3HP or 4.5HP, or something else entirely?

[MattyP]

Trying to figure out what size all the motors are on my new milling machine. On the plate of the main motor, it's got 2 numbers listed under the HP rating, a 3HP and a 1.5HP.

Is this somehow a combined metric, or is this more ratings of the motor if you run it at different settings?

 

[MrWhoopee]

Looks like a two speed motor, 3 hp @1750 rpm, 1.5 hp @ 860 rpm.
Two speed motors were fairly common on BP clones, my Kent has one. Nice feature.

 

[mmcmdl]

The Encos use them also . Very nice features as MrWhoopie said .

 

[rabler]

You'll need to find a wiring data plate to determine which wires drive which speed.

 

[MrWhoopee]

Show us a picture of the power switch (and the mill, just because).

 

[MattyP]

So unfortunately, there doesn't appear to be any sort of wiring diagram plate on the motor. Perhaps it's too old. I don't know. Just sort of guessing. The switch does seem to have a High and Low 3rd knob, so I'm guessing that's what this is dealing with.

 

[Beckerkumm]

Here is a motor connection diagram for either a separate winding 2 speeds motor or a Dahlander connected two speed. The Dahlander type is more common and more difficult to use a vfd with but if you run utility three phase or phase perfect or rpc, you shouldn't have a problem. Dave

 

[matthewsx]

Sweet Gorton

 

[MrWhoopee]

I see what appears to be a cord with plug attached. Is there a reason we're puzzling over the motor wiring?

 

[mksj]

In general if you were to use a VFD, you would leave it wired for 4P (1750 RPM@60Hz) 3 Hp, and at 30 Hz the torque would remain flat and the Hp would be 1.5 Hp. This assumes you do not have 3 phase. The motor is a fairly large motor frame (254), if you are looking for a replacement motor I have worked with a couple of people that have replaced the motor with either a 3 or 5 Hp inverter/vector motor, these can easily be run to 120 Hz or higher. So you run a smaller motor pulley and this will give you a much wider operating range using a VFD (like 20-180Hz). Only problem is sometimes these mills use longer shafts then the stock motors. Example below.

BALDOR, DOUBLE SHAFT OUTPUT Motor, 5 HP, 3 PH, SPEC 07J404X255Z1, D0197 | eBay

SHAFT SIZES.

www.ebay.com