Split Phase Generators
Split Phase Generators
(OP)
I have a question regarding the use of the diesel generator with 120/240 center tap winding. For American systems the center tap becomes the neutral and this effectively (relative to the natural) makes two phases 180 deg apart. We can get 2 x 120 V single phase outputs (Phase to Natural) and/or get 240 V output (phase to phase).
I want to use this generator on a 240 V multiple earth neutral (MEN) system, where the earth and neutral are bonded. Obviously I can’t do this directly. I have access to the terminals of the two 120 V windings, L1/ L2 and R1/R2. What I propose to do is joint L2 and R1 and isolate them. Bond R2 to earth and this becomes the neutral. L1 then becomes the 240V Phase.
Another though is to use a 1:1 transformer to establish the neutral on the secondary side and bond this to earth. On the primary side I would just connect R1 and L2 as before. L1 and R2 would be connected to the primary terminals of the transformer without one leg being bonded to earth.
This requires more equipment I wish to avoid. Does anyone have any experience connecting a split phase generator this way. Though more then welcome.
Thanks in advance
I want to use this generator on a 240 V multiple earth neutral (MEN) system, where the earth and neutral are bonded. Obviously I can’t do this directly. I have access to the terminals of the two 120 V windings, L1/ L2 and R1/R2. What I propose to do is joint L2 and R1 and isolate them. Bond R2 to earth and this becomes the neutral. L1 then becomes the 240V Phase.
Another though is to use a 1:1 transformer to establish the neutral on the secondary side and bond this to earth. On the primary side I would just connect R1 and L2 as before. L1 and R2 would be connected to the primary terminals of the transformer without one leg being bonded to earth.
This requires more equipment I wish to avoid. Does anyone have any experience connecting a split phase generator this way. Though more then welcome.
Thanks in advance





RE: Split Phase Generators
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(2B)+(2B)' ?
RE: Split Phase Generators
RE: Split Phase Generators
Both windings are IN PHASE.
In NEMA world the a 120/240 Volt transformer has the center tap brought out as the neutral. Voltages are L1,120V - Neutral - 120V L2.
In IEC I understand that single phase is considered to be derived from three phase systems. With this in mind, one end of the single phase winding is the neutral of the three phase system and voltages are L1, 240V - Neutral.
When I did a lot of installations of F. G. Wilson gensets, (They claimed to be number three in the world of gensets at that time.), The same generator ends were used for both NEMA systems and for IEC systems.
The voltage rating has nothing to do with the insulation strength.
The voltage rating has to do with both standard voltages and with saturation. A given winding may be rated for anywhere from 110 Volts to about 140 Volts depending on the intended application and on the intended frequency.
All of the windings are regularly checked with a 1000 Volt megger.
If the generator is intended for IEC land it will probably show the 240 Volt connection on the nameplate.
It sounds as if you intend to use a generator configured for NEMA land on an IEC system.
If you are dropping from 60 Hz to 50 Hz, don't forget to change the UFRO jumper to the 50 Hz connection. Your voltages will be unstable if you run 50 Hz on the 60 Hz UFRO connection.
Standard no-load frequency on a nominal 50 Hz set is 51.5 Hz. (+3% or 3% droop) Here also, an improper no load frequency will interfere with the functioning of the UFRO and may lead to voltage instability.
Bill
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"Why not the best?"
Jimmy Carter
RE: Split Phase Generators
If the two separate 120V sockets were in phase I would be able to join the two “Hot” wires from each outlet together. However if I were to do this I would put a short circuit across the two winding connected in series. Therefor the question as to whether the 120 windings are in phase or not is dependent on the voltage selection made. They are in phase when connected in parallel to produce 120V only.
I intent to use the generator in the Philippines which uses a combination of both NEMA and IEC type arrangements and multitude of arrangements in between. For my case the local distribution is a 240V single phase system derived from a single wire earth return high voltage distribution system. The the LV neutral in bonded at the transformer solidly to earth. Most locally available domestic distribution boards use two pole circuit breakers with no earth bars and neutral bars. I am wiring my house as per IEC practise and the main switchboard has both earth and neutral busbars. The neutral and earth bars are bonded together. A separate earth rod provided locally and bonded to the earth bar. Outgoing circuits are protected with IEC single pole MCB’s and the incomer is fitted with earth leakage circuit breaker. Philippines are a 60 Hz system and so is the generator.
RE: Split Phase Generators
It's called single phase for a reason.
Don't confuse reversed polarity with phase shift.
Bill
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"Why not the best?"
Jimmy Carter
RE: Split Phase Generators
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Split Phase Generators
I find that calling a reversed polarity a phase shift is often misleading. Particularly when we deal with many phase shifts of less than 180 degrees that may not involve a reconnection.
I can't recall you ever calling a series parallel connection a phase shift.
I was intrigued by the thread title, "Split Phase Generator" I am familiar with split phase motors but not split phase generators.
For everyone who calls this a phase shift, there are several millions who would call it a series parallel connection.
Do you recall the old voltage regulators with the movable core and winding?
These had a movable, rotatable core and secondary winding. For full boost, the core would be positioned so that the induced voltage would be in-phase with the line voltage. As the line voltage increased, the controls would physically turn the secondary core and winding so that the induced voltage and the amount of boost was less. At the half-way point in the travel the induced voltage would be zero. If the line voltage continued to rise, the core would be turned further and the induced voltage would be of the oposite polarity and would start bucking the line voltage.
Some may call this a phase shift even though the induced voltage did not actually shift phase but was reduced to zero and then increased in the opposite polarity.
Arguments of this type are more suited to pub discussions. I agree that a polarity reversal may be drawn as a vector at 180 degrees to the original reference. However I would also argue that a shift implies going through the intermediate phase angles. O, 30, 60, 90 120, 150 and 180 degrees.
I would love to continue this discussion with you in a pub sometime. We could both give our minds a workout and leave leave the pub as good friends without ever coming to an agreement.
To the OP:
This has little to do with your concerns. "A Rose by any other name". The circuit will work regardless of what you call it.
You need not worry about the voltage. The windings will withstand 240 Volts and more to ground.
Bill
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"Why not the best?"
Jimmy Carter
RE: Split Phase Generators
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(2B)+(2B)' ?
RE: Split Phase Generators
RE: Split Phase Generators
We need to see us in a pub and have a mental work-out! Would love that, too!
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Split Phase Generators
The lingo aside, referencing the linked diagram, I take it you wish to move the ground point from the center down to the lower left hand corner. I see no problem in doing so as long as all grounding points are accessible.
RE: Split Phase Generators
LeithJS
Are you saying this is a 2 phase system?
No it's single phase
I think the term Phase is loosely applied to mean wire, winding or angle.
RE: Split Phase Generators
If the
RE: Split Phase Generators
RE: Split Phase Generators
Are there any two phase systems left in North America?
I understand that there was still a 25 Cycle generating station in operation a couple of years ago, but 25 Cycle is relatively new compared to two phase. I use the term Cycles intentionally. As far as I know, the last 25 Cycle station was built years before Hertz became the recognized term for frequency.
Bill
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"Why not the best?"
Jimmy Carter
RE: Split Phase Generators
Single phase involves no phase displacements.
Two phase involves a 90 degree phase displacement.
Three phase involves two different 120 degree displacements.
RE: Split Phase Generators
"Split Phase Generators"
I am familiar with split phase motors. A phase displacement is produced by pairing two windings with widely different X:R ratios.
One winding is a normal motor winding with low resistance and a fair amount of inductive reactance.
The second winding has relatively high resistance and a lower X:R ratio.
No series parallel involved. Putting these windings in series would defeat the purpose and there would be no phase displacement to develop starting torque.
I thought that this thread would be about some offbeat excitation system.
Bill
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"Why not the best?"
Jimmy Carter
RE: Split Phase Generators
According to https://en.wikipedia.org/wiki/Two-phase_electric_power, yes.
RE: Split Phase Generators
This is a dual voltage, single phase generator with two identical windings suitable for either series are parallel connection.
The controversy ensuing from calling this a split phase generator and calling a reversed polarity a 180 degree phase shift should be indication enough that these terms should not be used in this context.
Bill
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"Why not the best?"
Jimmy Carter
RE: Split Phase Generators
RE: Split Phase Generators
I think that this little "app" can be of some use.
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Split Phase Generators
While central tap is tied to neutral, may have illusion that hot legs are as 2 phases, but it's not true.
Think about if tap is not centred and it's at 25%; will be a (60V + 180V)/240V; such of asymmetry may help to see that is not a two phase system.
RE: Split Phase Generators
RE: Split Phase Generators
In any winding with central tap, if make tap as a reference point, "hot" connections are in opposite polarity being part of a unique induced voltage, not two voltages displaced at 180 degree.
Anyway, you may call it two phase system or split phase, no problem.
RE: Split Phase Generators
Suppose you have an untapped, ungrounded winding. One cannot connect the two ends together without causing a short. Must be two phase?
Suppose you have a winding with two taps. One cannot connect any two of the four terminals together without causing a short circuit. If one of the four terminals is chosen at random to be grounded, we must have a three phase system?
Sorry, the arguments don't hold up.
Did you ever get your original question answered to your satisfaction?
RE: Split Phase Generators
Gunnar Englund
www.gke.org
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Half full - Half empty? I don't mind. It's what in it that counts.
RE: Split Phase Generators
Thete are many systems and amazing variations in terminology to describe the same thing. All I would consider valid if the aim is to have a common understanding. I have seen this discussion many times before and there appears be two schools of thought. The idea I am trying to convey is that the reference point is very important when determining if two supplies are in phase or not. The load does not necessarily determine the supply arrangement.
RE: Split Phase Generators
I'll buy the next round in the pub Gunnar.
Bill
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"Why not the best?"
Jimmy Carter