Transformer selection buck boost or other

cgmaster · Oct 30, 2017

I am installing a new Kitamura mill. I am running off of a phase converter. The input for the Kitamura is 200 to 220 max. I have about 245 coming from the phase converter. I am looking at transformers to correct the voltage. The mill rating is 30KVA.

What are my options?

I am looking at buck boost and think I would need a 16/32 volt. From what I understand I would need 2 transformers. I have never used buck boost transformers and will be reading about them tonight and how to connect them. any help would be appreciated.

Thank you.

Finegrain · Oct 30, 2017

I went through this with my Brother Speedio. Went with a pair of buck/boost transformers from McMaster-Carr, wired to deliver 208V. I was skeptical at the small wiring size within the transformers, but the system works great.

Regards.

Mike

TDegenhart · Oct 31, 2017

This has been talked about at length. The KVA rating of the transformer is just the difference available and what's needed. If the machine needs 10 KVA and the line voltage is such that the supply will only be 8 KVA at the required current, then only 2 KVA are needed in the buck/boost transformer. The small wire is just for core excitation.

Tom

cgmaster · Oct 31, 2017

Would getting a standard transformer be a better idea? I can get a multi tap transformer that was on a Mazak a guy has 2 of them one is 52 KVA and the other is 34 KVA. Would using a larger transformer cause any problems? I can actually get either one cheaper than the Buck boost.

The mill I am using it on is 30KVA.

Bruce Griffing · Nov 1, 2017

I have a Kitty that I run from a Phase Perfect with two buck boost transformers between the PP and the Kitty. My line voltage is 247. I could put a single buck boost in front of the PP, but since the PP is limited at a continuous current level, I actually gain max current by using a pair of BB transformers after the PP. In your case, if you are only powering the Kitty, it would be simpler to put a single BB in front of the rotary.

TDegenhart · Nov 1, 2017

cgmaster said:
Would getting a standard transformer be a better idea? I can get a multi tap transformer that was on a Mazak a guy has 2 of them one is 52 KVA and the other is 34 KVA. Would using a larger transformer cause any problems? I can actually get either one cheaper than the Buck boost.

The mill I am using it on is 30KVA.

You could put one in front of the rotary, knowing of course that you will be totally isolating the load from the line. The green safety of course goes through. Will the loss of ground reference to the electronics cause a problem? There has been a lot of binary bits spilled on this subject without a definite conclusion. The other downside is a greater core loss (heat).

Tom

cgmaster · Nov 1, 2017

I ended up getting a transformer from a Mazak.

Here are the specs.

52.5 KVA Total

Input: 200-480V
200, 220, 230, 240, 380, 415, 440, 460, 480

Output: 42 KVA @ 210V - 3 Ph
0.8 KVA @ 100-115V - 1 Ph
2.5 KVA @ 100-115V - 1 Ph
7.2 KVA @ 180/200V - 3 Ph

I plan to connect it right before the machine. On my other machines I have the ground seperated from the main electrical ground however 2 people recently told me I needed to tie the grounds to the electrical service.

Bruce Griffing · Nov 1, 2017

My Kitty is a delta load. So the neutral reference is not really necessary. Given the transformer, the point is moot now anyway.

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