3 Phase HVDC supply with MOTs / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

3 Phase HVDC supply with MOTs

1 2 3 4 next

Move Thread

LAN_403

Kizmo

Tue Jan 06 2009, 11:48PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Im slowly putting together maybe largest MOT powered TC ever made. Since where i live (Finland) its not proper way to load power distribution network by putting huge pile of transformers in one phase only. 3ph power can be found almost any place here, even summer cottages may have 3~ service so why not use it with TC? 400V phase to phase and 230V N-L @ 50Hz.

Basic idea is to build rectified 3ph MOT stack and then use DC Resonant charging toplogy. I have harvested MOTs for about year now and i have torn apart more than hundred ovens so far. For this project i will use 3 + 3 identical transformers rated 2100VAC .85amp and 2300VAC 0.65amp. Each phase will have 2 mots in antiparallel, primary and secondary windings are connected in star configuration. Secondary star point is connected to mains ground.

First setup is here: (THIS IS ONLY PROOF OF CONCEPT PROTOTYPE. FINISHED DEVICE WILL BE SAFER AND BETTER)

Youtube clip:

Then i made quickndirty 6-pulse HV rectifier from 24 microwave oven diodes and results were spectacular!! (remember, nothing is resonating here, no capacitor involved)

Youtube clip:

It sounds really weird, input power was around 8kW and output voltage 8kVDC. My ballasts (3 identical mots left in first picture) were toasting really badly after 15min of use. Transformer bank itself was barely warm to hand.

Line voltage without load: 234VAC
Line voltage with load: 233VAC
Voltage after ballast withoud load: 190VAC
Voltage after ballast with load: 109VAC

You dont need to be very smart to see what makes those poor ballasts toast so badly. I really need to wind my own adjustable ballasts which can take serius beating. I think i can push these well over 10kVA without much trouble. Im planning to submerge all transformers and rectifier in oil just for cooling purposes. I have already nice tank with wheels :)

GeordieBoy

Thu Jan 08 2009, 04:02PM

Registered Member #1232 Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881

The 300Hz tone that you can hear in the second video is because it is using a 6-pulse rectifier. The DC output has a significant AC ripple component at 6 times the line frequency ie. 300Hz

DC also arcs better than AC because in the case of the 6-pulse rectifier the output voltage never falls right down to zero beetween the mains peaks. Arcs are generally more stable because, unlike AC there are no current zeros for the arc to cool and extinguish.

-Richie,

Alexandre

Thu Jan 08 2009, 04:17PM

Registered Member #1228 Joined: Tue Jan 15 2008, 01:08AM
Location: Curitiba, Brazil
Posts: 162

NICE!amazed

Kizmo

Thu Jan 08 2009, 04:43PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

GeordieBoy wrote ...

..DC also arcs better than AC because in the case of the 6-pulse rectifier the output voltage never falls right down to zero beetween the mains peaks. Arcs are generally more stable because, unlike AC there are no current zeros for the arc to cool and extinguish.

-Richie,

Yep and there is 3 times the power of a single 2mot pack. One strange thing i noticed was that it was extremely hard to get jacobs ladders work with DC. It was almost impossible and every time arc got stuck it melted 3mm steel rods and whole thing collapsed

I will make new ballasts soon so we will see some +10kVA DC action! And then some oil cooling and +15kVA... :)

Dr. Dark Current

Thu Jan 08 2009, 05:03PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Kizmo wrote ...

I will make new ballasts soon so we will see some +10kVA DC action! And then some oil cooling and +15kVA... :)

...And then add some resonant caps!

This was with JUST 3 caps per 2 MOTs, imagine using 4-6 caps!!! 3 meter arcs anyone?

Kizmo

Thu Jan 15 2009, 03:25PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Update 15.1.2009

When im buying beer for myself i usually go for 12pack instead of 6pack. Looks like same thing applies here as well:

12 MOTs, each rated at least 1.3kVA

Test run @ 10kVA, transformers didnt even get warm! Everything except ballasts were stone cold.

And here is control panel, i got the case from local cemetary (old fuse/main switch box from early 60s)

Next step is to mount all transformers in steel tank and finish extrenal wiring + ballasts.

Small video about near 10kVA run (did some fine tuning & real measurements)

Dr. Dark Current

Thu Jan 15 2009, 03:38PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Kizmo wrote ...
Update 15.1.2009

When im buying beer for myself i usually go for 12pack instead of 6pack. Looks like same thing applies here as well:

12 MOTs, each rated at least 1.3kVA

How much do you dare to depress me

Firefox

Sat Jan 24 2009, 02:17AM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

Since our latest posts have been wiped by some jerkball's

worm, let me reiterate: Awesome! Now I double dare you to take all those MOCs and MODs and make a three phase CW multiplier for your MOT stack.

Hazmatt_(The Underdog)

Sat Jan 24 2009, 08:41AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I'd like to see some proper HV wire on this project or maybe just some RG8X without the shield, and finished off with 3 large beehive bushings.

I like to see things over done, but I get worried about over-KILL sometimes, if you know what I mean.

Kizmo

Sat Jan 24 2009, 11:16AM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

When it comes to finished product safety is my number one concern. I have bought some proper 10kV high tension wire for internal wiring. Whole thing will be installed in steel tank and submerged in transformer oil including rectifier bridge so this device outputs HVDC only. And i bought few ceramic HV feed through insulators too.

Maybe i put together another 3 phase stack to test resonant capacitors and voltage multipliers :)

1 2 3 4 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob