Electronics > Projects, Designs, and Technical Stuff
"Electronic" load - different approach (power resistor with DC/DC stage)
(1/2) > >>
Miyuki:
Hi folks,

Im preparing to build big electronic load, but not with dumping power to transistors at huge heatsink but to use big brake resistor. It is rated 2500W/400V so have low current and can be placed anywhere on long cable and can dissipate this power without any active cooling very reliable as it is industry thing.

I plan to build buck-boost stage with constant input current mode which will dump power to this resistor and will be used for higher voltage situations like 50-500V
And then second pre boost stage for lower voltages, coupled inductor boost for voltages bellow 50V

Two stage design because at high voltage stage is better to use IGBTs and low voltage stage can use high speed MOSFETS with schottky diodes

Will be used to test DC/DC stages and so
Just wonder have anyone electronic load using big power resistor ?
nctnico:
One of my products is a DC load for battery discharging. I'm using power resistors (switched in various configuration) on a heatsink with a fan. The most powerful version dissipates 2500W maximum (continuous!) in a 3U case of about 40cm deep. The big advantage of resistors is that you can run them much hotter compared to transistors.
T3sl4co1l:
Most of the cost is in the resistors; you aren't saving much by reducing the semiconductor dissipation towards zero, versus a modest fraction of the total.  You also spend a lot more in design cost, at least, and also inductors and support circuitry.

So, I usually do a power-DAC structure, using a unary ADC like LM3914 (or an MCU, now that it's going obsolete), and a small analog sink to fill in the gaps.

Tim
Miyuki:
I also thought that big resistors are expensive, but than found that this braking resistors are really cheap even new and almost free when used


I want to build it also to learn something new
I think I can keep BOM cost up to 100$ as I try to optimize costs of this type of projects
David Hess:
I have done it the opposite way with a higher voltage source driving a lower voltage resistor bank made from water filled copper pipe.  Another thing I did once which worked well was to use a bank of rechargeable batteries as a load.

Maintaining stable operation over a variable wide voltage ratio is a problem as usual with switching regulators if both continuous and discontinuous conduction modes are supported.  A tapped inductor or additional transformer can be used to help with large transformation ratios.  I never tried it with a flyback transformer but I have used an inverter stage before.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod