Mill Speeds

[dnelso]

I have done some tests to see what the actual speed of my IH mill with a vfd. Here are the results.
L1 = 203 rpm
L2 = 382 rpm
L3 = 667 rpm
H1 = 962 rpm
H2 = 1810 rpm
H3 = 3167 rpm
All runs were with mobil 1 dte light at 60 hz
Later DN

[BobWarfield]

Is the VFD frequency maxed out at the highest speed H3, or did you just decide to call it quits there?

It would be tempting to apply some temperature probes to the spindle bearings and see how fast that gear head will tolerate with the VFD frequency cranked up. I would quit when the bearings start to hit 140 degrees under load.

My VFD will run up to 360Hz, which should spin the motor quite a bit faster than it's 60Hz rated speed!

Best,

Bob "Never enough rpms for aluminum" Warfield

[wildcat]

Before increasing the frequency past 60Hz be sure the motor can support it.

[dnelso]

The tag on the motor says 60 hz and and the gears were designed for that so unless i build a new spindle and go belt drive i will be sticking to what i got. I have been thinking of building a belt drive because most of my work is in aluminum and the extra speed would help.

[SMW Precision]

Originally Posted by dnelso The tag on the motor says 60 hz and and the gears were designed for that so unless i build a new spindle and go belt drive i will be sticking to what i got. I have been thinking of building a belt drive because most of my work is in aluminum and the extra speed would help.

I would take care running at 60hz on highest speed. We switched from a 1700 rpm to a 3450 rpm motor so max speed at 60hz would be about 4,000 rpm instead of 2,000 rpm.
Also depending on VFD unit the suggested Lesson motor can be run between 3-60hz that what is my motor and a vertorless VFD can do. I believe the VFD unit can be set as high as 240hz. What a scary thought I never want to mix machining and ballistic's.

[dnelso]

With my leeson motor at 60hz it will only turn 3167.I have been running it at this speed for over a year and had no problems.The difference in speed is because of the frictional losses in the gear head.I used a 3hp hitachi drive.

[BobWarfield]

Review Leeson's literature on their VFD's and 1050 Stock catalog, particularly the "Technical Information" section of the stock catalog. It looks to me like that section indicates the motors are good to 90Hz, which would get you 50% overspeed with a VFD, though you may experience some loss of torque.

They also make a line of motors designed for overspeed applications with VFD's that may be of interest if you haven't ordered a motor yet.

I think a bigger problem than your Leeson motor will be the IH gearbox. Goosing it all the way to 4500 rpm seems doubtful from a longevity standpoint.

Best,

BW

[philbur]

I though that the practical limit for a standard 3 phase 60 hz induction motor was of the order of 120 hz. You can buy 3 phase induction motors that have been uprated to handle higher hz's.

Regards
Phil

Originally Posted by BobWarfield Review Leeson's literature on their VFD's and 1050 Stock catalog, particularly the "Technical Information" section of the stock catalog. It looks to me like that section indicates the motors are good to 90Hz, which would get you 50% overspeed with a VFD, though you may experience some loss of torque. They also make a line of motors designed for overspeed applications with VFD's that may be of interest if you haven't ordered a motor yet. I think a bigger problem than your Leeson motor will be the IH gearbox. Goosing it all the way to 4500 rpm seems doubtful from a longevity standpoint. Best, BW

[Cruiser]

what the vfd can do and what the motor can do is two differant worlds. vfd can go down to 3 motor is not to go below 8, for cooling, and as for the going higher ..... better have some good info first about the motor .

[SMW Precision]

Originally Posted by Cruiser what the vfd can do and what the motor can do is two differant worlds. vfd can go down to 3 motor is not to go below 8, for cooling, and as for the going higher ..... better have some good info first about the motor .

I agree the 3-60hz specifications were from the Lesson for the motor I am running. Specifications should alway be used with some judgement. They are not an absolute rather a range. Just because you can do it does not mean you should.

[wildcat]

Originally Posted by BobWarfield Review Leeson's literature on their VFD's and 1050 Stock catalog, particularly the "Technical Information" section of the stock catalog. It looks to me like that section indicates the motors are good to 90Hz, which would get you 50% overspeed with a VFD, though you may experience some loss of torque.

Here http://www.leeson.com/cgi-bin/nicefe...nical_info.pdf Leeson says that 3600RPM motors should not be run faster than 75Hz without analysis (no idea what "analysis" means in this situation - temp? insulation degradation?). Also note this chart applies only to motors with the heavier insulation. Here http://www.leeson.com/news/1998-09_IRIS.htm Leeson says that the heavier insulation is "now offered at no extra cost on all its stock three-phase" but does does that mean they apply the coating to all three phase motors or only those requested?

In whatever case the ultimate upper speed of the VFD+motor is only academic since one would be operating outside IH specs and thus all bets and warranties are off. Whatever time savings you gain from a small increase in speed might be completely erased by the time to repair damages.