Powering 3-ph tools off 1-ph power

[jgeorg]

Dave, 'unobtainium' tubes shouldn't be a problem. In the broadcast industry we've been replacing them with sillycone for years. There used to be direct plug-in solid state replacements available. If not, it's easy enough to homebrew some. Thank's for the explaination. There was something about diodes in a old lathe that I just couldn't quite figure out.
John

 

[kweaver]

Dave check me on this. I've taken out the L2 contact finger from the switch to use the stud as a junction block for the Neutral wire from the mains to go straight into the motor since the L2 shouldn't connect to Mot5. I shouldn't get "lite up" should I ? I had to reroute the yellow and blue wires in the motor to get them long enough to work with. They sure didn't leave any more than it took to reach the spades !

 

[dkamp]

John- since I don't own one of those drives, and don't have a schematic or tube-complement list, I can't tell 'ya for sure... but I know the Unobtaniums carry the entire motor current... which is something like 100A for the armature and 70A for each field... in the 250v range... pretty hefty. I do know the guys that've dealt with 'em have determined that the best plan-of-action was to either find a new set of tubes (even buying another 10EE as a donor!), or replacing the DC drive system with a trio of modern DC drives (and ganging the field controls together), or yanking the whole deal and dropping in a 10hp AC motor and VVVF drive system. After working with the MG set last night, and AC drives in everything from elevators/escalators to trains, I'd find it really hard for an AC drive to beat the smoothness of that Ward-Leonard system... darned motor was running, and I didn't even know it... at just a few RPM, it had full-authority torque that I couldn't stop, and when I started cutting (boring down the middle), it didn't even flinch! It's pretty simple in theory, complicated in application, and heavy in reality, but man, it's effective! Let's hear it for WW2 era engineering!

 

[dkamp]

Ken- your diagram has me cornfused.

What's the significance of the yellow and blue dots, which is 'before', and which is after?

Typically, a split-phase motor has a PAIR of windings, where one side is always connected to line... and the other two have a RUN cap across 'em. The motor will run either direction off either of the main windings, the direction-of-start is a function of which of the PAIR is connected to the remaining line, and which is connected through the Run cap... the cap provides phase-shift to 'kick' the motor in the correct direction... once up to speed, the motor's inductance cancels most of the the capacitance (phase angle becomes complementary) and the second winding is just along for the ride. the The theory is simple, and wiring for a single-voltage AC motor is easy, but it gets pretty complex-looking when it's a multi-voltage motor... lots of wires and windings.

The drum switch- typically, they're rigged for 3-phase motors, where the drum has 3 terminals on each side, one for each leg... one terminal simply makes or breaks in both positions. The remaining two flip-flop two terminals between Forward and Reverse. When wiring this type of drum-switch to a single-phase capacitor-start, it's a bit of a brain-teaser. My guess is that's what you're dealing with, and it's why your diagram ain't quite making it through my head. I'll quick slug-down a Pepsi and see if that helps.

 

[kweaver]

Dave your Pep must not have worked or you're a real slow drinker since you've not came back. The yellow / blue dots are simple to understand since that is the motor wiring diagram ... it's the 2 wires that are changed to change direction. You can even see in the diagram that it says CW and CCW above them with the locations changed. The switch is made for 3ph , 2ph , split phase with / without a cap or DC.
The switch is F/F the colored motor jumpers for direction change.

Didn't mean to drive ya to drinkin' before noon ...

 

[dkamp]

Yeah, Ken- I see that part... it's the MOT, MOT1, MOT2... etc., and 4,5,1 I don't quite follow.

You probably already figured it out, but if you haven't:

Are the MOTx and MOT designations just dead terminals to whatever they labeled on the switch?

Are 4, 5, and 1 wires that go to the motor, or are they just dead terminals?

What's the internal wiring of this motor? Does yellow go to the start cap, or to a winding? Same for blue...

 

[kweaver]

Dave the top diagram is what's on the motor so you know as much as I do about it ... of course (left out) it does say to switch B/Y for direction. The Second block is the barrel switch diagramed as I took it off the 60 year old GE motor (damn smooth running before it smoked). The Third block is how I thought it should be wired to operate the motor correctly. As I said , I took the L2 finger contact off the switch and used the post as a junction to run the common supply line straight to the motor , breaking only the hot wire. The old configuration broke both supply lines. After having to make longer motor mount slides and pulling wire out through the case and re-routing back inside to gain length for the B/Y wires it fired to life @ 5:15am today. The new motor is loud and vibrates the lathe , the old one was smooth as silk and deadly quite. Now I need new belts but I'm not looking forward to taking the caps off the head stock and messing with the babbits. Funny how 60 years of oil will eat up a belt ... but it's still working

2 new bi-metal 93" bandsaw blades arrived today so now I'm ready to go back to making shavings and chips !

 

[dkamp]

Well, Ken- assuming that L1 is HOT, and L2 is Neutral (or vise-versa), and assuming what little I know about this particular motor, I'd say that MOTOR wires 4 and 5 select motor direction, but the one NOT selected doesn't look like it's supposed to be connected to L2.

If this is a capacitor-start motor, your wiring probably puts the starting-cap across the line, rather than in series with one, and across the other winding, hence your noise and vibration...
That motor SHOULD be quiet and smooth...

 

[bkiper]

Very handy info all. i have been using a rotary phase converter for years to run my Lindie 350 amp wire feed welder and an old metal lathe. I would like to find some one who is using the inverter style to see if they like it better}

 

[kide]

Bryan - I think you'll find an inverter to power a 350 amp welder to be a bit pricey... as you'd also find out if you had to replace the rotary unit with new... That's bigun size stuff (I'm guessing 50 amps or so per leg)..

 

[dfrisk]

Bryan - I've got a Danfoss VLT 2000 variable frequency drive that is supposed to convert single phase to 3-phase power that I got with the intention of running a 3-phase motor. But I've never actually wired it up... I don't rush into things like that... think I've had the VF drive for 17-18 yrs. I do have a small 3-phase motor for a hyd. power unit SON & I were going to use to run a shop press and tubing bender, plan was to run that motor with the VF drive.