Developing HV DC Pulses

It looks like this flyback has a lot of isolation, can I tie the output of this to ground? Ebay link was 9 lines long, so this,

So far not finding any 1kV transformers. Any reason I can't put a mutilpier on a MOT? Mikek

If you want to use the neon sign transformer you could use half of the secondary winding, case to either HV terminal, the other HV terminal not used. Half voltage but no HV connection to ground. Not optimal but easy.

Ground the transformer case, use one side, make a doubler or tripler.

Ground everything to minimize firefighting and funeral expenses.

You need R3 but no other resistors, unless you want to keep R1 to snoop cathode current.

It's not clear that this is a positive DC solution; if you're chopping DC with a vacuum tube triode, negative ground has to be where the common connection point is.

The old CCTV transformers... still have some stock; this one at Digikey does 2kV out

No reason not to; it is a bit overkill, but as long as the problem dies, and stays dead...

Those MOT units can output a lot of power, which you don't need, and the low (60 Hz?) input frequency types are heavy. But, a variac would probably control output easily.

I could do that and add a multiplier to get the 8kV we are using at this time. I like easy. I need more HV diodes, another order.

I'm making this thing a bit modular, because there is still AC, halfwave DC, DC and Pulsed DC to look at. DC has not tested well, probably not viable, but, many different types of emulsions to test. Power Supply, Pulser Circuit, and then Voltage divider with outputs to vessels. Here's my first iteration of how I'll wire the Pulser Circuit. Box is 10.5" wide x 8.5" deep x 4.5" tall. Plenty of room between conductors.

John I did note your comment about the resistors.

Mikek

Your bridge uses 4 diodes. A half-wave doubler would use two.

Hmm, yes. The 8kV diodes I have should work. I had an excuse to order 12kV diodes, I used it! Mikek

At low current, you can make a tripler or more. The tube pulser would work to crazy voltages, provided you keep the grid negative enough.

A c-w multiplier can make a lot more voltage than the diodes are rated for.

Yes, I see the diodes and the caps only need to be 2X peak input voltage. I have some 4700pf 20kV diodes coming. If we try running a 50% duty cycle at 5Hz, that's a long time to discharge a tripler. I'm not sure if 4700pf is enough capacitance to hold up to a 10MΩ, ie how much will it sag and how much ripple? Mikek

Mikek

4700 pF diodes?

The time constant is R*C. 4.7n * 10M = 47 milliseconds, kinda fast to filter 60 Hz ripple.

It should said capacitors.

Not sure I get it, half wave rectifier is 30 Hz, 33 milliseconds, that's a 1.42 time constants. or about a 75% drop in the voltage. (maybe I get it) I suspect I need a little over 3 Time constants to get under 10% with part losses. Maybe 0.02uF, I'll start looking-- :-( Looks like I may need to make it at least a quadrupler to lower the capacitor voltage needed to keep the cost down on the caps. Mikek

I found these 0.04uF 3kV caps at a good price. Have to do at least a tripler to stay under 3kV input voltage.

Ebay link shortened. What do you think? Mikek

60 Hz half-wave rectified has one recharge blip every 16 milliseconds. So does a multiplier.

A c-w multiplier has the caps effectively in series, so the effective capacitance is small. Spice it.

A high frequency power supply solves a lot of problems.

Yes, but you would need an isolating trasformer that's good to stand off 10Kv or whatever voltage the neon transformer makes.

What does the datasheet say?

The age of toobs is past.

If you don't mind that one end of the secondary is grounded, and aren't worried by the deadly current capability. A neon transfromer will tickle you a bit, an MOT will toast you.

The bridge is not usable for producing a ground referenced HVDC from a transformer with a grounded secondary, but full wave rectification is possible with 2 diodes from a center tapped transformer with a single diode in each transformer HV to the filter cap, return to grounded CT. This gives you full wave rectification at half voltage. Substitute a half wave doubler for both diodes to get back to full voltage, still ground referenced.

Hi Glen, I'm not sure how to draw what you describe, but I found this, that uses the earth grounded CT as the negative lead of the HV. I think this solves the Neutral/ground problem. Is this what you described?

Thanks, Mikek

You don't really need the bottom half; your load current will be low.

Yes, that's it. It does solve the ground problem, but like John says you probably don't need the bottom half, which would double the available current at the same voltage. Your neutral/ground problem will be solved either way.