A Small Fan in Military-Grade Design

Many years ago, I picked up an unusual-looking fan. I tried to get it running back then, but it didn’t go well, so I eventually put it on a shelf. And now, after a long time, it’s turned up in my hands again.

I came across it while looking for transformers at home for my previous article. I found all sorts of things, and if you’re interested, I can put together a few short articles about these finds.

The fan was stored with the control board I’d made for it.


It’s a seriously rugged design: a metal housing and metal impellers.


Since this is a high-speed fan, you can see the balancing marks. It runs beautifully, with no vibration at all. And since the impellers rotate in opposite directions, there’s no tendency for the housing to spin either.


The full model designation is very much in the style of Soviet products:
2DVO-0.7.60-367-4


The rotation direction and airflow direction are marked on it.

As I mentioned, I bought it a looong time ago, probably 15–17 years ago, if not longer. I bought it simply because I liked the way it looked—it really is beautifully made. Some things are just impossible to walk past :)


The only downside was that there was no information about it. The internet was still in its infancy back then, and even the all-knowing Google didn’t exist. All I knew was that its operating frequency was 400 Hz and that it was a three-phase fan.

But after finding the fan again, I started looking for information about it. First I came across a model with the 366 suffix.


Later, I found the specifications for my model, 367, although they seem to be the same.


The fan contains two three-phase motors. According to the description, they’re rated for 200 V, run at 400 Hz, and spin at 10,600 rpm. The important thing is that the fan is designed for continuous operation and high air pressure, which means it can push air through a heatsink with closely spaced fins.
Six wires, marked with metal tags, are brought out for connection.


I was a little surprised to find that the windings have different DC resistances, ranging from 174 Ω.


Down to 142 Ω. Quite strange.


The inductance also varies, although the difference is much smaller than for the DC resistance.
The windings are listed in the same order.


So as the resistance decreases, the inductance increases.


Since the fan needed three-phase power, I designed and built a control board—in essence, a simple three-phase inverter.
My mistake was that I didn’t have any documentation, so I assumed the operating voltage was 27 V rather than 200 V, as stated in the datasheet. I thought the fan came from avionics, where 27 V is a common supply voltage.



The board is extremely simple. A 561LA7 serves as the oscillator, followed by a 561IE8 counter/decoder, then three pairs of switches forming three half-bridges. The logic ICs are powered by a 78L12 regulator—the most modern component on the board.
The motor windings are connected in delta to reduce the operating voltage.
I used KT817 and KT816 transistors as the output devices. The components I had on hand limited the maximum supply voltage to 35 V.


I drew the board layout on graph paper, then transferred it to the copper-clad board using a ruling pen. That’s why it looks a bit old-fashioned :)
Also, the motor windings were originally connected in star, so I had to cut traces and reconnect them when modifying the board. There may have been another reason too, but I don’t remember.


But the main thing is that it all works :) Of course, not nearly as well as I’d like, but it works.
1. The fan starts at 15 V.
2. It keeps running down to 9 V, drawing only about half a watt.
3. If I disconnect the power and then reconnect it, it starts at 12 V instead of 15 V.
4. The highest voltage I could safely use with the board was 35 V. The components won’t withstand any more, and I’d hate to burn it out. At that voltage, it draws 6 W, compared with the rated 37 W.
By the way, I’ve seen somewhere that this fan model is rated for 115 V. If we assume that power increases quadratically, then the actual supply voltage is about 115 V. One possibility is 115 V with the windings connected in delta, and 200 V in star.


All in all, a small, useful gadget. I even had the crazy idea of using it in a new electronic load: it needs good airflow over the heatsinks, and with a fan like this I could try to make it compact. It will be pretty noisy, though.

And as a bonus, I made a short video.