3 phase ST gen heads

[tlfrantz1]

Anybody out there sell 3 phase ST gen heads? I want two phases as backup for the house and three phase for my garage. Is this possible to do or will the gods of smoke frown on my set-up?

Thanks!

[ronmar]

3 phase heads typically run a lower voltage, something like 208VAC between any two legs...  Sending a 3 phase in different directions can lead to balance issues in the gen head.  What do you have that needs 3 phase, and how do you power it now?

[rcavictim]

That would work just fine.  Remember that the two phases to the house will only represent 2/3rds of the total generator nameplate output available.  If you need 100% of the capability of your prime mover on two of the three phases, oversize the head accordingly.  Your 120 volts each phase to neutral (Wye) will be on target but the voltage between legs will be lower than the usual 230 volts.  Theoretically it will be 208 volts.  It is a compromise I live with no problems really.  I have a 9 kW, 3-phase plant in the shop and send two phases (6 kW) to the house.  Works like a charm.

[tlfrantz1]

Thanks for info; I'm still in the planning stages now but I hope soon to have a lathe, a Bridgeport mill and a 3 phase welder. I love three phase, but I live in a single phase world.

[rcavictim]

Thanks for info; I'm still in the planning stages now but I hope soon to have a lathe, a Bridgeport mill and a 3 phase welder. I love three phase, but I live in a single phase world.

I have only single phase from the street here as well.  For years I struggled with the DIY rotary converter I made which worked fairly well in a pinch to run everything in my shop except the welder which wanted MUCH more power than I could give it.  The thing that pressed me to go with a 3-phase head on my standby generator is that the rotary converter used to spin the utility meter like crazy even when I was not using any power on the output side of my rotary converter.  Now that I have *real* 3-phase power my lathe has more torque and the welder has much more power.  Still I only have 9 kW available from my 1.5 litre VW diesel genset (direct drive @1800 RPM) and the welder is still challenged for heavy jobs. For those I crank up my gasoline powered Lincoln Ranger 250 (on loan to build my wind turbine).  That girl is thirsty however.

I am in the early stages of making a standby backup which can step in and do everything the VW plant does based on a brand new Changfa 1115 engine now in hand.  In addition to a 3-phase ST type head directly driven, this plant will include a belt driven (with belt release lever) 20 kW DC generator (400 amps @ 50 VDC continuous) I have which will be used as a welder.  I have this monster and might as well use it!  I still need to acquire a 3-phase 1800 RPM, 2-bearing generating head rated at 12-15 kW.

[gpkull]

RCA did you have power factor correction (pfc) caps or even a balanced rpc. unless monsters rpcs are usually not that bad power wise even unloaded. i do not know what your set up was but i do know 3 phase can be made very cheap from single using the rpc design properly balanced or even a vfd.

[adhall]

I have a friend with a machine shop who for many years used a homemade rotary phase convertor made from a 50 Hp motor. He recently bought a CNC machining center and decided he needed better power for it so he also purchased an electronic phase convertor. It wasn't cheap, but to my eyes appears to be very rugged and has performed beautifully for him. The three legs remain nicely balanced even under a wide range of loads. He is particularly happy with how much more power his "big" lathe (30 Hp) has now. He is also happy not to listen to the constant humming of that old 50 Hp motor.

This device monitors the incoming single phase power and generates a third leg at the proper phase angle and voltage. You can run multiple machines from it at the same time. In fact, my friend took the output from the phase convertor to a 3-phase breaker panel and uses that to distribute power to all the machines in his shop (about 8 in all).

Here is the link to the manufacturer's web site:

http://www.phaseperfect.com/

(Please note, I have no connections with this company, financial or otherwise etc. etc.)

Best regards,
Andy Hall

[rcavictim]

RCA did you have power factor correction (pfc) caps or even a balanced rpc. unless monsters rpcs are usually not that bad power wise even unloaded. i do not know what your set up was but i do know 3 phase can be made very cheap from single using the rpc design properly balanced or even a vfd.

Yes, I had added motor run caps according to tuning for least amount of current per leg as seen with a clamp on ammeter.  That certainly helped noticeably, but that 7.5 HP, 3-phase motor in my converter used to run really hot and that heat had to come from the 230 single phase mains. 

Funny thing, the way my 3-phase power from the VW plant is now introduced into the machine shop room it also spins that 3-phase 7.5 HP motor in my old converter because the associated 208 to 550 volt, 3-phase transformer, part of the converter is required to run my lathe. The resonating capacitors have been removed.  The 7.5 HP motor now runs cool and so much smoother sounding and the fuel rack on the VW plant doesn't have to open hardly at all to spin it.

[gpkull]

just thought i would ask. i also run a 7.5 rpc. its a1969 marathon and if i  remember correctly it pulls 6 or 7 amps idle. never has run hot at most warm. it does hum (an ac growl) when idling but as soon as i load it it goes to the tune of a normal motor. i have no cnc so balance is not so critical although it is close. my budget has no phase perfect in it and for under a $100.00 i have had 3 ph. i did score many parts next to nothing, not the norm for me. i run a 2 hp rpc on my bp mill also. in a 40 hr week i believe my power bill will go up 20.00 or so. RCA i cant imagine were all that heat came from (wasted energy i understand) but i never had that issue. from the gurues of electrons you use 1.73 amps single phase for every 1 amp of 3 ph. i do know there is no free lunch maybe part of the loss is heat. glad to hear you got your set up running cooler (more efficient).