| Electronics > Projects, Designs, and Technical Stuff |
| Unusual motor circuit |
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| Excavatoree:
--- Quote from: SeanB on October 25, 2018, 05:21:02 am ---Well, the motor does say operating frequency is from 360Hz to 1600Hz, so it is avionics related, and for sure a cooling fan for some aircraft equipment. The right hand of the ratings plate says 360-1600cy, which is 360Hz to 1600Hz, 115VAC single phase off an aircraft avionics supply. It will not run off 60Hz mains long before spectacularly burning out. --- End quote --- it says 60/ 60-360-1600 CY. It runs just fine on 60 Hz. Now, I haven't left it running for hours, but I've connected it and let it run for a few seconds. It gives no indication anything is wrong - nothing gets hot, no smells, no sparks, etc. I'll leave it running for a few minutes and then edit this post. (47 minutes, no problems.) I just don't understand the two wires that receive power for the less than a second it takes for the relay armature to move the contacts. I've disconnected the relay and applied power to just those two wires, and there's no difference in operation. I don't believe it is a starting winding because the motor doesn't have time to move even one rotation before the relay switches. Those two wires are powered very briefly, if at all. I speculate that the relay is not an ordinary relay, but frequency selective. At higher frequency, the coil doesn't pull the armature, and the other two wires are used. That's really just a wild ass guess. I've never heard of a frequency selective relay. I'm not asserting that's true, just saying that's the only explanation I can come up with that fits my observations. I welcome any and all input. |
| Excavatoree:
I've been visiting the surplus dealer from which this came since I was Sagan's age. There were two, one ran by an older man, Mr. B, the other by a man and his son, Mr. O.H. and Mr. M.H. which I've talked about before, in another thread with pictures. The H's and Mr. B rarely spoke of one another, despite the fact they were within a half mile (slightly less than 1 kilometer) of each other. Mr. B never retired, he just slowed down more and more until he died. Mr. M.H., who took over after his father died, was offered a boat load of money for the land and he retired about a year or two ago. Sadly, I haven't spoken with him since. Typically, the aircraft stuff was 400 Cycles. (Mr. B. always said "Cycles" instead of Hertz, which I picked up and had to convert myself from later.) Mr. B. always had 400 Hz transformers laying around, some other 400 Hz equipment, and two 55 gallon drums (200 liter) full of small, 400 Hz motors - they were worthless back in the 70s. Now, I'd love to have some of that 400 CY stuff - a cheap variable freq drive would power it all. He processed it all for scrap. He recovered gold, copper and aluminum. I think he just gave the steel away. Sorry to make a boring thread even more boring, but I was thinking about all that after thinking about aircraft surplus. I should make a thread about my old aircraft fuel gauge that I managed to get working with an Arduino (I'm embarrassed) and an Adafruit motor shield. (even more embarrassing. I really need to build my own driver. I wanted to see if I could get it working) |
| ArthurDent:
Here is an example of what I said above. I once owned a military version of the HP 524A frequency counter called the FR-38 B/U that was from the 1960s. The commercial version was made to operate from 50/60 hz and had a low end fan motor (first photo) to help cool the 600 watts of heat the 60+ vacuum tubes generated. The military version used a high end fan motor similar to the one you’ve shown because a lot of military installations might have 400 hz or similar power. The military specs for a lot of test gear that would never be used in aircraft were rated for a wide line frequency range of 50-1000 cycles as seen in the photo of the rating tag I have attached. |
| richard.cs:
Could it be that the relay pulls in at 60 Hz but (due to it coil inductance) not at 400 Hz, and so the winding configuration is changed for 60 Hz and 400 Hz operation? Perhaps with more of the winding in circuit at 60 Hz and less at 400 Hz. Otherwise some kind of braking function. I don't think it's start related given that there is no delay, either it's specifically to do something with the supply off (like braking) or it's frequency selective. |
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