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3 phase to single phase

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eyeofthefly

New Member
i have a 3 phase ac generator and need help with converting it to single phase output can anyone help this ac generator is a bendix 3 phase 10kv 8000 rpm unit
 

eyeofthefly

New Member
bendix 3 phase to 1 phase

on the plate above the number 10 it says k.v.a.
the next thing on the plate says freq 400
next to that it says phase 3
then whight 31.7 lbs then theres an arrow stating diretion
 

Exo

Active Member
Is that all there is on the plate?
10kVA is the power of the generator, it isn't the voltage...

If the voltage isn't on the plate try measuring it...
 

Exo

Active Member
So, it produces 115 / 200 V

How much do you need? if you want 115V connect it in a "triangle" confuguration
Connect it in a "star" configuration for 200V

What do you want to power with it ?
 

Sebi

Active Member
The data label say: freq: 400Hz, i think this is some aerospace board device. The 3phase with 400Hz optimal for rectifying and you can use the DC power for bulbs, heating elements. You can also loading each phase independently. The 115V 400Hz good for any device with SMPS input.
Universal (serial) motor also can run, but forget the synchron motors.
 

eyeofthefly

New Member
3phase to single phase

so i need to build some kind of circut to go from the seven bolts that stick out of this ac generator and make it a single phase 120vac or 200vac power supply to like run a refrigarater or big color tv and some lites could this power a whole house if i could spin the ac generator at 8000rpm i need some kind of scematic
 

john1

Active Member
Hi eyeofthefly,

Its too high a wave(freq) for normal use.
If your house is 220v you could go across two phases,
and feed the lighting circuits only.
Don't use it to feed florries (strip lights),
use it for filament types only.
If your house is 115/110 then you could use one of the legs,
but only at about 3 Kw.
Again, only for filament lights,
the freq is too high for anything inductive or capacitive.
Some other items would work ok,
things that are not frequency sensitive like
an electric kettle (check power)
an electric toaster (unless it has electronics inside, some do)
electric blanket ? maybe
electric cooker ? ... its clock would not work right, check power.

There is no easy way to reduce the frequency from this unit
from 400 Cycles to match normal household 50 Cycles.

As Sebi says,
you might do better to rectify it to DC,
and use that.
That wouldn't hurt any florries, but it wouldn't work them.
That would work your filament lamps ok.
And if the rectifiers are big enough it would work a cooker ok.
DC might damage some items however,
so be careful with any motor driven items,
if they don't work, switch it off quick, and don't try to use it.
If it does work, switch it off after a very short time,
like three or four seconds, and see if you think its getting hot,
if ok, try a bit longer, some motors will run, but overheat.
Some motors will run OK. you'll have to see for yourself.

Before applying it to your house, check all appliances and
fittings are off. Anything left on might not like DC (or 400 C/s)

And there are some laws about switching generators to house
electrics. Sometimes Power Board officials have found cables live
when working on a fault, due to someone running a generator
elsewhere. They get the severe hump about that.
So make sure you isolate.

Best of luck with it, John :)
 

Klaus

New Member
Well folks, its a generator he's got there. It will provide an output frequency which is directly linked to the RPM it is driven with. It appears to be designed to be driven from a gas turbine, or something like it, at 8000RPM. At this RPM it would put out its plate rated power. There is no law that says one cannot drive it at some lower RPM to get some lower frequency/ voltage/ power out.

One could experiment with that.

I second the cautions given about connecting it to house wiring which is also connected to the power grid. There would be a puff of smoke and blown fuses if the power came back on from the grid while the generator was still running.

If one wants to power frequency dependent devices ( motors, electronic equipment) from a generator one is required to closely regulate the load RPM of the generator which in turn gives a stable frequency output. This means having some tacho feedback to regulate the power of the driving device (engine, water wheel, etc.). It is far simpler to rectify the AC output of this particular generator, as mentioned, and use it exclusively for powering filament type lights or heating elements. No need to worry about frequency in that case
:wink:
 

eyeofthefly

New Member
3phase to single phase

well thanks for the info on the 400 hertz i wasnt even thinking about that well here is another thought how about the generator powering a c to some hefty diodes to make it dc then to an inverter
 

crust

Member
I dont think it is a wise choice to connect such a generator to the utility grid by way of your house mains. The proper way to do this is to use a "transfer switch" which is an electronic switch that monitors the incoming power and switches generators into the circuit if it detects a failure. Ideally, you (and your local utility) would prefer that you keep your generator isolated from the rest of the grid.
 

Klaus

New Member
Yes, it could work. You need 6 diodes to rectify the AC. Of course, the rectified voltage might not suit the inverter input so you you have more possible complications. I am not sure if inverters are suitable to directly connect to a generator output, usually they connect to a battery bank which in turn gets charged from a generator etc.
Its not so simple, is it? 8)
 

eyeofthefly

New Member
3phase to single phase

am i getting this right if i turn the generator at a slower speed than 8000 rpm ill get a lower hertz?
 

Exo

Active Member
Yes, if you have 400Hz at 8000RPM
It'll give 50Hz at 1000RPM...

But it will lose a lot of its power at such a low speed.
 

eyeofthefly

New Member
3phase to single phase

well now im realy getting ito things here im disasembling this unit just to see what i got and mabey to understand what to do with it and show you all to and help me better this device so here are some pics for you all to see
 

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eyeofthefly

New Member
here are more pics because the web only lets in three at a time now im a bit confused because this small winding seems to be connected to the large winding inside the two wires comming from the large winding are connected by what looks like a diode and the three wires comming off the small winding go out to a small plug that has 5 wires
 

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john1

Active Member
Hi eyeofthefly,

Yes, you are right.
you will get a lower frequency out by running it at a lower speed.

But,
you will also get a lower voltage output, you may need to increase
the flywheel weight, You may be able to counter with a step-up
transformer.
You haven't said if your house is 110/115 or 220/230 volts.

How is this unit driven?

Running an engine at one eighth of its intended speed may not be
practical. Maybe its pulley driven ?

John
 

john1

Active Member
just looking at the pics.
very interesting.
how is it driven?
what voltage is your house?

still trying to make out what that bit is with diodes on it.
it might be to feed the field ...
 
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