AC fractional synchronous motor

split-phase motor using capacitor | in | | | +--wwwwwww-+ | | | _ 3 \ / \ 3 \ Rotor 3 | \_/ 3 | 3 +---||-----+

if you oick the wrong two terminals it'll run backwards. capacitor-run motors don't have the switch.

- ?? 100% natural

I've just found out that the motor must have an open coil.

2K between Blue and Yellow ("1" & "2") No continuity between Red and Green ("X" & "Y").

So, I cannot do anything with this motor. :c(

Keep looking, it may be fine.

Purely synchronous machines only work when they're already spinning at close to synchronous speed. So real-world synchronous machines have some scheme to start them up (usually as an inductive machine), then a way to switch them to being synchronous. Often the rotor will be shorted during startup, then driven with a DC current for synchronous operation. This _may_ happen with a centrifugal switch inside the motor. If so, the DC current wire would appear as an open circuit until the motor is up to speed.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

I connected an ohmmeter across "X" and "Y". No continuity even when rotor spins at full speed of an electric drill (used to spin the rotor).

Although this motor is marked synchronous, it does not (appear) to have a permanent magnet rotor, or means of energising the rotor.

Okay, so I looked into the paper-feed mechanism (of a vintage chart recorder) that the motor is part of. The paper-feed mechanism is in two parts (LH and RH)which are physically connected by way of having a common spindle.

Terminals on LH side I thought led to a centrifugal switch, but in fact go to a Crouzet synchronous motor (Type 392). This is I believe is self-starting (reluctance / hysteresis - whatever).

The shaft of this synchronous motor (on the LH side) connects to the shaft of the motor I'm examining (on the RH side) which is simply marked "synchronous". But, the connection is not solid, I mean there's a kind of one direction clutch in-between the two motor spindles. It does not transmit torque one way, but does the other.

So, for the paper-drive mechanism we have:

RH LH

---M1------Clutch------M2----

M1 is the Crouzet synchronous motor connected via the one way clutch to M2 the motor marked "synchronous".

Now, the speed of the paper feed could be set electrically by a simple manual (spst)switch. That changes speed of paper drive by a factor of 60.

I personally cannot see M1 being powerful enough to drive the paper feed, but am no expert and might. M1 the Crouzet motor is like the motor you get on a microwave cooker. M2 looks like a precision engineered unit.

A capacitor seems to permanently connected across "1" and "2", of the coil with continuity.

I'll try to supply a circuit.

Is M2 really a motor I now ask myself. :c)

I think it is just a small induction motor. I feel no "stepping" as I turn the shaft.

I think it is just a small induction motor. I feel no "stepping" as I turn the shaft.

If no continuity between red and green, this item surely is no good.

I'd say it is a motor myself. Terminals marked "1" "2" "X" "Y".

It's a long shot how ever, you may have a brushless AC type that has a partially integrated field for the DC part.. Most of the brushless types have their own 3 pole rectifiers on the rotor assembly connected to the coils, just for low DC current as needed.. Larger motors normally also include a stator field that is rectified to produce a DC field for which rotor assembly on the DC source spins through to derives it's energy. Like I said, most do all this inside and have electronics or a centrifugal switch on those that has a combination squirrel case motor to get started. (self starting)

The type of motor you have, is not self starting, obviously.. which most likely explains the need for the clutch from another source to get it started ? That being the case, I think what you have there is a motor that may have a bridge rectifier in it on one set of the Leeds that needs the be energized when the external start motor disconnects to put the motor into full operating sync mode.

The verify this.. Put your meter in Diode test mode and see if you can get ~ 1.2 reading on one set of the leads(swapping leads).. If so, these leads need to be energized with some AC/DC volts to produce the field needed for the brushes field inside. This field most likely can be turned at the same time as the main stator if the starting motor has enough torque to over come the synchronized locked rotor. This may explain why you are getting a seemingly open effect on one of the pairs, when testing.

Most of these motors are 3 phase how ever, you may have a split phase type (2 phase 180 poles) and it needs to be spinning into the desired direction to start..

Jamie

Do I have an hysteresis synchronous motor a bit like:

Do I have an hysteresis synchronous motor a bit like:

Same colours for wires. (Not that that necessarily means much).

You would need to take that apart and look at the rotor to determine that. It should still have some small magnetic properties in it from the last run cycle. But those are not a good motor to use if you want to have it fall back in place on the next start up because the magnetics in the core can change position. After all, you must remember the stator in this case is the only thing that is polarizing it and until it reaches it near speed it isn't going to be fixed.

This is the case like one starting in squirrel cage mode and then switching over to synch mode. Only its done with out switches of course. Once the speed gets near normal then poles on the core magnetized tracks with the line frequency, Hence the term hysteresis which in magnetics means that it holds its last value of polarization for a bit before fading away or being canceled by another.

In the case of IDing it, the rotor should be smooth with no lines and no wire on it.

Personally, and its just me of course, I would say the Green wire is a case ground and the other three are just standard capacitor start type of set up.. If that being the case, one of those wires are the center tap for example. We have at work, motors we use that are synch motors with the blue wire as the common and you select either the RED or Black wire for the connection from the L1 and then use the cap from that L1 connection over to the other remaining lead. Basically, we just have the cap across the Black and Red wire, connect L2 to the blue wire and then depending on which direction we need to go, we just connect the L1 to either the Red or black wire, leaving the cap connected across those same Red and Black wires..

If you put the meter on these leads, the blue wire is the center tap and the cap is being used to produce the phase shift with the other winding. and our green wire is just a case ground.

Have a good day..

Jamie

Further data here:

I still cannot figure things out. :c)

anything that small is probably like the motors used in old tape recorders and won't have starting switches and junk like that- just a small capacitor.

the possibly open winding does sound suspect.

Thread also here:

Lets just look at what the overall situation is:

This is the machine:

----------- In order that the paper is taken from the spool containing the blank chart paper, the shaft on the paper feed gearing assembly must rotate CW (looking from the assembly's shaft end, that is looking RIGHT). If you bolt a motor onto this gearing assembly it would therefore would need to be a CCW motor looking at the motor from the spindle end (assuming one spindle).

.............LEFT..........................RIGHT

---M1>-----Clutch---------

It just came to me the error I was making. So simple.

The true picture is this:

SPINDLE M1>------------------------------X X ---SHAFT X

Bolting on M2 does not put it's axis concentric with SHAFT. The pinion on M2 spindle cogs with a pinion on SHAFT. And that will lead to a reversal of whatever way the M1 and M2's spindle turns. So, M1 will make sprokets move the correct way.

Also, this solves the speed problem. The pinion on the spindle is smaller than the one on SHAFT. SHAFT needs to revolve at 16.67 RPM, but the spindle needs to be running at a different speed, at 25 RPM, because cogs/pinions will reduce the RPM from 25 to 16.67 RPM.

What doea this do for the HIGH speedsituation? The spindle should rotate 60 times 25 RPM = 1500 RPM. SHAFT turns at 1000 RPM.

This means: *M2 has to be a synchronous motor!*

Mine will be faulty, because I should get continuity for two coils. I only get one, between blue and yellow and not red and green.