Static phase converter question

[BH Davis]

Question for you phase converter pros.

Can I change the capacitors on a 8 to 12 hp STATIC converter to make it suitable for a 5 hp motor? If so would that be the only thing in the box that needs changing or would I also need to swap the resistor for a matching resistance to the new setup?

For the purpose of this question please assume that I know enough about electrical equipment in order to safely do this sort of alteration.

BH

 

[gregs]

Question for you phase converter pros.

Can I change the capacitors on a 8 to 12 hp STATIC converter to make it suitable for a 5 hp motor? If so would that be the only thing in the box that needs changing or would I also need to swap the resistor for a matching resistance to the new setup?

For the purpose of this question please assume that I know enough about electrical equipment in order to safely do this sort of alteration.

BH

I built my own rotary phase converter which is just basically a static phase converter running an idler motor. If I remember correctly the static portion is typically the same inside. The caps are selected for the size of motor you are trying to run. I think it was around 70mfd per hp. If the resistor you are asking about is the one across the capacitor terminals, that shouldnt make a difference. Thats just a bleed resistor

 

[marinusdees]

Question for you phase converter pros.

Can I change the capacitors on a 8 to 12 hp STATIC converter to make it suitable for a 5 hp motor? If so would that be the only thing in the box that needs changing or would I also need to swap the resistor for a matching resistance to the new setup?

For the purpose of this question please assume that I know enough about electrical equipment in order to safely do this sort of alteration.

BH

You can. Keep in mind that a static converter will only make the motor provide 2/3 (roughly) rated horsepower. This is because the static converter only actually provides two real legs and a "phantom" or "dummy" leg. to get the motor started, using the capacitors to shift the phase of one leg. If you want full horsepower, run another three phase motor in parallel (idler motor). This will provide real three phase, eg, a real as opposed to dummy third leg. This is in essence a rotary phase converter.

 

[BH Davis]

Yup, I'm well aware of the hp reduction with a static converter. However in this case I'm running a 5hp 3-phase motor on a dust collector in a situation where a 3hp motor would give me more than adequate suction.

I also could just use my existing 10hp rotary converter that is sitting idle. I just have a hard time with the idea, electrical use wise, of having to spin a 10 hp converter motor to power a 5 hp collector motor. Plus in my retirement shop the collector will have a lot of on/off cycles. It doesn't make sense to leave it running all day as could be the case in a commercial shop situation.

Hence the thought of down sizing a used 8-12 hp static converter that I can pick up inexpensively.

Thanks for the feedback.

BH

 

[BH Davis]

Results: worked out great. The 8 to 12 hp Phas-a-matic had three 400-480 mfd capacitors. Perfect. I just desoldered the wire going from #1 to the other two and it fired up the 5hp motor first shot. Red indicator light worked as it should as well. Seems like a winner. And it had been sitting in the original box on a shelf for about 20 years so is basically new.

BH