Harmonic mitigating transformers

[sceepe]

Anybody ever designed / installed / used a harmonic mitigating transformer? If so What did you think? Any practical concerns or problems I need to be aware of. What about the extra costs?

I have a commercial facility with all of the electronics loads segregated from the other loads in subpanels. I have always used K rated transformers and 200% neutrals to supply these panels in order to survive the harmonics. However, I have been considering going with harmonic mitigating transformers in hopes of actually reducing the harmonics in the system. I am curious as to what are the down sides of doing this.

P.S. I got a new photo for the profile. Thought you all would enjoy.

[ December 13, 2005, 05:30 AM: Message edited by: sceepe ]

 

[charlie b]

Re: Harmonic mitigating transformers

I have attended a demonstration of one such transformer. It was impressive. But would the transformer be worth the extra costs? I don't know. If you factor in a reduced heat load, and therefore reduced HVAC initial costs and operating costs, it might have a reasonable payback period.

The essential difference in that special transformer has to do with the way it is wound. There is some magical pattern something along these lines: Phase A is wound part of the way down this core, then it is run to another core and wound in the opposite direction. The other two phases get similar treatment. The effect is that certain orders of harmonics can't make it through the transformer.

There is something you should recognize about K-rated transformers They do nothing to block harmonics, but rather are built strong enough to take the punishment that harmonics inflict. There is more copper, and a greater ability to reject heat. They will therefore be able to pass the harmonics, and will generate the I2R losses associated with the harmonics, but will not themselves be damaged by overheating. It's not a fix, nor even a bandage. It's like your kid telling you the school bullies keep pushing him to the ground, and you responding by sending your kid to school in a bicycle helmet and knee pads. You get less damage to the kid, but it does nothing to deal with the bullies.

 

[Nick]

Re: Harmonic mitigating transformers

I installed a few in a television station a few years ago. We didn't do a power quality survey afterwords so I can only assume they worked as advertised. I haven't heard of any problems at the facility.