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Forum Index : Electronics : Brake switch

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radman
Newbie

Joined: 29/11/2011
Location: United States
Posts: 12
Posted: 11:25pm 15 Feb 2012
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I hope someone can help with this, I am about to launch a new 3 phase 24 volt turbine and I am using a two pole breaker switch to short out the mil. But I am not sure how to wire it. I plan to mount the box on the tower, this will make for an easy way disconnect when I need to lay down the machine, from the breaker the wiring will go to the rectifiers and on two the rest of the system about 40 feet away in the shop.
Regards, Mike
 
VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 11:45pm 15 Feb 2012
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Hi Radman

It can be damaging to the alternator to short out the windings without some resistance in the circuit as the inertia of the rotating blades can cause very high current for a short period of time until rotation ceases, this can damage the windings.

It would be better to have your relay in the shed with another loop wired extension lead on it as a resistance, I have trialled two 10 amp power leads from hardware store total length about 50 meters.

With a two contact switch you can connect two phases and the third one is left in the loop to the shorting point at the end of the leads as it will only see the other two phases when the switch is engaged.

All the best

Bob
Foolin Around
 
radman
Newbie

Joined: 29/11/2011
Location: United States
Posts: 12
Posted: 12:01am 16 Feb 2012
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Hey Bob, thanks for quick reply, so are saying I could use a power cord wired to the poles instead of a short wire connecting the two poles?

Mike
 
VK4AYQ
Guru

Joined: 02/12/2009
Location: Australia
Posts: 2539
Posted: 05:03am 16 Feb 2012
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Hi Radman

You use the resistance in the long cord to protect the alternator windings, two of the alternator wires are connected to the switch input side and the third wire from the alternator goes to the shorting point at the end of the lead where all three wires are connected. when the switch is closed the phases 1 and two are connected to he loop wires and there is no shorting bar at the switch.

All the best

Bob
Foolin Around
 
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