Motor Specification Query

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Bob Minchin - 12 Dec 2006 19:56 GMT

Tis is the rating plate on a dewalt saw.
Can anyone suggest the meaning of P1 and P2?

http://i115.photobucket.com/albums/n313/9fingersphotos/rating.jpg

The only interpretation I could guess at is electrical power in =P1
and mechanical work out is =P2
but this would mean 3.4 hp input and about 700 watts waste heat.

It is a 3 phase induction motor.

I want to see what rating inverter I will need to use to run the saw.

TIA

Bob

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Andrew Mawson - 12 Dec 2006 20:58 GMT

> Tis is the rating plate on a dewalt saw.
> Can anyone suggest the meaning of P1 and P2?
[quoted text clipped - 12 lines]
>
> Bob

Consumption wired as Star or Delta ?

AWEM

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Bob Minchin - 12 Dec 2006 21:21 GMT

> > Tis is the rating plate on a dewalt saw.
> > Can anyone suggest the meaning of P1 and P2?
[quoted text clipped - 17 lines]
>
> AWEM

Hi Andrew,

I'd have expected star and Delta powers to be the same.
the two current ratings are in the correct ratio for star & delta
I also note that the product of the voltage & current in either star or
delta is roughly the P2 figure which suggests this is the VA rating which
should be greater than the true power consumed.

Hmm!

Confused of Romsey

Bob

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Andrew Mawson - 12 Dec 2006 21:37 GMT

> > > Tis is the rating plate on a dewalt saw.
> > > Can anyone suggest the meaning of P1 and P2?

http://i115.photobucket.com/albums/n313/9fingersphotos/rating.jpg

> > > The only interpretation I could guess at is electrical power in =P1
> > > and mechanical work out is =P2
[quoted text clipped - 26 lines]
>
> Bob

Star and delta power will vary if the voltage stays the same. This is
why big motors use star/delta starters

AWEM

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Bob Minchin - 12 Dec 2006 22:05 GMT

> > "Andrew Mawson" <andrew@no_spam_please_mawson.org.uk> wrote in
> message
[quoted text clipped - 43 lines]
>
> AWEM

True but I don't think this is the meaning in this instance as the ratio of
the powers quoted is not the same as the ratio of the currents quoted.

I have just seen elsewhere a saw of the same brand with Power in and Power
out quoted in similar proportions.

If i end up buying the thing I'll just have to make some measurement to
satisfy my curiosity!

Bob

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Christopher Tidy - 13 Dec 2006 03:37 GMT

> Hi Andrew,
>
[quoted text clipped - 3 lines]
> delta is roughly the P2 figure which suggests this is the VA rating which
> should be greater than the true power consumed.

Bob,

I think you're missing out the famous square root of 3 in your
calculations. Taking this into account, the apparent power will be
about 2.8 kVA in either case. I think it's possible that the lower
power figure is a continuous rating, and the higher figure an
intermittent rating.

Best wishes,

Chris

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Tim Leech - 12 Dec 2006 22:09 GMT

>Tis is the rating plate on a dewalt saw.
>Can anyone suggest the meaning of P1 and P2?
[quoted text clipped - 12 lines]
>
>Bob

My guess is that you're right. Rating plates for stuff like welding
sets uses that convention,of a suffix (1) for input and (2) for
output.

OK, so it's inefficient <g>

Tim

Dutton Dry-Dock
Traditional & Modern canal craft repairs
Vintage diesel engine service

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Model Forum / General / Models / December 2006

Motor Specification Query