yes no maby get out of here!!

[omegaghost]

well i am faced with a dellemia. i want to replace the three phase 1 1/2 hp nema 184 motor on my lathe. as i have no three phase power to my house this is also being where my shop is. and i do not care for static converter and a rotary converter is to pricey for me. so i have a fellow that can sell me a 1 1/2 hp singel phase 184t motor for 200.00 or a 3 hp 180vdc motor and driver with a speed control in a nema 180 for the same price. so this is my question which one? this might help as well my lathe is a 1960s 2557 vh logan the one with the expandbal and colapsibal pully for speed change. so tell me all about it.

[Al_The_Man]

I would go for the DC, definately, you may want to get rid of the Vari-speed pulley though.
How have you been running it so far?
Al.

[omegaghost]

i have not been runnig it just got it two weeks ago. im dieing to make chips on it so bad for the time being i am cleaning everything and learning a lot about lathes in concept and function. looks to be well made machine alot better than my import benchtop mill.

[omegaghost]

hey AL the man aside from the ajustibal speed with the dc motor what other perks that are better with dc

[Al_The_Man]

Full benefit depends on the quality of the controller also, but a DC motor tends to have a fairly flat torque curve from zero speed to maximum rpm, dropping down slightly as the rpm rises.
Al.

[handlewanker]

Hi, for my choice I'd base it this way.
How many machines are you going to have/already have in 1PH.
Here's a few:-
1- lathe, probably 1-1/2 HP.
2- Mill, also 1-1/2 Hp.
3-bench grinder, about 3/4HP.
4-Saw bench, about 1-1/2HP.
5-Bandsaw, about 1-1/2hp.
6-Power hacksaw, cold saw,abrasive cut off saw about 1-1/2HP.
7-Pedestal drill,5/8" cap, about 1HP
8-Wood planer, about 1-1/2HP.
9-Air compressor, 1HP
There must be a dozen other machines used.
All the motors driving them can be 3PH run from a single 3HP rotary phase converter, or if more than one machine is run at a time a 5HP will give a margin for capacity.
3PH motors are cheap to buy, whereas 1PH motors cost the earth, especially in the 1-1/2hp bracket, try replacing one.
By cost I mean A$50 for a 1HP motor to A$150 for a 3HP.
They are also pretty bullet proof when it comes to cranking up the amps.
There's a pretty good reason that home air compressors are so puny and pathetic, and that is cost of the 1PH motor, also they aren't rated to run for too long.
I may be wrong, but I reckon if you could buy a cheap belt drive 1PH air compressor and change the motor to 3PH you'd be streets ahead of the rivals.
It would probably be a bit difficult to change the motor/compressor arrangement on a direct drive home compressor, as the motor and pump unit are mated together.
That's something I want to explore one day, mounting two pump units from two of these compressors with burnt out motors, and driving them from a single 3PH motor.
It would require some reworking, but they go cheap when the motors go.
The beauty is that they could all be powered from ONE rotary converter.
I can just see the 110volt brigade quaking in their boots at the thought of 400volts across two phases.
Ian.

[omegaghost]

i had given some thought about geting a phase converter. but the more i read about them the more confused i became it seemed as though every fisherman had a differnt lure pros and cons from home made to static to rotary and on and on so i just decided to K.I.S.S. keep it simple stuiped that and a lack of time and money i know a little investment now would save me more later but it is what it is and thank you for you"re input

[omegaghost]

wow just put my motor on and this thing is working fantastic i can go from 2000 rpm to 8 rpm and the torque is just nuts. its so cool when my lathe chaters at a speed i just turn a nobb and it is gone i feel spoiled

[handlewanker]

Hi 'Mega, What's this I hear? In post 7 you've wistfully scratched around in the bottom of the piggy bank hoping to find a bob or two to scratch yourself with, when lo and behold in post 8 you are now belting the living guts out of some motor, I suppose it's 3 ph, and ooing and wowing and otherwise extolling the attributes of what can only be guessed at, is a 3 phase converter with speed control and all the other things it can do.
Welcome to the world of 3ph speed control and all it has to offer.
Now you'd better look for all those 3ph motors that you've discarded as being not usefull.
One word of caution in the sudden rush of euphoria, make sure you DON'T overload the power rating of the whatever it is you've got.
Now we want to know the whole story, where did the money come from, what did you buy, and what made you go for broke.
Oh, and a last word of caution, when you start driving equipment at higher speeds, make sure the lube' is up to scratch or you'll be spending more time unseizing bearings etc.
Ian

[Al_The_Man]

I thought it was a DC motor?
Al.

[handlewanker]

DC? oops, I must 'ave been thinking of real motors. Didn't DC die with old Tom Edison, or was that the incandescent blow torch? I can't remember, too far back.
Maybe old 'mega will put us out of our misery and spill the beans.
I still hope he's gone to 3ph, I'd hate to have to look for DC motors for a project.
Which brings me to a story that a little bit of knowledge is a dangerous thing.
Some years ago, about '97 last century, I bought a Bridgeport mill from the firm I worked for when they downsized the toolroom.
The first problem was it was 3 phase and I only had single phase.
So it was, do I get a 2HP single phase motor and attempt to fit it, or investigate the phase change method I'd read and heard about?
The 2HP was out, due to the arm and a leg syndrome.
Having read about using capacitors and an inductor, whatever that was, to effect a miraculous appearance of two more phases I decided to give it a go.
Off came the motor and it was quite plain that there were more wires than you could shake a stick at.
In the box at the top on the motor casing, there is a reversing switch, and this had the three supply wires going into it with three more wires coming out going into the motor.
There are also three more wires held together in a skruit connector.
Having learned to be methodical years ago, I made a sketch of the various connections and then pulled everything apart.
It soon became apparent that the three wires tied together and the three wires going into the motor were definately related, a meter across the wires gave me three pairs that had about 8 ohms between each.
I deduced that the three pairs tied together were the star point and the other three were the other ends of the stator coils.
Now according to someone or other you connected the single phase mains supply to two of the wires and attached a capacitor of about 100 Uf 400 volts across the last wire and the live input wire.
You also had an inductor in the circuit to smooth things down a bit and add a bit of balance to the phases.
I thought I'd better try this out on another motor I had spare to see what would happen.
Just to be on the safe side I added a 3 amp fuse in the input line.
Beauty, it started and ran like a dog on heat.
So now we're in business.
All was assembled and neatly put together with proper crimped connections and spade terminals.
It was noticed that after running for about ten minutes the motor got a bit warm, not actually smell the insulation cooking warm, but sausage on the barbie warm.
I shut down and waited for 1/2 an hour. The same thing happened.
Maybe a bit more capacitance to ush things along a bit, so another 20 Uf was added. It helped, for about 15 mins.
I ran it like this for almost 8 years, doing short runs and shutting down as soon as poss to keep the motor cool.
I even added a small fan to the top of the casing to force draught the motor, and this prolonged the melt down time to twenty minutes continuous running, which was OK, as I rarerly ran it for long periods.
Now it can be told, having come across this forum and the discusion on phase converters, it was apparent that I should have used another 3 PH motor to generat the extra two phases etc etc.
Someone up there loves me.
I've just obtained a 3HP motor for $50 on Ebay,and an electrical box, $10, to put the capacitors and related switch gear in, and a pair of 10amp 3PH switched sockets for $20, so now it'll be a proper set-up.
I think you can call that a learning curve.
In the meantime the Bridgeport has found a new home at my mate's factory. He always drooled at the thought of having a Bridgeport so when I bid on and got another turret mill, an Ajax, on Ebay, I let him have it.
The Ajax is a british made mill, almost identical to the 'port, a bit longer table at 56", and having a built in feed motor and fast traverse for all directions, with built in coolant pump.
The spindle taper is INT 40, so I let all the R8 tooling, from the Bridgeport, go to my mate.
Now I'm back on Ebay to get an INT 40 milling chuck with ER 32 collets.
I don't want one of the collet sets, that my local tool dealer advised me to get, only the metric sizes of 6, 8, 10, 12, 16, 20 and two other metric sizes of 7mm and 13 mm to cover the imperial range.
The ER series of collets will collapse down 1mm so the range shown will cover all the milling cutters from 1/4" shank up to 3/4" shank and the equivalent metric sizes up to 20mm.
The Bridgeport weighs about .8 tons, and the Ajax weighs about 1.3 tons, with most of the weight going into the knee casting that houses the feed motor and gearbox.
Ian.

[Al_The_Man]

DC? oops, I must 'ave been thinking of real motors. Didn't DC die with old Tom Edison, or was that the incandescent blow torch? I can't remember, too far back.

DC motors are far from dead, the older Gettys servo style motors that Fanuc & Mitsubishi used still come up on ebay and make excellent spindle motors, it is usually the controller that is costly.
But in your case, it you have a 3 phase spindle motor, 5hp or under, I would not bother with the RPC, just use a VFD with single phase in, gives you 3 ph out.
Al.