Power Transformer Driver. - Page 1
Forum section: electronics / projects

author: CM800
author_rank: Frequent Contributor
timestamp: March 08, 2015, 07:05:42 pm
content: I am currently working on developing a medium frequency transformer driver (10-50kHz)The input voltage will be single phase or 3 phase and the maximum power draw shall be 10kWWhat I wish to do is to be able to set a maximum input current and a maximum primary current for the transformer I connect it to.My plan is to have a power stage consisting of a buck-boost converter to allow for the 3 phase 415V (560VDC rectified) input.The buck-boost will then go into a full-bridge of CM300 IGBTs. driven by opto-isolated gate drivers with each one having an isolated +15V & -15V split rail supply.Cooling of the power electronics will be done by a water / oil cooled loop going through an aluminum water-block to a radiator however for development purposes I shall be running it on simply a -very- large heatsink.My current issue is trying to decide what method I should control so as to allow a good response time to a control dial that raises and lowers the duty cycle. If it hits either of the current limits imposed by 2 other dials it shall the duty cycle back to keep it under those limits by 10% of the setting.The transformers in question are X-ray power transformers and other similar ones.Does anyone have any suggestions or questions?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 08, 2015, 08:23:20 pm
content: I'm curious why there would be a requirement for high frequency switching power, with three phase control. Only thing that comes to mind... turbomolecular pump??! Those might run fast enough to need power that fast, but other than that...Is this the kind of x-ray system that's used to scan freight and stuff? It's insanely powerful otherwise... or it's a physics apparatus, or a strange military weapon...A TL494 will achieve what you desire, but you'll need quite a lot of hardware besides it to make a safe and reliable drive at that frequency and power level.Tim

author: CM800
author_rank: Frequent Contributor
timestamp: March 08, 2015, 08:47:59 pm
content: Quote from: T3sl4co1l on March 08, 2015, 08:23:20 pmNo no no, this is not for work, this is home / hobbiest use.I have a large 70kV X-ray transformer. I also have a friend who has 5-10 of the damn things and wants a better driver for them.Gonna be running shorted out, doing fancy arcs / Jacobs ladders etc.due to it being home use, Safety is not requiredI shall be using a fiber optic linked remote anyway.

author: CM800
author_rank: Frequent Contributor
timestamp: March 09, 2015, 08:10:54 pm
content: Fiber optic cables have arrived:My next plan is to build the power stage before moving onto the more complex controller.Initial design of power stage:

author: Circlotron
author_rank: Super Contributor
timestamp: March 10, 2015, 02:10:05 am
content: The input diodes should be pointing upwards.Have you ever worked on stuff this powerful before? I would suggest starting with a smaller one, say 100 watts, and if you finally get that working okay then scale it up from there. Then wait for a knock at the door from your local radio communications authority because you are wiping out every service in a 50 mile radius.

author: qwaarjet
author_rank: Regular Contributor
timestamp: March 10, 2015, 02:26:58 am
content: There is wide variety of SMPS control chips that could be used for this purpose. Since you are using this for arcs, constant current control is more important than voltage . I've used the TIs UC1846 in a 1.5KW system. This NASA brief, if you ignoir the arcjet parts, tell tell how to make one wicked arc suppy based on ithttp://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19860015937.pdfDo you want to control voltage/current remotely or just on/off.I not big on safety but at this kind a power some basic safety interlocks would be good idea. Very lease fuses and and emergency mains disconnect.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: March 10, 2015, 02:29:50 am
content: Hi,You should not need the boost stage, Q1 in your drawing.The other thing to bear in mind is that (medical) X-ray transformers are design to run for a few seconds at full power. Typically the absolute maximum exposure is 600 mAs on a 10 kW machine this would be 6 seconds at 100mA. There is typically 30 seconds to a minute between exposure while the patient is being repositioned.Some X-ray machines have a low power setting, called fluoroscopy, which is long (minutes) of exposure at less than 6mA.Can you post a picture of your transformer or oil tank?Regards,Jay_Diddy_B

author: CM800
author_rank: Frequent Contributor
timestamp: March 10, 2015, 07:48:40 am
content: Quote from: Circlotron on March 10, 2015, 02:10:05 amFuck, that slipped my mind (don't worry, when I assemble it, I usually look closer, that and I have a 3 phase Diode Module.)I have done familiar power work stuff before and I am familiar with general safety around single and 3 phase systems.(and fixed)Quote from: Jay_Diddy_B on March 10, 2015, 02:29:50 amI understand that but also, I have a friend who has far larger transformers and I may be getting some in the future, that and I have been contemplating designing my own one too for long use.Here is the transformer I shall be developing the drive with most of all (It's my largest one... for now)Quote from: qwaarjet on March 10, 2015, 02:26:58 amThanks for that, this will be useful! I shall read it soon (this evening)I intend to have full control remotely, using 2 way fiber communication between two micro controllers.For safety I will have a deadman's switch with a large contractor. That is actually already built into my variac box so I won't need to worry about that for now.

author: eneuro
author_rank: Super Contributor
timestamp: March 10, 2015, 10:55:51 am
content: Quote from: TCWilliamson on March 10, 2015, 07:48:40 amNo ideal diodes for D1..D7?Quote from: TCWilliamson on March 09, 2015, 08:10:54 pmWhat, if you needed longer distance to find safe distance to run this thing?Probably cheapy DVD RW burner red laser could be fine if encrypted communication established and much more distance between "control room" and "fireworks"...

author: CM800
author_rank: Frequent Contributor
timestamp: March 10, 2015, 12:58:43 pm
content: Quote from: eneuro on March 10, 2015, 10:55:51 amHaha, I only really brought 10m if I use the same cable for a tesla coil too. When 'playing around' I will be arcing with a 2m PVC stick so it becomes redundent.Quote from: blueskull on March 10, 2015, 10:08:35 amI admit I didn't understand half of what you said there... however I shall look into that book..The thing with this is it doesn't have to be perfect, I don't need accurate inputs and so on.I really do want to learn more about this stuff. My full time job is actually going to be designing 3 phase brushless drives as it is. (apprentice currently.)