Unusual motor circuit - Page 1
Forum section: electronics / projects

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 14, 2018, 08:17:40 pm
content: My dad purchased a motor with 6 leads coming from it. Two go to a capacitor, and the other four go to a double pole relay as shown.Power is applied to both the relay coil and the common contacts of the relay. Thus, wires 1 and 3 of the motor don't get power for very long, if at all. (EDIT: The relay is instantaneous, no delay, Wires 1 and 3 are powered with the coil that pulls the contacts way from wires 1 and 3) Power is applied to wires 2 and 4. I can even bypass the relay and simply apply power to wires 2 and 4 and the motor will turn.Why on earth would this relay be added to the assembly and connected this way? There is no information available on the motor, other than what I can see.Please forgive the crudity of my schematic. (EDIT) The motor is AC, pay no attention to the symbol being incorrect. I needed a symbol with 6 wires, so I very quickly made one from something that looked close.EDIT: The motor is multi frequency. Could a relay be constructed to only switch with low frequency applied to the coil? Maybe that's it. I tested at 60 Hz. Maybe at higher frequency, the relay doesn't do anything, and the other wires are powered.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 14, 2018, 08:54:21 pm
content: Probably a strangely wired start relay. The motor might be able to start without it but won't have full starting torque.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 14, 2018, 09:08:51 pm
content: Quote from: NiHaoMike on October 14, 2018, 08:54:21 pmI forgot to say the relay has no delay. When power is applied, it's applied to the common terminals of the relay and the coil at the same time, and the coil switches immediately. I can't see how powering those two wires for such a brief time can affect anything. However, I'm totally ignorant, so it may have an effect, somehow, that I just don't realize.

author: rstofer
author_rank: Super Contributor
timestamp: October 14, 2018, 09:13:06 pm
content: What did the motor come from? This fact alone may lead to the requirement for the relay.Is there any possibility that the relay performs dynamic braking by shorting the windings to ground?

author: amyk
author_rank: Super Contributor
timestamp: October 14, 2018, 09:17:04 pm
content: What type of motor is it? Voltage? Current? Your diagram shows a DC source, but the capacitor suggests it's an AC motor.Pictures would also be very useful.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 14, 2018, 09:18:50 pm
content: Quote from: rstofer on October 14, 2018, 09:13:06 pmI have no idea on earth what this think is from. It's a motor, the relay, the capacitor, and a thermal interrupter/fuse that I didn't add to the schematic all mounted on a plate a bit smaller than an a4 sheet. The motor has a fan blade on it. It seems to be completely impractical.As near as I can tell, my schematic is accurate, and when power is removed the other motor terminals are not shorted. Unless there are usually more wires attached to that relay or something. It is US government surplus, so maybe it is simply added to drive the cost up. (Add an unnecessary 10 dollar relay, charge 100 bucks for it)I

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 14, 2018, 09:20:18 pm
content: Quote from: amyk on October 14, 2018, 09:17:04 pmThat's one of the crudities I mentioned. It was a "quick and very dirty" KICAD schematic, I had to make a motor symbol with enough wires.It's an AC motor. It works at 110V 60 Hz. I have no indication that's what it was designed for. (Edit: it's labeled 60/ 60 - 360 - 1600 CY as well as 115V, 1 phase)

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: October 14, 2018, 09:54:12 pm
content: My guess is a starter winding. This is a very fine winding with a lot of resistance and not much inductance. Since it has less phase shift than the main winding, both energised creates a two-phase magnetisation for starting. The relay cuts in when the main winding current is abnormally high, which will be if the rotor is stationary. A soon as it's rotating fast enough for the current to reduce, the relay drops out.Note that the starter winding gets hot very quickly and can only stand a few seconds of operation.There are also types that use a capacitor to phase-shift the starter winding current.

author: drussell
author_rank: Super Contributor
timestamp: October 14, 2018, 10:32:23 pm
content: Photos of the actual unit would be helpful.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 14, 2018, 11:02:28 pm
content: Here are some equally crude pictures. Sorry, this post wasn't planned as well as it should have been.Motor Label Text:Eastern Air devices, INCBrooklyn, N.Y. U.S.A. (cue Dave)Variable Frequency Motor1 PH115V.25/.60 A.0.4 MFD. CAPCONT. DUTY60/ 60-360-1600 CY

author: amyk
author_rank: Super Contributor
timestamp: October 14, 2018, 11:35:08 pm
content: Quote from: Excavatoree on October 14, 2018, 09:18:50 pmThat and the fact that EADis somewhataerospace-relatedsuggests this may have been used on a plane with 400Hz supply, and the extra winding may be a "sense" winding that is switched into the supply when it's not powered, used for monitoring speed or similar.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 15, 2018, 08:49:26 pm
content: I connected the power terminals to my ancient Rigol DS1104b and spun the motor. I didn't see any indication of a signal.I forgot to add the printing on the relay:Allied Control Co. Inc.SKHX-218827115P22I can find several other Allied Control relays, but no information about that one.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 25, 2018, 12:13:28 am
content: Quote from: amyk on October 14, 2018, 11:35:08 pmI don't know if I tried finding their website or not, I might have assumed that they were long out of business. I send them an E-mail, but I seriously doubt I'll hear back from them.

author: ArthurDent
author_rank: Super Contributor
timestamp: October 25, 2018, 03:58:50 am
content: I believe the motor was from about the 1960s and used as a cooling fan in a piece of test equipment that was used by the military but not in aircraft. If it were designed for aircraft use it would have been just 400Hz instead of being also for 60Hz which made it much heavier. It is shock mounted to try to make it quieter.I think there may be an error in your wiring diagram because in one of the photos it shows there is only one blue wire coming out of the motor going to the capacitor and the other side of the capacitor goes to 2 white wires that I'm assuming are line neutral. There are also two unconnected wires in one of your photos that aren't shown on your drawing.Here is a poor quality photo I found of another EAD fan from about the same time period.

author: SeanB
author_rank: Super Contributor
timestamp: October 25, 2018, 05:21:02 am
content: 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.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 25, 2018, 01:08:33 pm
content: Quote from: SeanB on October 25, 2018, 05:21:02 amit 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.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 25, 2018, 01:39:33 pm
content: 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)

author: ArthurDent
author_rank: Super Contributor
timestamp: October 25, 2018, 02:29:48 pm
content: 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.

author: richard.cs
author_rank: Super Contributor
timestamp: October 26, 2018, 12:19:48 pm
content: 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.