dc motor chassis as ground

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Newz2000
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dc motor chassis as ground

Post by Newz2000 » Tue Aug 30, 2005 1:47 pm

I used a dmm to check the continuity between the motor chassis/shaft and both wires leading to the motor. The chassis and shaft have continuity with each other, but do not have continuity with either of the leads to the motor. Is there any reason not to simply attach one of the leads on the motor directly to its chassis and then ground the chassis?<p>The motor will not be reversing, but does that even matter?

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Chris Smith
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Re: dc motor chassis as ground

Post by Chris Smith » Tue Aug 30, 2005 2:08 pm

The chassis and rotor shaft have a common connection, its called the shaft bearings. <p>If the windings are not connected to the chassis, then no power will flow into the windings your way. <p>The DC motor goes through the windings and a commutator either segmented or slip ring style, but this route doesn’t usually involve the body or the shaft bearings. <p>Also any pathway of power that goes through the bushings or ball bearings will arc, damaging the bearings. <p>Thats why they use slip rings and commutators.

Newz2000
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Re: dc motor chassis as ground

Post by Newz2000 » Tue Aug 30, 2005 2:13 pm

I tested it before I posted and it works, I'm just curious if there's a reason I shouldn't do this.<p>Here is what I want to do, tell me if this will cause problems:
battery - to motor chassis via screw
battery + to motor red wire
motor black wire to motor chassis via drop of solder.<p>My goal is to connect other components to ground via the motor chassis.

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Chris Smith
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Re: dc motor chassis as ground

Post by Chris Smith » Tue Aug 30, 2005 4:39 pm

As long as there is good isolation in the windings its ok. If the isolation leaks, you risk damaging the bearings for starters. <p>Grounding the body is good for Shielding RF, so yes, its ok to do that.

rstofer
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Re: dc motor chassis as ground

Post by rstofer » Tue Aug 30, 2005 5:02 pm

Why not? The starter motor in you can works the same way.<p>Now, I am assuming this is a LOW VOLTAGE motor. All bets are off if the thing is running at hundreds of volts.<p>12V or so should be fine.

Robert Reed
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Re: dc motor chassis as ground

Post by Robert Reed » Tue Aug 30, 2005 5:39 pm

Matt
Most motors are metal framed and that inturn affixed to a platfom in some way--probably bolted down. This would be especially true for mobile use. Probably every motor in your vehicle is grounded via its mounting bolts. This will work the same way as residential wiring, the common (or in your case- the neg batt. lead) carries the return current and the grounding mechanism, although at the same potential carries nothing. Or at least until certain faults may occur.

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