Lesson learned about electrics

[Ultradog MN]

Two years ago I built a rotary phase converter.
I had gotten a 7.5 hp 3 ph motor for free and bought a kit with all the capacitors, etc and found a 12x14in enclosure box on CL to put it all in.
At the time, I had second thoughts about the motor because it spins 3450 rpms and I thought a 17xx motor would use less power - because it spins slower.
But you guys assured me it wouldn't make a whole lot of difference.
I had my electric guru friend Steve wire it up for me and he is kind of a gizmo freak.
He handed me these gizmos and said to cut the openings in the enclosure cover which I did and he wired them in.
Fast forward 2 years and last week I bought a 7.5 hp 3 ph 1725 rpm motor at the U of Minn surplus outlet for $20. It had a noisy bearing so I replaced both of them ~$50.
Then I installed it in place of the old 3450 motor.
Thinking I'd make a smug post, I took a photo of the readout gizmos before and after I switched motors.
But no smugness now. You guys were right - of course, there's not much difference in energy used.
This photo shows the old motor using 543.3 watts at idle.

And here is the new motor using 507.4 watts at idle.

35.9 watts difference. So you guys were right, motor speed is Not a big deal.
One big difference between them is the amount of noise they make.
The old one was Really Loud. So loud I put it outside with a 5 gal. pail over it to keep the rain off.

The new one is Much quieter and I put it inside.
Meanwhile, thanks for all the great help we get here.

 

[Geo-TH,In]

My dad passed in 1985.
He made both static and rotary converters.
He didn't have your fancy display.
He would experiment with the rotor motor by using a lathe and removing some of the material off the rotor until he got the amps balanced on each leg the best he could.

Dad was flying by the seat of his pants.
If you have a spare 3 phase motor try removing some material from the rotor and see if there is any change.. Dad would cut off the motor shaft so no one would come in contact with it..

That's all I know about 3 phase converters..

 

[Ultradog MN]

A friend of mine has a rpc and none of the capacitors, etc to start it.
His has a 6in T bar on the end of the motor shaft.
To start it he gives the t bar a kick with his foot to spin it then hits the switch.
Works good.
Bought it from an old machinist who used it that way for 30 years.
I asked my electric friend Steve about balancing the phases. He said don't worry about it.
I've wondered what the elect gurus here would say about my numbers there.

 

[Geo-TH,In]

My dad used capacitors to start his rotor motor.
He made phase converts for farmers. Everything was automatic.
Some motors were for irrigation and drainage pumps.
A local farmer has 2 rotor motors to power his irrigation pumps.
He runs more than one pump at a time.

All that matters is if yours works, great.

 

[Destroked 450]

Sent you a text a couple days ago
Did you get it

 

[Geo-TH,In]

Here's a picture of my neighbors 3 phase converters.
Some of his irrigation pumps are

Over a quarter mile away. These rotor motors has the shaft ends cut off an capped with a cover.
My dad jury rigged a convertor for his craftsman table saw. He used air conditioner hard start kits to get his rotor spinning.

Nothing would stop the 3 phase motor on his tablet saw.