[PSUBS-MAILIST] DC Systems Primer

[Dan H.]

Those high voltage DC motors are designed for variable speed drives where the power is first line voltage AC then converted to DC through a motor controller for accurate motor speeds and torque.  They aren't practical for a battery powered system.

For battery powered systems your probably better off to stick to the lower voltage motors.  With an inverter I guess you could convert the battery power to high voltage AC then convert it to DC, but I'm pretty sure you'd find it impractical with the extra equipment.  

It's hard to beat golf cart controllers for speed regulation and there's tons of them out there.  Battery powered floor scrubbers use a variety of DC motors too. 

Dan H.

  ----- Original Message ----- 
  From: Joe Perkel 
  To: Psubbers Mailist 
  Sent: Tuesday, October 15, 2013 11:02 PM
  Subject: [PSUBS-MAILIST] DC Systems Primer


  Since my Navy "A" school is some 30+ years ago, I need a little help in trying to understand and match up something close to Georges motors. What I dont understand is why is there such an array of DC motors in the 1 - 3 hp range with wildly varing input voltages?

  If you notice those Tecnadyne thrusters have stupendous input voltages up to 330vdc. I dont understand why and need a primer on DC systems for this application. Can anyone point me to one?

  What I'm trying to do is to slim down the housing, get more bollard thrust from the prop by adding a real kort nozzle, and use a mag coupling instead of a shaft seal, all else remaining essentially the same.

  I want to slim down Georges T-Rex cans with similar power specs, but new and improved components, keeping the items conducive to homebuilding, like the housings and mountings, electrical penetrators, shaft seals if I cant do mag couplings. 

  What I've found so far http://www.baldor.com/support/literature_load.asp?LitNumber=FL1210  fractional hp and up to 3 hp @ 1800 rpm but, here again @ 320vdc !?

  Whats attractive about this one is the dimensions, 6.5" on the mounting flange would fit quite nicely in the 6 nom SCH40 pipe which is 6.625"

  But I dont know what im doing with regard to the input voltage / output power / torque relationship and how to match this all up correctly.  All Ive confirmed so far is that Georges motors were TENV (totally enclosed non-ventilated), 36vdc @ 1800 to 3600 rpm for 1/2 and 3 hp respectively.

  Joe




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