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# Thread: 3PH. Variable speed

1. Aluminum
Join Date
Nov 2001
Location
Carthage,Mo.USA
Posts
184
Ok,I've got my 5hp. 3ph. motor running on 220 1ph.,using capacitors in conjunction with a push button starter and a 3ph. relay. Starts fine! Output is ok on three wires from the 5hp. Now how do I control the speed of my mill motor,a 1hp.3ph. 1750rpm. ? Do they make a 3ph Variac? Need some suggestions!

2. Senior Member
Join Date
Apr 2001
Location
Jasper,MO U.S.A.
Posts
291
George,

Sounds like you built a dandy converter, but I have to break some news to you. You are stuck at 1750 rpm, motor speed with an induction motor is determined by the frequency of the electricity feeding it. Theorectically this 1750 rpm motor will sync. in at 1800 rpm, but there is a little bit of stator lag.

Tis the reason that VFD's are getting so popular, variable frequency drive, the frequency can be changed. We use a bunch of them at work, they are replacing the rotary frequency inverters which are needed to increase the speed of a 3ph motor. We run a lot of 18,000 rpm spindle motors, fastest a 3ph motor can be made to run on 60cycle current is 3,600 or 3450 rpm.

HS

3. Aluminum
Join Date
Nov 2001
Location
Carthage,Mo.USA
Posts
184
Originally posted by halfnut:
George,

Sounds like you built a dandy converter, but I have to break some news to you. You are stuck at 1750 rpm, motor speed with an induction motor is determined by the frequency of the electricity feeding it. Theorectically this 1750 rpm motor will sync. in at 1800 rpm, but there is a little bit of stator lag.

Tis the reason that VFD's are getting so popular, variable frequency drive, the frequency can be changed. We use a bunch of them at work, they are replacing the rotary frequency inverters which are needed to increase the speed of a 3ph motor. We run a lot of 18,000 rpm spindle motors, fastest a 3ph motor can be made to run on 60cycle current is 3,600 or 3450 rpm.

HS
Thanks 1/2Nut!! Looks like back to the drawing board.So much for pulling my hair out,there wasn't much hair left anyway! I've asked around about speed controls,but haven't had any luck so far. I've got a variable pitch pulley that I'll use as soon as I figure out a mounting system and belt tightener mechanism. Fortuneatly I'm in no rush! Things turn up in weird places,if you're not in a hurry. George

4. Senior Member
Join Date
Apr 2001
Location
Jasper,MO U.S.A.
Posts
291
George,

What are you buiding, I'm going to have to come down and visit you one of these days. Got your address in the phone book, Esther road, where ever that is. Between 9th and 10th roads I presume, or is that 90th and 100th. I love these 911 addresses, I'd rather turn south at the red barn and back east at the big tree. I love giving people directions, then I'll tell them a more proper way.

Sounds like you are putting a drive on some sort of an older milling machine.

5. George. Read down the "Phase Converters and VFD" threads until you find VFD's for newbies. It will tell you all about how to vary the RPM of three phase motors.

If you can't find it, change your preferences from the home page so you can see back posting a year or more.

6. Aluminum
Join Date
Nov 2001
Location
Carthage,Mo.USA
Posts
184
Originally posted by halfnut:
George,

What are you buiding, I'm going to have to come down and visit you one of these days. Got your address in the phone book, Esther road, where ever that is. Between 9th and 10th roads I presume, or is that 90th and 100th. I love these 911 addresses, I'd rather turn south at the red barn and back east at the big tree. I love giving people directions, then I'll tell them a more proper way.

Sounds like you are putting a drive on some sort of an older milling machine.
1/2 Nut,I'm playing! When I figure out the VFD,I'd like to replace the motor on my Jet Mill/Drill with a 3ph motor with a means of adjusting the speed without shifting belts. Also two of my neighbors have antique lathes that we will probably rework the motors on.
Co.Rd 90 is about 400ft down the hill East of out yellow mailbox. We're North of Center Creek. Yup,South of Elm Rd. We're home every day,almost all the time,except when we're gone,so call first.
Forrest,I've read that,it didn't sink into the gray matter! I appreciate the help and information everyone gives freely on these pages!!!!! You're never too old to learn new or old tricks! No one I know of has had the pleasure of trying every angle to do something! My wife has come up with great ideas to some of my mechanical problems and she HATES machinery! Thanks George

7. Senior Member
Join Date
Apr 2001
Location
Jasper,MO U.S.A.
Posts
291
George,

I can find you from those directions, I've travelled all about this area as a kid with my dad. His name is Charles Sprenkle, he artificially bred cows, I've been in most barns in the country, but that was a few years ago.

There are several places selling these VFD's at reasonable prices, I might have one or two of them bookmarked. My Roundtower mill is a step pulley machine, it would be nice to have a VFD on it. One great thing about this step pulley machine is that the belts last a long time, variable speed machines at work eat a belt every time you turn around it seems.

Put a VFD on a step pulley machine and I think it would be better than a variable speed machine. Probably quieter also. Have you ever met Bud Combs in Neosho, I used to work for him, he had a Famco mill that absolutely growled.

8. Plastic
Join Date
Nov 2001
Location
Utah, USA
Posts
8
I am currently changing my Jet mill (JVM-836) to 3 phase and a VFD. The first problem I ran into was the Jet motor shaft is metric (0.950 diameter measured) and american motor standard is 0.875 diameter. Therefore, the pulley must be adapted. I am talking with Jet to see if they have an unbored pulley. Otherwise, I am either going to bore and sleeve the pulley or turn an adapter shaft.

I can't wait to get a variable speed range.
Jim

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