for that type of job. Most motor ships will be higher ( maybe double ) but if you find an old guy who still does small motors as a side line, you are golden. Rewinding long narrow motors is expensive but the short fat ones are easier so that might be an option. Dave

 

[Barncat]

It is a 440 motor, or at least started and ran fine from the RPC through a step up transformer. It started a little slow, most likely because my rpc is undersized for it. At some point I will finish the 25hp rpc I am working on, then that won’t be a problem. Thanks for the help everyone. As of now, it is going to stay wired for 440 and be used from the transformer.