+/- 30 kV(60 kV) LAB HV powersupply with custom flyback transformers, variable / Projects / Forums

Forums

4hv.org :: Forums :: Projects

« Previous topic | Next topic »

+/- 30 kV(60 kV) LAB HV powersupply with custom flyback transformers, variable

1 2 3 next

Move Thread

LAN_403

Erlend^SE

Mon Feb 03 2014, 08:30PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Hi

I am going to build a +30 kV and -30 kV variable supply.

Currently I am negotiating details with someone who can make the transformers.
(if others want the transformers too, please tell.. it helps in getting volume discounts)

Transformer:
OEM/Special "flyback" pair (one +30 kV, the other -30 kV), probably driven in half-bridge.
Built in temperature sensor
Voltage feedback (via internal resistor)
Current sensing (external, on board)
Shielded 2 meter output cable (shield is grounded)
5 mA output (will ask more around)
Primary: 2x12V (for 12/24V supply)

Driver:
TL494 with FET-driver if I am going for half-bridge, UC3842 if I am going for flyback instead.
May look into more common parts given they can do high+low side FET drive.

Other:
Microcontroller to set and messure current limits and voltages.
RS485 link for computer control (also useful for whatever other aux board I decide to use, related or not)

Added:
Transformer schematic (round ones):

Picture of transformers before shipping:

Update:
Getting near actual high voltage test:

Ethernet link works, just need to do way more software on computer and microcontroller.

Thomas W

Mon Feb 03 2014, 09:37PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

I would be interested in such transforemrs, but im looking for around 3kW on each one, 30Kv @ 100mA pity your one is so much less >_<

But a very interesting project, i shall be following this with great intrest.

Sulaiman

Tue Feb 04 2014, 03:51PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

I suspect that over time the eht cables will get shorter and shorter due to different terminations, and are bulky/messy when not in use.
If possible/economical, eht terminals/connectors may be better.

To be able to 'play' or experiment at early stages of testing safely,
try to minimise or make switchable the output capacitance.
doesn't take much capacitance at +/- 30 kV to destroy components or give one heck of a shock !

build in a 'discharge' system

adding a high value/voltage resistance in series with a neon
(neon at 0v side, resistor to eht side is easier)
across each output gives a visual 'caution' indicator and a small load to make output voltage regulation easier at light loads.
(e.g. 10 x 3.5 kV rated 33 MOhm in series = 330 MOhm = 100uA @ 33kV = max. neon current)

Erlend^SE

Tue Feb 04 2014, 04:42PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Sulaiman wrote ...

I suspect that over time the eht cables will get shorter and shorter due to different terminations, and are bulky/messy when not in use.
If possible/economical, eht terminals/connectors may be better.

Yep, will have to figure out some connection box, but 2 meters cables give some safety distance from supply.

I am looking for some standoffs, maybe the "suction cup" of TV type over the ends joining some HV "outlet".

Sulaiman wrote ...

To be able to 'play' or experiment at early stages of testing safely,
try to minimise or make switchable the output capacitance.
doesn't take much capacitance at +/- 30 kV to destroy components or give one heck of a shock !

I plan to have no output capacitance added, anyway, the cable is with grounded shielding so laying the cable over stuff should be no problem.

Sulaiman wrote ...

build in a 'discharge' system

adding a high value/voltage resistance in series with a neon
(neon at 0v side, resistor to eht side is easier)
across each output gives a visual 'caution' indicator and a small load to make output voltage regulation easier at light loads.
(e.g. 10 x 3.5 kV rated 33 MOhm in series = 330 MOhm = 100uA @ 33kV = max. neon current)

Actually, the transformer will have a 300 MOhm resistor internally, and I plan to mostly do powered on discharge (monitor voltage as it goes down)

It won't be able to hold a voltage once input power is lost.

THere won't be any unshielded voltages above 48V or so near the controller.

Sulaiman

Tue Feb 04 2014, 04:53PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

The cheapest eht connectors that I have seen are modified automotive spark plugs.
Ceramic eht terminals can be cheap or insanely expensive on eBay.

Re. output capacitance;
- none = voltage ripple
- stored energy at 31.6 kV = 0.5 mJ per pF (cable etc.) = ouch!

'pro' looking is a key switch to enable
and a 'trip' circuit break-to-operate,
e.g. hold a n.o. button switch to maintain power, or don't break a thin wire 'barrier' etc.
NOT electronically but electro-mechanically where practical.
e.g. auxiliary isolated low voltage supply (ac or dc)
to a suitable relay coil in series with keyswitch and 'loop' terminals.
could be screw terminals or 3.5mm jack etc.
normally open Relay contacts in series with output stage power etc..

Erlend^SE

Tue Mar 11 2014, 08:46PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Update:

Internal resistor: 300 Mega-ohm - confirmed
Output current: 10 mA @ 30 kV (300W per transformer) - confirmed
System max voltage into isolated load: 60 kV (dual transformer, 600W) - by design
Driver topology: 30 KHz half-bridge flyback driver (need to figure out the deal with it)
Seller: really helpful

Transformer got built in temperature sensor.

The PCB itself won't have voltages above 30V (safe to touch), input is 12V or 24V.

Made the purchase, agreed on transformer casing/shell type, windings, PCB mounting via through hole.

Andy

Thu Apr 17 2014, 11:07PM

Registered Member #4266 Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874

Hi Erlend^SE
Hows the project going? Would we be able to have a diagram of the circuit?

Thanks

Erlend^SE

Wed Apr 23 2014, 09:45PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Erlend^SE

Mon Oct 26 2015, 09:58PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Hi

Getting close to getting my board-design order-able.

I have decided to go for H-bridge driver and microcontroller PWM.

I may have failed to keep it simple!

Sulaiman

Mon Oct 26 2015, 10:15PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

MAY have failed to keep it simple ?

WOW !
that looks like a nicely designed pcb.
I hope that it performs as good as it looks ... great.

1 2 3 next

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