StepupTransformer function by stepdown transformer
StepupTransformer function by stepdown transformer
(OP)
There is a 440V/6.6kV transformer fed by 440V switchboard but 6.6kV/440V transformer needs for 6.6kV shore power. For the cost point of view, I'm very curious if 440V/6.6kV transformer can be used for both step up function and step down(6.6kV/440V) function. I don't know if it is implemented praticably. If possible, it is big advantage in cost point of view as one transformer is not needed.






RE: StepupTransformer function by stepdown transformer
The 440/6,6 transformer is wound to compensate for the internal voltage drop (represented by the Uk percent number).
That means that you have more turns than theoretically needed on the 6,6 kV side.
When you connect the other way round, you will get a lower voltage than expected on the 440 V side. And when you load it, it will drop even more. The no-load voltage will be about Uk % too low and the full load voltage will be 2xUk % low.
Otherwise you should be OK.
RE: StepupTransformer function by stepdown transformer
RE: StepupTransformer function by stepdown transformer
Are you talking VT?
This is - as I understand - a power transformer.
RE: StepupTransformer function by stepdown transformer
RE: StepupTransformer function by stepdown transformer
Must have got that thing wrong. Long time ago. Have to find a text to be convinced.
RE: StepupTransformer function by stepdown transformer
RE: StepupTransformer function by stepdown transformer
I think the shkim2000's main issue on reversing the power flow should be the neutral grounding.
A step up transformer should have a star windings at HV(6.6kV) side while the LV side is a delta. If this transformer is to be used a step-down, then there will be a problem to give the 440V system a grounded neutral.
Voltage drop should not be an issue as every transformer is provided with tap changing facility at the HV windings.
RE: StepupTransformer function by stepdown transformer
The great thing with this site is that if you give bad advice, it usually gets corrected so quickly that it doesn't do any harm. And the one that gives bad advice also learns in the process.
I like that!
RE: StepupTransformer function by stepdown transformer
RE: StepupTransformer function by stepdown transformer
The difference is that that thread was about low-power transformers where the compensation exists. This thread is about larger transformers - and I have just learned that they do not have it.
RE: StepupTransformer function by stepdown transformer
If I order a 240v to 24v 100amp transformer, I expect to see 24.0 volts at the output when fully loaded. Voltage drops in both primary and secondary are compensated for by slight adjustment of the turns ratio by the original designer. I had no idea the biggies were any different.
RE: StepupTransformer function by stepdown transformer
The key issue for the application of the step up transformer as a step down is the three phase connection. For the application of the Power Transformers you have source side and load side and the fair design is to have Y with grounded neutral at source side in order to detect ground faults.
RE: StepupTransformer function by stepdown transformer
For the 40 VA to 75 VA control transformers that have a nominal 24 volt secondary the open circuit voltage is usually 27 volts. Since these transformers supply small wire sizes and have higher impedance to limit short circuits, the extra voltage works out to about 24 volts at about 75% load.
A 6,600/440 volt transformer of any size is not going to have extra secondary turns. However, the primary has voltage adjustment taps that can be changed while the transformer is deenergized.
RE: StepupTransformer function by stepdown transformer
This will not be an issue for wye-wye connected banks, but may be an issue for wye-delta or delta-wye banks which create a 30° shift, and could result in a 60° shift rather than 0° when two are in series!