AC or DC motor

Discussion in 'General Electronics Chat' started by moh, Jan 19, 2010.

  1. moh

    Thread Starter Member

    Apr 23, 2009
    19
    0
    HI,

    Can anyone explain what is better Ac or Dc motors.

    thanks
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    depends on your application.....
     
  3. moh

    Thread Starter Member

    Apr 23, 2009
    19
    0
    For making small elevator lift, lifting weight 0.5 kg and for conveyor belt.

    I heard AC last long but have RFI problems and DC life expectancy is very low but easy to control.

    What is more economical in both.?

    Who is the overall winner?

    In industry people use AC induction motors usually 3 phase.Why do they prefer it over DC?
     
    Last edited: Jan 19, 2010
  4. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
    efficiency is a factor.

    think awhile about a golf cart.
    DC motors, batteries, and in the early days, resistive network for speed control.
    Battery life was pathetic because battery life was wasted via heat loss through the resistors.

    Then came the SCR motor controllers. A little less crap of a system but not by much. Anybody here have experience with the ge EV-10?
    In a nut shell: Take a stored DC supply, oscillate it, transformer the oscillated signal, SCR it for a variable speed output, further rectify that and then send it to a DC motor. Like I said, just a little less crappy.

    Then PWM MOSFET controllers became standard. SEVCON, CURTIS, etc.
    we can see the benefit of the PWM but still the DC motor is the headache in the system. The fact that a brush is hitting both the + and - at the same time on the commutator illuminates the evidence of lower efficiency. Leagues above the scr but still not quite there yet.

    Now in the world of electric drive systems is the 3 phase AC drive system.
    Attached is the manual for an AC motor controller we use in one of our models of equipment we build/sell.

    The AC motor will have less moving parts, are physically smaller, brushless, less expensive to purchase and operate, run cooler, demand less current per load demand, and can be completely enclosed as heat venting is not required as it is with a DC motor.

    again, the advent of the 3 phase AC motor controller being used with a DC battery pack will be eliminating DC motors being utilized, at least in the mobile equipment industry, in the near future.

    all the pluses for AC in the industrial world and now in the mobile equipment world will be soon evident with this type of control.
     
    Last edited: Jan 19, 2010
  5. rvh002@gmail.com

    Active Member

    May 15, 2009
    118
    2
    Also, 3phase or single phase AC power is available out of the plug. DC power is not and has to be "manufactured"
     
  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    AC motors have little RFI problem, DC does have but easily surpressed. For small lift I would use DC as is easily speed controlled & reversed, for conveyor, size unknown, would use AC for mostly fixed speed & no reversing. Life is long for either.
     
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