I am a hobby machinist and have a Series 1 Bridgeport.Yesterday, I toasted my rotary phase converter. Before I spend $500 on a new one, I'd like to look at the possibility of replacing the Bridgeport three phase motors with single phase 220v motors.Has anybody done this?
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Single Phase Bridgeport 1
- Thread starter swall
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I've seen it done but don't know how it was accomplished.
I was going to purchase a surplus Bridgeport from our company but couldn't get the 3 Phase power needed. I'm only 800' away from a power company source.
You might post your question in the "Electric Motors & Controls Engineering Forum" for answer.
I was going to purchase a surplus Bridgeport from our company but couldn't get the 3 Phase power needed. I'm only 800' away from a power company source.
You might post your question in the "Electric Motors & Controls Engineering Forum" for answer.
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Uncle Syd--I had the option of getting 3 phase from the power company, as I am only 80' away from a 3 phase line.But it was cost prohibitive.They wanted $1000 to run the lines to my shop. Then they told me I would not be allowed to retain single phase service, so more costs would have been incurred for inside re-wiring and three phase panels. And finally, three phase service costs 17% more than single phase.
swall
That is essentially the reason I didn't go that route, cost.
They made no mention of only one service as my shop is on a separate service from the house. My electrical engineering buddies at work talked about the cheaper operation on 3-Phase though I'm thinking a 17% surcharge would mitigate any savings.
I think I had better see if I can find out how the drive for the Bridgeport was converted.
Does Bridgeport make a single phase drive?
That is essentially the reason I didn't go that route, cost.
They made no mention of only one service as my shop is on a separate service from the house. My electrical engineering buddies at work talked about the cheaper operation on 3-Phase though I'm thinking a 17% surcharge would mitigate any savings.
I think I had better see if I can find out how the drive for the Bridgeport was converted.
Does Bridgeport make a single phase drive?
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- #7
Griffy--the one I toasted was my home made unit.Haven't done the forensics yet, so I don't know what caused the idler motor to go up in smoke.Happened on start-up.Got a spark when I hit the momentary start button.I released it and the idler motor was running, but growling bad.A moment later the motor smoked and then I killed the power. The unit had been working pretty good up until then. I built it using a 5hp idler motor with 75mfd (oil filled can units) on the L1-L3 leg and 50mfd on the L2-L3 leg.I used (4)150 mfd ac electrolytics as my momentary starter using the aforementioned push button switch. I had less than $80 in it.
I have not seen it done but I think you would need a single phase motor, starter and switch. You would also need to find the proper frame motor or a conversion adapter. Grainger would have the parts but you might spend more on the conversion than what it is worth. Hear is a static phase converter for $138.
good luck
good luck
ornerynorsk
Industrial
A static converter should work fine on a motor that small. A rotary is very easy to build out of an old 3 phase motor also.
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- #10
There is a gentleman on EBay that has plans to build a rotary phase converter for low dollars. If you are handy, this maybe the way to go. If you do an EBay search for "phase plans" I'm sure you will find them. The unit looked good from what I could see. I like running 3 phase power on any machine tools. With single phase you lose the ability to reverse the motor. I do allot of power tapping. Actually there a several guys selling plans for rotary converters, about 5 –10 bucks. If your motor is still good the odds are you can build a new converter for under a hundred bucks. Just a suggestion.
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tgc99--you raise a good point about being able to reverse a 3phase motor.I hadn't thought about that! Since a 3 phase Bridgeport is fully reversible, a single phase conversion would throw a monkey wrench into the works, wouldn't it? BTW, I found the trouble with my home made converter.One of my 150mfd electrolytic capacitors on my momentary start circuit had shorted.This caused L3 to be connected to L1 and the idler motor was trying to start on single phase.The only harm to the motor seems to be that the overheat condition melted the grease out of the rear bearing. I used a pull rope to spin it up and then hit the power switch.It seemed to run OK, albeit noisy due to the bearing.The capacitor is only a $4 item at the surplus store. A cheap fix. A new bearing, if it comes to that is about $15.
A tester for capacitors is a must have item for anyone running phase convertors. You absolutely WILL need it at some point.
Bridgeports and similar run just fine on simple static phase convertors. I have over 8 years on one convertor with no problems. I couldn't begin to guess how many reversals I made while tapping holes.
Rotary convertors come into their own when dealing with higher inertia, harder starting loads such as lathes with significant chucks and such.
Some high end rotary convertors have banks of capacitors that fire through a contactor for extremely high torque requirements. Expect the contacts to require replacement on a regular basis. Keep a spare set in the shop.
Also, keep a suitable fire extinguisher handy and make sure the location of the convertor will not prevent access to it's disconnect in the event of a fire. Those capacitors really stink when they burn....![[wink]](/data/assets/smilies/wink.gif "[wink] [wink]")
My 2c
Bridgeports and similar run just fine on simple static phase convertors. I have over 8 years on one convertor with no problems. I couldn't begin to guess how many reversals I made while tapping holes.
Rotary convertors come into their own when dealing with higher inertia, harder starting loads such as lathes with significant chucks and such.
Some high end rotary convertors have banks of capacitors that fire through a contactor for extremely high torque requirements. Expect the contacts to require replacement on a regular basis. Keep a spare set in the shop.
Also, keep a suitable fire extinguisher handy and make sure the location of the convertor will not prevent access to it's disconnect in the event of a fire. Those capacitors really stink when they burn....
My 2c- Thread starter
- #15
Griffy--Yes, I had been using a pull rope until I got my capacitance self starter circuit to work. I also had been thinking of the small single phase motor as a starter and even bought one.But once I got the capacitance self starter to to work, I never went ahead with the motor idea.I am back to the rope start for now, until I get some more capicitors for the self starter circuit.
tgmcg
Mechanical
- Feb 21, 2004
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I'm running a 3HP/3ph spindle motor off the clothes dryer outlet by using a Yaskawa inverter mounted inside the CNC controller enclosure. Installed it myself. The inverter approach is terrific in that it also provides continuously variable speed control which together with the mill's built-in 2-speed gearbox provides great speed range adjustability. Inverter also provides soft start, overload protection, and braking.
The only proviso is that the motor should be wound with "inverter grade" wire, otherwise motor service life may be reduced. I wound up having to rewind a 30 yr old motor after 18 months time on the inverter. Not sure if it was the inverter or simply motor age that finally killed the motor.
What will a single phase motor do for you that's better than what the inverter provides?
The only proviso is that the motor should be wound with "inverter grade" wire, otherwise motor service life may be reduced. I wound up having to rewind a 30 yr old motor after 18 months time on the inverter. Not sure if it was the inverter or simply motor age that finally killed the motor.
What will a single phase motor do for you that's better than what the inverter provides?
Swall,
I have done it both ways, i.e. static and rotary. I toasted one static after years of service and have been using another static for years with no problems. The static phase converter (rated for starting 5-7.5hp)starts a 5hp lathe which serves as an idler and all the other 3 Phase machines are wired in parallel via a separate circuit breaker box.
Kapitan's ebay suggestion sounds very reasonable but you can likely get by even cheaper if you can invest the time by reworking your rotary: get a used 1/2hp single phase motor and mechanically link it to your 3 Phase idler motor via a v-belt. Wire a momentary switch to the single phase motor. Wire L1 & L2 single phase input to your 3 phase idler via a circuit breaker switch. Leave your 220V single phase input switch to the 3 phase idler motor OFF while you momentarily start the single phase motor which in turn will spin the 3 phase motor. Once the 3 phase is spinning at 60% syncrhonous speed (you can hear it ramp-up), switch ON the 220V L1, L2 input to the 3 phase idler which will now run on single phase but will act like a generator and put out three phase power. L3 obviously only exists downstream of your idler. This is not as simple as your capacitor fix but I believe it is more robust and safer.
Jesus is THE life,
Leonard
I have done it both ways, i.e. static and rotary. I toasted one static after years of service and have been using another static for years with no problems. The static phase converter (rated for starting 5-7.5hp)starts a 5hp lathe which serves as an idler and all the other 3 Phase machines are wired in parallel via a separate circuit breaker box.
Kapitan's ebay suggestion sounds very reasonable but you can likely get by even cheaper if you can invest the time by reworking your rotary: get a used 1/2hp single phase motor and mechanically link it to your 3 Phase idler motor via a v-belt. Wire a momentary switch to the single phase motor. Wire L1 & L2 single phase input to your 3 phase idler via a circuit breaker switch. Leave your 220V single phase input switch to the 3 phase idler motor OFF while you momentarily start the single phase motor which in turn will spin the 3 phase motor. Once the 3 phase is spinning at 60% syncrhonous speed (you can hear it ramp-up), switch ON the 220V L1, L2 input to the 3 phase idler which will now run on single phase but will act like a generator and put out three phase power. L3 obviously only exists downstream of your idler. This is not as simple as your capacitor fix but I believe it is more robust and safer.
Jesus is THE life,
Leonard
- Thread starter
- #18
Thanks, metman. Currently, I am up and running again with my capacitor based system.But the more I think about it, the more I like the motor starter approach.I will keep this idea in my back pocket, as I already have a suitable single phase motor and a box of pulleys.
I installed a single phase motor on my series 1. The orignal motor has a long shaft, the replacement 2hp 56c frame motor didn't. So I had to make an dished adapter plate to sink the motor down into the housing, to line up the belts. I lost some of the belt adjustment by doing this but it is workable. The 5/8" shaft needed a bushing to fit the orignal pulley's 3/4" bore. Been running trouble free for a few years now.
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