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phase converter questions
I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph
dust collector. I connected them to a Phase-a-matic static phase converter; They start and run ok, but they do seem to draw a bit more current running on single phase than 3phase. I figured that the big grinder would act like a rotary phase converter for the dust collector, but I don't see any current in the third leg with a clamp on ampmeter. Input is L1 and L2. I measure L1:L3 208V L2:L3 224V Should I experiement with some run caps or just leave it alone? Another interesting fact is that the baldor grinder is rated 1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell mill and that motor is rated 4.6 amps. Is baldor guiltly of over rating like sears? chuck |
Is the rockwell mill three phase or single?
bob g. Charles A. Sherwood wrote: I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph dust collector. I connected them to a Phase-a-matic static phase converter; They start and run ok, but they do seem to draw a bit more current running on single phase than 3phase. I figured that the big grinder would act like a rotary phase converter for the dust collector, but I don't see any current in the third leg with a clamp on ampmeter. Input is L1 and L2. I measure L1:L3 208V L2:L3 224V Should I experiement with some run caps or just leave it alone? Another interesting fact is that the baldor grinder is rated 1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell mill and that motor is rated 4.6 amps. Is baldor guiltly of over rating like sears? chuck |
"Charles A. Sherwood" wrote in message ... I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph dust collector. I connected them to a Phase-a-matic static phase converter; They start and run ok, but they do seem to draw a bit more current running on single phase than 3phase. I figured that the big grinder would act like a rotary phase converter for the dust collector, but I don't see any current in the third leg with a clamp on ampmeter. Input is L1 and L2. I measure L1:L3 208V L2:L3 224V Should I experiement with some run caps or just leave it alone? Another interesting fact is that the baldor grinder is rated 1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell mill and that motor is rated 4.6 amps. Is baldor guiltly of over rating like sears? chuck |
With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase machine on single phase current. The third leg is only intergized for starting. After start-up the motor runs as a single phase machine with current through 2 of its 3 sets of windings. Bob Swinney "Charles A. Sherwood" wrote in message ... I recently bought a 1.5HP 3ph Baldor 10 inch grinder with 1/2HP 3Ph dust collector. I connected them to a Phase-a-matic static phase converter; They start and run ok, but they do seem to draw a bit more current running on single phase than 3phase. I figured that the big grinder would act like a rotary phase converter for the dust collector, but I don't see any current in the third leg with a clamp on ampmeter. Input is L1 and L2. I measure L1:L3 208V L2:L3 224V Should I experiement with some run caps or just leave it alone? Another interesting fact is that the baldor grinder is rated 1.5 HP but FL current is 2.5 amps. I have 1.5HP on my rockwell mill and that motor is rated 4.6 amps. Is baldor guiltly of over rating like sears? chuck |
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"Old Nick" wrote in message ... Why is a rotary phase convert better than a 3-phase alternator driven by a high-current single phase motor? First reason is complexity. Second is efficiency, I'd imagine, though I'm not an expert. RPCs seem complex and prone to all sorts of vagaries (with SPC even more so). Why not obtain high current 1 PH power, or several sources of 1 PH power, and run a motor that runs a 3-phase alternator? You think this is simpler than an RPC? I built an RPC from plans on the 'net a few weeks ago, and it was a *lot* simpler than I'd thought. I wouldn't want to bother with a generator setup unless I really had no other choice. Pete |
Pete sez:
"You think this is simpler than an RPC? I built an RPC from plans on the 'net a few weeks ago, and it was a *lot* simpler than I thought. I wouldn't want to bother with a generator setup unless I really had no other choice." Right on, Pete! Also, it is a lot easier to find surplus 3-phase motors for conversion to RPCs than it is to find alternators. Alternators should be driven at a constant speed, regardless of load - not an easy thing. Alternators need a separate source of direct current for magnetic excitation - also adding to the complexity. Granted, alternators can be "permanent magnet", eliminating the need for excitation power, but those types, AFAIK, are not readily available or cost efficient in smaller sizes. The only example I can think of might be a welding/AC supply "generator" that outputs 3-phase 220v AC. Again, not nearly as economical as a RPC. IMO, the only justification for an alternator would be if there was no commercial power available. Bob Swinney "Pete Bergstrom" wrote in message . .. "Old Nick" wrote in message ... Why is a rotary phase convert better than a 3-phase alternator driven by a high-current single phase motor? First reason is complexity. Second is efficiency, I'd imagine, though I'm not an expert. RPCs seem complex and prone to all sorts of vagaries (with SPC even more so). Why not obtain high current 1 PH power, or several sources of 1 PH power, and run a motor that runs a 3-phase alternator? Pete |
"Robert Swinney" wrote in message ... Pete sez: "You think this is simpler than an RPC? I built an RPC from plans on the 'net a few weeks ago, and it was a *lot* simpler than I thought. I wouldn't want to bother with a generator setup unless I really had no other choice." Right on, Pete! Also, it is a lot easier to find surplus 3-phase motors for conversion to RPCs than it is to find alternators. Alternators should be In addition to the RPC plan I used (http://www.frugalmachinist.com/rpc.html), I'll also recommend Bob's article in Home Shop Machinist Nov-Dec 2001 "Induction Motors and Rotary Phase Converters". I bought the back issue as part of my research. I had originally planned to buy a VFD, but since my mill also has a coolant pump I ended up building the RPC to power it. |
The Baldor is rated at 1.5 hp, but unless you are using it the motor
is not going to draw much current. The better the motor the less current it will draw. Well if you do the math 2.5amps @ 240V 3 ph is 2.5*240*1.7 = 1000 watts. No way is that 1.5HP. |
With a static phase converter, zero current in the third leg is normal
(after the brief starting interval) when you are running a 3 phase machine on single phase current. The third leg is only intergized for starting. But in this case I have two motors in parallel. The big 1.5HP grinder motor and the little 1/2 HP blower. The big grinder motor is pretty much unloaded and the the blower motor which is always loaded because it is moving lots of air. I expected to see some current in the third leg but I don't see any. chuck |
Why is a rotary phase convert better than a 3-phase alternator driven
by a high-current single phase motor? Its cheaper, simpler, and smaller. But I still think the alternator will generate more balanced 3ph power. |
conversion to RPCs than it is to find alternators. Alternators should be
driven at a constant speed, regardless of load - not an easy thing. Not all the hard. There are governors on industrial engines that do it well. Even the consumer quality generators do a pretty decent job of it. Alternators need a separate source of direct current for magnetic excitation - also adding to the complexity. Modern brushless alternators have the excitor built in and will be self starting and self exciting. Some require an external regulator which uses a tiny amount of generated AC to power the field. For example the field on my 15KW unit is 30VDC at 1 amp. This tiny control voltage is produced by the bassler regulator which is powered by the alternator itself. |
In article , Old Nick says...
RPCs seem complex and prone to all sorts of vagaries You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg Your idea of using a large single phase motor to power an excited field 3~ alternator is in principle the best way to do this. However because hardly anyone ever actually purchases a 3~ alternator in the 5 hp range, and likewise 5 hp single phase motors, the trouble is that those two things are incredibly expensive and never available on the surplus market. 5 to 10 hp three phase motors on the other hand are literally given away for scrap value on a regular basis. Likewise the small 1/4 hp pony motors to start the thing. Folks build what they can afford, and what works. If you advocate the more correct design, be prepared to put your wallet into the breech to implement it. At the end of the day, nobody will be able to tell the difference between the power on your wires, and the power on my wires. Your wires will wind up costing well over $1K. Mine are under ten bucks. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Your idea of using a large single phase motor to power an excited field 3~ alternator is in principle the best way to do this. However because hardly anyone ever actually purchases a 3~ alternator in the 5 hp range, and likewise 5 hp single phase motors, the trouble is that those two things are incredibly expensive and never available on the surplus market. 5 to 10 hp three phase motors on the other hand are literally given away for scrap value on a regular basis. Likewise the small 1/4 hp pony motors to start the thing. Folks build what they can afford, and what works. If you advocate the more correct design, be prepared to put your wallet into the breech to implement it. At the end of the day, nobody will be able to tell the difference between the power on your wires, and the power on my wires. Your wires will wind up costing well over $1K. Mine are under ten bucks. I assume you are refering to me because I proposed the motor driving alternator design a while back. (but you quoted someone else) I have looked for surplus motors to build a phase converter but frankly I have not found the oasis where they are available for cheap. The shipping costs are usually the killer. One of the reasons I proposed building a motor alternator setup is exactly what you quote above. I already have the alternator and a 5HP motor to drive it. So to me it is cheap. I started experimenting with a static phase converter because I found a used one and a couple people here stated it would be adequate for my needs. So far it seems to be working; but running a 3ph motor on 2 windings rubs me the wrong way; Especially when the run current in those two windings is higher than the full load current spec of the motor. Someday I will build that motor alternater setup and experiment with it too. But for now, I got lots of projects .. chuck |
In article , Charles A. Sherwood says...
I assume you are refering to me because I proposed the motor driving alternator design a while back. (but you quoted someone else) My comments were specific to Nick who proposed an *electrically* driven alternator to create a three phase supply, instead of a rotary converter. I have looked for surplus motors to build a phase converter but frankly I have not found the oasis where they are available for cheap. The shipping costs are usually the killer. One of the reasons I proposed building a motor alternator setup is exactly what you quote above. I already have the alternator and a 5HP motor to drive it. So to me it is cheap. Obviously in your case the 'works well and is cheap' approach to life says you should use what you have available. I would do the same thing if I had a prime mover available, and no other easy way to get an idler motor. I started experimenting with a static phase converter because I found a used one and a couple people here stated it would be adequate for my needs. So far it seems to be working; but running a 3ph motor on 2 windings rubs me the wrong way; Especially when the run current in those two windings is higher than the full load current spec of the motor. Be aware that not all of that is 'real' power. Do see how much it really is consuming, you need to check the phase angle or have a true rms wattmeter available. It might not be as much as you think from an ampclamp check. Someday I will build that motor alternater setup and experiment with it too. But for now, I got lots of projects .. I understand that! I think I'm in the same boat as you on this. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
"Charles A. Sherwood" wrote in message ... I have looked for surplus motors to build a phase converter but frankly I have not found the oasis where they are available for cheap. The shipping costs are usually the killer. If you're in the Twin Cities (or nearby), Minnesota, I'll tell you where to find a surplus motor. I got a 3HP GE motor for $30 (I countered a $50 original price, figuring that $10/hp was fair). It's running very nicely in my garage. The surplus store near my house (Axman) has 5HP motors for $200+, but they're NOS rather than slightly used. Pete |
Ever heard of a motor-generator where both functions were incorporated
onto one armature? Such things exist. A rotary phase converter is sort of the same thing. It'll give you good, real, three phase power, unlike a static. It can use a few caps to correct for power factor but is more efficient of weight and materials than a separate motor driving a generator. Seems like perhaps the old Lincoln DC welding supplies may have been built this way (don't hold me to this). rhg Old Nick wrote: On 24 Aug 2004 19:25:25 GMT, (Charles A. Sherwood) vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email PMFJI Why is a rotary phase convert better than a 3-phase alternator driven by a high-current single phase motor? RPCs seem complex and prone to all sorts of vagaries (with SPC even more so). Why not obtain high current 1 PH power, or several sources of 1 PH power, and run a motor that runs a 3-phase alternator? ************************************************** *** Marriage. Where two people decide to get together so that neither of them can do what they want to because of the other one. |
That's the way I understood your description in the first place and when
you said no current in the third leg, I figured I'd read it wrong. I use a 2hp idler to run a 1/2 hp on an old lathe and there is current in the third leg. If there were no current in the third leg, you couldn't start a three phase motor off a rotary converter. BTW, using the old rope start rotary converter, if you started the converter in the wrong direction (who could be absent minded enough to do that?) The load would also run in the wrong direction. The load certainly found something to use in that third leg. bob g. Charles A. Sherwood wrote: With a static phase converter, zero current in the third leg is normal (after the brief starting interval) when you are running a 3 phase machine on single phase current. The third leg is only intergized for starting. But in this case I have two motors in parallel. The big 1.5HP grinder motor and the little 1/2 HP blower. The big grinder motor is pretty much unloaded and the the blower motor which is always loaded because it is moving lots of air. I expected to see some current in the third leg but I don't see any. chuck |
Source of 3 ph alternator and price?
bob g. Charles A. Sherwood wrote: conversion to RPCs than it is to find alternators. Alternators should be driven at a constant speed, regardless of load - not an easy thing. Not all the hard. There are governors on industrial engines that do it well. Even the consumer quality generators do a pretty decent job of it. Alternators need a separate source of direct current for magnetic excitation - also adding to the complexity. Modern brushless alternators have the excitor built in and will be self starting and self exciting. Some require an external regulator which uses a tiny amount of generated AC to power the field. For example the field on my 15KW unit is 30VDC at 1 amp. This tiny control voltage is produced by the bassler regulator which is powered by the alternator itself. |
Maybe my imagination but motors running under load on a static converter
seem to vibrate. My imagination? Anybody else? bob g. Charles A. Sherwood wrote: Your idea of using a large single phase motor to power an excited field 3~ alternator is in principle the best way to do this. However because hardly anyone ever actually purchases a 3~ alternator in the 5 hp range, and likewise 5 hp single phase motors, the trouble is that those two things are incredibly expensive and never available on the surplus market. 5 to 10 hp three phase motors on the other hand are literally given away for scrap value on a regular basis. Likewise the small 1/4 hp pony motors to start the thing. Folks build what they can afford, and what works. If you advocate the more correct design, be prepared to put your wallet into the breech to implement it. At the end of the day, nobody will be able to tell the difference between the power on your wires, and the power on my wires. Your wires will wind up costing well over $1K. Mine are under ten bucks. I assume you are refering to me because I proposed the motor driving alternator design a while back. (but you quoted someone else) I have looked for surplus motors to build a phase converter but frankly I have not found the oasis where they are available for cheap. The shipping costs are usually the killer. One of the reasons I proposed building a motor alternator setup is exactly what you quote above. I already have the alternator and a 5HP motor to drive it. So to me it is cheap. I started experimenting with a static phase converter because I found a used one and a couple people here stated it would be adequate for my needs. So far it seems to be working; but running a 3ph motor on 2 windings rubs me the wrong way; Especially when the run current in those two windings is higher than the full load current spec of the motor. Someday I will build that motor alternater setup and experiment with it too. But for now, I got lots of projects .. chuck |
Are the motors truly in parallel? As in; all three legs of one motor
connected to all three legs of the other motor? If so, you should see some 3rd leg current between the motors. Is there a separate switch on the 1/2 HP motor? If they are in parallel you should be able to switch on and start the 1/2 HP motor *after* the 1.5 HP motor is up to speed. The larger motor will be generating some unbalanced 3-phase power by transformer action. It is acting like an idler motor in a rotary phase converter configuration. Bob Swinney "Charles A. Sherwood" wrote in message ... With a static phase converter, zero current in the third leg is normal (after the brief starting interval) when you are running a 3 phase machine on single phase current. The third leg is only intergized for starting. But in this case I have two motors in parallel. The big 1.5HP grinder motor and the little 1/2 HP blower. The big grinder motor is pretty much unloaded and the the blower motor which is always loaded because it is moving lots of air. I expected to see some current in the third leg but I don't see any. chuck |
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On 25 Aug 2004 13:18:31 -0700, jim rozen
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email In article , Old Nick says... RPCs seem complex and prone to all sorts of vagaries You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. Ahah! OK. So simply throw grunt at the thing and avoid the fiddly bits? That was something I had seen, but not understood (absorbed into my soggy brain) the reason for, I think G I agree about the lack of cheap/free 3PH alternators in the lower ranges. They usually have a motor (fuel) attached. I did have the opportunity yo buy one reasonably cheap. Did it work???? shrug. I never went there, because I was not sure if my idea was the right way to go. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he snip Your wires will wind up costing well over $1K. Mine are under ten bucks. Jim ************************************************** *** I have decided that I should not be offended by anybody's behaviour but my own......the theory's good, anyway. |
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In article , Robert Galloway says...
Ever heard of a motor-generator where both functions were incorporated onto one armature? Such things exist. Ah, the classic "dynamotor" of ww2 fame. My first radio had the B+ supplied by one of those - with the 'primary' run off a train transformer! I wasn't sure if it was actually going to work, it seemed like a whacky idea with this little thing screaming away at speed. Then I touched the output terminals and got one heck of a shock. Yep, it works! Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
On 25 Aug 2004 15:01:18 -0700, jim rozen
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email In article , Charles A. Sherwood says... I assume you are refering to me because I proposed the motor driving alternator design a while back. (but you quoted someone else) My comments were specific to Nick who proposed an *electrically* driven alternator to create a three phase supply, instead of a rotary converter. I win! I win! GG Obviously in your case the 'works well and is cheap' approach to life says you should use what you have available. I would do the same thing if I had a prime mover available, and no other easy way to get an idler motor. AHereas I have to admit I do _not_ have the stuff available. Someday I will build that motor alternater setup and experiment with it too. But for now, I got lots of projects .. I understand that! I think I'm in the same boat as you on this. Yes. My question also was not rhetorical, but is certainly theoretical at present......some day...(sigh) :- ************************************************** *** I have decided that I should not be offended by anybody's behaviour but my own......the theory's good, anyway. |
On 25 Aug 2004 13:18:31 -0700, jim rozen
vaguely proposed a theory .......and in reply I say!: remove ns from my header address to reply via email I did some reading. I remember now what my reservation was. While you can throw plenty into the RPC, they are not good at allowing the driven motor to produce full power. I am wondering what happens to welders etc. Welding is one area where I see real bargains for very powerful MIGs etc. I have seen a MIG that gets 350A from 240 volt, but it was a new model, brand new with a VERy "new" price! You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. ************************************************** *** I have decided that I should not be offended by anybody's behaviour but my own......the theory's good, anyway. |
On 25 Aug 2004 13:18:31 -0700, jim rozen
wrote: You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting to be turned into a RPC. Pony motors Ive got by the score. Gunner, who was given a Hardinge DV-59 today. Disassembled but complete....sigh Anyone need any Federal air gauges? Got about a dozen of them G Schaublin Lever action tailstock with built in collet holder in the nose of the ram? Scored today.... VBG) "In my humble opinion, the petty carping levied against Bush by the Democrats proves again, it is better to have your eye plucked out by an eagle than to be nibbled to death by ducks." - Norman Liebmann |
In article ,
Robert Galloway wrote: Maybe my imagination but motors running under load on a static converter seem to vibrate. My imagination? Anybody else? Reasonable enough -- as you really running it purely from single phase after it spins up to speed. The available torque goes through zero twice per cycle (that is, at 1/120 of a second intervals in the USA). Real three phase -- or synthesized three phase from either a rotary converter or a VFD does not, as when the torque from one phase is approaching zero, another phase is approaching peak, and a third is just past peak. People who replace a three phase motor on a surface grinder with a single phase motor notice a difference (degradation) in the resulting finish. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
In article ,
Old Nick wrote: On 25 Aug 2004 13:18:31 -0700, jim rozen vaguely proposed a theory ......and in reply I say!: remove ns from my header address to reply via email I did some reading. I remember now what my reservation was. While you can throw plenty into the RPC, they are not good at allowing the driven motor to produce full power. This is a problem with a "static" phase converter, but for a reasonably sized rotary converter -- especially one which has been tuned and balanced by tweaking capacitance on the windings -- you should be able to get full power out of the driven motor. I am wondering what happens to welders etc. Welding is one area where I see real bargains for very powerful MIGs etc. I have seen a MIG that gets 350A from 240 volt, but it was a new model, brand new with a VERy "new" price! No experience with this, but I can't see any serious reason to expect problems running it from a RPC. Here, I am not sure what will happen from a VFD -- given that you have a switching regulator synthesizing the output of the VFD, and possibly another one converting the input to the welder into DC, so they might interfere with each other. (I would also expect similar problems running a typical computer from a VFD, too.) But welders (and computers) don't need the variable frequency, so I see little reason for using a VFD for this. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
In article ,
Gunner wrote: On 25 Aug 2004 13:18:31 -0700, jim rozen wrote: You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting to be turned into a RPC. Pony motors Ive got by the score. *What* wiring diagram? Switch power to two windings of the idler motor, and to the single-phase pony motor to spin it up, then switch off the pony after it has thrown its belt. (Based on what I remember of Jim's setup.) Wire the three windings of the idler to the three inputs of the target tool. You just need a larger idler than with a well tuned one, and since you are not tuning for the power factor, you may blow circuit breakers more often than you would like, depending on the size of the idler motor. You also might have problems running electronics from the generated power if it is across the wild (generated) leg. If you can be sure that all electronics are connected to the primary two input lines from the power company, you should be fine. Note, also, that this has *no* safety circuit to disconnect the idler when the power fails, so when it comes back on, the motor will sit there humming until it burns up, or trips the breaker. So *always* turn it off when you walk away. If *I* were going for a rotary, I would want the safety circuits, self starting, and properly tuned to reduce the reactive current drawn from the wall. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
In article ,
jim rozen wrote: In article , Robert Galloway says... Ever heard of a motor-generator where both functions were incorporated onto one armature? Such things exist. Ah, the classic "dynamotor" of ww2 fame. Yep. Somewhere around, I have something even closer to what is being discussed. It is a DC input (28 VDC) 120 V 400 Hz three-phase output (to drive old aircraft instruments). It screams, but it works. Enjoy, DoN. -- Email: | Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
Hey Gunner,
I was going to use a 20HP motor too. I kicked it into gear with a pony motor, and it was drawing 80 plus amps. I've settled for a 7-1/2HP, which is still drawing 20 or so. Take care. Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXX On Thu, 26 Aug 2004 03:52:18 GMT, Gunner wrote: On 25 Aug 2004 13:18:31 -0700, jim rozen wrote: You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting to be turned into a RPC. Pony motors Ive got by the score. Gunner, who was given a Hardinge DV-59 today. Disassembled but complete....sigh Anyone need any Federal air gauges? Got about a dozen of them G Schaublin Lever action tailstock with built in collet holder in the nose of the ram? Scored today.... VBG) "In my humble opinion, the petty carping levied against Bush by the Democrats proves again, it is better to have your eye plucked out by an eagle than to be nibbled to death by ducks." - Norman Liebmann |
Gunner sez:
"Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting to be turned into a RPC. Pony motors Ive got by the score." Wiring, schmiring, Gunner! Get after it, dude. I think it could be started with about 1400 microFarad of motor start caps, but that wouldn't be code, now would it? Bob Swinney "Gunner" wrote in message ... On 25 Aug 2004 13:18:31 -0700, jim rozen wrote: You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg Gunner, who was given a Hardinge DV-59 today. Disassembled but complete....sigh Anyone need any Federal air gauges? Got about a dozen of them G Schaublin Lever action tailstock with built in collet holder in the nose of the ram? Scored today.... VBG) "In my humble opinion, the petty carping levied against Bush by the Democrats proves again, it is better to have your eye plucked out by an eagle than to be nibbled to death by ducks." - Norman Liebmann |
Not to worry, Brian. That 20 amps you see with a clamp on meter is highly
reactive - meaning the real draw (voltage and current in phase) is much less. Even a perfectly "balanced" 7-1/2 HP rotary will show 20 amps, or so, reactive current in the 3rd leg when running unloaded. It's the nature of the beast, so to speak. Same as with the 80 amps you saw on the 20 HP motor - it was largely reactive current and had little bad effect, other than heating up the wiring if you didn't take that into account. Bob Swinney "Brian Lawson" wrote in message ... Hey Gunner, I was going to use a 20HP motor too. I kicked it into gear with a pony motor, and it was drawing 80 plus amps. I've settled for a 7-1/2HP, which is still drawing 20 or so. Take care. Brian Lawson, Bothwell, Ontario. XXXXXXXXXXXXXXXXXXXX On Thu, 26 Aug 2004 03:52:18 GMT, Gunner wrote: On 25 Aug 2004 13:18:31 -0700, jim rozen wrote: You have to understand that most of the designs you see are highly optimized. Using an oversized idler motor that is started with a pony motor means you don't need any power factor correction, no balancing, and no starting circuitry. It gets built for free, runs forever, and never has to be thought about. Example is the patented "jim's stone age converter" seen he http://www.metalworking.com/DropBox/_2000_retired_files/Conv.jpg Got a wiring diagram? Ive got a 20hp 3600rpm Western Electric waiting to be turned into a RPC. Pony motors Ive got by the score. Gunner, who was given a Hardinge DV-59 today. Disassembled but complete....sigh Anyone need any Federal air gauges? Got about a dozen of them G Schaublin Lever action tailstock with built in collet holder in the nose of the ram? Scored today.... VBG) "In my humble opinion, the petty carping levied against Bush by the Democrats proves again, it is better to have your eye plucked out by an eagle than to be nibbled to death by ducks." - Norman Liebmann |
As did the transmitters of early 2-way radios. Ever wonder how they got
400+ volts of B-plus from a 6 volt car battery? Dynamotor that came on with mash-to-talk. Bob Swinney "jim rozen" wrote in message ... In article , Robert Galloway says... Ever heard of a motor-generator where both functions were incorporated onto one armature? Such things exist. Ah, the classic "dynamotor" of ww2 fame. My first radio had the B+ supplied by one of those - with the 'primary' run off a train transformer! I wasn't sure if it was actually going to work, it seemed like a whacky idea with this little thing screaming away at speed. Then I touched the output terminals and got one heck of a shock. Yep, it works! Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Are the motors truly in parallel? As in; all three legs of one motor
connected to all three legs of the other motor? If so, you should see some They are both on the same contactor and start at the same time. However they are connected together before the overload controls. One contactor suppling power to seperate "heaters" for each motor. The third wire of the static converter connects to the third wire of the motors through the heaters. Seems like the logical way to wire it (at least to me). I could connect the third legs together before the heaters, but I really don't think that would make any difference. I see no current in the third leg with a clamp on ampmeter after the motors have started. The voltage in the third leg is 208 and 224 with respect to the other two legs. I guess there is no current because the voltage is low. 3rd leg current between the motors. Is there a separate switch on the 1/2 HP motor? If they are in parallel you should be able to switch on and start the 1/2 HP motor *after* the 1.5 HP motor is up to speed. Probably could, but the motors are hard wired together. |
Source of 3 ph alternator and price?
I found mine in the newspaper. I think he got them at an auction when an importer was scrapping a bunch of stuff. chuck |
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