How can I determine the HP rating, Info of an electric motor? Nameplate is defaced.

Good day to all,

I would like to ask how will I know the HP rating and Electrical information of an electric motor?

Its name plate has been removed from its body

If it is possible, What particular info is needed?
Knowing the dimension of the motor and diameter of the shafting may help in determining those info?

Many thanks to all!!!

By the style and frame size, I can usually tell a motor HP by looking at it. Look up a motor manufacturers table of frame sizes and see which frame size and style your motor is. Older motors are between one and 2 frame sizes larger depending on age.

As I deal with IEC motors I cannot help with NEMA sizes.

tnx for the reply, anyways i will post a picture of my motor and its dimensions tomorrow.

Electric Motor Pictures & dimensions

As promised Here are the pictures of my electric motor

Picture 1:


Picture 2:


Picture 3:


Picture 4:


Picture 5:


Picture 6:


Dimensions:



Thanks in advance for your inputs and comments that will lead for the identification of this Electric Motor.

Well, what guage wire is comming out??

You can learn quite a bit about how much current it will draw by determining the wire guage. It LOOKS like 10 or 12 guage wire, more like 12. If it's 12 guage wire, I'm going to guess it's probably a 5hp motor, but it could be 7.5. If it's 10 ga, it's probably a 7.5, but it COULD be a 10hp motor. I doubt it's a 10hp motor, it's a little on the small size, and is too old of a style to be that powerful, and that compact. You never know though, and if it is a 10 hp motor, it probably isn't continuous duty. It could also be some oddball motor, and you wouldn't know unitl you did more tests. I'm also guessing that the way you'd wire it is to hook each pair of wires twisted together comming out of the 3 holes to each of the 3 phases for 220v. For 440v, you'd twist 1 wire from each hole together, and hook the other 3 to each of the 3 phases. I wouldn't TRY that until you test it with an ohm meter, and see how much resistance each winding has. If I'm correct about how to wire this, you should get double the resistance wiring it the way I said for 440v, than you would for 220v. You should get the same resistance between all 3 pairs when you twist each pair. Somebody posted a while back the approximate DC resistance of the windings for motors of different horsepower ratings, so measuring the resistance would help a LOT! I have $5 says it's a 220/440v 3 phase 5hp 4 pole motor. DON'T TRY HOOKING IT UP UNTIL YOU GET CONFIRMATION!

Another thing I just noticed is there's bare wire looped around each of the wires. Two wires have 1 loop, two have 2 loops, and two have 3 loops. I bet if you tested between each pair having the same number of loops, you'd find the ends of each winding. If you were to wire it for 440v, you'd have to take 1 wire with each different number of loops, and twist them together, otherwise it wouldn't work. I dunno ANY of this for sure, so check it with a meter first.

first of all thanks for the input sir.

JunkyardJ said:

You can learn quite a bit about how much current it will draw by determining the wire guage. It LOOKS like 10 or 12 guage wire, more like 12.

Click to expand...

I'm going to check the wire size, and will post it later.

JunkyardJ said:

If it's 12 guage wire, I'm going to guess it's probably a 5hp motor, but it could be 7.5. If it's 10 ga, it's probably a 7.5, but it COULD be a 10hp motor. I doubt it's a 10hp motor, it's a little on the small size, and is too old of a style to be that powerful, and that compact.

Click to expand...

I Maybe wrong but my estimated size for this motor is more than 10HP because of its size and weight.
I roughly estimate its weight at around 70 to 100 Kilos



Above is the dimension
Lenght of the casing = 420mm = 16.53"
Diameter of the Casing = 310mm = 12.20"
Diameter of Shafting = 41mm = 1.61"

Please take note of the size of the Chairs wheeled base and the size of the motor in the picture below

JunkyardJ said:

Another thing I just noticed is there's bare wire looped around each of the wires. Two wires have 1 loop, two have 2 loops, and two have 3 loops. I bet if you tested between each pair having the same number of loops, you'd find the ends of each winding. If you were to wire it for 440v, you'd have to take 1 wire with each different number of loops, and twist them together, otherwise it wouldn't work. I dunno ANY of this for sure, so check it with a meter first.

Click to expand...

I have checked the loop count of the bare wires and found out that its looped 1 to 6

maybe it signifies the number of loops = motor wiring terminal number



Tnx
Marlon,

If you had any way to temporarily connect this motor up to "real" three phase power and then measure the current draw with your clampmeter then it would be easy to tell. Dave

becksmachine said:

If you had any way to temporarily connect this motor up to "real" three phase power and then measure the current draw with your clampmeter then it would be easy to tell. Dave

Click to expand...

Maybe it would be easy if I have a 3Phase supply, but actually the reason why I want to know the Electrical info of this motor is because I wanted to use this motor to be my Idler motor for an RPC.

But since don't have the info yet, I am not sure if this will suffice or over specs for my requirement.

Thanks
Marlon,

Well, my old 2 HP Lima drive has about a 12" diameter motor!

When motors are that old, you can't tell SQUAT by the size. The motor on my B&S mill is a 2hp 6 pole 1200 rpm, and it's about 12" diameter, and longer than 12". The wires comming out of it are 14 guage, and it weighs a LOT! The motor on my surface grinder is HUGE too, it's only 1.5hp, draws 4.5 amps, and is BIGGER in diameter than the motor on the mill. It's a little shorter, but it's OBVIOUSLY ancient. It's made by GE, and I'm SURE it's REALLY HEAVY! You CANNOT say how much power a motor makes by it's size and weight with ANY certainty. This is why I've given such a wide range of possibliities, and unless it has BIGGER than 10ga wire going in, I'm ALMOST SURE it's not over 10hp. I think the MAX that motor could be is 10hp. I dunno for sure, just a guess, I COULD be wrong.

JunkyardJ said:

and unless it has BIGGER than 10ga wire going in, I'm ALMOST SURE it's not over 10hp. I think the MAX that motor could be is 10hp. I dunno for sure, just a guess, I COULD be wrong.

Click to expand...

I have tried to mesure the wires coming out of the motor although it is a stranded wire I assume that the wire is #8, I have seen #12, #10 THHN wires but it is smaller than the wire coming out of the motor. Please bare with me, I am not so sure of the exact wire #.

I also measured the wire coming out of the motor using vernier caliper and the diameter of the wire plus its outer covering is 5.6mm.

This is the actual size of the motor, I placed a 1 galon plastic container beside as size reference.






Again many tnx

One more thing, the reason I wanted to know the Electrical info of this motor is for me to verify if I can use this motor as an idler for my RPC to be.

My requirement for the RPC project is to run:
1 lathe machine with 7.5HP motor
1 lathe machine with 3HP motor
1 3HP Vertical mill.
1 3HP Horizontal mill

The one dimension on a motor that is closely related to HP is the shaft diameter, because if the shaft is too small, it will fail under full load. The 41mm shaft diameter you show equates to 1 5/8”. Follow that through the tables on the Gates web site:

http://www.gates.com/facts/documents/Gf000177.pdf

Table two shows that this diameter shaft was used with 254, 256, 284 and 286 frame motors. Table one gives these HP values that were / are standard for these frames:

254 5HP
256 7.5HP
284 10HP
286 15HP..

I would then go to a diagram of the different mounting dimensions, such as this one:

http://www.blowerwheel.com/nema-motor-frame-chart.htm

and compare the mounting hole and shaft to base dimension to try to narrow it down further.

Good luck. Hope it turns out to be a 284 or 286 frame.


[FONT=&quot]Dennis[/FONT]

The two dimensions used to describe IEC frame motors are the shaft height from the mounting base, in the case roughly 160mm and the length of the mounting bolt centres. A 160 IEC frame TEFC motor is usually 15 or 20 HP depending on length.

Probably 15 Hp, if the motor is old enough to have class B insulation it will be less but it looks like a style of motor which would have class E or higher insulation.

The stated shaft diameter of 41mm leads me to think this is a NEMA motor, since 41mm is almost the perfect conversion of the Imperial 1 5/8". The IEC standard shaft for this size motor is 42mm. However, there micght be some useful data here:

http://www.baldor.com/pdf/IEC_chart_04.pdf

Dennis

Well, if it's 8 or 10 ga, I've UNDERESTIMATED it!

If it's bigger than 10 ga wire comming out of it, or 10ga, it very well could be 10 or 15 HP. My guess is it's at least 7.5, usually a 5hp motor will have 12 guage wire, sometimes they go cheap and use 14 if they're putting windings in parallel for 220v. I still think that motor is too small, and of such an age that it probably isn't 15 hp, allthough if that's 8ga wire comming out, it very well may be! It really would help to measure the resistance with an ohm meter. You could measure the windings in this motor, and compare with the resistance of the motors on your machine. If it has less resistance than the 7.5 hp motor, it probably is a 10hp or bigger. As for shaft size being a good indicator for horsepower, I'd have to call BS on that. I've personally seen a 5hp motor, and a 1/4 hp motor with 5/8" shafts. I've also seen a 1hp motor with a 7/8" shaft, and seen things with up to 20 hp with SMALLER shafts (1") than 1 5/8". Shaft size varies so widely on motors, that's NOT a good indicator of hp output. However, you can be reasonably sure a motor with 6 10ga+ wires comming out of it, a 1 5/8" shaft, a foot in diameter, 16" long, with a LIFITNG EYE on top is more than 3hp.

Modelman I am almost certain that it is a NEMA motor, I had a 7.5Hp one with identical end covers to the one shown but it was around the IEC 132 frame size. I trade any NEMA motors I get with a scrap dealer to get TEFC IEC motors ( A good deal in my book).

The motor appears to be wired delta, the little loops of wire are coil identifiers not phase identifiers, I would guess it is a 440V motor, if you hook a 220V motor up to 440V the breaker or overload will trip but if you hook a 440V motor to 240V the motor may stall.

motor ID

Could it be that it is a wye=high volts delta=low volts? The frame size ie. mounting base, shaft size, and shaft height above the base should narrow it down to 2-3 different HP ratings dependant on speed. Most common is1750 but 3450 and 1175 also not uncommon. A careful look at the windings might give you a clue to speed 2 poles 3450, 4 poles 1750 and 6 poles 1175. If you take the rotor out you can check the number of poles by putting a battery on two leads., then check with a small compass. Once you establish number of poles and frame size the HP rating most likely will be apparent. You might be able to put 120 volts AC on two leads and start it with a rope around the shaft, no load it will most likely run near normal speed thus saving the trouble of disassembly by checking with a tach. Should be a good candidate for an idler motor.