Tesla coil progress

[rjenkinsgb]

How is three phase different than just adding the frequency?

Single phase "pulses"; the voltage drops to zero twice per AC cycle.

Three phase is totally balanced, you can draw the same amount of power all the way through the AC cycle, with suitable loads.

It also inherently has a rotation, with the three offset voltages, so motors run smoother and do not need capacitors to start or run, as with many types of single phase AC induction motors.

 

[Western]

A year or so ago I replaced the old single phase motor with a three phase motor and three phase variable frequency drive.
The difference between the two motors is amazing.

What size is the motor Jim and what sort of VFD are you using. I'm assuming you run it off single phase still??

 

[JimB]

What size is the motor Jim and what sort of VFD are you using. I'm assuming you run it off single phase still??

Rather than hijacking billbobs thread, I have continued the discussion about my lathe motor here:

A new motor for my lathe

Split off from this thread: https://www.electro-tech-online.com/threads/tesla-coil-progress.160927/page-2#post-1397824 JimB said: I have a small lathe, a Myford ML7 which is nearly as old as I am. A year or so ago I replaced the old single phase motor with a three phase motor and three phase...

www.electro-tech-online.com

JimB

 

[billybob]

Rather than hijacking billbobs thread, I have continued the discussion about my lathe motor here:

A new motor for my lathe

Split off from this thread: https://www.electro-tech-online.com/threads/tesla-coil-progress.160927/page-2#post-1397824 JimB said: I have a small lathe, a Myford ML7 which is nearly as old as I am. A year or so ago I replaced the old single phase motor with a three phase motor and three phase...

www.electro-tech-online.com

JimB

My lathe was a few lego bricks.

 

[billybob]

Alright, I know it’s been a while, but I’m saving some of the progress for later. I do have a question though. I have become very fond of my variac recently and don’t know if I really want to include it in the Tesla coil. Would including it help at all? Wouldnt some of the power be lost as internal heating in the variac? I am working on a rotary spark gap to increase performance a little and have a dimmer switch to control that so the variac is unnecessary there. The only benefit I see of having a variac would be the ”soft start“ so nothing blows or to much current at one time.

Also can I upload videos? I really want to show off this thing when it’s done

 

[DerStrom8]

Alright, I know it’s been a while, but I’m saving some of the progress for later. I do have a question though. I have become very fond of my variac recently and don’t know if I really want to include it in the Tesla coil. Would including it help at all? Wouldnt some of the power be lost as internal heating in the variac? I am working on a rotary spark gap to increase performance a little and have a dimmer switch to control that so the variac is unnecessary there. The only benefit I see of having a variac would be the ”soft start“ so nothing blows or to much current at one time.

Also can I upload videos? I really want to show off this thing when it’s done

Variacs give you a good amount of control over the charge/discharge rate of the primary tank capacitor. It will allow you to better match the output of your transformer to the capacitor, thus improving efficiency.

Yes, you can upload videos. Use the Insert -> Media option to include videos from Youtube. You can also try the "Attach files" button at the bottom of the editor, but that may restrict what types of files you can include, as well as file size.

 

[billybob]

Variacs give you a good amount of control over the charge/discharge rate of the primary tank capacitor. It will allow you to better match the output of your transformer to the capacitor, thus improving efficiency.

Yes, you can upload videos. Use the Insert -> Media option to include videos from Youtube. You can also try the "Attach files" button at the bottom of the editor, but that may restrict what types of files you can include, as well as file size.

I guess I’ll wire it up for the variac then. If I need it later I’ll figure something out.

Ah found it. Does it limit the quality or the length of the video?

 

[DerStrom8]

Ah found it. Does it limit the quality or the length of the video?

I suspect both. It would limit the file size, so a short high-quality video or a long low-quality video might not be upload-able. Youtube is your best bet.

 

[billybob]

I suspect this should be simple math, but I need some guidance here. This is my rotary spark gap so far.

I need six points and have calculated the Circumference of the circle to be 18.84 inches with a radius of 3 inches
How can I mark the points evenly spaced? I divided the circumference by 6 and got 3.14 inches but how can I mark that? Would a compass help?

 

[billybob]

This is kinda what I’m going for.

 

[DerStrom8]

You should measure angles, not distance. Draw three lines, starting at the edge, through the center, all the way to the opposite edge. Each line needs to be 360/6 = 60 degrees from the previous one. Place your electrodes on these lines.

 

[billybob]

You should measure angles, not distance. Draw three lines, starting at the edge, through the center, all the way to the opposite edge. Each line needs to be 360/6 = 60 degrees from the previous one. Place your electrodes on these lines.

Ah so simple! Gonna have to find a protractor then. Thanks Derstrom.

 

[DerStrom8]

You can technically do it by taking measurements but it will require a bit more math.

 

[JimB]

There is a very easy way to divide a circle into six parts around its circumference.

Use compasses to draw the circle with the desired radius. Leave the compasses set to the circle radius for the following steps.
Select a point on the circumference for one of the six points.
Put the spike of the compasses on the selected point and mark another point on the circumference using the compasses.
Move the spike of the compasses to the new mark and create a third mark on the circumference.
Continue around the circumference until you have made six marks.

JimB

 

[billybob]

There is a very easy way to divide a circle into six parts around its circumference.

Use compasses to draw the circle with the desired radius. Leave the compasses set to the circle radius for the following steps.
Select a point on the circumference for one of the six points.
Put the spike of the compasses on the selected point and mark another point on the circumference using the compasses.
Move the spike of the compasses to the new mark and create a third mark on the circumference.
Continue around the circumference until you have made six marks.

JimB

That might work if the center was even with the board, but it isn’t, so once the compass is at the 180 mark it is about an inch or so too far just by looking at it. If that isn’t the problem the radius is three inches when measured with the compass, but when marking from point to point around the circle it will always be too much because it lost some of its Circumference and it would now be a hexagon and not a circle.

 

[billybob]

I don’t know if I misunderstood you JimB, but this video explains how it’s possible.

 

[billybob]

Well now begs the question.... Six contacts or eight?

 

[JimB]

I don’t know if I misunderstood you JimB, but this video explains how it’s possible.

Similar idea, just a variation on a theme.

That might work if the center was even with the board, but it isn’t,

OK, that is a bit of a problem, but the video shows a method which may work.
But if the board does not have a centre, how will you draw the circle?

JimB

 

[billybob]

Similar idea, just a variation on a theme.


OK, that is a bit of a problem, but the video shows a method which may work.
But if the board does not have a centre, how will you draw the circle?

JimB

It does have a center it’s just raised a bit, so it will draw a perfect circle, but unfortunately not be able to do your suggestion.

 

[billybob]

Hold up. Would that really work though? If your suggestion caused the points to be off a bit it would do the same if I tried the video.