Can anyone give me their opinion on the generator in the picture (name plate).
Can I obtain a single phase output from it at around 230 volts if I can get at the
output wireing of the three phases.
Thanks,
Yob
woelen - 27-10-2022 at 06:44
You should have 4 wires, one so-called null/zero-wire and three phase wires.
Between any two phase wires you'll see appr. 400 V AC, and between any one of the phase wires and the null/zero-wire you'll see appr. 230 V AC. Each
of these 230 V AC voltages, relative to null, have a relative phase shift of +/- 120 degrees.Fulmen - 27-10-2022 at 11:44
The 350/420V marking is weird, Google gives me no relevant hits. But yeah, it's 400-ish volts in star-configuration. So it should give 200-240V
(according to the original marking) in delta wiring. yobbo II - 27-10-2022 at 14:37
Thanks for replys,
The voltage threw me out too.
I think maybe the 380/420 (I misread the plate) is saying that the voltage will be somewhere from 380 to 420 volts as you vary the load and perhaps
the revs. within the specifications/ recommendations of the device?
From: https://blog.uk.tdk-lambda.com/uk/2020/01/28/points-to-consi...
"
When selecting a power supply, it is very important to know where it will be operated and what input voltages are available. In Europe, the AC three
phase voltage is a “harmonised” 400Vac. Actually, the voltage in mainland Europe is 380Vac and 415Vac in the UK. In the US, however, the three
phase voltage can be 208Vac or 480Vac. "
If the item is delta connected only there may be no neutral wire available.
Would this be unusual?
Another edit!
I see at the bottom of the plate is says: WDG CONN. = STAR
Is this effectively saying there is a wye (star) connection to the outside?
(ie. four wires)
Getting ready for the blackout after the big bombsss drop.............
Yob
[Edited on 27-10-2022 by yobbo II]Fulmen - 29-10-2022 at 01:55
I see at the bottom of the plate is says: WDG CONN. = STAR
Is this effectively saying there is a wye (star) connection to the outside?
(ie. four wires)
I dunno, it's your generator. Can't you just check? Most motors can be rewired, but I don't know if that's the case for generators. Ideally you should
have all 6 wires (2 per phase). Sulaiman - 29-10-2022 at 02:13
I expect four wires (3 phases + neutral)
Plus two wires to the field coil,
usually via slip-rings to the rotor.
Diagnosis with an ohm meter ok
Ideally check insulation at 500v or more.
Especially check for insulation from the chassis - which really should be 'grounded'
Three single phase outputs of 10kVA each
(probably around 8 kW usable)
From memory (?) the outputs are rectified and fed to the rotor.
The field current may be controlled for constant output voltage.
PS for a smoother running engine,
balance the loads on the three phases as far as practicable.
You can if course use '3 phase' loads such as induction motors.
Same principles as a car alternator.
It is possible that all six wires to the stator are available, but this unit looks like it is not simply re-configured.
Check : carbon brushes, free shaft rotation, (the rectifiers with field coil are a load) bearings, burns in control box,
[Edited on 29-10-2022 by Sulaiman]yobbo II - 29-10-2022 at 14:21
Thanks,
I cannot check anything as I don't own the generator yet and it is online.
I had not though of a problem with a single phase load on the one coil.
This means the machine will be harder to rotate (supplying power to one single phase load) 120 degreese of its 360 degree rotation?
Is that what you are saying regarding the 'smoother runnning engine'?
I presume that I can run one (just one) single phase 8kw load (as you suggest) without too much uneven loading of the engine/generator combination.
Could I not run a larger single phase load (just one single phase load) than 8kW if I am just going to run one (just one) single phase load.
If I were to run three, single phase loads then I would be limited to (as you suggest) to 8kW x 3? ie. I cannot expent to get 30kW out of the
generator unless I run a proper 3 phase load.
Sorry about all the questions.
Yob
[Edited on 29-10-2022 by yobbo II]Sulaiman - 29-10-2022 at 17:14
The power available is volts x amps
The voltage is determined by rpm and field current
The current is determined by the load(s)
and is limited by I2R heating of the stator windings.
Using only one phase would allow a little more current, but not a lot.
These machines are rated for long continuous use, so will be capable of higher power than rated for, but its a risk.
To make full use of the generator all three phases should be used,
You could re-wire your distribution system fot three phase power, but that would be a lot of work, or expensive.
Easier would be splitting off one or more heavy loads such as air conditioning, heating, cooking etc. to make use of more than one phase.
This of course means re-configuring during no power, so keep a torch handy
If you can keep your single phase load below about 10 kW then change-over would be simpler.
Add a 50A circuit breaker to each used generator phase to prevent burned windings.
Don't worry about the motor:generator smoothness too much, its a tiny consideration that is easily compensated for by a flywheel, it is such a small
effect that just the rotational inertia of motor and generator is probably sufficient.
I have seen large backup systems fail due to lack of maintenance (flat batteries and evaporated fuel) so test regularly.
