Motor Horsepower
 

If an electric motor with 80% efficiency is pulling 16A at 120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?

Jon

Motor Horsepower
 

On 2011-02-09, Jon Danniken wrote:
If an electric motor with 80% efficiency is pulling 16A at 120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?


Sounds right to me.

i

Motor Horsepower
 

On Wed, 9 Feb 2011 13:00:32 -0800, "Jon Danniken"
wrote:

If an electric motor with 80% efficiency is pulling 16A at 120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?


If you're trying to figure out how much HP is being produced at the
shaft you also need to account for power factor. A typical small
induction motor will draw around 60% of its nameplate current with
*no* load.

80% efficiency sounds high for a 2HP single phase motor. Full load
amps for a normal 2HP induction motor is closer to 25A @ 120V.

--
Ned Simmons

Motor Horsepower
 

Yes, I'll agree with that.

--
Christopher A. Young
Learn more about Jesus
www.lds.org
..


"Jon Danniken" wrote
in message ...
If an electric motor with 80% efficiency is pulling 16A at
120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?

Jon

Motor Horsepower
 

On Wed, 09 Feb 2011 15:10:56 -0600, Ignoramus25972
wrote:

On 2011-02-09, Jon Danniken wrote:
If an electric motor with 80% efficiency is pulling 16A at 120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?


Sounds right to me.

i
Pretty close for 16 amp running current - but how much does it draw
on startup??? Most motors that will draw 16 amps on startup will draw
closer to 7 under normal running conditions - which is 1 HP.
Not 2 many real 2HP motors will start on a standard 15 amp breaker or
fuse, and many will not start on a standard 20 amp breaker or fuse. A
20 amp slow-blow fuse will GENERALLY start a 2HP motor under a
reasonable(light) load like an unloaded compressor or a 10" table saw.

Motor Horsepower
 

Jon Danniken wrote:
If an electric motor with 80% efficiency is pulling 16A at 120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?

Jon

Motor Horsepower
 

"Jon Danniken" wrote in message
...
If an electric motor with 80% efficiency is pulling 16A at 120V, what is
the horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?

I also mostly agree based on a chart I have here.

2 HP AO smith 120V motor pulls:
16.4 to 16.6 at 3600 RPM
17 to 17.8 for 1800 RPM
--


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Motor Horsepower
 

Ignoramus25972 wrote:
On 2011-02-09, Jon Danniken
wrote:
If an electric motor with 80% efficiency is pulling 16A at 120V,
what is the horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?


Sounds right to me.

Thanks Iggy, I appreciate that.

Jon

Motor Horsepower
 

Joe AutoDrill wrote:
"Jon Danniken" wrote in message
...
If an electric motor with 80% efficiency is pulling 16A at 120V,
what is the horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?

I also mostly agree based on a chart I have here.

2 HP AO smith 120V motor pulls:
16.4 to 16.6 at 3600 RPM
17 to 17.8 for 1800 RPM

Thanks Joe, that is in line with my measurements as well.

Jon

Motor Horsepower
 

On Thu, 10 Feb 2011 11:09:37 -0500, "Joe AutoDrill"
wrote:

"Jon Danniken" wrote in message
...
If an electric motor with 80% efficiency is pulling 16A at 120V, what is
the horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?

I also mostly agree based on a chart I have here.

2 HP AO smith 120V motor pulls:
16.4 to 16.6 at 3600 RPM
17 to 17.8 for 1800 RPM

That must be a capacitor start/capacitor run motor, not a more typical
cap start. The run capacitor improves the power factor, lowering the
line current.

--
Ned Simmons

Motor Horsepower
 

On 02/09/2011 03:00 PM, Jon Danniken wrote:
If an electric motor with 80% efficiency is pulling 16A at 120V, what is the
horsepower?

Going by (16)(120)(0.8)/746, I get about 2 HP.

Is this right?
Unless you measure the current with a phase-sensitive ammeter, you are
measuring two totally unrelated values. The problem with AC (I'm
assuming from "120 V" that this is an AC motor) is that the phase angle
is extremely important. Many motors will have only a small variation in
measured current from no-load to full load. the difference is that the
phase angle between voltage and current shifts dramatically from no load
(current lags nearly 90 degrees from voltage) to full load, where
current and voltage are nearly in phase. The POWER drawn changes just
as dramatically, from maybe 200 Watts to 1900 W. But, you will likely
see a 2 HP motor will draw 11 - 13 A at idle.

Jon