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Author Topic: ST Gen 3 phase to single phase conversion.  (Read 3845 times)

matt

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ST Gen 3 phase to single phase conversion.
« on: October 05, 2008, 03:18:48 PM »
Hi all,

Anyone know a trick to convert a 3 phase ST generator to output single phase?

Can it be done???

Sorry for the dumb question. I am a simpleton in matters such as these.

regards,
Matt

MacGyver

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Re: ST Gen 3 phase to single phase conversion.
« Reply #1 on: October 05, 2008, 04:08:48 PM »
Sorry... no easy tricks.
Your choices are to either have the unit rewound for single phase, or to rectify the 3-phase output and feed it into an inverter to get single phase.
Steve

JKson (PS) 6/1 'roid & ST 7.5

mobile_bob

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Re: ST Gen 3 phase to single phase conversion.
« Reply #2 on: October 05, 2008, 04:38:26 PM »
if it is a 12 wire head, which i suspect it is because it is built for the more common world market
simply connect it as wye, then take 120 off of each phase referenced to the neutral position.

now you will be limited to 2/3 capacity of the head, in most cases unless you are feeding a 3 phase panel and want
3 circuits of 120 single phase then you can get full capacity.  if you want 220/240 that you can't have, although any two legs of
a wye connected head will provide 208 vac which might still work out for you. depends on what you need or want and what the future
goals are.  if you have no need for 3 phase your probably better off selling or trading your head and get a single phase unit.

(if i am wrong on this someone will jump in and say so i am sure) :)

failing that, how big of a head is it?  i got a few single phase heads of various sizes i would be willing to trade
you out of your 3 phase head with.

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

Jim Mc

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Re: ST Gen 3 phase to single phase conversion.
« Reply #3 on: October 06, 2008, 04:13:42 AM »
Yeah, let us know how many wires the ST head has.  If it has 6 or 12, converting between single phase 120/240 and 3-phase is simple.  If the head has only 3 or 4 wires, it's not possible without rewiring it.  You will lose some capacity, as MB mentions.  In other words, your 3kW 3-phase head will probably become a 2kW single phase head...

Jim



listeroidsusa1

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Re: ST Gen 3 phase to single phase conversion.
« Reply #4 on: October 07, 2008, 02:26:56 AM »
If your ST 3 phase generator is like mine (20kw) the windings remain the same and the field connection is changed for 220/440 operation. As Bob said, the generator  can be used at 2/3 capacity for 110 single phase. Any 2 legs will give 208 (or 277 on the high winding) Many large commercial gen sets that are specified single phase are shipped with the 3 phase units but with the third leg unconnected. It won't hurt a thing AND you can still have 3 phase for those shop tools that others pass up due to the 3 phase.

matt

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Re: ST Gen 3 phase to single phase conversion.
« Reply #5 on: October 12, 2008, 12:07:16 AM »
moer info.....

It is a STC 10

Presently wired for 3x 240v operation (50Hz)

Obviously I can only get at present 3.33Kva each leg.
I do not know exactly how many wires as yet are coming off the windings.

If I fully load only one leg, will the field volts increase to make the unloaded legs dangerously increase in voltage...ie 280v or similar?

regards
matt

Jim Mc

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Re: ST Gen 3 phase to single phase conversion.
« Reply #6 on: October 12, 2008, 01:11:39 AM »
No.  Loading one leg doesn't have such dire consequences...

Doug

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Re: ST Gen 3 phase to single phase conversion.
« Reply #7 on: October 12, 2008, 04:54:54 PM »
Matt:

You sent me a PM so I will give you my advice.

This is a realy big job, you will have to strip all the copper out of the ST stator and put in a new single phase winding.

There is nothing here you can't do but its expensive, time consuming and requires some skills and materials that most people just don't have.

If you insist on trying this I can give you some advice. The magnoetic core densities of the new winding must be the same as the old one. This means you will need to do the math and find out what they were for a 50Hz 3 phase machine and then recalculate them for a single phase them design a winding from scratch.
It's a Good Life, If You Don't Weaken

matt

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Re: ST Gen 3 phase to single phase conversion.
« Reply #8 on: October 13, 2008, 03:36:20 PM »
Thanks Doug and everyone for the advice.

It looks too complicated to bother changing. I will use it as is with 3x 240v 50Hz with around 3KVA each leg.

regards,
matt