Parallelling of XFMR's

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juan7010

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Minooka
kingpb said:
electrics, I'm trying to understand your operating situation more clearly.

Are you wanting to operate in parallel all the time, or only momentarily when you switch from one transformer to the other?

I will reserve further comments until I can understand your situation better.:)
Click to expand...

I know this question dates a while back, but I have a similar situation. The following transformers are in parallel. They are continuously operating. The are feed by a single source, being the utility incoming.


XFMR 1:

2500/3125 FFA
43800 PRI
2520 x 5040 DELTA / 4360 y x 8720 y SEC
6.5 %Z
TAP A (46200)

XFMR 2:

2500/3125 FFA
24000 x 48000 PRI
2500 x 5000 DELTA / 4330 y x 8660 y SEC
6.3 %Z
TAP B (46000)

Question:>

How can I find out the effects of circulating current on the load?

How much circulating current I should expect?

If operating at Full Load will the circulating current disappear?

I have a program called PTW*SKM. I am able to simulate the power flow on these two transformers but I cannot seem to find a way to show that circulating current.

Thanks.
 
charlie b

charlie b

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rcwilson

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Location
Redmond, WA
Circulating current will not show up directly. It will be seen as an increase in the current on one transformer and a decrease in current on the other.

For example, say the transformers are supplying a 200 A load and share equally, 100 amps in each. But there is 20 amps cirulating current running around through the transformers, the HV and LV busses. In one transformer it is in the positive direction, negative direction in the other. Measured load would be 100 + 20 = 120 Amps in one transformer and 100-20= 80 Amps in the other. Total load = 120 + 80 = 200 Amps. Circulating current is approximately 1/2 of the difference = (120-80)/2 = 20 Amps

This is very simplified, but you should be able to get the circulating current by comparing the loading of the two units. Another way to see it in your simulation is to make the transformer's identical and check the load distribution. Try both sets of values. Also try differnt taps just to see what happens and record the currents, watts, vars to see the effects.
 
J

juan7010

Member
Location
Minooka
rcwilson said:
Circulating current will not show up directly. It will be seen as an increase in the current on one transformer and a decrease in current on the other.

For example, say the transformers are supplying a 200 A load and share equally, 100 amps in each. But there is 20 amps cirulating current running around through the transformers, the HV and LV busses. In one transformer it is in the positive direction, negative direction in the other. Measured load would be 100 + 20 = 120 Amps in one transformer and 100-20= 80 Amps in the other. Total load = 120 + 80 = 200 Amps. Circulating current is approximately 1/2 of the difference = (120-80)/2 = 20 Amps

This is very simplified, but you should be able to get the circulating current by comparing the loading of the two units. Another way to see it in your simulation is to make the transformer's identical and check the load distribution. Try both sets of values. Also try differnt taps just to see what happens and record the currents, watts, vars to see the effects.
Click to expand...

Thank you!

I will try that, I'll post the results later.
 
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