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synchronous spark gap

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Bud

Mon Aug 31 2015, 11:42AM

Registered Member #54930 Joined: Tue Apr 28 2015, 01:38PM
Location: pittsfield ohio
Posts: 25

Hi All, Can anyone comment on RSPG's. I have a washing machine motor that has been converted to be synchronous @ 1550~ rpm.......checked it with a strobe light and it is steady. The question is this? Is there an advantage of electrically controlling timing the motor to get in phase vs mechanically rotating the motor to get in time? I would think that once mechanically set the motor will always be in phase and the contacts would always be in the correct alignment. Yes No What?

Any help would be appreciated.

Bud

1441021301 54930 FT0 12 Strike Tesla Coil

klugesmith

Mon Aug 31 2015, 07:50PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Hi Bud. Nice TC you got there. Could you clarify "synchronous @ 1550~ rpm.......checked it with a strobe light and it is steady." Sounds like the RPM value on motor nameplate, which would be the speed under load before modification. It would be the synchronous speed when power frequency is about 51.7 Hz.

Please tell us about your strobe light!

Did you convert the motor by making four well-balanced flat spots on the armature stack? Then its rotation phase should be the same after every start, except for an arbitrary multiple of 90 degrees, plus a shift that depends on load torque. Adjustments made mechanically should be just as stable as those made electrically. I think the mechanical approach (by turning the motor case or the fixed-electrode plate) is just as easy, just as robust, and can just as easily be tweaked while the coil is running. Remotely adjustability would be a nice feature.

This advice is from someone who has never made a Tesla coil. But I have collected, made, and/or played with many kinds of synchronous motor and line-synchronous stroboscopes. My synchronous conversion of a MWO fan motor was successful (with an asterisk).

Signification

Tue Sept 01 2015, 12:26PM

Registered Member #54278 Joined: Sat Jan 17 2015, 04:42AM
Location: Amite, La.
Posts: 367

@klugesmith:
Do you know the resistance and wattage of that monster train-brake resistor in the photo? Also the weight?

Bud

Tue Sept 01 2015, 01:00PM

Registered Member #54930 Joined: Tue Apr 28 2015, 01:38PM
Location: pittsfield ohio
Posts: 25

Hi klugesmith, I did machine 4 flats on the rotor according to the specs on the HVTESLA website of 25% of the rotor diameter. It does synchronize very well as much as I can see. For a strobe light I took my sears engine strobe light from many years ago and hooked it up to a 12v battery and held the ignition lead clamp close to my VTTC primary while it was on low power. I know this may sound a little archaic but it was the only way I knew how as it runs on 60 hz.. I recently stumbled upon the plans to modify a radio shack party strobe light which is a much safer way to go. I am not sure of the exact motor RPM but I wanted to clarify it was not 3600` rpm 2 flats but 1500` rpm 4 flats 60 hz........4 contacts. My plans are to build two rotational plates (one for the motor and one for the spark gap frame) that allows me to turn the plate ~45 degrees so that I can line up the electrodes at 60 hz.

Not sure if this washing machine motor will have enough HP to overcome the wind friction of the rotating electrodes but we will soon see. Nothing ventured nothing gained. The motor was free to me.

I will definitely take some video shots and put up a youtube video showing how this all works once complete. I have my own tool and die facility with 22 emloyees. Can engineer and build just about anything.....the big trick is knowing how it works before hand.

Bud

Bud

Tue Sept 01 2015, 03:46PM

Registered Member #54930 Joined: Tue Apr 28 2015, 01:38PM
Location: pittsfield ohio
Posts: 25

klugesmith

Wed Sept 02 2015, 01:18AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Hi Bud.
Long time since 60 Hz synchronous stroboscopes have been discussed here.
Here is a link to the one I used for that video. Light source is a nominal 1-watt LED. No xenon or high voltages are involved.
The only integrated circuit is a single 555.

Previously posted to 4hv in 2011. Has it been that long since the 555 contest?

Forgot that it mentions me burning out an AC wallplug transformer
by drawing power through a half-wave rectifier.

@Sig: I forgot the measured resistance of my serpentine cast iron resistor, and never knew the power rating.
The limiting ambient temperature for power derating is probably well over 200 degrees C.

Bud

Wed Sept 02 2015, 02:00PM

Registered Member #54930 Joined: Tue Apr 28 2015, 01:38PM
Location: pittsfield ohio
Posts: 25

Hi siginification, In regards to the train brake I am not sure what you are referring to. the only thing that comes to mind is the monster variac I have. It is 85 amp. Has the big dial on top of a 36" high case 2 ft X 3 ft approx.. I got it several years ago on ebay and I picked it up not far from my home. It came from the Perry nuclear facility east of Cleveland Ohio. A very rare find! Works really nice for this big coil.

Bud

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