1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Connecting 240 volts to a motor

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Anonymous, Jul 7, 2002.

  1. Anonymous

    Anonymous New Member

    Joined:
    Jul 5, 2002
    Messages:
    33
    Likes:
    0
    Hello

    I have a 220/240v motor which came from an old electronic heater, the
    kind that blows out hot air. I want to directly connect this to a 240
    volt electric wall socket.

    I have 2 red wires coming out of this motor and the electric cable
    connecting to the wall socket also has 2 wires, one earth (brown),
    the other is neutral (blue)

    Now, does it matter which electric wire connects to the wire on the
    motor? and what will be the consequence of this? If so, how can I tell
    which wire on the motor is live and which is neutral?

    If it doesn't matter which wire goes where, I presumably can connect
    it any way I like and it will work?

    Thanks for any input,

    Sean
     
  2. Anonymous

    Anonymous New Member

    Joined:
    Jul 5, 2002
    Messages:
    33
    Likes:
    0
    It doesn't matter which way around you connect the wires. It will work
    either way.

    BTW FYI the brown wire is actually active, NOT earth. Since you made this
    mistake, it sounds like it's best for a qualified person to do the
    connection, or at least check it before you use it.

    Also, as there seems only to be two wires coming from the plug, I am
    assuming the plug is a moulded type with only two pins. If so, and if the
    heater element is still connected, be careful about the rating of the cable.
    Many heaters use the full 10 amps (Australia) of a power point. A "normal"
    two pin plug with only two wires is usually rated at only 7.5 Amps.

    Cheers,
    Phil
     
  3. Chris

    Chris New Member

    Joined:
    Jul 9, 2002
    Messages:
    4
    Likes:
    1
    Location:
    Dubuque Iowa USA
    Single Phase AC changes direction 50/60 times a second, so polairty is no problim. However 240VAC can kill. Quickly.....
    So be careful..

    Have Fun
    Chris
     
    • Like Like x 1
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Prof.Insane

    Prof.Insane New Member

    Joined:
    Jul 23, 2002
    Messages:
    48
    Likes:
    0
    Location:
    UK

    What IF.....

    What if the neutral wire is grounded inside of the motor? The neutral is grounded at the power station. If the wires are connected the wrong way around and the motor neutral is grounded it will blow the RCD's in your house, or maybe the fuses.

    -Chris (Not the moderator :!: )
     
  6. Phasor

    Phasor Member

    Joined:
    Aug 14, 2002
    Messages:
    703
    Likes:
    0
    Location:
    Sydney, Australia
    If there is no earth on the motor, the polarity is not important.

    HOWEVER, this is assuming it is of the plastic type. If it has metal parts, they should be earthed, and therefore, polarity IS important. But then again, seeing that there is no earth wire on the motor, probably the first case applies.
     
  7. mechie

    mechie New Member

    Joined:
    Sep 4, 2002
    Messages:
    591
    Likes:
    3
    Location:
    Lincolnshire, England
    Series or parallel?

    Are we missing a point here?
    If you dissect a cheap hairdrier you will probably find that the heater has THREE connections - it works as a voltage dropper for a low voltage motor (circa 50 to 150v) - or some variation on this theme.
    I have also seen capacitors used as voltage droppers for low voltage motors in heaters.
    :!: Play with mains at your Peril :!:
    More information would be required of the original circuit to make any sort of safe recommendation.

    ps. Prof. Insane - a power station is a long way from your house, produces 400kV (UK supergrid) and has a resistor between its star point and earth - this is for fault detection, NOT earthing.

    pps. this has evoked some response over the last few months 'ant'it?
     
  8. indeep

    indeep New Member

    Joined:
    Sep 20, 2002
    Messages:
    5
    Likes:
    1
    Location:
    Colorado
    You know theres a little detail here that seems to be overlook.

    If you have a 240 volt moter then i hope you have a 240volt plug if so then there is no netrual but two hot legs of 120v each.
     
  9. Phasor

    Phasor Member

    Joined:
    Aug 14, 2002
    Messages:
    703
    Likes:
    0
    Location:
    Sydney, Australia
    There would be very few places in the world, where electricity is supplied at 120V per phase, with the phases 180 electrical degrees apart (as would be required to give 240V).

    FYI, electricity supply in Australia is 240V per phase, or 415V between phases. In fact, a large proportion of the world is 220-240/400-415V (with a 3 phase system).

    And besides, who would bother putting a polyphase motor in a little heater?
    :)
     
  10. indeep

    indeep New Member

    Joined:
    Sep 20, 2002
    Messages:
    5
    Likes:
    1
    Location:
    Colorado
    I dont know where you are but in USa 240 volt consists of two 120 volt legs.
     
    • Like Like x 1

Share This Page