Build a Variable High Voltage Power Supply

I needed a variable 0 to 50KV high voltage power supply for my high voltage experiments that wouldn't break the bank, so I built my own.

With just a few parts from old microwave ovens, TV sets, and an oil burner, you can build an affordable instrument for whatever you wish to snap,crackle, or pop!

The key component is the voltage multiplier, which I covered in the High Voltage Multiplier instructable. Build it first, then drop it into this project for a variable output.

Step 1: Theory of Operation

The diagram shows the supply in the de-energized condition and the case closed.

Mains voltage is applied to the power supply thru a 120 VAC Panel connector. With the case closed, current passes through a 5 Amp fuse, F1 and through the case safety switch, S1 causing the Ready indicator, I1 to light when the power switch S2 is placed in the ON position to energize the supply.

At this time, the power supply is NOT ON but in a state of readiness to enegize the high voltage stage.

When pushbutton S3 is pressed, relay K1 energizes and remains energized after S3 is released.

Current passes through Variac, VT1 which adjusts the input voltage to the OBT. The OBT steps up the input voltage to a maximum of 6,000 VAC. The output of the OBT is fed to the high voltage multiplier, HVM where it is multiplied to 51,000 VDC output.

To de-energize the supply, place S2 in the OFF position. K1 will de-energize and remove power from the OBT and HVM and all indicators will extinguish.

The case safety switch and the power contactor are not necessary for this supply to work. I thought the ability to power on and off by using a pushbutton was cool. Thats all. The second schematic shows them removed.

Step 2: Gather the Parts

All the parts with the exception of the variac used for voltage control came from my junk collection or Ebay. Here's the list:

CHASSIS - Texas Instruments TI99 Computer case. Any metal box will do as long as there is enough room for the parts. An electrical box will do just fine. The computer case had a switch, an AC plug adaptor, and a removable lid so it was perfect.

F1 - 5 Amp fuse with holder (Radio Shack).

HVM - HV Multiplier - This is a build it yourself part made up of (6) 12KV High Voltage Diodes and (6) 470 picofarad 20KV High Voltage ceramic doorknob capacitors. You can buy all the parts on Ebay. I have already posted an instructable on this. Just search for High Voltage Multiplier.

I1 - READY Indicator - GREEN 120 volt Neon lamp (Radio Shack). An old 120 volt Neon indicator from a microwave oven is what I used here.

I2 - HV ON Indicator - RED 120 volt Neon lamp (Radio Shack).

K1 - Contactor - 120VAC 10 Amp DPST Relay with a 120VAC coil.

OBT - Oil Burner Transformer salvaged from an old oil burner from a mobile home rated at 120VAC @ 2.25 Amps on the input and 6Kv 20Ma on the output. The single pole type was used here. This can be purchased from a burner service company for about $65.00

S1 - SPST N.O. Cherry Microswitch for case safety.
S2 - DPST Toggle or rocker switch for power on.
S3 - SPST N.O. 120VAC Pushbutton switch.

VT1 - A variac was purchased for $60 from an electrical supply house. Any dimmer that can handle inductive loads up to 5 amps will work. The variac can control 2.5 amps. Just enough for the OBT.

MISC - You will need some wire lugs and various colors of wire scavenged from power cords for the internal wiring.

Step 3: Lay Out the Chassis

If your box has stuff in it, gut it. Take everything out of it except essential parts. I kept the power switch and the AC Adaptor. Everything else, GONE!

If your box has HANDSIZED holes in it, patch em. You don't want little ones (or a nosey neighbor) sticking their paw in the box with power on. Mine needed a cover for the back and a new face plate made of sheet aluminum. It would have cost me less to just use an electrical box instead.

Next, layout all the parts in the approximate locations shown giving yourself plenty of room for wiring. Space is essential in this project because we want to limit the possibility of arcing between high voltage components.

Drill holes where needed for mounting the parts and secure your parts using whatever hardware you have for working with sheet metal.

Step 4: Wire the Low Voltage Side

Decide if you are going to include a power contactor and case safety switch. If so, use the first schematic. If not, then use the second schematic.

Wire the supply starting with the AC connector, fuse holder, switches, variac and power contactor.

Test each stage of your build to make sure your wiring is correct.

Next wire up the OBT and test the range of the variac.

To test the output of the OBT, hold a GROUNDED screwdriver near the OBT output terminal.

If you see an arc, good. Power off the supply and disconnect it from Mains and move to the next step.

Step 5: Complete the Build

Depending on how you built your multiplier, you need to mount it to the chassis so it doesn't move around. In my case, I made a pair of homemade U shaped wooden mounts and glued the multiplier to the mounts using contact cement.

When dry, mount the multiplier in the chassis and wire it to the OBT and ground.

For the output, I passed the 50KV lead through the chassis using a 2 inch large rubber stopper as a grommet and some corona dope to prevent arcing. This worked until I passed the 35KV mark and then it arced over.

So I bought a screw on PVC plug and passed a 2 inch brass screw through the center, then filled it with 30 minute epoxy and let it cure.

I secured the feed through to the chassis with a piece of threaded PVC pipe to match. I then cut my 50KV lead to length and soldered it to the screw head on the back of my feed through.

I coated the whole assembly with corona dope, let it dry, and tried again. This time I succeeded and got to the 50KV mark at 100 percent without any arcing

Step 6: Power UP and Test It

*** WARNING ***
THESE NEXT STEPS ARE DANGEROUS.

Connect the power to the supply and turn on the main power switch. The "Ready" Indicator should light.

Set the voltage to 50 percent and press the HV ON pushbutton.

The HV ON Indicator will light and you will hear a slight hissing sound. This is okay. If you hear any snaps or arcing, determine where the problem is, shut off the supply, and dope the area. When it dries, test again.

With a grounded screw driver, bring the tip of the screw driver in close proximity to the output stud and watch for sparks.

*** WARNING ***
DO NOT TOUCH THE OUTPUT STUD WITH THE SCREWDRIVER. PERMANENT DAMAGE WILL RESULT.

If you are confident in your building skills, or hungry for sparks, SLOWLY ramp up the voltage to 100 percent and test again with the screwdriver.

Success will be indicated by the 2 inch long spark that you get from the supply.

*** WARNING ***
DO NOT ATTEMPT TO MEASURE THE OUTPUT OF THIS DEVICE WITHOUT SPECIAL TEST EQUIPMENT OR THE PROPER SAFETY EQUIPMENT.

*** DANGER DANGER DANGER DANGER DANGER DANGER ***

THE CURRENT PRODUCED BY THIS SUPPLY ALONG WITH THE HIGH VOLTAGE MAKES THIS DEVICE DANGEROUSLY LETHAL! DO NOT TOUCH THE HIGH VOLTAGE STUD DURING OPERATION. THIS THING WILL KILL YOU! GROUND THE STUD AFTER EACH SHUTDOWN TO DRAIN ANY REMAINING POTENTIAL.

Step 7: Safety Rules, and Disclaimer

SAFETY FIRST!

ALWAYS wear rubber safety gloves and stand on a rubber safety mat when operating this supply.

ALWAYS wear protective goggles when power is on. Especially if you plan to power a laser with this unit.

NEVER touch anything or device that is connected to the supply while it is in operation without adequate protection.

NEVER defeat the safety switch on the case or operate this supply with the lid removed.

DISCONNECT the supply from power before opening or working on it.

FOCUS your attention on what you are doing with this device. Eliminate any distractions or annoyances in the area where you use this device.

DO NOT ALLOW others to operate or work in the same area of this device without adequate supervision or safety training.

REMEMBER, Smokey says, only YOU can prevent People Fires!

*** DISCLAIMER ***
You, the builder and user, bear the responsibility for your own safety in building, testing, and using this supply. By building this device, you acknowledge the risks involved in it's operation and accept those risks as a result. I will in no way be held responsible for your actions, including your death by this instrument and you accept these terms by building and using this device.

Comments

[miicchhii]

"Multiplier for raising the 6000 volt to 50000 volt at the same current"?
So you get more power out, than you put in or am i getting something wrong?

[HenryH38]

The current will be reduced by the ratio of the 2 voltages.

[aclark17]

You multiply the voltage but it's in ratio to the amperage, the actual power in watts is the same, with the voltage higher the amperage drops considerably.

[DR55]

Can I use TIP 3055 npn transistor is place of 2n2222 sir on mini ht generator

[corbonzo]

Sorry if this is a stupid thing to ask.but i dont have money for a variac, i was wondering if a 120vac light dimmer used in houses would work. it says rated for 600 watts which would mean 5 amps right? sooo would that work? a reply would be great!

[aclark17]

Well, assuming a dimmer is an appropriate alternative, yes, that would be 5 amps, but only at 120v. That's the rating though, I'm curious if this worked? I would be afraid of it just shooting straight up to mains on my OBT and burning it out from the surge.

[RetiredResearchEngineer]

My load has very high impedance so I need virtually no current (<< 1 mA) but I would like to reduce the ripple on the output so it is negligible.  A simple RC low-pass filter with a resistor and a capacitor in series across the original output should do the trick. I don't want to have to find a 100 kV cap so I'll just join a few 20 kV caps in series to create a cap unit that will handle the voltage. My new + output will come from the junction of the resistor and the + end of the caps (the low-pass filter output).

Member Machine mentioned earlier that a front panel meter would be nice and I agree. He had some concerns about using a voltage divider so the meter could work with some reasonable voltage like 0 to 10 V instead of 0 to 50 kV. I've done the resistor voltage divider thing successfully at 50 kV using a 5000:1 voltage divider. I then connected the divided voltage output to an analog DC voltmeter calibrated to 0 - 10 V.

One final comment.  I plan to use a 3PDT relay for K1 so the third pole can be used to discharge the HV output through an appropriately sized current limiting resistor.  I plan to connect the HV output to one end of the resistor and the other end of the resistor to the common of the third pole on K1.  The NC contact of the third pole goes to ground.  Whenever K1 is not energized, the HV output is routed to ground through the current limiting resistor.

Do you see any problems with any of the above enhancement assuming I use appropriately rated components and good HV insulation practice?

[aclark17]

Isn't it already connected to ground even if you used case to input ground? The only reason you would need to do that with the tripole is if you didn't use an actual ground... or am I missing something?

Edit: Genius work with the voltage divider and meter, I am totally going to use that idea!

[1_21_gigawatts]

Will this be able to drop the voltage on the load (virtually) instantaneously to zero, or will there be some drain time? I need the load to ramp to high voltage and then cut to zero for testing purposes.

[aclark17]

What you need is a bleed resistor rated to a high enough wattage and that will drain any leftover. This does sometimes keep voltage mixed in the multiplier, but if you use an actual ground I don't think you will have any problems.

[ReoB]

There'll always be drain time, I think what you need to add is thyratron and another transformer to instantaneously cut the voltage to zero.

[rehanm51]

i want 50 volt and 20 amp dc power supply

[aclark17]

You could honestly just wind your own transformer for that. Look up an instructable for converting a computer power supply into a benchtop one, that will get you at least 24v and should be fairly close to 20A, is DC, and you could use a single stage voltage multiplier to get 48v, or wind/buy a transformer to get the voltage you want.

[Samuel Aplin]

For K1 could I use a 12 amp 120v dpst relay instead of a 10 amp?

[aclark17]

Bit late, but yes, it simply must be rated high enough that it won't burn up. This is in reference to a switch though, mind you.

[leuvenga]

I need to obtain High Voltage Power Supplier. I need Output voltage: 0 to 30 kV. Current: 0.5 mA to 1.5 mA. Below you had some properties that I need.

Could you help me to develop this home made?

TK

Best regards

Daniel

[purnendu laskar]

Dear Sir,

I require such a power supply for my research work. Can you sell me such power supply of very low current?

Purnenu Laskar

[rajvindra.raj.pratap]

Hello,

Attached is the equipment from the Celilo Converter Station located at The Dalles, Oregon. Time is of essence on this deal, we would be on site from Monday Oct 13th.

Existing 1100 MW converter station will be demolished, starting October 14th, making way for the new 3820 MW converter station. There are more equipment available in the Converter Building than what is listed.

Click on the link provided below for Pictures & Equipment List.

https://drive.google.com/folderview?id=0B4DG_beH4sBDVm9yc2t5QnFHQUE&usp=sharing

[rajvindra.raj.pratap]

Hello,

Attached is the equipment from the Celilo Converter Station located at The Dalles, Oregon. Time is of essence on this deal, we would be on site from Monday Oct 13th.

Existing 1100 MW converter station will be demolished, starting October 14th, making way for the new 3820 MW converter station. There are more equipment available in the Converter Building than what is listed.

Click on the link provided below for Pictures & Equipment List.

https://drive.google.com/folderview?id=0B4DG_beH4sBDVm9yc2t5QnFHQUE&usp=sharing

[jpayton]

What is the output current of this?