The typical VFD (not the regenerating type) has a transistor that switches the braking resistor on when the DC bus voltage rises from energy coming back from the motor during deceleration. It is only switched on for a fraction of a second to keep the DC bus voltage below some preset threshold. So, the braking resistor will not be dissipating power until it is needed.
Regenerating type VFDs would not have a braking resistor.
Jon
technically, he only needs 2 buck boost transformers to do the job but 3 smaller ones would do it just as well.
And in your your case, it sounds like (probably) you actually do have three phase power, just that it's in the form that is commonly called "open delta"
The phase converter output is wired Wye. The spindle motor is 15 HP. And some jobs peg the load meter at 120%. Just briefly. The chips coming off sound like hail hitting the inside of the lathe. Eric
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Wye -- good! That makes the buck-boost easier to set up.
O.K. 15 HP *That* is impressive.
Make sure that the interlock on the door is good. :-)
I'm not sure when I will lose connection -- but the way they are talking, we should have a significant period without power, so don't be surprised if I stop posting in the next few days. (Just to the west of the Washington DC Beltway in Virginia, and lots of rain and wind promised. :-(
Good luck, DoN.
Now at the plant to make two people working the second shift. Hope this is the last week!
The transformers are: Square D Cat. # 1.5S46F, 1.5KVA, 115C temp rise.
HV: 240 or 120 LV 32 or 16.
Each weighs 35.5 lbs. Three transformers.
I will send a private email with pictures.
Paul
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