Calculating the current of a household appliance

Discussion in 'General Electronics Chat' started by electrophile, May 28, 2016.

  1. electrophile

    Thread Starter Member

    Aug 30, 2013
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    I'm trying to build a ceiling fan regulator which incorporates a triac. I was trying to figure out the current rating for this and I was hoping someone would let me know if this is the right way to do it. Here goes:

    The ceiling fan is rated for 75W. For 220VAC and a power factor of about 0.85 (from my research on the web but feel free to correct me) would the current be:

    75/(220 x 0.85) = 0.4 A?

    If this is correct, can I use a 1A (constant on-state) rated triac?
     
  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I'd use a higher current version. Not much difference in price, greater safety margin.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I agree, with triac's there is not a lot of point sizing them tight.
    Max.
     
  4. be80be

    Senior Member

    Jul 5, 2008
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    Ceiling fans dont last long if you wanting to use this for speed control too.
    Plus it will start humming loud
     
  5. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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  6. be80be

    Senior Member

    Jul 5, 2008
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    I replace about 50 to 75 fans a year that people put on a dimmer they use capacitors to change speed and don't like dimmers at all
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I have had mine for 25 yrs, buzzes a little at low rpm but not a problem.
    Max.
     
  8. be80be

    Senior Member

    Jul 5, 2008
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    That's cool but most new ones are lucky to make it a year before you can't stand to be in the room with them and forget to turn it up to full speed to start the fan and your just cooking the wires in it. I'm a electrician 35 years I've seen most anything that can go bad happen there are dimmable fans but most are not made to use dimmer
     
    GopherT likes this.
  9. KeepItSimpleStupid

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    Mar 4, 2014
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  10. electrophile

    Thread Starter Member

    Aug 30, 2013
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    @Alec_t and @MaxHeadRoom Thanks. I however, have a space constraint and the 1A ones fit in quite nicely. I saw a few 4A in DPAK cases which could also work.

    Thanks. What would you recommend for fan speed control?
     
  11. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
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  12. electrophile

    Thread Starter Member

    Aug 30, 2013
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