Made a phase converter 3 days ago


That was kind of a fun gig. Someone paid me $350 to make a pahse
converter out of parts that cost me about $50 (10 HP Baldor motor,
fused disconnect switch, oil caps etc). Took me about 1.5 hours to
do. This is a rope start phase converter with both legs balanced with
capacitors (90 uF per leg on a 10 HP idler).
At idle, the voltages were something like 243, 247, and 248 volts.
i
Reply to
Ignoramus5013
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Are those voltages measured with out a load? Seem a bit high.
Paul
Reply to
co_farmer
Without a load. The load is at customer's place.
This voltage is what I get at home, a bit high. Sometimes I get 245 volts.
i
Reply to
Ignoramus5013
I'm confused. If you have capacitors handy for balancing, why can't you switch one in as a start cap? Or does that just make for endless complications?
Reply to
Tim Wescott
Here's what I know.
1. This Baldor motor does not start from all six of the balancing capacitors connected to one leg (180 uF). It just does not.
2. The way I made the converter, it starts with a rope pull, and when it runs it is well balanced, by three caps on one side and three caps on the other (L1-L3 and L2-L3). It is quiet (all you hear is the motor, fan etc, almost no humming).
3. To start this motor electrically, would require a starting circuit, which is of course doable, but much more expensive for the buyer and I did not have start caps on hand. This is not a sophisticated guy and he is okay with rope start.
4. For some mystery reason, my own 10 HP Century motor in my own phase converter, starts great from almost the same amount of capacitors (188 uF), but the 10 HP Baldor does not. So I was lucky with my phase converter in that I did not need to have electrolytic caps for starting.
The buyer's application is a 7.5 HP wood shaper and he told me that it works very well with the RPC (I doubt he really would push it so far, as to get full output from it).
i
Reply to
Ignoramus5013
Perhaps his power company is like MY power company..the bastards...and they deliver it high...often way way too high.
Which means my VFDs go into error and refuse to start.
Gunner
I am the Sword of my Family and the Shield of my Nation. If sent, I will crush everything you have built, burn everything you love, and kill every one of you. (Hebrew quote)
Reply to
Gunner Asch
Years ago, like 1975 or so or, uncle sent me out to a friends place to look at his rpc. Honking big 25 hp motor and rope start. Guy made a living grinding broaches like in engine main bearings and camshaft bores.
Every morning, rope start, switch on the motor, switch on the grinders. I'm not sure he even had caps on his system but it earned him a living until he retired years later.
Sometimes good enough is.
Wes
Reply to
Wes
Yep. He must have been very strong.
I remember how in 1975 I was given a toy circus truck and took it all apart. My mom was upset. I was 4
i
Reply to
Ignoramus5013
What's that Lassie? You say that Ignoramus5013 fell down the old rec.crafts.metalworking mine and will die if we don't mount a rescue by Tue, 14 Sep 2010 11:58:06 -0500:
could you have added a second small motor to spin up the idler motor?
Reply to
dan
Generally an old treadmill motor works pretty good for that. Or a "starterator" from an old Kohler garden tractor motor
Reply to
clare
I could, but it would have cost him big bucks.
i
Reply to
Ignoramus5013
What are your product liability insurance costs ?
Best Regards Tom.
Reply to
azotic

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