Wasn't quite sure where to put this one.
Long story short, I stumbled across a listing for a 10 horsepower DC separately-excited motor for surprisingly cheap and it got me thinking. Given that these are largely considered to be antiquated technology nowadays, I've never really had reason to delve into DC motor theory too deeply.
My understanding is that shunt-type motors like this don't have the same starting torque as series motors, but do possess relatively flat torque-speed curves. That is to say, they are largely constant-speed motors, not unlike induction motors.
Just to tickle my intellect, how suited would one of these motors be to driving a variable torque load like an air compressor pump? What kind of locked-rotor currents are typical for them? Can they be D.O.L. started or is reduced voltage starting necessary?
Also, I've noticed that a 150 VDC field winding seems to be industry standard for them. Where exactly is this voltage typically derived from? A rectifier and a rheostat? A special transformer? Variac? Is it typical to control the speed of these motors by varying the field strength or are they intended to be used as single-speed motors?
Long story short, I stumbled across a listing for a 10 horsepower DC separately-excited motor for surprisingly cheap and it got me thinking. Given that these are largely considered to be antiquated technology nowadays, I've never really had reason to delve into DC motor theory too deeply.
My understanding is that shunt-type motors like this don't have the same starting torque as series motors, but do possess relatively flat torque-speed curves. That is to say, they are largely constant-speed motors, not unlike induction motors.
Just to tickle my intellect, how suited would one of these motors be to driving a variable torque load like an air compressor pump? What kind of locked-rotor currents are typical for them? Can they be D.O.L. started or is reduced voltage starting necessary?
Also, I've noticed that a 150 VDC field winding seems to be industry standard for them. Where exactly is this voltage typically derived from? A rectifier and a rheostat? A special transformer? Variac? Is it typical to control the speed of these motors by varying the field strength or are they intended to be used as single-speed motors?
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