adccommunitymod (AutomationDirect) asked a question.
VFD torque/hp losses at 120hz.
Created Date: July 10,2009
Created By: davecassano
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Hello. This is my first post. We have a 300hp motor @ 1180rpm but it's 2300v. It is coupled to a torque converter then a gearbox to turn a massive drum debarker. We are thinking about going to a 300hp motor @ 593rpm, 480v. To make up the lost rpm we would use a vfd. I worry that we will lose too much hp and torque at such a high frequency. Any info from you would be a huge help. Thank you, David Cassano
Created Date: July 10,2009
Created by: milldrone
To make up the lost rpm we would use a vfd. I worry that we will lose too much hp and torque at such a high frequency. Any info from you would be a huge help.
David Cassano
Dave,
You are right about the loss of torque and HP. I would expect that a motor in the 300hp 600 rpm base speed range would have bearing or balance problems at this speed also. Also as you know the torque would drop off at speeds above 60 Hz., but the HP would remain constant until about 70 Hz or so. (it's hard to tell with large low speed motors.) At 120 Hz I would expect (if you can get the motor to run at this speed) about 100 Hp. So you would have about 1/3 the amount of torque that a 300 Hp @ 1200 rpm would have
You do not mention if the 2300V motor is the existing motor. If it is you will have a rather large wire capacity problem also.
Created Date: July 10,2009
Created by: Bob S BN
Not sure what your after in switching motors in the first place, variable speed??
A quick check shows BALDOR has a 480 motor at the right speed, may help
Catalog Number: M44306T-4
Description: 300HP,1185RPM,3PH,60HZ,449TY,18184M,TEFC
Ship Weight: 2831 lbs.
List Price: $39,417
Just a thought,
Created Date: August 01,2009
Created by: genroxbro
VFD torque/hp losses at 120hz
Dear Mukesh,
If you really need 140 nominal torque during starting, then use a squirrel cage electric motor with a saddle torque of 155 to be sure that there always will be speed acceleration and start Direct On Line.
Whether there are VFD drives that can increase the voltage, I do not know.
If such a motor does not exist, oversize the drive motor.
I do not know whether a hydraulic torque converter can do the starting up as well.
Your question is best asked to a supplier.
Let us know your findings, please
Success
Teus
Let me introduce myself.
Created Date: August 01,2012
Created by: richard525
Hello. This is my first post. We have a 300hp motor @ 1180rpm but it's 2300v. It is coupled to a torque converter then a gearbox to turn a massive drum debarker. We are thinking about going to a 300hp motor @ 593rpm, 480v. To make up the lost rpm we would use a vfd. I worry that we will lose too much hp and torque at such a high frequency. Any info from you would be a huge help.
Thank you,
David Cassano
David,
What do you mean by losing hp and torque at high frequency?
In fact, I don't think these 3 factors have any relationship. But you may need a set-up tranformer if you need 2300v for a 480v motor.
Richard
Created Date: August 01,2012
Created by: Do-more PE
This post is three years old. Please don't raise old posts from the dead. You never can tell when one of them will turn on us and then things will get messy. :)
Locking this thread.
Created Date: July 10,2009
Created by: davecassano
Hello. This is my first post. We have a 300hp motor @ 1180rpm but it's 2300v. It is coupled to a torque converter then a gearbox to turn a massive drum debarker. We are thinking about going to a 300hp motor @ 593rpm, 480v. To make up the lost rpm we would use a vfd. I worry that we will lose too much hp and torque at such a high frequency. Any info from you would be a huge help.
Thank you,
David Cassano