Choosing a 240Vac motor switch

Discussion in 'General Electronics Chat' started by jonnydolt, Mar 14, 2019 at 12:36 PM.

  1. jonnydolt

    Thread Starter Member

    Oct 23, 2015
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    I need assistance in choosing switch's please.For example one of the motors I have is a reversible CSCR single-phase 240 vac motor
    Type: GMYL90L2-2.PNG GMYL90L2-2
    Power: 3KW/4HP
    Speed: 2 Pole (2800rpm)
    Maximum amperage draws: 18.2Amp ...........I have been on ebay,mouser and others searching for an AC 20 amp switch.My understanding is I need one that has rated current (Ie (AC-3)) of 20 amps, is capable of 3kw induction motors, a rated voltage(Ue) of at least 240v an Ith of 20 amps at 40 degrees C (for my area) and a rated insulation voltage (UI) of at least 250 volts.From most searches I have found that most rate their switch's by the Ith value only,this to me seems to be an false capacity for the switch's full load draw.Am I totally wrong in my understanding of the above values? What I would like is an Estop switch and a push button red/green on/off switch with led's.Many thanks for taking the time to read
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    5,112
    You can use any standard 3ph contactor and use it on a 1ph motor.
    They also have the option of overloads as an option.
    They come rated in HP at the required voltage.
    If using a 3 phase contactor it is usual to loop one side through the 3rd contact.
    Here is motor diagrams in ladder format.
    Do you need disconnect or contactor?
    Max.
     
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  3. jonnydolt

    Thread Starter Member

    Oct 23, 2015
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    These are the contactors I purchaced https://www.ebay.com.au/itm/2X-AC-C...e=STRK:MEBIDX:IT&_trksid=p2060353.m2749.l2649 Not sure what you mean by "Disconnect"
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is a Telemecanique (Schnieder) and should work, the aux contact is used to latch in a stop/start P.B. station, which can take 24vdc LEDs if you want indication.
    What is the voltage of the contactor coil?
    A disconnect is a switch often used ahead of the contactor, just a safety feature.
    Normally any fusing goes between the disconnect and contactor, the neutral if used is not fused.
    Max.
     
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  5. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    Yes it will have a disconnect I call them power points lol .I actually have multiple motors and projects.I used the 3kw motor as an example as it will have the largest draw.The 3Kw motor is the most simplest,it will be used in an air compressor build and will plug into a 15 amp dedicated circuit.I also have a 2.2kw single phase motor and it will be used in a table saw build it draws 13.7amps so I guess it will also have to have a dedicated 15 amp circuit,I was also going to use one of those contactors an estop and red/green on off switch.The next project is a 2 x 72" belt grinder.I have a 2.2Kw 3 phase motor and a single phase to 3 phase vfd for this and shielded cables,contactor,tachometer,led's,rail mount fuse,potentiometer, voltmeter .and ammeter,lots of bells and whistles.The next project is an Oscillating spindle sander with a 2.2kw 240v motor I have all the motors etc and the wiring in the shed is not done yet so I can put in what I need, but getting the correct machinery switch's has been a real conundrum for me and a huge learning curve with lots of confusion
     
  6. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    220V Coil 18A
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The coil is not 18Amps though!;)
    Max.
     
  8. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    Most of my electrical stuff has been house wiring etc and bits and bobs on cars and other 12v stuff.I have lots of learning to do lol.To find out what I needed to do for the VFD job I used this you tube
     
  9. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    really bummer will check it out.I bought 4 of those.A costly mistake lol
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    17,094
    5,112
    You do not want the coil to consume 18amps!
    The one you have should be only around an amp or two, it is switched by the control circuit/switches.
    The contacts are rated for the 18A.
    Max.
     
  11. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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  12. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    contactor info.PNG AC3 is 18?
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That is the rated working current of the CONTACTS not the Coil which is at the bottom and they only show the optional coil voltages, not the current, which for yours is <2a.
    Max.
     
  14. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    Yes the contacts thats what I meant for 18amps not consumption
     
  15. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    The contactor,this is basically a relay? and this takes some of the switching strain away from the on/off switch's after the contactor?
     
  16. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Exactly that, a form of relay.
    It has an armature that is activated by the coil, this allows low level switching devices to complete the circuit.
    For future reference, if a 24vdc supply is also required for the system for ind lights etc, it also pays to purchase a contactor that has a coil of corresponding DC voltage.
    24vdc is pretty much the standard for control circuitry, the old standard a few decades ago was 120vac/240vac.
    Max.
     
  17. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    If you have time Max scroll through to 16:12 and you will see what I plan for the grinder build
     
  18. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
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    dc that makes sense everything after the power supply would be a whole lot safer
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
    17,094
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    Technically he should have the fuse before the contactor, also I didn't see how he wired the coil but normally it would be in a E-Stop circuit, and not part of a normal start/stop circuit, Especially for a VFD, unless he has a separate stop P.B. for the low level VFD input, IOW never use the contactor for normal start/stop when using a VFD..
    Max.
     
  20. jonnydolt

    Thread Starter Member

    Oct 23, 2015
    67
    1
    Yes on the lathe it has a potentiometer,estop and on/off switch
     
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