Using a small DC drive as a variable dc power supply. - Page 1
Forum section: electronics / beginners

author: gobblock
author_rank: Newbie
timestamp: June 22, 2016, 10:55:37 pm
content: greetings my sparky brothers of the air conditioned bench variety! I'm not really a beginner but I come from another dimension of the electron than most of you it seems, so I thought I should put this in the beginner forum. Also I am brand new to the forum.Basically I've been dealing with many small dc drives for fractional dc motors at work, and it occurred to me that the drives themselves are actually very affordable for hobby projects.I've been working on a control cabinet which will require a very large dc power supply (~1kw) to drive a very large led array through 4 current mirror boards I made with through hole technology. Right now I'm just controlling the lights by using a chunky relay to switch them on and off based on digital plc i/o.Is there any reason I couldn't replace my 24v power supply that feeds the current mirrors with a dc drive? The drives I'm looking at are 0-90VDC and 0-18ADC with 0-10vdc control signal for 'speed' which is actually just armature voltage control afaik (or my intensity). Obviously I would have to rearrange my LED series/parallel arrangement, and make sure my current mirrors can handle the whatever voltage I end up using, and make sure I can get a output range by (de)linearizing the i/o mapping. I have another project I would like to use my 24v 850w power supply for, and this upgrade would free it up for that while opening up a few CUBIC FEET of space inside my control panel, all the while providing new things to learn and costing less than buying a duplicate power supply. This is the family of drives I was primarily considering.http://www.kbelectronics.com/manuals/kbic_manual.pdfI guess my question is, what are the circuit safety considerations I should consider before attempting this? Is there anything specific to scr drives I should consider? obviously The voltage is much higher and more dangerous than what is available in general electronics supply/discussion but where I work we consider anything under 4160vac low voltage and best practice and procedure are burned into my habit. (I will admit I sometimes squirm watching electronics people work, all that exposed conductor and you guys just dig right in with your hands). I've just never heard of anyone ever using a motor drive for weekend warrior work because they typically the 40-60 dollars I'm looking at now and put a few more numbers on the left side of it and don't bother with the decimal. I would probably keep the voltage under 100vdc just to make it easier to totally overspec all the insulation and physical isolation. So far I have been putting sub-ohm resistors in each led string to give the string sub fuses some time to blow in the even of some semiconductor shenanigans with the leds should any of the current mirrors malfunction before too much damage can be done to the leds on the substring or the central power circuits.I know from experience that these projects can get sticky, like when I built a solar setup to charge the dc bus of an ac inverter drive and tried to put out 120vac out. That is the week I fully realized the implications of pwm vs pure sinusoidal waveforms. I mean it worked and no damages, but I didn't exactly trust it to chug along in my basement unsupervised for decades.So a few nuggets of knowledge or experience might save me a revision cycle or two.