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Connecting 240 volts to a motor

Anonymous

New Member
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
 

Anonymous

New Member
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
 

Chris

New Member
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
 
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Prof.Insane

New Member
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 :!: )
 

Phasor

Member
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.
 

mechie

New Member
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?
 

indeep

New Member
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.
 

Phasor

Member
indeep said:
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.
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?
:)
 

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