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TECO L510 VFD ON SOUTH BEND LATHE, LOST 50% of my torque

leod

Aluminum
Joined
May 24, 2014
Location
oregon city, or
I was excited about being able to fine tune my speed and even turn it a little faster on my old south bend, and couldn't believe that little box could replace my rotary phase convertor and perform those magic tricks. It turns out my disbelief was well founded. can't even start with the belt engaged and slows way down after I engage it. Love the EV-110 I have on my Bridgeport. I checked out a couple of folks stories that used one on their lathe and said it worked fine. forgot to check out what size though, probably not 16" like mine. Sure would be nice if the forum search worked on this site.
 
No. You de rate your 3 phase motor by 1/3. You should know this going in. If you need 2 h.p. you purchase a 3 h.p. v.f.d. and motor. I run my 14x40 on a teco 2 h.p drive and 2 h.p. motor with that I dont have any problems. O.P. look in your drive and see if you can increase the torque out put. I dont know where mine is set and I cant check for a few days, sorry.
 
One other thing, check to see if the motor needs to be wired delta or wye, it may make a difference. I do know if you are converting single phase to three phase the motor must be wired 220 volt 3 phase not 440 3 phase. I did not look at your drives specs so take my words with caution.
 
Most VFDs I've seen have a setting for constant versus variable torque. Constant torque is used for machinery generally. Variable is used for equipment where torque is a factor of speed like fans or blowers. It is possible that this is set wrong for your application. Check to see that you have it set to constant torque or equivalent.

Best Regards,
Bob
 
I was excited about being able to fine tune my speed and even turn it a little faster on my old south bend, and couldn't believe that little box could replace my rotary phase convertor and perform those magic tricks. It turns out my disbelief was well founded. can't even start with the belt engaged and slows way down after I engage it. Love the EV-110 I have on my Bridgeport. I checked out a couple of folks stories that used one on their lathe and said it worked fine. forgot to check out what size though, probably not 16" like mine. Sure would be nice if the forum search worked on this site.

You have a problem not directly inherent to the VFD use. Go back through the MANY posts on VFD function and use. Read the operators manual.
Something is missing in your set up or selection.
 
I was excited about being able to fine tune my speed and even turn it a little faster on my old south bend, and couldn't believe that little box could replace my rotary phase convertor and perform those magic tricks. It turns out my disbelief was well founded. can't even start with the belt engaged and slows way down after I engage it. Love the EV-110 I have on my Bridgeport. I checked out a couple of folks stories that used one on their lathe and said it worked fine. forgot to check out what size though, probably not 16" like mine. Sure would be nice if the forum search worked on this site.[/QUOTE

What is VFD power? (could be up to 1HP)

What is motor power?

So... Do you get an error message, or a shutdown?

Or do you just get what you think is less torque?

There IS a sub-forum for this..... it could use to be moved.
 
You don't lose torque with a FVD. Period. A three phase motor develops full rated torque at full load amps whether its on a VFD or across the line.

Is the three phase motor connected for 230 Volts? A three phase motor connected for 460 volts will develop less 1/4 its rated torque if run on 230 volts.

Have you read the book that comes with it? Have you set the parameters to suit your particular application? Most VFD's come with default settings that include very slow acceleration lasting 10 seconds or more. The motor seems like it's slowly building up to speed because of heavy load whereas it's actually following its over-conservative default programming. The accel can be adjusted to any value but I prefer 2 seconds or so.

Are you using the existing speed changing correctly. A motor develops its rated power at 60 Hz at full motor torque. Halve the frequency and you halve the RPM but still at full rated torque. At 15 Hz you get 1/4 the rated motor HP still at full motor torque and so on in proportion to nearly zero HZ. It may seem like the motor is "losing torque" but the problem is misapplied physics not motor torque - that and pervasive motor-head perversion of technical terms: "torgue" is not power.

If you wish to take full HP cuts you HAVE to use the belt speeds or the gear changes to keep the motor at or near 60 Hz. Light cuts you can use whatever VFD and mechanical speed setting that works but if you want stock removal you have to use the mechanical reduction to keep the motor in its sweet spot..

And you HAVE to use a three phase motor with a VFD; it will not work with a single phase motor.

Maybe I'm being impatient. If so, I'm sorry but a good VFD whose parameters are set correctly and run with a good appropriately sized three phase motor connected for the rated voltage cannot fail to function properly.

Something is wrong.and there's a 99% chance it aint the VFD itself.

No. You de rate your 3 phase motor by 1/3. You should know this going in. If you need 2 h.p. you purchase a 3 h.p. v.f.d. and motor. I run my 14x40 on a teco 2 h.p drive and 2 h.p. motor with that I dont have any problems. O.P. look in your drive and see if you can increase the torque out put. I dont know where mine is set and I cant check for a few days, sorry.

Randy, three phase motors run from a VFD run to full nameplate ratings. The VFD put s out sine coded PWM to the motor leads leading the motor to think its running from clean three phase. Thus the motor develops full power.
 
I so glad Forrest is around to nail all the myths that propagate on the internet and get passed on by as fact by the unknowing!

As has been said, you lose nothing if you run at 60hz... The simple version : Within a reasonable range you will lose HP below 60hz (torque is constant), and will lose torque above (HP stays constant). If you installed the VFD to get more speed, then at 120hz (probably a little less) you will have 50% of 60hz torque, and similar HP.

With VFD programming you can boost torque at low rpm, and even muck around with the base frequency set point, but if you don't understand what you are doing... don't.

I suspect you have not set some of the VFD parameters correctly, but without more information on your set up it's hard to advise.
 
Lakeside53

Please explain how I am incorrect about de rating the vfd and motor. You said at 120hz you would have 50% of the 60hz torque. So if you increased you motor and vfd size wouldn't you be running where you wanted to be when you turn up you frequency?
 
Hi
Lakeside and Forrest are exactly right.
Nothing is derated. Physics limits power and torque.

Below the motor rated speed, it can produce more than 100% torque, but only until the motor windings melt from over current.
Above rated speed, there isn't enough voltage supply to the VFD for it to drive more current through the motor to develop more power.

As stated by others, a correctly applied VFD does not cause any derating or loss of motor performance.
The physical properties of motors limit power and torque at above/below rated motor speed.
 
Lakeside53

Please explain how I am incorrect about de rating the vfd and motor. You said at 120hz you would have 50% of the 60hz torque. So if you increased you motor and vfd size wouldn't you be running where you wanted to be when you turn up you frequency?

Where you are incorrect is ... there is no arbitrary "you need to derate by 1/3".

As answered above. At 60hz (for a 60hz motor) you have exactly the power your motor is rated for - no derating because of a vfd at all. If you want X hp (X=60hz equiv) at 15hz, then you will need a motor and VFD roughly 4X as big; at 120hz 2X as big. For a machine conversion it's often easier to use the vfd in conjunction gears and belts as required. For many uses you consume so little hp that you can just flip the speed knob up or down. If you need to hog metal, gear down. If you need more speed, gear up.
 
At 120Hz, a 240/480 motor, wired for 240, can produce double its rated 60Hz HP.

Same current, same losses (almost), double voltage....double speed, same torque double HP either way.. Same V/hz.

The OP has some issue.... Either he was really bogging the motor he has before the VFD, and has current limit problems, or he has a voltage issue, or ????


Millions of good VFD installs say he needs to check everything out and see where the error is.
 
I think the idea about Derating motors comes from confusing a VFD with a STATIC "PHASE CONVERTER" aka capacitor start circuit.
The really inexpensive static "phase converters" are just capacitors which get the motor started, and then motor itself creates the third phase.
When running a 3 phase motor off one of these, power output is 2/3 of rated power.

You could then use that motor as rotary phase converter to start your machine motors, and in that case you would need at least a 5 HP as your RPC to start a 3 HP machine.

These are completely different from VFD's though.

Or it could be that he is trying to use metric electrons on an american made south bend.
 
My confusion I believe comes from the thought that using 220 volt single phase in to a three phase drive you needed to de rate the motor. Gotta go phones dying thanks all.
 
That is now unusual in a VFDs 3hp or below, but yes, above there is often derating when using 3 phase drives on single phase. The exact amount depends on the manf. My ABB 7.5hp vfd's are only good for 1.5 on single phase. Hitachi is closer to 1/2.
 
I think the idea about Derating motors comes from confusing a VFD with a STATIC "PHASE CONVERTER" aka capacitor start circuit.
The really inexpensive static "phase converters" are just capacitors which get the motor started, and then motor itself creates the third phase.
When running a 3 phase motor off one of these, power output is 2/3 of rated power.

You could then use that motor as rotary phase converter to start your machine motors, and in that case you would need at least a 5 HP as your RPC to start a 3 HP machine.

These are completely different from VFD's though.

Or it could be that he is trying to use metric electrons on an american made south bend.

Pretty sure the derating is for single-phase input.

You could twist the Earth on its axis with a properly spec'ed VFD.
 
How about those numbers? No info, no helpee. We need to know what you are working with to see what the problem may be.

It is sure enough possible to have a torque reduction with a VFD, but you need to mismatch things, or put in wrong settings to do it. With the numbers, we can start to develop what the settings SHOULD be.
 
Pretty sure the derating is for single-phase input.

You could twist the Earth on its axis with a properly spec'ed VFD.

Yes I agree.

Of course its for single phase input, if you had 3 phase to input, you wouldn't need a converter.

If you buy the correct VFD, no derating is necessary.
 








 
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