Transformer for a 6 pulse rectifier
Transformer for a 6 pulse rectifier
(OP)
Need some advice for a transformer-rectifier for electroplating application.
Quantity - 2 nos.
KVA - 600
Voltage - 11 KV / 100 V
Configuration and usage - Both of them connected to the same 11 KV bus on the primary side. One transformer or both the transformers may be used depending on the load requirement.
Requirement - Minimum harmonics
Given the above, what is the best transformer winding connection that would give the minimum harmonics and circulating currents (if any)
1. Both transformers Delta / Delta
2. Both transformers Wye / Delta
3. One transformer Wye / Delta and the second one Delta / Delta
Quantity - 2 nos.
KVA - 600
Voltage - 11 KV / 100 V
Configuration and usage - Both of them connected to the same 11 KV bus on the primary side. One transformer or both the transformers may be used depending on the load requirement.
Requirement - Minimum harmonics
Given the above, what is the best transformer winding connection that would give the minimum harmonics and circulating currents (if any)
1. Both transformers Delta / Delta
2. Both transformers Wye / Delta
3. One transformer Wye / Delta and the second one Delta / Delta
Muthu
www.edison.co.in





RE: Transformer for a 6 pulse rectifier
RE: Transformer for a 6 pulse rectifier
Muthu
www.edison.co.in
RE: Transformer for a 6 pulse rectifier
That said, I agree that #3 is probably the best solution to minimise harmonics if both units are in service and operating at similar loads and with similar delay angles. Change the firing delay of either unit and the harmonics might actually get worse if they start to add in phase rather than cancelling.
If these units are independent maybe you should think about a passive filter to suppress the 5th and 7th harmonics?
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If we learn from our mistakes I'm getting a great education!
RE: Transformer for a 6 pulse rectifier
Rafiq Bulsara
http://www.srengineersct.com
RE: Transformer for a 6 pulse rectifier
When operated individually, which one will need those 5th and 7th harmonic filters ? Wye connected or Delta connected ?
And do they have to be bypassed when operating in parallel ?
Muthu
www.edison.co.in
RE: Transformer for a 6 pulse rectifier
Muthu:
Option #1 and #2 with bridge-connected rectifiers does result in a 6-pulse system.
Option #3 does result in a 12-pulse system with minimized harmonics. It is of paramount importance, however, that you either stick to wye OR delta on the low voltage side of both transformers. If you select wye on the first transformer and delta on the other you most likely may not be able to match the number of turns for 100 volts.
Reason: Wye number of turns = 0.5774 * delta number of turns.
Regards
Wolf
www.hydropower-consult.com
RE: Transformer for a 6 pulse rectifier
If you go with #3 or #4 you have to have two independent rectifiers sharing a common dc bus, you can't have the transformers directly in parallel (you probably know that already, but maybe not everybody else). When you are running both transformer/rectifier sets you will have a 12-pulse rectifier and your first harmonics of note will be the 11th and 13th, the 5th and 7th having canceled at the high side of the transformers.
RE: Transformer for a 6 pulse rectifier
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If we learn from our mistakes I'm getting a great education!
RE: Transformer for a 6 pulse rectifier
In such scenario, which is the best primary winding combination that result least harmonics on the primary ?
Muthu
www.edison.co.in
RE: Transformer for a 6 pulse rectifier
RE: Transformer for a 6 pulse rectifier
Is there any online reference for such harmonic study ?
Muthu
www.edison.co.in
RE: Transformer for a 6 pulse rectifier
As an example see this. Read the first half of the first page.
ht
You can google more, perhaps.
Rafiq Bulsara
http://www.srengineersct.com
RE: Transformer for a 6 pulse rectifier
RE: Transformer for a 6 pulse rectifier
Thanks again David for staying with this Luddite. I'll go with option 3 - one trafo delta and other wye.
Thanks you, scotty and wolf. Appreciate your inputs.
Muthu
www.edison.co.in
RE: Transformer for a 6 pulse rectifier
RE: Transformer for a 6 pulse rectifier
Buy a standard MV transformer 11 kV/400 V or 11 kV /690 V and 2 separate 12-pulse plating rectfiers operating from Low voltage.
(Plating rectifier: unit combining transformer, rectifier and control, designed by several smaller suppliers according to customers specifications)
Designing plating rectfiers is a quite special thing as you have to be aware that plating always needs a kind of voltage control. Currently there is no statement how you plan to do this. Unless you choose the classic variable transformer, voltage control will cause varying harmonics and variable reactive power demand which is both quite difficult to deal with at MV for such a (low) power level.
See:
www.munk.de
www.rgb-heythekker.de
www.befeld-systeme.de
You will find a link to several other languages on all of these sites.