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230v to 110v Circuit Required Please

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Nigel Goodwin

Super Moderator
Most Helpful Member
Hero999 said:
It's understandable how to came to that assumption but it's incorrect.

A split phase system
4050-Split_phase2.png

https://en.wikipedia.org/wiki/Split_phase

A two phase system
There's no fancy picture here but I'll offer two simple quotes:
"Two-phase electrical power was an early 20th century polyphase alternating current electric power distribution system. Two circuits, or "phases", were used, with voltages 90 electrical degrees apart in time."
---snip----
"Three-wire, 120/240 volt single phase power used in the USA and Canada is sometimes incorrectly called "two-phase". The proper term is split phase or 3-wire single-phase."
https://en.wikipedia.org/wiki/Two_phase

I see what you mean, you're telling us about a system used in 1895! - does this have any relevence in the 21st century?.

As for the American system being incorrectly called 'two phase', I would have thought it's a better, more sensible, name for it - and makes more sense than reserving the name for a long obselete system?. I'm presuming they don't still use that antiquated system for driving motors anywhere?.
 

Hero999

Banned
I don't know.

The term split phase makes perfect sense to me - it's a single phase split by a centre tapped transformer.
 

yngndrw

New Member
By two phase, I ment if you take a three phase supply and connect across two of the phases. It is unbalanced but you have about 415V. I've always known that as two phase anyway, it's used in some factories.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
yngndrw said:
By two phase, I ment if you take a three phase supply and connect across two of the phases. It is unbalanced but you have about 415V. I've always known that as two phase anyway, it's used in some factories.

That should really upset the electricity board! :D

Presumably it's been specifically installed for that use, with a solid neutral?, which you wouldn't normally have.
 

yngndrw

New Member
I've seen them used in dairy farms where full three phase with neutral is available. The three phase is used through a star-delta timer to drive the main milk separator while the two phase motors are used in small(ish) pumps.

I guess it's to reduce the cost of the motor. I've never really asked why, I was just helping my dad build the controllers.

Looking at a graph of a three phase sine wave, two phase should give a peek voltage of about 75% of the full peek voltage.
 

Hero999

Banned
yngndrw said:
By two phase, I ment if you take a three phase supply and connect across two of the phases. It is unbalanced but you have about 415V. I've always known that as two phase anyway, it's used in some factories.
That, is (as you say) two phases of a three phase supply.

Normally you use a three phase plug but only use two of the pin and as Nigel says, the electricity company won't happy if you draw huge loads from one or two phases, there again it's just as likely that someone else is drawing just as much power from other phases to roughly ballance it out.
 

ecerfoglio

New Member
Nigel Goodwin said:
I see what you mean, you're telling us about a system used in 1895! - does this have any relevence in the 21st century?.

As for the American system being incorrectly called 'two phase', I would have thought it's a better, more sensible, name for it - and makes more sense than reserving the name for a long obselete system?. I'm presuming they don't still use that antiquated system for driving motors anywhere?.

The two phase system (90º) is used in some (AC) servo motors: One phase is allways "on" while the other one varies its voltage from "full foward" thru cero to "full reverse".

Of course, to obtain the "foward" (0º) and the "reverse" (180º) voltages they use a split phase transformer :p - even a variable one ("Variac") to regulate the voltage (and phase).

The 90º phase can be obtained (from a three phase system) with some exotic connections: for example if you take one phase (0º - 180º) between two of the 3 phases, between the third phase and the neutral you have 90º.

Of course, it's only a means to drive the motor. a two phase motor (90º) is a polyphase motor (like a 3 phase one).

With an split phase supply (180º) you have to use a single phase motor. A single phase (induction) motor needs some auxiliar starting system (2nd winding, capacitor, shadow pole, etc)

Power distribution is allways a three phase system. (with or without a "star centre" neutral) or, for short distances and small loads, a single phase system (or may be split phase).
 

RODALCO

Well-Known Member
The system Hero999 describes is also used a lot in rural New Zealand.

From the 3 phase line a 2 phase transformer with secondairies of 2 x 230 Volts or 2 x 240 Volts is used with the windings in parallel.

With the windings in series 460 or 480 Volts can be taken off for a 1 Ø motor with an extrernal capacitor to create the phaseshift.

In the second case the neutral will be on the link between the secondairies to keep the phase to neutral; voltages below 250 Volts.

This set up is also used on the SWER systems which have only a 1 phase line fed from an isolating TX at a voltage of 6.6 or 11 kV.
 

RODALCO

Well-Known Member
To add to this post is that the first TX is connected to L1 and L2, the second TX to L2 and L3, the third TX to L3 and L1 to keep the system balanced.

For the SWER the same applies.
The isolating TX is supplied from 2 phases. The output is 1 phase and the other terminal is earthed.

The isolating TX is used to avoid tripping the line protection on earth fault.
 

Hero999

Banned
RODALCO said:
The system Hero999 describes is also used a lot in rural New Zealand.

From the 3 phase line a 2 phase transformer with secondairies of 2 x 230 Volts or 2 x 240 Volts is used with the windings in parallel.

With the windings in series 460 or 480 Volts can be taken off for a 1 Ø motor with an extrernal capacitor to create the phaseshift.

In the second case the neutral will be on the link between the secondairies to keep the phase to neutral; voltages below 250 Volts.

This set up is also used on the SWER systems which have only a 1 phase line fed from an isolating TX at a voltage of 6.6 or 11 kV.
I think you're missing the point. That's a split phase system, not a two phase system.
 

RODALCO

Well-Known Member
Correct! with the common neutral the phases are 180° apart. we refer this as a 1 Ø system for the secondary, regardless if 230 or 460 Volts is supplied.

For the primary, it is a single phase supply taken of 2 phases of the network.
 

Gordz

New Member
You may get away with connecting a diode in series with the charger, without knowing exactly how your charger is designed it would be all guesswork. If it is an 'international' charger it may have a doubler inside, but it is likely that an autotransformer is your answer here.
 

Hero999

Banned
Never connect a diode in series with anything other than a resistive load such as a heater of incandescent lamp.

If the charger has a transformer on the input it'll go into core saturation and melt down.

If the charger uses a switch mode power supply then the higher input voltage will pop the capacitors and destroy the switching transistors.

The only way of powering anything other than a simple resistive load of a higher voltage source is to use a transformer.
 

audioguru

Well-Known Member
Most Helpful Member
The Lithium battery charger has a 3A low voltage output. Since it is probably a single "3.6V" cell then the charger's max output voltage is 4.2V and the power is only 12.6W.

If the charger has a very poor transformer then its primary power is 25W.
A stepdown transformer that is 230V to 110V at only 25W is small.
 

Hero999

Banned
Yeah, but how many 25VA 230:110V transformers have you seen?

100VA is normally the smallest size they come in.
 
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