Transformer with the same primary & secondary voltage

[zimmerDN]

Does this type of transformer exist? Primary and Secondary voltages are both the same, 600V, but it's Delta to Wye connected, 3-phase, ~400KVA.

The reason for asking is, I want to take advantage of the taps in a transformer to give a small boost to voltage that is too low. Can this be achieved another way?

 

[dpc]

1:1 ratio transformers exist and are commonly used to isolate system grounds via the delta-wye connection. In the US, this is done routinely for 480 Delta to 480/277 V wye.

If you just want a small increase in voltage, it is more economical to use a boost autotransformer. Look in Eaton or GE catalog for "buck/boost" transformers. For 400 kVA of load, if you want to boost the voltage by 10%, you would need roughly a 40 kVA autotransformer.

 

[nkn5]

Yes it exists. Two reasons I know,
1. To reduce the fault current on the other side transformers. Say if you are wiring to distribution boards for light fixtures etc.
2. Your question. To correct the voltage if required.

 

[jraef]

But to be clear, the difference will be that a Buck-Boost transformer is typically an AUTOtransformer (or arrangement of them) so there is no isolation from line to load. A Delta-Wye transformer is typically an ISOLATION transformer, meaning magnetically isolated between line and load. If you want to go that way, they are often sold as "Drive Isolation Transformers" because that is the most common use. If you don't care about isolation, use the B-B transformer option because dpc is right, it will cost a fraction of the isolation type.

"Will work for (the memory of) salami"

 

[zimmerDN]

Is it good (and common) practice to use isolation transformer to boost the voltage? What is the limitation on boosting the voltage and are there any drawbacks to using isolation transformer?

 

[dpc]

It's not common to use a two-winding transformer to simply boost voltage a small amount. There's no limit on boosting voltage (not sure I understand your question). The main drawback is the cost and size of the transformer and the fact that it requires suitable primary and secondary protection.

 

[zimmerDN]

One disadvantage I can think of is if the load at the end of this circuit suddenly drops and voltage drop is reduced then the transformer might be suddenly be over compensating creating a power surge.

Are there auto tap changers in a transformer? Are they reliable?

What about a voltage regulator?

 

[crshears]

Both autotransformers and two-winding transformers are made with tapchangers; some of them are off-load or off-potential tapchangers, frequently hand-operated, for use where very infrequent ratio adjustments are required and the removal of the transformer from service can be tolerated. Others are motor-driven, fully automated under-load tapchangers actuated by a voltage regulation scheme.

If they're well made, tapchangers are generally extremely reliable.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[unclebob]

Your existing transformer has taps already. Why not use them?

 

[squeeky]

Dear People, I am in the agricultural business in Africa. We very often use 400v to 400v, three phase Y Y 0 transformers on computer installations. They isolate the "normal supply" and act as a "filter to noise. We have had problems with UPS machines turning on and off frequently not to voltage drops but also high frequency changes in the voltage levels. High, in this case, is several voltage swings greater than 5% up and down with in 5 seconds. It seems to work very well. It also isolates the earthing and earth faults from the main network from the Computers. Noise generated by VSDs does not get through.