Transformer Mixup

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J

jghrist

Senior Member
The secondary of a Delta-Wye transformer will be 30? out of phase with the secondary of a Delta-Delta transformer. If the tranfer scheme is closed transition you cannot use two sources 30? out of phase.
 
zog

zog

Senior Member
Location
Charlotte, NC
jghrist said:
The secondary of a Delta-Wye transformer will be 30? out of phase with the secondary of a Delta-Delta transformer. If the tranfer scheme is closed transition you cannot use two sources 30? out of phase.
Click to expand...

That is what I keep saying, everyone is just worried about the grounding. Hope someone listens to you. :)
 
SG-1

SG-1

Senior Member
Location
Ware Shoals, South Carolina
jumper said:
"The transformer will be used in an 83 throw-over scheme with an existing delta-delta transformer. "

What does this mean?
Click to expand...

An 83 throw-over scheme is basically a transfer switch of some type. A transfer switch would fall under the ANSI device number 83. They can be a simple off the shelf type or they can be a one of a kind engineered type that is very complex. Does that help clear the confusion I caused ?
 
SG-1

SG-1

Senior Member
Location
Ware Shoals, South Carolina
I have two big points so far:

1. The 30 degree phase shift is a disaster waiting to happen.

2. The delta may be specified for motor loads, to prevent single phasing due to a winding loss.

Question:

Would the two different connections react differently to harmonics ? It occurred to me that delta-delta would trap the harmonics on the load side where they are generated. I do not know if the delta-wye connection would pass the harmonics or trap them.
 
SG-1

SG-1

Senior Member
Location
Ware Shoals, South Carolina
Lets say I am measuring the voltages on the 83 (transfer switch).

SOURCE 1
L1 to L2 = 230V
L2 to L3 = 230V
L1 to L3 = 230V

SOURCE 2
L1 to L2 = 230V
L2 to L3 = 230V
L1 to L3 = 230V

If I were to measure between Source 1 Line 1 & Source 2 Line 1 how much voltage appears on the meter ? A 30 degree phase shift between the sources exists.

Can I just use the COS of 30 & come up with 31volts ?
 
H

hardworkingstiff

Senior Member
Location
Wilmington, NC
Was the secondary voltage of the received transformer ever stated?

Is it 208Y/120 or is it 230Y/133?

It seems odd if it came in at a line-line voltage of 230 when wired delta-wye, no?

Edit: I guess since it's going to another country???? Which country and what's their standard voltage?
 
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B

BJ Conner

Senior Member
Location
97006
SG-1 said:
Lets say I am measuring the voltages on the 83 (transfer switch).

SOURCE 1
L1 to L2 = 230V
L2 to L3 = 230V
L1 to L3 = 230V

SOURCE 2
L1 to L2 = 230V
L2 to L3 = 230V
L1 to L3 = 230V

If I were to measure between Source 1 Line 1 & Source 2 Line 1 how much voltage appears on the meter ? A 30 degree phase shift between the sources exists.

Can I just use the COS of 30 & come up with 31volts ?
Click to expand...

USe the 2x (SIN15) and you get 119 volts.
Are you parelling the two sources? If not what difference does the phase shift make?
Are the utility sources in phase? If not adding a phase shifting transformer would bring then in phase at point you want to transfer. It would make it possible to make a closed transition. This should be an easy question to answer, not seeing everything is leading to lots of guesses. Gotta drawing of the system?//
 
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SG-1

SG-1

Senior Member
Location
Ware Shoals, South Carolina
hardworkingstiff said:
Was the secondary voltage of the received transformer ever stated?

Is it 208Y/120 or is it 230Y/133?

It seems odd if it came in at a line-line voltage of 230 when wired delta-wye, no?

Edit: I guess since it's going to another country???? Which country and what's their standard voltage?
Click to expand...

The transformer was special ordered with a 230 volt L-L secondary. The engineer thought he was ordering a delta-delta. It may be that the supplier is at fault.

The country is Canada.

I have no idea of their standard voltages.
 
SG-1

SG-1

Senior Member
Location
Ware Shoals, South Carolina
BJ Conner said:
USe the 2x (SIN15) and you get 119 volts.
Are you parelling the two sources? If not what difference does the phase shift make?
Are the utility sources in phase? If not adding a phase shifting transformer would bring then in phase at point you want to transfer. It would make it possible to make a closed transition. This should be an easy question to answer, not seeing everything is leading to lots of guesses. Gotta drawing of the system?//
Click to expand...

It is the lack of information about the customers existing system that makes me nervous.

I am gathering information to see that the right thing gets done.

Thanks for the voltage, I did not expect it to be that high.
 
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mxslick

mxslick

Senior Member
Location
SE Idaho
Let's just hope there is not going to be an earth-shattering Kaboom!!
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C

Christoff84

Member
Location
Ontario, Canada
SG-1 said:
The transformer was special ordered with a 230 volt L-L secondary. The engineer thought he was ordering a delta-delta. It may be that the supplier is at fault.

The country is Canada.

I have no idea of their standard voltages.
Click to expand...

Our standard voltages are 600/347, 240/120, 208/120. The NEC may not apply but the CEC will and the provincial codes as well. I'd make sure everything is stamped CSA as well, inspectors really like that.
 
M

mull982

Senior Member
BJ Conner said:
USe the 2x (SIN15) and you get 119 volts.
Are you parelling the two sources? If not what difference does the phase shift make?
Are the utility sources in phase? If not adding a phase shifting transformer would bring then in phase at point you want to transfer. It would make it possible to make a closed transition. This should be an easy question to answer, not seeing everything is leading to lots of guesses. Gotta drawing of the system?//
Click to expand...

Couldn't you also just use sin 30deg. This results in 115V difference.
 
W

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
If you are given two 'line to neutral' sources of the same voltage but arbitrary phase difference (think 'wye' connection, but random angle rather than fixed 120 degree phase angle) and want to calculate the 'line-line' voltage, then you use 2*sin(angle/2). For small angles this value is pretty similar to sin(angle), but from 120 to 180 degrees (where the answer is that line-line = 2x line-neutral) you will see why you need 2*sin(angle/2)

-Jon
 
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