DC Motor speed control
DC Motor speed control
(OP)
Hi
I want to modify a wire drawing machine from torque control to speed control
The machine consist in 5 drawing blocks. Each has it´s own torque control board. The feedback for the control is taken fron the current consumed by each motor´s SCR rectifier.
I want to change the torque control system to a speed control. The feedback signal will be coming from a dancer pulley instaled on each block (potenciometer)
Do you know any company that sell the control board that I nedd to do this?
Thanks
I want to modify a wire drawing machine from torque control to speed control
The machine consist in 5 drawing blocks. Each has it´s own torque control board. The feedback for the control is taken fron the current consumed by each motor´s SCR rectifier.
I want to change the torque control system to a speed control. The feedback signal will be coming from a dancer pulley instaled on each block (potenciometer)
Do you know any company that sell the control board that I nedd to do this?
Thanks





RE: DC Motor speed control
You could also go to a hall effect sensor and count pulses per second. I would think this would be more accurate.
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If it is broken, fix it. If it isn't broken, I'll soon fix that.
RE: DC Motor speed control
RE: DC Motor speed control
http://www.kb-controls.com/
RE: DC Motor speed control
For "real" speed control, you need to add tachometers or encoders to each motor. Or do you have them installed already?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: DC Motor speed control
The motors already have tachometers. In my 1st post I made a mistake. The feedback will be from the tachometers and the reference speed value from the dancers + individual potentiometers to do a fine adjustment on each black
Where can I get this "crude speed control"?(EMF feedback, actually)
Any guidelines?
Thanks
RE: DC Motor speed control
Please give me machine type and drive manufacturer/type. I know the guys that used to build and commision those machines and their drives.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: DC Motor speed control
Please give me machine type and drive manufacturer/type. I know the guys that used to build and commission those machines and their drives.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: DC Motor speed control
We have 2 machine. Both Arboga
One has the Philips drives and is for small diameter wire. This machine is in operation and already has speed control system working
The other for big wire has the torque control with Styrkonsult drives (90% sure) an its out of operation. This is the machine that I want to modify. I do not have the machine type. But I have plenty of pictures to try to identify it
Can I send you the pictures or maybe you help me contact the guys that used to build and commission those machines and their drives
RE: DC Motor speed control
Bill
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"Why not the best?"
Jimmy Carter
RE: DC Motor speed control
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: DC Motor speed control
I will be sending the pictures and any other information that could help to Id the machine
RE: DC Motor speed control
Just out of curiosity, is the crude speed control or EMF feedback accomplished by monitoring the back EMF induced on the armature and converting this EMF into a speed?
How is this monitoring physically accomplished seeing that there are brushes between the armature and any external monitoring devices?
RE: DC Motor speed control
The error introduced by the brushes is actually the least problem. The non-linear part of the voltage drop is only half a volt or less. That is not more than a tenth of a percent when you have an armature voltage in the 400 - 600 V range.
Using a constant-current excitation scheme keeps the excitation error small and by calibrating for normal operating conditions, you can keep the armature resistance influence quite low in normal operation.
It is possible to have a speed error less than 1 percent over a 30 - 100 % load change. Good enough for many purposes.
BTW, I have received photographs of the machine and also contacted a friend that immediately identified the machine and also found the original manufacturer. That guy still has spare parts and will be in contact with lukin1977 today or tomorrow. Another great example of how well Eng-Tips works.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: DC Motor speed control
I wrote to him a couple of hours ago. Still waiting for his response
Thanks again for your help!
In this case the feedback comes from a tachometer coupled to the each motor shaft (close loop). EMF feedback is called an open loop feedback, right?
RE: DC Motor speed control
Open loop would not produce a very reliable result. It is OK for dimmers and heaters, but not for DC motors.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...