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Selecting A Vfd Drive For A Vintage Motor


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#1 joeysmokedporter

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Posted 22 August 2009 - 09:25 PM

I recently acquired a vintage GK Heller lab-scale stirring motor. It is a DC, shunt wound motor with armature 0-130VDC/600 mA, and field 80-130VDC/140mA. I got the motor but am having a difficult time selecting a controller that will work with it and not fry it. As I am an amateur, and looking to use this for a homebrewing application, I know enough to be able to put a controller together if I can find a drawing, but I'm not exactly sure what I'm looking for.

In selecting a controller, does the controller's maximum current need to be lower than my armature's current rating? Do you have any suggestions for what i should be looking for in selecting a controller?

thanks for your assistance.

#2 marke

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Posted 22 August 2009 - 10:02 PM

Hello joeysmokedporter

Welcome to the forum

You are looking for a DC controller, not VFD. VFDs are Variable Frequency Drives and are used for AC motors.

You need a DC controller designed for a shunt wound motor with a field voltage that is compatible with the motor and a current that is the same as the field rating.
The field can be either a controlled voltage or a controlled current.
You quote a field voltage of 80v - 130V. At the higher voltage, the maximum speed will be slower. If you want the maximum speed, use the lower voltage.

The armature supply will need to be variable from 0 - 130 VDC at 600mA or higher.
The rated current of the armature supply must be greater than the armature rating of the motor.

Best regards,
Mark.

NB do not operate the motor without field current applied.

#3 joeysmokedporter

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Posted 23 August 2009 - 11:55 AM

Mark--

thanks for your reply, for correcting my terminology, and for clarifying my question about current rating. I found a controller made for shunt wound motors that might work for me--it is a Dart Controls model 15DV2A, listed in Grainger's catalog as item 5JJ57 (link below). Maximum current of 2A is > my motor armature current of 600mA. Since I'm in the US, my household current is 120VAC, so I'm presuming my output from this would be 100VDC for field and 0-90VDC for armature. Do you think this selection would be ok for my motor? Is it correct that since the 0-90VDC range on the controller is less than the 0-130VDC range on the motor that I won't achieve full speed, or is there another implication that I should be aware of?

Thanks again for your assistance.

JSP (aka Russ - Westminster, MD USA)

http://www.grainger....ger/items/5JJ57



#4 marke

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Posted 23 August 2009 - 06:45 PM

Based on the information given, it looks OK to me.

Best regards,
Mark.




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