Power Advice

This topic has 11 replies, 7 voices, and was last updated 24 August 2013 at 10:27 by The Merry Miller.

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21 August 2013 at 19:31 #127492
Alan .204
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@alan-204
We have just got our new machine all cleaned up and ready to go but now we are pondering on the best way to run it, it's three phase and we only have 240 the motors could be rewired to run of inverters but there are three of them 1hp-and .75hp and .5hp can you run three motor's of one inverter? we don't need variable speed as the machine is a surface grinder, do we go for a phase converter advice please, just been shouted for my tee.

Regards Alan.
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21 August 2013 at 19:31 #22784
Alan .204
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@alan-204
21 August 2013 at 19:42 #127494
Robbo
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@robbo
For ease of use, and as you don't need the facilities of a VFD, then a phase converter would be the way to go. And you can use it for other machines you may get, whereas the inverter would be dedicated to one machine/motor.

You can run more than one motor from a VFD(inverter), by wiring them piggyback fashion, but they both run at the same time, and I think trying it with 3 motors is too much.

Hope you enjoyed you tea (Facebook and Twitter intruding here)!

Phil
21 August 2013 at 20:18 #127497
Alan .204
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@alan-204
Thanks Phil that's pretty much what i thought but thought I had better ask in case there was something else I didn't know about.

Al.
21 August 2013 at 22:24 #127513
Alan .204
Participant
@alan-204
Hi Phil I don't know what size phase converter to look for to run these motor, what size KW converter do you think I should look for, I'm wondering if it would need to be a bit bigger in order to start the older type motors, what do you think, by the way I haven't found out yet how you convert KW in to HP.

Al.
22 August 2013 at 08:03 #127529
roy entwistle
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@royentwistle24699
746 KW is 1 HP

Roy ( or it was at Worsley Tech 65 years ago )
22 August 2013 at 08:44 #127534
roy entwistle
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@royentwistle24699
Slip of the old grey cells 746 W = 1 HP

It's allowable at 80

Roy
22 August 2013 at 08:49 #127535
Les Jones 1
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@lesjones1
Roy.
I don't think 746 KW was ever equal to one horse power. I think 746 KW has always been equal to1000 HP. If you are right I will have to get my mains supply upgraded to 3000 amps and I will not be able to afford the cost of running my lathe.

Les.
22 August 2013 at 09:05 #127538
Trevorh
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@trevorh
Kw x 1.341 = HP

regards
24 August 2013 at 09:58 #127733
Robbo
Participant
@robbo
Well done Roy, I am happy to see that I am not alone!

Have always used rule of thumb that 750 watts equals 1 HP, near enough for our purposes and easier to reckon for the more elderly like Roy and I.

Converters usually have a lower and upper range of output/ motor size in HP/watts, so I should reckon on one with the total motor HP (2¼ HP,- about 1700 watts as the lower figure, that allows for the older motors requiring a bit more.

Fractional horsepower motors, especially older ones, never translate HP to watts exactly, I have found.

Phil

Don't know how that smiley got in there, it's supposed to be close bracket, but it won't go away.

Edited By Robbo on 24/08/2013 09:58:51

Edited By Robbo on 24/08/2013 09:59:44
24 August 2013 at 10:08 #127737
Russell Eberhardt
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@russelleberhardt48058
Posted by Robbo on 24/08/2013 09:58:08:

Don't know how that smiley got in there, it's supposed to be close bracket, but it won't go away.

Just put a space in front of the close bracket symbol.

Russell
24 August 2013 at 10:27 #127741
The Merry Miller
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@themerrymiller
Trevorh,

Are you sure about that Trevor??

Len. P.
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