480V grinder on 240V ?????

[Waorani]

Someone gave me this US Electrical Tool Co. 3-phase, 5hp, 14" grinder. Motor plate says 460V and switch is labeled 480V. No sign of a plate showing wiring for 240V or even a place to access internal wire leads like on more modern motors. Just for kicks I hooked it up to my converter and it seemed to run fine at 240V. Short of it having been rewound (unlikely), what am I missing here? Will I burn it up running it at 240? It's a 50s era beast of a machine. Took 25min to spin down given the two massive wheels.

 

[Malleus]

It'll be fine, it just won't develop full HP. Keep an eye on the current draw; as long as it doesn't trip the breaker, you'll be OK. If it does, check the windings for an open somewhere.

 

[Waorani]

It'll be fine, it just won't develop full HP. Keep an eye on the current draw; as long as it doesn't trip the breaker, you'll be OK. If it does, check the windings for an open somewhere.

Thanks. It's only pulling 1amp on each leg once running. Startup was almost 14amp on the one leg I checked. Assume same on others but will check once it winds down. Don't imagine I'll ever need 5hp anyway.

ETA - 14amp at startup on all legs. Tried hand spinning wheels prior to start but didn't make a difference.

 

[Malleus]

Inrush current is always huge, but momentary. Modern controllers have overload protection built into them. I don't have any idea how it was done in the '50s; probably just really large busbars. Stock was cheap back then.

As long as it's on a circuit that's protected against the inrush current, you'll never see a problem.

 

[WarDamnEagle]

Nice buy!

 

[Waorani]

Inrush current is always huge, but momentary. Modern controllers have overload protection built into them. I don't have any idea how it was done in the '50s; probably just really large busbars. Stock was cheap back then.

As long as it's on a circuit that's protected against the inrush current, you'll never see a problem.

Safety switch in back is basic with 3 30A fuses so 14A isn't even close.

 

[DangerNoodle]

You can usually rewind from high to low voltage on those motors somewhere. I would be surprised if there isn't a way to access the windings. It will take a higher amperage but shouldn't hurt anything. I'm running a 415 lathe on 220 single with a VFD and a motor rewind. It's been happy so far.

 

[Waorani]

I'm an idiot! Tucked under the safety switch on the back and under a thick layer of industrial soot was a box with all the wires and fortunately a little diagram showing high/low hookups. That's what I'm used to seeing but between the guy that gave it to me and getting it in my head there was no access to be able to rewire to low voltage I just didn't look close enough. I'd have found it eventually but @DangerNoodle comment got me there faster!

So now I'm pulling 67, 67 and 47 amps on startup and 4.5 - 5 on each leg running. Assume the 47 is on my generated leg? All feeding from a 15amp 3ph breaker that's not tripping.

 

[DangerNoodle]

I'm an idiot! Tucked under the safety switch on the back and under a thick layer of industrial soot was a box with all the wires and fortunately a little diagram showing high/low hookups. That's what I'm used to seeing but between the guy that gave it to me and getting it in my head there was no access to be able to rewire to low voltage I just didn't look close enough. I'd have found it eventually but @DangerNoodle comment got me there faster!

So now I'm pulling 67, 67 and 47 amps on startup and 4.5 - 5 on each leg running. Assume the 47 is on my generated leg? All feeding from a 15amp 3ph breaker that's not tripping.

Nice! That's a surprisingly high amp load, but at the same time not really with how much energy it would take to get all of that spinning.

 

[Waorani]

Could be meter error and I had to measure multiple times because the high was just a split second. Lower end Fluke clamp meter.

 

[Waorani]

Got curious and pulled the wheels - 24.5lb ea. Almost 50lb total so quite a load to get spinning. 4.5amp/leg with no stones start and run.

 

[WarDamnEagle]

Got curious and pulled the wheels - 24.5lb ea. Almost 50lb total so quite a load to get spinning. 4.5amp/leg with no stones start and run.

Now aren't you glad you didn't buy that wimpy little Baldor grinder that I got from Alabama Power.

 

[e9999]

Great find! Better not drop one of them wheels, could get expensive quickly