Rating for 1.75 kw electric motor

[georgetroy]

I was reading the motor label on my Vicmarc 300 and it said 1.75 kw. I was thinking this would be equivalent to a 3 hp motor does that seem about right? GT

 

[Mark Mandell]

George,

I seem to remember that 1 hp is equal to 746 W, and if so, then your motor's a bit over 2 1/4hp.

m

 

[georgetroy]

Thanks for the reply Mark,
Is your Stubby rating the same way and if so what is it? I think it's 2hp for the 750 model and choice of 2 or 3hp for the 1000. Both motors maybe from the same mfg. The one on my Vic 175 is an AEG Europe motor. GT

 

[hcgernhardt]

An interesting note about horsepower: be careful about how they are determining the ratings. The wattage noted may not, in fact, be directly related to the shaft horsepower. We seem to be having a similar discussion over on Sawmill Creek:

http://www.sawmillcreek.org/showpost.php?p=363985&postcount=66

Overall---I'm wondering if it really matters how many horses your motor has as long as it gets the job done?

 

[Mark Mandell]

George,

Mine is an AEG as well and rated 3hp/2.2kw @ 50hz, 230v

m

 

[Jim Carroll]

I tend to agree on how do we actually know what we are getting. There should be a world wide standard on ratings.
Most motor ratings do not show if it is input wattage/Hp or output wattage/Hp.
Some motors are not as efficient as others with some only having an efficiency of about 60%.

We had this same discussion some time ago about hand drills with a 750 watt drill some have great torque and others would not pull the skin of a rice pudding.

If all motors and power tools had an output wattage then it would be easier to compare one against another.

As indicated earlier though some machines come with big motors and most guys would never use the full potential of the motor but it sounds good to say my machine has a 3hp motor what does your have.

 

[Mark Mandell]

As indicated earlier though some machines come with big motors and most guys would never use the full potential of the motor but it sounds good to say my machine has a 3hp motor what does your have.

I opted for the 3hp on my Stubby 1000 not for the Argh! factor, but because I was planning on doing large stuff and wanted the extra capaciity. I quickly found that I could have saved the extra $650 that third horse cost me. 2hp is plenty to most spin anything.

m

 

[Bill Boehme]

A motor with a 1.75 kW rating would be 2.3 HP. There is not an issue of whether the name plate refers to input electrical power or output mechanical power -- it is always output mechanical power -- the difference is that most of the rest of the world uses SI units of measure and so the output mechanical power is specified in kW. The conversion factor from kW to HP is 1.341 or 0.7457 if going the other way (HP to kW). This conversion has nothing to do with motor efficiency since both are simply different units for measuring the same thing.

JUST SOME MISCELLANEOUS RAMBLING FOLLOWS: One of the earlier posts mentioned the conversion from watts to horsepower (746 watts = 1 HP) which is fine if you want to convert output watts to horsepower, however, as a caution against comparing input power against output power, one cannot simply take the input voltage and current by themselves to arrive at the horsepower output of a motor. The efficiency of the motor must also be taken into consideration. Manfacturers state efficiency under full load conditions, but efficiency drops off when the motor is operating under less than full load conditions. In fact, efficiency is zero when the motor is unloaded, and by logical extension, the output power is also zero.

Bill

 

[MichaelMouse]

There should be a world wide standard on ratings.

If all motors and power tools had an output wattage then it would be easier to compare one against another.

As indicated earlier though some machines come with big motors and most guys would never use the full potential of the motor but it sounds good to say my machine has a 3hp motor what does your have.

Didn't go back and read that post, did you? Reason for no world-wide standard is that it would be easier to compare.

You think it's because guys try to one-up another? I don't believe it. Just heard my "5HP" (115 volt) 15 amp compresser top off down the basement. Nice thing is, the motor's smaller than the "1HP" 14 amp lathe motor which can swing a 400mm by 150mm piece of hard maple with enough force left to make any catch a risk to your wrist.

 

[Bill Boehme]

Just heard my "5HP" (115 volt) 15 amp compresser top off down the basement. Nice thing is, the motor's smaller than the "1HP" 14 amp lathe motor ........

Machines with "application specific" motors are apparently able to be granted a "bye" on honesty and ignore the power rating of the motor itself; and instead, are able to treat the machine and motor as an inseparable entity for the purpose of arriving at a marketing driven power rating that is typically referred to as something like "maximum developed". For a machine like a compressor, there is a lot of potential energy stored in a fully charged tank of air. The amount of power that can be obtained at the first instant from the fully charged tank may actually be what is claimed, but after that it quickly drops to the actual power output of the motor. I also strongly suspect that the "max developed" power of a typical consumer compressor is not seen when using the stock regulator (most likely no regulator at all for the fastest blow-down).

Bill