My new power supply...

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
Post Reply
User avatar
John Taylor
Posts: 97
Joined: Wed Jun 22, 2011 5:43 pm
Real name:
Location: Dardanelle, Arkansas

My new power supply...

Post by John Taylor » Fri Sep 19, 2014 11:11 pm

I have started building a new power supply and thought I might share some of the details as I go. This is probably going to be overkill, but I have either scrounged all the parts or bought them cheaply from a popular online auction site. My first images are of my voltage multiplier board bolted to my voltage divider. The multiplier is an 8-stage full-wave multiplier that was originally part of a 100kv power supply that I purchased online. I populated it with 20kv .001 uF ceramic capacitors. At the top of the circuit board are 8 5000 ohm high voltage resistors and then I have a 75000 ohm 300 watt resistor to give 115kohms of current limiting.
I will feed this multiplier from a hand-wound ferrite core transformer with 7 turns on primary and 150 turns on the secondary. My objective is to do this as cheaply as possible, while ending up with a professional grade supply, so I wound this transformer with 16 gauge enameled wire on the primary and 20 gauge stranded, vinyl insulated wire on the secondary with high temperature fiberglass tape between windings.
The voltage divider started life as a flyback transformer bank that had 8 200meg high voltage resistors on it. I removed the flybacks and added precision resistors of 1.6 meg to derive a 1000:1 division. Across this resistance is a MOV rated at 130volts for meter protection. I will measure the voltage through a 200v digital panel meter which I have calibrated to accurately reflect my applied voltage. I also have a 5 watt 1% 200ohm resistor in series with ground for measuring current. This also has a 130v MOV across it for protection. This feeds an identical panel meter which I have calibrated to read 5ma for each volt dropped across the resistor.
The transformer is driven at around 240khz and a 0-700v square wave by 4 paralleled ECG2533 Horizontal output transistors with balancing resistors. The square wave is coming from a frequency generator now and voltage is controlled by a variac which takes 0-140vac and feeds into a current-limited voltage quadrupler. The variac is only for testing everything else. I will put together a PWM regulator to feed the whole thing after everything else is working.
I have tested up to 50kv in dry air, but will submerge the high voltage portions in oil before going higher. (The corona was getting scary!) The high voltage assembly will fit snug a section of 6" pvc with cleanouts (screw on pieces).
Before criticizing my attempts, please understand I am trying to build a professional-grade power supply as cheaply as possible and am going for function more than looks. I am definitely open to any suggestions from members as well as questions. I will try to update this link as I progress on.
Attachments
Hvps6.jpg
Ferrite core transformer (obviously hand made) layer separated with fiberglass tape, outside covered with Scotch 88 vinyl electrical tape
hvps5.jpg
HUGE Voltage multiplier with current limiting resistor ( 7700uf electrolytics from old inverter) making over 700 vdc
hvps4.jpg
Driver transistors on heatsink scrounged from old linear power supply
hvps3.jpg
Multiplier / voltage divider assembly
hvps2.jpg
Multiplier / voltage divider assembly
hvps1.jpg
Multiplier / voltage divider assembly

User avatar
Richard Hull
Moderator
Posts: 11941
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: My new power supply...

Post by Richard Hull » Sat Sep 20, 2014 4:35 am

Nice looking work there. Keep us informed. Do you have any idea about the current capability or is that to be determined?

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

User avatar
John Taylor
Posts: 97
Joined: Wed Jun 22, 2011 5:43 pm
Real name:
Location: Dardanelle, Arkansas

Re: My new power supply...

Post by John Taylor » Sat Sep 20, 2014 11:13 am

I still don't know about current capability, but right now that transformer would limit me quite a bit. I have found a couple of German made x-ray heads (Heimann) that I will rob the much larger cores from and experimentally determine what their flux saturation is and wind two identical transformers to be connected in parallel. I know the driving voltage and frequency for the x-ray transformers and I will count primary turns as I dismantle them.

My thought on current output is that I will be limited more on input power capabilities. I only have 30 amp 240vac available in my small shop.

Part of the reason for this project is just the fun of it, but also to get rid of my current 60 Hz, large stored energy power supply run from a large 200:1 potential transformer.

I also just realized I have this thread in the images section and probably should have put this much discussion in the power supply section. I will limit my discussion here and try to send more images as I build.

Post Reply