Question Phase Converters

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Akela

Grumbler in Training
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Sep 10, 2010
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Hi,

I run a Pistorious MN200 with 2 Baldor 3 phase 1.5HP motors. As a tenant, I have always had 3phase power in my stores. I am now buying a building that currently has single phase power. I have the Utility company investigating my options for bringing in 3phase service. They would need to do significant work on their supply end (3 transformers, new outside meter, etc) and I am not sure they will do it at no cost to me. Either way, I would need to pay for everything on the load side after the meter - run a new line from the meter to a new three phase electrical box, probably new breakers and then transfer everything over . This alone is a $3500 adventure which I had planned on doing but now I am thinking Phase Converter may be a better option. I already have 200amp service (1PH) in the building with plenty of room in the box for adding circuits. The only 3PH motors are the two on the Pistorious, everything else including my seal 4468Heat press is 220,230 or 240 1PH
I have read good things about rotary phase converters and talked with a few people that are using them with great results. If set up correctly I understand they are seamless and transparent in operation.

Do any of you have experience using rotary phase converters with Pistorious saws? If so, what size PH converter are you running? - Normally the PH converters are sized by the starting amps and HP of the largest 3PH motor on the system. Its a little tricky with a double miter saw since BOTH 1.5HP motors start at the same time. Logic would say that the converter be sized based on doubling the HP and starting amps of one motor but I need to call a few PH converter suppliers to find out for sure.

I would love to hear from anyone that has experience using a rotary phase converter with a Pistorious 3PH double miter saw.

thanks, Akela
 
I have no idea where you are, but you might throw in one more option.....

"Replace the motors with single phase".

We did this about 15 years ago, and found it to be about half the price
and trouble of going converter.
 
The 3PH motors on the saw now are really top shelf Baldor TE units, I hate to see them go but swapping out the motors is definitely an option I will price out as well. thanks
 
When I moved my shop and became a home based framer, I switched out my 3 phase for single phase motors.

My motor recently died and I found a local company that repaired it for me.

Be careful if you buy a new single phase Baldor motor. The 'off the shelf' motors have a longer shaft that will hit the in feed table from Pistorius, but you could notch the table. Pistiorius had their version custom made with a shorter shaft to solve that issue.

Reg. single phase Baldor motor is about $425.00
Special order single phase Baldor motor is about $675.00

Pistorius also used single phase Franklin motors which are less expensive and available off the shelf with shorter shafts.

I found this info on Phase convertors:
http://www.phase-a-matic.com/RotaryDescription.htm
 
A rotary phase converter will work fine for you, but unless you want to increase your opportunities for expansion by having 3 Phase I concur with the others - it will be a whole lot cheaper and simpler to go with the replacements. As to the cost, you can probably sell those 3 Phase ones to someone else and recover some of your investment. Or keep them in case you ever do get 3 Phase.
 
One advantage of 3-phase motors is their operating efficiency, but if you use a phase converter, they become inefficient. Phase converters are generally a good idea when single phase replacements are not a viable option, such as when the motors are specially modified to fit a special application. That's not the case for your double miter saw.

Replace the 3-phase motors with single phase motors. If your motors are in very good condition, some suppliers might offer you an attractive trade-in option. And you might get a good price for them on eBay or Craigs List. Check the listings.
 
Please correct me if I am wrong, but isn't a phase converter an "active" device, meaning it draws current to make 3 phase power?

If so, wouldn't efficiencies and money saved by operating on 3 phase be lost over the long run?

By the time the line is run to/from the converter plus the operating costs- wouldn't replacing the motors cost less in the long run? Especially if only using the converter for a single saw. Wouldn't the saw have a higher potential salability if it is single phase?
 
We have 8 three phase motors here all running off a 7.5 HP rotary phase convertor. While three phase motors may be a little more efficient, their main advantage is that they are more reliable than single phase motors. One thing you might want to consider if you're going to replace the motors on your MN is wiring. It's different for three phase and I'm sure your MN has magnetic starters. Find out from an electrician if they'll work with single phase power. There's some intricate wiring in our MN's control box with four low voltage fuses. It might work with single phase power, but who knows? I do know it'd be expensive to replace.
 
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