Re: AC Split phase motor????

[Terry Fritz <twftesla-at-xxxxxxxxxx>]

Hi All,

I don't know how much good it does, but I have MOVs across the motor's AC
wires to ground on my gaps.  I also have a line filter but that would not
affect this problem.  I also have a rod contacting (just barely) the rotor
shaft to conduct arcs off the shaft to ground rather than going though the
bearings.

http://hot-streamer-dot-com/TeslaCoils/MyCoils/BigCoil/Rgap.jpg

I connect the motor grounds to the RF ground since I don't carry AC line
ground into the coil area.

The MOVs may provide a safe path for a strike but the windings have high
inductance so it is hard to say.  I more worry about the powerful primary
circuit finding it's way to the motor (shaft) rather than a streamer hit.
The motors are well enclosed so it would not be possible for a hit to a
bare winding.  Of course, once an arc path from AC line to ground were
established, the damage would be sever but limited by fusing.

If more were known about the damage and it's cause, protecting against
these motor failures would be easy I would think.  The stuff I do is just
guessing without any real idea about what actually destroys motors.

Cheers,

	Terry


At 10:22 AM 11/12/2000 -0500, you wrote:
>In a message dated 11/11/00 6:13:21 PM Eastern Standard Time, 
>tesla-at-pupman-dot-com writes:
>
>> Thanks Bert,
>>  
>>  It sounds like you nailed it.  The instantaneous HV on the motor case
>>  probably found the nearby mains windings very tempting !
>>  
>>  This is one reason why I connect my motor chassis to the utility ground
>>  instead of the RF ground.  The RF ground is very noisy when the coil is
>>  running,  and this must put considerable stress on the insulation between
>>  the case and the windings.
>>  
>>  I opened up the damaged motor,  but unfortunately the run winding of
>>  my motor had opened deep inside the stator,  and I didn't have the
>>  patience to rewind it.  I agree about the follow-through current.
>>  
>>                       Cheers,
>>  
>>                       -Richie,
>>  
>
>Richie, Bert, David,
>
>I too, ground my motors to the utility ground, and I've had no
>failures dispite a number of hits to the motor.  I wonder if David
>and/or the other fellow (Scot?) used the RF ground to ground
>their motor?
>
>John Freau
>