3 phase with 90 amps breaker

Discussion in 'General Electronics Chat' started by Garrix, Apr 10, 2015.

  1. Garrix

    Thread Starter New Member

    Apr 10, 2015
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    i have asked 3 different electrician and i got 3 different answer..so i'm here to ask the same question again..please help. My warehouse got 3 phase electrical..main triple breaker rate @ 90 amps..so can i pull max 90 amps @ each phase(90,90,90) or combine 3 phase (30,30,30) = 90 amps???
     
  2. Ramussons

    Active Member

    May 3, 2013
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    The specifications of the Circuit Breaker is unclear the way it's been mentioned.

    Can you repeat Exactly what the specs are or can you upload a photo of the specification plate?

    We don't know whether the Trip point is 90 Amps Per Phase or Total Current.
     
  3. Garrix

    Thread Starter New Member

    Apr 10, 2015
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    Thx :)
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    That is a 3 phase breaker rated at 90 Amps, so it will trip when it reaches maximum,
    all three phases must take the same current or it will trip due to imbalance.
     
    Last edited: Apr 10, 2015
    spark8217 likes this.
  5. hajivitra

    New Member

    Apr 7, 2015
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    nice question
    thanks
    [​IMG]
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    90 amps/phase, this does not mean that you will be drawing or capable of 270amps total, if that is what you mean.
    Max.
     
  7. Garrix

    Thread Starter New Member

    Apr 10, 2015
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    I did try to even out the loads into 3 phase 34,52,34 and one of my electrician said this is way over 90amps and maybe gonna cost fire.My other electrician said that i got plenty of power,i can pull up to 70amps on each phase to be safe....and they're both certified electrician for over 10 years :)
     
  8. #12

    Expert

    Nov 30, 2010
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    The first electrician is wrong. Proof: If you were in danger, the circuit breakers would pop.
    ps, the LAW for electricians is to wire things for 125% of the actual load. That's where the 70 amps came from. It's really 90A x 80% = 72 amps.
     
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  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    He is going to have to trade in his calculator, your maximum current at any given time in a single conductor is 52amps.
    Max.
     
  10. #12

    Expert

    Nov 30, 2010
    16,239
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    I went to Home Depot for some pipe and the clerk said, "I never made any allowance for the pipes to expand or contract because of temperature changes, and I was a licensed plumber for 30 years."

    I said, "Maybe that's why you are now a minimum wage clerk."

    It doesn't require a really smart person to pass the State Certification test.
    Proof: I have a State Certification in Air Conditioning. :D
     
  11. Ramussons

    Active Member

    May 3, 2013
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    From the photo, it seems that they are 90 Amps breakers on Each phase ganged together.

    To answer your question, yes, you can go to 90 Amps per Phase - totally 270 Amps. But that is only for surges, like the starting current of a motor or something like that.

    The wire and the terminations don't seem to be meant for continous 90 Amp load.

    That aside, a lot of inputs have been given by other members above, please take care.
     
  12. tranzz4md

    Member

    Apr 10, 2015
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    90 amps per phase. continuous??? more or less..... if any of the poles of that breaker receives more than 90A for a period of time - which will vary, and is plotted and available from the manufacturer- it will trip. You don't understand 3 phase electrical systems, or the differences between single and 3-phase loads, so you are confused. That's pretty typical, no sweat. For most loads, if you distribute, or balance them across the 3 phases or poles, your imbalance current on the "neutral" will be small, not additive, and you'll get a lot of power from your electrical service. Simply be sure none of your wiring or electrical equipment has been damaged or improperly installed and you will be safe and have a reliable system.
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That would sound as though at some point there would be a total of 270amps flowing, this does not take into consideration the fact that 90amps does not flow simultaneously through the three breakers at any given point in time.
    There is a phase difference and the direction of flow in each breaker.
    Max.
     
  14. Rocket.Man

    New Member

    Jan 1, 2012
    20
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    YES you can pull 90 from each wire. Look at the wire size it should be rated 90 amps not 30 amps.

    I worked in industry for 45 years. I wired all the machines and equipment in the factory. A 90 amp braker means it is 90 amp on each leg.

    Do you need proof? Look at a 15 amp single pole braker, now look at a 15 amp double pole brake, next look at a 15 amp triple pole brake. They all look the same only difference the triple is built as 1 unit with 3 brakes in the same case. Do you have a circuit box at home with a double pole braker to the kitchen stove, electric dryer and AC unit? Remove the 50 amp double and replace it with TWO 50 amp singles. NOTICE the singles often have a hole though the switch level this is for a pin to connect 2 signals together to make a double. You make a 50 amp double with two 50 amp singles.

    A 3 phase motor is a 3 phase generator in reverse. The generator makes electricity, the motor uses the electricity.

    [​IMG]
     
    Last edited: Apr 11, 2015
  15. MaxHeadRoom

    Expert

    Jul 18, 2013
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    True, but 90amps does not appear on all phases at any given instant in time, look at the three current wave forms to get an idea how and when the respective currents occur.
    http://www.electricaltechnology.org/2014/09/three-phase-current-values.html
    Max.
     
    Last edited: Apr 12, 2015
  16. Lundwall_Paul

    Member

    Oct 18, 2011
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    Right now I would be concerned about the corrosion on the breaker terminals and the aluminum wires that are attached. You can clean these and apply No-Ox.
     
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  17. tranzz4md

    Member

    Apr 10, 2015
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    [This E="Dodgydave, post: 843865, member: 170203"]That is a 3 phase breaker rated at 90 Amps, so it will trip when it reaches maximum,
    all three phases must take the same current or it will trip due to imbalance.[/QUOTE]

    This is absolutely untrue. Not even close to reality. Be careful what you post.
     
  18. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    This is absolutely untrue. Not even close to reality. Be careful what you post.[/QUOTE]

    the 3phase breakers i have worked on will trip if there is an imbalance in the phases.
     
  19. tranzz4md

    Member

    Apr 10, 2015
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    the 3phase breakers i have worked on will trip if there is an imbalance in the phases.[/QUOTE]
    I doubt youve worked on any. I've worked on thousands. a 3 pole breaker will full load on any single pole without any regard to the other poles. try one. go to manufacturers literature. GE, Siemens, Westinghouse, Cutler-Hammer, Square-D, Schneider, ITE, Mitsubishi, you name it. It's part of the test actually performed on them.

    I'll drop off the board before I get into any flaming.

    Enough already.
     
  20. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I've had a working familiarity with three phase power of all designs for about 20 years now and I agree standard three phase breakers will not trip if there is a current imbalance. Only special duty types designed to sense imbalances will do that.
     
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