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Generators in the home workshop

Using a Generator for a 3 phase supply

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Putney man31/08/2011 12:17:45
18 forum posts
I have a couple of machine tools with motors which can't use a 240 3 pahse VFD to run. Looking at the costs, a 3 phase generator seems a possibilty yet I have never heard of anyone using them to get round the problem. Anyone on the forum got any observations? The lathe is a Hardinge KL1 with the dual pole motor, and I have a number of other machines - making VFD's for each expensive (and I know I could run the Hardinge on one pole setting as a single speed and use the VFD to run it)
Putney man31/08/2011 12:21:23
18 forum posts
Clive Hartland31/08/2011 16:03:04
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2929 forum posts
41 photos
One thing about generating your own Leccie is cost, Its about 4 times what the power company charge.
The other aspect is noise from the generator, under load it will really grumble!
Outside, if its cold its a pig to start, I have been down to -18F and could hardly turn the engine over.
Allow TWICE the rating that you calculate for the load. If you say, calculate the load at 1.5Kva then buy a 3.5Kva.
A 1.5Kva will barely run a Lawnmower without getting hot!
My 1.5Kva will just run a 900W strimmer without too much load.
Apart from that and with not too much long use of the machine then it might be the only way instead of a VFD.
You could run a ring main with one VFD and just plug in the one machine you are using at a time.
 
Clive
Clive Hartland31/08/2011 19:11:23
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2929 forum posts
41 photos
Ah, Ring main and VFD its not possible so forget that idea.
It should be possible to get shielded male and female plug, have a flying lead from VFD and with female socket and a male plug on machines. Use one at a time as required.
Sorry about the mess up there.
 
Clive
Ian S C01/09/2011 11:05:58
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7468 forum posts
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If you arerunning an induction motoryou'll need at least twice the motor rating, plus the ability to take a brief overload of twice that again fror starting. I would expect that the large generator would run at the low load quite ecconomicly compaired to a small genny running flat out. Ian S C
Jon01/09/2011 19:33:42
1001 forum posts
49 photos
I would say three times the motor rating, i have blown inverters at double!
 
As in the beginners section its annoying people associating inverter purely as a VFD.
 
Why not plumb for one decent inverter to power whole workshop such as the MA7200 series from http://www.drivesdirect.co.uk Its then the equivalent of having your own 3ph supply, just plug the machine in and away you go.
This is a single 240V to 3ph 440V output not the associated cheap 220V used for VFD.

 
Putney man02/09/2011 12:15:27
18 forum posts
I didn't think inverters could handle different loads (Eg different motors) - is this inverter -as well as taking a stepped up 240 to 480 volt transformer, also able to supply balanced 3 phase into different sized motors (below its maximum rating).. And, how much are they - cause it is the cost of having multiple inverters for each motor - and the fact that they can't power 2 speed motors - I have a hardinge and a Boley 5lz, which made me think about a generator.
Jon03/09/2011 22:49:49
1001 forum posts
49 photos
Give Dave at Direct Drives a call.
Could well be problems with two speed motors, some Colchesters are like it.

The idea of the better inverters is to supply a pure 3ph of variable voltage by inset parameters as would be by the national grid.
Output of mine goes to the isolator and in turn the control panel tripping contactors upon switching Run on inverter. Lever spindle start mine runs at 400V programable.
Mate has a late Student and Bridgeport and can run both at same time, the MA7200 are meant for powering workshops.

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