# Electrical

#### harman16

Joined Apr 26, 2006
1
why a 2 Φ circuit does not exist?

#### Grant

Joined Mar 5, 2006
17
Originally posted by harman16@Apr 26 2006, 07:56 PM
why a 2 Φ circuit does not exist?
[post=16555]Quoted post[/post]​
We can use 2 phases together of a 3 phase supply to act as a single phase if it gives us the desired voltage we require for the equipment we want to power. This equipment is single phase- meaning the heating element or coil or lamp is run off just one phase, singular- "single phase".
Cheers,
Grant

#### kubeek

Joined Sep 20, 2005
5,796
Originally posted by harman16@Apr 26 2006, 10:56 AM
why a 2 Φ circuit does not exist?
[post=16555]Quoted post[/post]​
In short because the two phases add up and act like a single phase.

When you have a center-tapped supply transformer and take the center as a common point, then you have two phases, shifted by 180deg, on the opposite sides of the secondary. But when you take one end of the secondary as a common point, than you have just a single phase supply with two voltages.

#### Papabravo

Joined Feb 24, 2006
21,308
Originally posted by kubeek@Apr 26 2006, 10:07 AM
In short because the two phases add up and act like a single phase.

When you have a center-tapped supply transformer and take the center as a common point, then you have two phases, shifted by 180deg, on the opposite sides of the secondary. But when you take one end of the secondary as a common point, than you have just a single phase supply with two voltages.
[post=16561]Quoted post[/post]​
In brushless DC motors you want the phase with the current to be at 90 degrees or less away from the rotor, so that maximum torque can be applied while it is energized. In a two phase machine there is just no good way to satisfy this criteria.

#### alim

Joined Dec 27, 2005
113
Originally posted by harman16@Apr 26 2006, 04:56 AM
why a 2 Φ circuit does not exist?
[post=16555]Quoted post[/post]​
Hi 2 phase circuits were in existence before the advent of 3phase,in 2ph. the voltages are 90deg .out of phase .Kubeek refers to a centre tapped transformer as 2 ph. but that should be called a bi phase transformer.