Motor HP - Unusual Value on Label

I've been looking at an electric motor. In the HP section of the motor plate it says "25M" (yes, it is "M" and not "W".

Any idea what that really means?

Andy

Manufacturer and model plus case size might help

This is the label. Not sure it really helps - there's no manufacturer and the model no does not yield anything on Google.

I'm wondering if it's an odd decimal notation that signifies 0.025 HP - which would be ~18W

Andy

50Hz 1425 rpm 230v ccw rotation, continous duty cycle.. 0.53a is odd and does not tally with .25Hp ? 180watt would be .25 Hp. Could it be ex military ? Noel.

I agree.

And my thought about being notation for 0.025HP doesn't stack up either!

Andy

But it's about right for .125 HP (Metric)

My guess is a stamping mistake - the plate is missing a decimal point and a 1

I expect an apprentice did it!

Dave

Just multiplying volts by amps gives 122W. O. 125hp is 95W.this implies 80%efficiency, which is on the high side for a fhp motor. BUT we've forgotten the power factor, real power isn't volts * amps for a reactive load.

I've no idea what 25M means.

I think I've worked it out.

I believe the "M" denotes metric horsepower.

That's the units sussed. As for the value I conclude it must be 0.25 but with the decimal point missing.

The quoted voltage and current product is 122W which implies about 66% efficiency.

Andy

metric Hp is Ps I think ? And a horse is a horse imperial or foreign ! I would fall for 0.125 Hp then the rest is about right. Noel.

Metric hp is only very slightly less than imperial, so this doesn't sound right to me

I think PS is probably more common but, according to Wikipedia:

Metric Horsepower: hp(M) – also PS, KM, cv, hk, pk, ks or ch

Andy

So we have a 25 Metric Horsepower motor, in a surprisingly compact and efficient package

MichaelG.

Yes Michael ! And they also manufacture free lunches ! Oh, They also build perpetual motion machines as well. Noel.

… which was the point of my

It looks, to me, likely to be a synchronous induction motor of about 90 Watts? Just working on current, assumed power factor of Cos Theta = 0.8 and likely heat losses.

A pic of the motor might help. A usual 1/4 horse power induction motor would consume rather more than 1/2 an Amp and not be of fixed rotation.

As to the HP - maybe it was supplied by Hewlett Packard? (Joke)

Surely a synchronous motor would be 1800/1500 rpm.

The slower speed duncan is because of slip its still a sychnonous motor

Not according to this

A synchronous motor has magnets attached to the rotor (typically permanent magnets, but could be electromagnets and slip rings) and runs at some fraction of mains frequency, in this case it would be 1500 rpm.

An induction motor by definition cannot be synchronous

Synchronous/asynchronous. Point taken. I meant the type of motor on the typical scavenge pump on a dishwasher/ washing machine. Can’t remember what they are called. Fixed direction, cheap and also found on cooker oven fans.

Main dishwasher pump motor 3000 rpm (nominal) induction motor, I recovered one and used it on a drill grinding thing. Not well guarded, so I had to make up some covers.