Need help rectifying 120vAC to 115vDC

Discussion in 'The Projects Forum' started by Jordans5, May 7, 2014.

  1. Jordans5

    Thread Starter New Member

    May 7, 2014
    2
    0
    Hi, new here. Name is Jordan. My friend told me this would be a great place to seek advice.
    I have a 1/8 hp 115vDC Bodine NSH-54RL right angle gearmotor that I am using in a project. I need it to run off 120vAC household current and be able to control the RPM's of the motor.
    So far in my research ive found that i need to use a rectifier to convert the AC to DC and a capacitor to 'smooth out the current flow/RPMs'.
    I already have an AC speed controller in the form of a fan/light dimmer inline on an extension cord. (can i use this in my project or no?)

    So basically i want to learn what kind/size rectifier and capacitor to use.
    Would this work as my rectifier? http://www.amazon.com/dp/B00CQLLEOM...UTF8&colid=15W04GFTEUTK&coliid=I116BXVJRBHGX6

    And how would i control the speed (if i cant use my already made dimmer controller)

    Much thanks!
    Jordan
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Should work.
    Overkill!

    25 amp 600volt are common.

    Just connect bridge between dimmer and motor.
    No capacitor needed. Although a small value ac rated cap. on the ac terminals will make the bridge happy.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
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    There is also KB/Baldor SCR drives on ebay, they can often be had cheap.
    Max.
     
  4. Jordans5

    Thread Starter New Member

    May 7, 2014
    2
    0
    Awesome! Thanks Guys, sorry it took so long to get back to you. Thread update notification emails went into the spam folder for some reason.

    Is there a certain way to wire the rectifier? It is a 4 pole device. i would assume 2 are for the AC wires and the other 2 for DC pos / neg wires. Right?

    As for the capacitor, do i just wire it across the AC wires before the rectifier?

    Would my crude sketch be the correct way to wire it? with the speed controller on the ac side?
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Note..Rectification/smoothing alone will probably NOT be sufficient as you won't get 120VDC.. It will be higher. (DC is approx 1.4 times rectified AC)
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    Skip the capacitor. It's not needed. Certainly not across ac.

    Otherwise it's correct.
     
  7. #12

    Expert

    Nov 30, 2010
    16,261
    6,770
    Explanation: If you put a smoothing capacitor in, it will charge to the peak value of the power line, and that's about 170 volts. DC motors don't care much about smooth current, so just leave out the capacitor and you'll get a better approximation of the voltage the motor wants.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,515
    2,369
    BTW if you want RPM control, put a Triac style dimmer circuit in one line of the AC to the rectifier.
    As post #2.
    Max.
     
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