Thud wrote:Thanks for the info B,
I did the spin test after taking off the windings....this can & stator combo cogged at lest 4 times worse than a wound motor of the same size..quite dramatic. I guess I will proceed with my current plan to insulate these...& re-assemble
Must be cheap /quick manufacturing, they might not coat all the lams with bonding agent, and just use the wicking method that I suggested (which is much easier, but if you were making 100's of the things it would be better to automate a spray / stacking process).
On a side note, The term "cogging" is used to describe a few things, so it is best to avoid it and describe the force you measuring. Here are the things I have seen described as "Cogging" torque or force:
1: Most common: The force (or torque) required to move a stationary rotor from one lock up position to the next while there is no external load and no current running through the coils. This is often called starting torque in the generator world.
2: The force ( or torque) required to move a stationary rotor from one lock up position to the next while there is maximum current passing into the motor. This is more often called stall torque.
3: The variation in torque during a cycle while the machine is operating at maximum torque capacity. This is more often called torque ripple, and can be used for motor operation and generator operation
4: The amount of torque required to spin an un-loaded machine at some rotational velocity. This is more often called no-load torque (and is usually accompanied with a rotational velocity, i.e 0.8Nm @ 300RPM)
5: The observation of generally un-smooth operation of a motor or generator, ex, the motor has a bad cogging effect at low speed.
Thud wrote:While youe looking, I am going to re-wind this thing a little closer to the original resistance values & sacrrifice some copper fill. any other off the cuff observations or tips?
All the other motors / generators that I have taken apart have much more insulation between the coils and the stator. Usually combinations of kapton tape, Dupont Nomex 410, and sometimes Mylar. If you are going to use a little less copper this time, I would suggest better insulation. The problem with insulation is that it is a thermal insulator aswell. so the heat from the copper doesn't move to the stator as well. Having more copper in the machine is always better, if you are concerned that the resistance is too high, add some resistors externally (some copper wire, and maybe wrap it around a ferrite core to increase inductance aswell). You can easily remove the heat outside of the motor rather than producing it inside, and if you ever get a controller that can handle the low resistance / inductance you could remove the external resistors rather than having to re-wind.
I don't know your experience with winding, I imagine you have done a fair bit, so you probably already know this, but while you are winding, you might want to have a volt meter in diode checking mode (with the beep) handy and check the conductivity between the stator and the copper every couple turns. That can save you from completely winding a coil that you are going to have to remove and replace anyways. You can maybe even just un-wind a couple turns, add in some insulator and then keep going to remove the problem.