Replies

1. 
   coonass | Feb 11, 2010 07:37pm | #1

   John,

   Why not use a phase converter?

   http://www.phaseconverter.com/

   KK

1. 
   JohnCA07 | Feb 11, 2010 09:01pm | #2

   While I have heard of phase converters I was under the impression that my 220 volt single phase power would not be enough to use a phase converter. I'll look into this deeper and give Temco a call to see what they can suggest.

   Thanks for the suggestion.

2. 
   JohnCA07 | Feb 11, 2010 09:39pm | #3

   I looked closer at Temco's
   I looked closer at Temco's suggestions for motor size, load etc and it appears that I would need a 600amp single phase breaker to supply the power to run the phase converter required to power a Hard staring 50HP motor. I only have 100amp service so I don't think this would be an option. Again I'll talk to Temco to be certain.

   Temco sizing chart http://www.temcophaseconverter.com/phase-converter-sizing.html

3. 
   cap | Feb 11, 2010 11:00pm | #4

   Sure, there are generator sets that produce as much power as you need, of any type you want. Three-phase, 460V, 60 Hz, 400 Hz, whatever you want.

   If this is a hard-start load, your genset will have to be sized to accomodate the starting load, maybe with some voltage support in the form of power capacitors.

   Once you look into what a 3-phase genset of the size you need will cost you (capital cost of the unit, site work (you're going to need a pad for it), and costs to operate (fuel and maintenance)), the PG&E hookup will look like a real bargain at $18K.

   And FYI, the 3-phase service equipment and switchgear will not be cheap. You'll need them regardless of whether you're on the grid or a genset.

   Cliff

1. 
   coonass | Feb 11, 2010 11:34pm | #5

   After hurricane Gustaf the POCO brought in a generator that powered up the whole substation. About 40' long trailer.

   I think I would replace the electric motor with a diesel. Surplus Center has some for cheap.

   KK

4. 
   DanH | Feb 12, 2010 10:55pm | #6

   Sure it feasible. But how much do you suppose you'd pay for a 40KW 3-phase generator??

5. 
   junkhound | Feb 13, 2010 09:32am | #7

   Yep, my approach would be to yank one of the 100+ HP 4 cyl engines from a car in the back and put it in place of the 460 Vac motor. Take the engine from one of the cars on blocks in the front yard if you live in eastern TN

   Will you need to run 24/7? Would have suggested rotary phase converter and transformer till I saw you have a big whomping 100A service?

1. 
   Snort | Feb 13, 2010 09:43am | #8

   Art, what kind of motor would it take to crank a 100hp 3ph?

   We have a 3hp 3ph jointer, and made up a phase converter from a 10 hp 3ph w/ a 1/3hp washing machine motor as a starter...

   View Image

6. 
   junkhound | Feb 13, 2010 08:03pm | #9

   Interesting you ask that, as I have a 3 ph 100 HP 460V 1150 rpm motor sitting in the back just asking to be made into at rotary phase converter (would just use for 120/208 and 25 HP, big derating) Have not built the converter yet, another project for retirement??

   I figured I'd just use a series wound 1/2 hp dc motor -- let it get it up over 1200 rpm in 20-30 seconds, lotsa inertia on the rotor on that baby, 4" dia shaft even. Thought maybe a 3/4 HP 1750 1 phase 240 Vac motor may be able to get it to speed without burning out the start winding - or else rewind an old motor with heavier 2nd winding for capacitor run and let it run with high slip for 10 seconds to start.

1. 
   Snort | Feb 16, 2010 07:37pm | #11

   "I figured I'd just use a
   "I figured I'd just use a series wound 1/2 hp dc motor"

   Art, okay, series wound dc? What's cranking that? and why dc?... and although I could probably go to wikipedia about the series wound thing, your explanations are always so much cuter LOL

   Hey, the only way I am close to engineering is when my areonautical engineering student son calls to pick what's left of my brain about how he can keep the water out of his rental's basement. When I tell him to move to higher ground, it's just not enough of a challenge. We're going a step farther than French drains... new world Canadien drains, defying gravity!

   sorry about that... back to the phase converters Scotty...

7. 
   JohnCA07 | Feb 16, 2010 01:13pm | #10

   Thanks to everyone for your comments and suggestions.

   While I figured the generator wouldn't be inexpensive, I will only need to run this unit a few hours a week for now. With this little of usage I thought I might be able to save cost in this tight economy.

   I'll do my due diligence and price out the generator just to see where the cost comparison comes out at.

8. 
   junkhound | Feb 17, 2010 04:21am | #12

   A series wound dc motor wil go as fast as the load allows (e.g. unloaded it can blow itself apart)

   That out of the way, for spinning up a big inertial load, they are ideal IF you watch the speed, although for driving a big ac motor the windage/friction load is large enough to not run away.   At stall they will provide good torque, yet come up to speed. A small dc series wound does have enough torque to overcome the friction and windage losses.

   Your typical router is a series wound machine, on dc it will work even better than on ac.  Since a series wound dc motor works on both dc and ac, that is why they are often refered to as 'universal' motors.  aka - you could even use an old router for spin-up, esp if you use a speed control to ramp it up.

1. 
   Snort | Feb 17, 2010 06:22pm | #13

   I'm looking for an electrician named Tesla<G>

2. 
   plumber_bob | Feb 17, 2010 06:43pm | #14

   Yo! Junkhound,

   I'm peicing together some stuff to make a 3ph generator. I have 3 or 4 3ph 2horse motor, and one 5hp.

   I'm going to use a 19hp gas engine to power one or more.

   Can you tell me how to figure the size of running cap I need for them?

   Also do you have any concepts for engine speed control?

   Thanks

9. 
   junkhound | Feb 17, 2010 09:37pm | #15

   (I didn't sleep through motors class.)

   UH, if you did not sleep, you musta been on dope or lsd or sumtin' to still think series dc motor is self limiting at low loads..........

1. 
   DanH | Feb 23, 2010 09:24pm | #19

   Series motors are self-limiting because as the speed increases the current through the rotor is decreased due to induction, and, given the series configuration, the current through the field coil is likewise decreased.  Eventually the field coil current drops too low to sustain torque.

1. 
   junkhound | Feb 24, 2010 04:39am | #20

   FWIW, the only way I've seen series motors limit speed at low loads is when they get going so fast they throw the windings off the armature and literally self destruct. 

1. 
   DanH | Feb 24, 2010 06:14pm | #21

   How would a parallel motor be any different?  Remember, the parallel motor has less low-end torque for a given size, so it loves low loads.  And, as I said, the "theory" works out that parallel motors can run at infinite speed.

10. 
    plumber_bob | Feb 17, 2010 10:33pm | #16

    Junkhound,

    I may have mislead you. I'm wanting to use the motors as generators, for power outages, and such.

    I'm thinking that a 19hp engine can spin 2 motors fast enough to get them to 'light up'. The rpms are the same on both motors, so I think I can run them both at the same time. Plus I'm hoping that I'll also be able to run a 5hp gas engine that's being converted into an aircompressor, off of the 19hp engine.

    I'd like it to be a little power center of sorts.

    I have found a few articles about using 3 phase motors as generators but you have to have running caps, and the thing won't put out untill you get it slightly passed the standard rpms. Does this sound right?

    As for the caps, about all I found was to get 100mfd per hp, so a 5 hp motor would need 3, 500mfd caps to work. One between each leg, so that any two combinations have a cap in parallel with a load. Again does that sound right?

    Thanks dude for your help.

1. 
   junkhound | Feb 18, 2010 08:14am | #17

   P_bob

   I think you will be disappointed with any electrical results from what you are trying to do.

   An squirrel cage rotor  induction motor simply is not an efficient generator when run off-line and has very poor regulation - I'd not try using it to run any electronics or your TV, etc

   Per you specific query, here is a link

   http://www.redrok.com/cimtext.pdf

   That was the very first google hit searching "induction motor generator",  try googling the same phrase and you should get all the info you want. 

1. 
   plumber_bob | Feb 18, 2010 09:29am | #18

   Hey Junkhound!

   Thanks for that info, I did find a few more bits of info that will be useful.

   Most of the info I found, I had already been trough 2-3 times, so no real suprises there. My main goal would be to use this setup to run mainly lights. I have 2 generators that are store bought. One is a Honda EW171, it has enough adz to run my water heater. The other one is a Deville Bliss, (sp?). It can run most of my major appliances, but not all at once.

   Since you've mentioned the one from Harbor Freight, I've been thinking that if I build mine and make it look real nice, I may be able to sell it and buy one that I can mount to my tractor and then run the whole house from one generator.

   Also I have a nice filter for my electronic stuff. It will handle one PC, and the tv, +VCR.

   Anyway I'm just trying to avoid having to aquire several different caps to experiment with to find the right one.

   Thanks for your help dude!