gabriel,
What is the service factor on the nameplate? 1.0, 1.15, etc.
--
Al Reid
"gabriel" <[email protected]> wrote in message news:[email protected]...
> Bob Davis wrote:
>
> >> Yep, great link. I just found out my TS motor has 54% efficiency...
> >> Time to go shopping?
> > How did you calculate the efficiency?
>
> Using the HP equation:
>
> hp = v * i * eff / 746
>
> Plug in my values:
>
> 1.5hp = 115V * 18A * eff / 746
>
> Do a little algebra:
>
> eff = (1.5hp * 746) / (115V * 18A)
>
> Therefore:
>
> eff = 0.54 = 54%
>
> --
> gabriel
Thanks Dave...good reference.
Bob S.
"TeamCasa" <[email protected]> wrote in message
news:[email protected]...
> After several posts asking about Motor Horsepower, I found the simplest
> explanation on this website.
>
> http://www.elec-toolbox.com/Formulas/Motor/mtrform.htm
>
> Dave
>
>
We aim to please!
Dave
"TeamCasa" <[email protected]> wrote in message
news:[email protected]...
> After several posts asking about Motor Horsepower, I found the simplest
> explanation on this website.
>
> http://www.elec-toolbox.com/Formulas/Motor/mtrform.htm
>
> Dave
>
>
NEMA defines service factor as:
"The service factor of a general-purpose motor is a multiplier which,
when applied to the rated horsepower, indicates a permissible horsepower
rating loading which may be carried under the conditions specified for
the service factor."
For a 2-pole, 1/2 through 1 HP motor the SF is 1.25;
1/6 - 1/3 HP it's 1.35;
1/20 - 1/8 HP it's 1.4.
RB
gabriel wrote:
> Al Reid wrote:
>
>
>>What is the service factor on the nameplate? 1.0, 1.15, etc.
>
>
> Hmm... have to check, I'm not in front of the saw right now... What's a
> service factor?
>
Bob Davis wrote:
>> Yep, great link. I just found out my TS motor has 54% efficiency...
>> Time to go shopping?
> How did you calculate the efficiency?
Using the HP equation:
hp = v * i * eff / 746
Plug in my values:
1.5hp = 115V * 18A * eff / 746
Do a little algebra:
eff = (1.5hp * 746) / (115V * 18A)
Therefore:
eff = 0.54 = 54%
--
gabriel
Service Factor (SF) indicates how much above the nameplate rating a motor
can be loaded without causing serious degradation. On high service factor
motors (1.3 - 1.5) I have seen the nameplate amps shown at SF rather than at
rated HP. If the amps are at SF the efficiency is not as bad as you may
think.
My Delta contractor saw has a 1.5HP, 3450RPM, 1.15SF, 115/230V motor with
12.8FLA. That works out to be a 76% efficiency.
On the other hand, my pool pump is a 3/4HP, 1.5SP 115/230V motor that is
rated at 9.3 Amp (at SF). If I run the calculation assuming that it is
9.8FLA the efficiency is 52%. However, if I adjust for the fact that the
current is at SF (1.125 HP) the efficiency works out to be about 78%.
--
Al Reid
"It ain't what you don't know that gets you into trouble. It's what you know
for sure that just ain't so." --- Mark Twain
"gabriel" <[email protected]> wrote in message
news:[email protected]...
> Al Reid wrote:
>
> > What is the service factor on the nameplate? 1.0, 1.15, etc.
>
> Hmm... have to check, I'm not in front of the saw right now... What's a
> service factor?
>
> --
> gabriel
Thanks. You are right, the efficiency seems awful and it appears that it
really is. 18 amps is pretty high for a 1.5 hp motor. The motor on my jet
saw says 1 3/4 hp, 12 amps at 115 volt. Jet puts pretty good motors on
their equipment.
Bob
"gabriel" <[email protected]> wrote in message
news:[email protected]...
> Bob Davis wrote:
>
> >> Yep, great link. I just found out my TS motor has 54% efficiency...
> >> Time to go shopping?
> > How did you calculate the efficiency?
>
> Using the HP equation:
>
> hp = v * i * eff / 746
>
> Plug in my values:
>
> 1.5hp = 115V * 18A * eff / 746
>
> Do a little algebra:
>
> eff = (1.5hp * 746) / (115V * 18A)
>
> Therefore:
>
> eff = 0.54 = 54%
>
> --
> gabriel
How did you calculate the efficiency?
Bob
"gabriel" <[email protected]> wrote in message
news:[email protected]...
> Bob S. wrote:
>
> > Thanks Dave...good reference.
>
> Yep, great link. I just found out my TS motor has 54% efficiency... Time
> to go shopping?
>
> --
> gabriel