Most three phase loads are delta?

[ronaldrc]

Just a thought.

I hear electricians ask a lot is it delta or Wye?

But from looking at it from the line side most all three phase circuits are a delta.

Draw a panel and apply 4 loads from cir.#2 through #8 you've just made a delta.

Might not be balanced but its a delta.

 

[Ed MacLaren]

Re: Most three phase loads are delta?

I would suggest that many loads form wye connections.

- Any three 120 volt lighting or receptacle circuits supplied from a 208/120 volt panel, providing they are fed from different phases.

- Ditto for any three 277 volt lighting circuits supplied from a 277/480 volt panel, providing they are fed from different phases.

- The windings of many three phase motors are wye connected. That is the motor designer's decision.

- Any three single phase service transformers (POCO) that are supplied from one phase and the neutral of a four-wire line, providing they are fed from different phases.

Ed

[ February 27, 2005, 07:58 AM: Message edited by: Ed MacLaren ]

 

[jim dungar]

Re: Most three phase loads are delta?

Ed,

Good examples, except a three phase motor with wye connected windings is still a "delta" load on the power grid.

 

[rattus]

Re: Most three phase loads are delta?

Jim,

If all we know are line voltages and currents, how do we know the load configuration?

 

[ronaldrc]

Re: Most three phase loads are delta?

I should have not posted this as a separate thread probably but I did. Visualize what I am talking about any time we hook up a 3 phase panel the loads that come off it are in a parallel Delta. Its just not something we think about being that way or at least I didn't.

In my example I used Circuits 2,4,6 and 8 but since we are talking about single phase loads we normally wouldn't hook two wire to a breaker terminal so I will change the breakers.

Start with A phase loads to #2 and #4, B phase #10 and #12, C phase #18 and #20 we just made a delta connection on this system.

Also if you use the circuits between these circuits they will form a delta.

 

[Ed MacLaren]

Re: Most three phase loads are delta?

any time we hook up a 3 phase panel the loads that come off it are in a parallel Delta

How can you say that without specifying the system voltages or the load voltage?

It will depend on whether the individual loads are connected line-to-line (480 volt load on 480/277 volt panel) or, line-to-neutral (277 volt load on 480/277 volt panel).

a three phase motor with wye connected windings is still a "delta" load on the power grid.

Right, Jim. No neutral to the motor.

Ed

[ February 27, 2005, 11:32 AM: Message edited by: Ed MacLaren ]

 

[ronaldrc]

Re: Most three phase loads are delta?

Ed I'm not saying its a balanced three phase load or a intentionally designed circuit but looking at the configuration from the line side or the grid side its a delta connection.

 

[rattus]

Re: Most three phase loads are delta?

Jim and Ed,

I think we are saying that we can treat any balanced load as a wye or delta.

With no neutral, there is no way to tell how the windings are connected just by observing line currents.

 

[ronaldrc]

Re: Most three phase loads are delta?

I'm viewing these circuits purely from line to line no neutral.

 

[ronaldrc]

Re: Most three phase loads are delta?

This was just a observation I made and it has never been pointed out to me in my 35 years in the trade.

Didn't mean to mislead anyone I should have said all line to line loads excluding the loads connected to neutrals and grounded conductors.

But you have to admit that even on a separately derived secondary wye 120/208 the 208 loads if viewed from the bus of the power panel would be a delta.As far as a wye configured load like a motor I think maybe that maybe open for discussion.

Ronald

 

[bigjohn67]

Re: Most three phase loads are delta?

If you are running a motor you can use an open delta and collectively get 208 using 2 auto transformers. Now if this equipment requires 208 3phase because of electronic controllers, a 208/120 wye should be provided. The controller may not be able to take the high leg of the 208 volt open delta.

 

[mro]

Re: Most three phase loads are delta?

Hey! Let's all go fishing at the Delta!!!
Wye Not


ha ha ha ha (nevermind)