
Torque limit
#1
Posted 12 September 2005 - 06:48 AM
We have actually installed one 900 k W motor driven by a VSD , and this drive runs two independent rollers but with only one main gearbox. We are having regularly gear damage on one of the roller, because one roller could at a particular time take the full 900 k W torque available at the output shaft of the gearbox. The drive is set for V/F application.
The obvious solution would be to have independent drives for each roller, but this solution is too expensive for us for the time being.
I am thinking of one torque limiting device !!!!!!!!! attached to the shaft of each roller so that we could trip or stop the VSD if the torque exceeds a particular limt.I am wondering if such a device exists.
I am welcoming suggestions from orum members.
Bob
#2
Posted 12 September 2005 - 10:43 AM
Another means is to provide a torque sensing assembly to the rotor and electronic signal from the torque sensor can be used to trip the VFD on over torque .
Most of the electronic drive also reads the torque delivered .
You can set the torque limit and drive shall trip on overtorque condition.
Regards
#3
Posted 12 September 2005 - 10:48 AM
Bob
#4
Posted 12 September 2005 - 11:02 AM
May be torque sensor should be a good solution .
Can check with FF420 torque transducer of datum electronics ( both contact and non contact types are available ) or may be many more similar kind of sensors available with other manufacturers .
Out put is in form of 4-20ma or 0-10 volts , something that you can comfortably process to serve your purpose .
Regards
#5
Posted 12 September 2005 - 04:34 PM
Here is one I have used in the past on a test bench application. I'm not sure if it is meant for production machinery, but you could ask them.
http://www.hbm.com/p...ctDataSheet.htm
#6
Posted 12 September 2005 - 08:07 PM
One solution is to fit a fluid coupling to each roller. - a simple mechanical means of limiting the torque.
Best regards,
Mark Empson | administrator
Skype Contact = markempson | phone +64 274 363 067
LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters
#7
Posted 13 September 2005 - 05:20 AM
Fluid coupling to my understanding are used for equipment that needs large starting torque like Centrifuge and polymer powder homogenisers rather than for limiting overtorque .
Fluid coupling do operate as a protective device in case of overtorque by operating the fusible plug and splashing out oil thus disengaging the coupling between motor and the driven equipment . Its generally a very undesired situation and I don't think that this shall be comfortable way of protecting .
Also retrofitting a fluid coupling may not be very easy.
Regards
#8
Posted 13 September 2005 - 06:19 AM
Yes, the fluid coupling is often used as you described because it limits the troque transfer. It is a torque limiting device that does not trip, if the torque gets too high, it slows down.
The fusible plug operates, not on torque, but on temperature. If the torue is excessive for a long time, the slip losses will cause too much emperature rise and this will blow th plug.
Best regards,
Mark Empson | administrator
Skype Contact = markempson | phone +64 274 363 067
LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters
#9
Posted 13 September 2005 - 03:32 PM

There are mechancial means of protecting the components. While I tend to think the fusible plug fluid coupling is too messy, it s probably easier to clean that up than to replace the roller. There are also non-fluidic devices called Torque Tamers that would do essentially the same thing, but work on a principle similar to an automotive clutch. Two plates and a fiber disc designed to slip at a specific speed (edit: should have said torque). If you can istall something like that, you can then add a simple speed detection system to the rollers so that if one starts to slip, you can shut down the drive.
#10
Posted 15 September 2005 - 06:35 AM
Any way which ever method is used retrofitting shall involve cost and difficulty but I agree that this is may be more cleaner than fluid coupling .
regards
#11
Posted 15 September 2005 - 09:53 AM
Tell me, basically how is the torque sensor mounted? I believe my system should be retrofitted to fit the sensor. I am talking shaft diameter of about one metre.
I have requested quotations from Datum electronics and some others but without success.
Bob
#12
Posted 15 September 2005 - 11:00 AM
bob
Torque sensor can be fitted into any size of shaft , can you give a bit more description about the arrangement of rollers? its basically difficult to visualise the arrangement of rollers from the brief description of system you have provided .
is any one circular face of the roller free for retrofitting the torque sensing assembly ? Is it possible to make bore at the circular face cetre of roller to attach the the torque sensor assembly via load beam and gear assembly ? Such sensors can be set to required torque value and can generate trip command if the value is crossed .Also 4-20ma monitoring signal is abailable
Regards
#13
Guest__*
Posted 15 September 2005 - 11:07 AM
The 900 k W motor drives a reduction gear box to which is coupled a main gear wheel. Geared to the latter are two other gear wheels which drive two independent rollers. Basically, it should be fitted to the shaft driving the independent roller.Could it be mounted at the shaft end ?
I believe the sensor should be mounted between two seperate shafts .
Bob
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users