AWG and PWM

Discussion in 'General Electronics Chat' started by jlatshaw, Jul 25, 2013.

  1. jlatshaw

    Thread Starter New Member

    Jul 20, 2013
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    0
    Hi,
    I have a quick question about wire gauges and what is a safe amount of current to run through each gauge.
    With my project, I should never see more than 20 amps of current, so I'd like to pick a gauge that will work well for 20 amps for current ( though I plan to operate below 20 amps).

    I found this chart:
    http://diyaudioprojects.com/Technical/American-Wire-Gauge/

    And according to this I would need an 8 gauge wire which I think is bigger than what I need?

    My motor that I have that is rated for 18.5 amps of current and has 14 AWG, which according to this chart, should not support that big of a current.

    So I am a bit confused here. What is a good AWG for a max current load of 20 amps (the smaller/cost effective the better).


    Also, with regards to PWM (for speed controllers), all those really do is limit the amount of current flow through the PWM and by limiting that, we can control the motors speed because we can control how much current the motor sees, right?

    Thanks,
    -James
     
  2. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    *8 ga. is definitely an overkill... Google " copper wire ampacity " should yield a useable table for you...

    About the most comprehensive table for copper wire, can be found in the ARRL radio amateurs' handbook...
    Normal household "romex" , as specified by NEC, and most local building codes, will call for #12 to handle 20 amps... # 10 for 30 amps...

    Reality indicates a lot of people routinely run household circuits to their max, so a little overkill never hurts...
     
    Last edited: Jul 25, 2013
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    google "NEC 310.16"
    14 awg is the right size.. (assuming no other reasons to derate)

    I push 65A through 8 AWG all day long.
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,791
  5. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    How long is the wire run ??
     
  6. jlatshaw

    Thread Starter New Member

    Jul 20, 2013
    28
    0
    Thanks for the input all, and it's a very short, 15 feet all together.

    Thanks,
    -James
     
  7. crutschow

    Expert

    Mar 14, 2008
    13,014
    3,234
    PWM controls the motor speed by varying the duty-cycle of the waveform which varies the average voltage (not current) applied to the motor. The current is determined by this average voltage applied across the impedance of the motor as determined by the load it is driving.
     
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