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HV Flyback Bench Top Power Supply for Lab.

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Patrick

Fri Jul 22 2011, 06:38AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

This device is a permanent labratory (Bench top) type HV SMPS.

Device: Flyback HV transformer Driven by 555 timer and MOSFET, open loop-no regulation.

Purpose: For callibration of HV measurement probes, DeSeversky lifter research, and for HV insulation characterizing.

Features: Oil tank, Thermistor, Line powered (120Vac, 2.5A), 555 timer, FAN 7382N gate drive, MOSFET STW13NK100Z, Large heat sinks, AC low voltage transformer, Flyback transformer primary sees 57Vdc at about 4 amps average (30 Turns).

Components:
STW13NK100Z MOSFET (TO-247)
STmicro NE555N (DIP-8)
FAN 7382N (DIP-8)
Vishay 1.5KE300A TVS
Caddock 0.5 Ohm, resistor (TO-126)
HR 6329, Bought from Killa-X, (inside 1.2 Liter oil tank).

Datasheets:

]fan7382n_gate_driver.pdf[/file]
]mp9000_series_resistor.pdf[/file]
]ne555n_timer.pdf[/file]
]ntc104-rc_thermistor.pdf[/file]
]stw13nk100z_mosfet.pdf[/file]

Some initial specs....
200+ watts... 35kV, 16kHz, 555 timer. I estimate the output currrent to be 5mA, but will measure the output volts and current later today.

using 555 timer, 260 Watts (input), 34uS on, 29.2uS off, 57V @ about 4 amps.
About 15.7kHz (53% Duty Cycle). Temp has so far peaked at 104 degrees F, after a 30 sec run.

strikes every time on two 0.5" ball bearings 1.18" (30mm) apart, almost every time 1.38" (35mm) apart. Should be near 35kV i think

Overview of whole PS, Canola oil filled flyback tank on right, configured with ball spark gap.

Flyback oil tank (left), Main caps in blue, circuit board.

Hot arc.

Current profile through flyback and 0.5 Ohm resistor, (Primary current), peaks at 5.8 V, so 5.8V / 0.5 Ohms = 11.6 peak amps.

Oil tank schematic.

Power chopping circuit.

97degrees F, at the top surface of the acrylic tank. The small bubbles on the center and left are from the heat of expansion from oil filling the now hot ferrite gap, the larger bubble on right is for thermal expansion of the oil, the air bubble shrunk about 0.2 inches in overall diameter while at 97 degree F (ferrite is at 118 peak temp F). Time to let it cool off. I do worry that the pressure will blow out the gasket sealer. I may have to replace the four nylon screws with metal screws.

New pics, case is nearing completion.

radhoo

Fri Jul 22 2011, 08:49AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

Good initiative, but why did you submerge the flyback under oil? I see no advantages other than lowering the temperature on heavy loads.

Patrick

Fri Jul 22 2011, 09:01AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

radhoo wrote ...

Good initiative, but why did you submerge the flyback under oil? I see no advantages other than lowering the temperature on heavy loads.

Yes, to keep it cool..

radhoo

Fri Jul 22 2011, 11:06AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

In my tests I've seen that is MUCH better to use concentric primary and secondary coils in a flyback. In this case you would have obtained better energy transfer and larger arcs using one of the primary original windings.

Also since this is a lab supply, why not use a HV resistor to get a feedback from the output, to regulate the output?

Proud Mary

Fri Jul 22 2011, 03:23PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

radhoo wrote ...

In my tests I've seen that is MUCH better to use concentric primary and secondary coils in a flyback.

Absolutely, Radu. I've found that by using the drive circuitry for which an LOPT was originally designed, that hundreds of hours of trouble-free continuous operation results.

Patrick

Fri Jul 22 2011, 04:41PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Proud Mary wrote ...

radhoo wrote ...

In my tests I've seen that is MUCH better to use concentric primary and secondary coils in a flyback.

Absolutely, Radu. I've found that by using the drive circuitry for which an LOPT was originally designed, that hundreds of hours of trouble-free continuous operation results.

I have 3 flybacks of the same type, ill trythe original primary then and well see if theres a difference. Arnt the normal primaries meant to run off 90 or more volts though? if i could find a schematic that would make it easier.

Proud Mary

Fri Jul 22 2011, 06:02PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Patrick wrote ...

Proud Mary wrote ...

radhoo wrote ...

In my tests I've seen that is MUCH better to use concentric primary and secondary coils in a flyback.

Absolutely, Radu. I've found that by using the drive circuitry for which an LOPT was originally designed, that hundreds of hours of trouble-free continuous operation results.

Arnt the normal primaries meant to run off 90 or more volts though? if i could find a schematic that would make it easier.

Generally between 90 & 110V.

Here is a typical basic circuit:

Patrick

Fri Jul 22 2011, 06:08PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Proud Mary wrote ...

Patrick wrote ...

Proud Mary wrote ...

radhoo wrote ...

In my tests I've seen that is MUCH better to use concentric primary and secondary coils in a flyback.

Absolutely, Radu. I've found that by using the drive circuitry for which an LOPT was originally designed, that hundreds of hours of trouble-free continuous operation results.

Arnt the normal primaries meant to run off 90 or more volts though? if i could find a schematic that would make it easier.

Generally between 90 & 110V.

Here is a typical basic circuit:

ill try the original primary, but its hard to figure out, there are 8 different pin combinations which reveal 0.3 to 0.6 ohms, and Killa-X and i have no way of knowing the number type.

New pics!!!

Proud Mary

Fri Jul 22 2011, 06:13PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Patrick wrote ...

ill try the original primary, but its hard to figure out, there are 8 different pin combinations which reveal 0.3 to 0.6 ohms, and Killa-X and i have no way of knowing the number type.

Are there no numbers on the LOPTs that we could cross-reference in the HR Diemen catalogue?

Added afterthought: it isn't unusual for an LOPT primary to have several auto-transformer taps on it - the idea with modern LOPT design is to supply power to as many sub-circuits of the whole TV or monitor as possible.

Patrick

Fri Jul 22 2011, 06:16PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Proud Mary wrote ...

Are there no numbers on the LOPTs that we could cross-reference in the HR Diemen catalogue?

From PM, Killa-X :

"I wont know anymore about them than you would, seeing i bought them on ebay as a "Factory Outlet" meaning, my spend on 24, all 24 could have been dead. they are all rejects for whatever reason. At least, thats what the seller claims. All 24 do work. I only had 3 that came shipped with 100% smashed cores.

I have tried searching the info on them with whats listed and found nothing sadly. Says TCE 70234 Feb 205 2:01

then theres a ba code. My phone says its:

70234509789660 which brings nothing on google."

My label says :

2G25023 A1A
TCE 35.0 Kv
RXE

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