Recent content by jdb

How about this hypothesis: Check out the FEMM run for a CA120 by Miles here: http://endless-sphere.com/forums/viewtopic.php?f=30&t=43306&start=50#p667907. Look at the stator teeth in the +/- 45, and +/- 135 positions. Note how the hammerheads are being used to short the flux between the two...

Why does the inductance vary with rotor position (aka, it has some saliency)? I've seen this behavior before for some other BLDC motor reports on this site, too. If the PM's have a relative permeability of 1, and the back iron is a basic cylinder, why does the stator coil's self flux linkage...

Thanks for the reference! It turns out that the winding factor is equal to power factor squared. Winding factor is proportional to the ratio of joule losses, where power factor is proportional to the ratio of phase current. cos(15 deg)^2 is 0.933.

I did mean power factor. Lets work with AabBCc ... for exposition, since that is how it is actually wound. Coils A and a are 30 degrees apart from each other, magnetically. If they are connected in series, then their net BEMF would be 15 degrees apart from each individual coils' BEMF...

I was just looking at the magnetic simulations way back on page 5 and had a lightbulb moment: This is a 6-phase motor! Look at the flux relationship as you go around the motor. Each hammer is magnetically only 30 degrees apart from each other (as opposed to 60 degrees). What is the winding...

In the alpha-beta reference frame, the controller's output voltage will always be sinusoidal. But the motor's BEMF may not be. Therefore, the harmonic currents will be purely reactive. The equivalent circuit for each harmonic is the BEMF of the motor in series with its own windings, and it's...

The DQ transform has effects similar to an FM modulator: It shifts the frequency down by multiplying the signal with the input frequency. Unlike a radio FM modulator, which has a real-valued input and complex-valued multiplier, the DQ transform has a complex-valued input and complex-valued...

Yeah, 2 kHz. (120,000 cycles/min) / (60 sec/min) = 2000 cycles/sec. 4.5 kW is a lot of heat. Could you tell whether it was the controller or the motor that was absorbing most of it?

2 kHz? What do you expect the iron losses to be at that speed?

Totally, massively off-topic now :) C++ is a big language. I use it at work and have had the privilege of advising my coworkers as we transitioned from C to C++ on our last big project. You'll see a lot of people saying that C++ is "bloated," or comes with too much "overhead" or other...

I have been recommended those ICs previously on another forum. The problem is that I don't trust a microcontroller to be fast enough to limit the current in the way I am trying. I may be wrong about that. I'm going on the assumption that microcontrollers are slow in comparison to discretes...

I just saw this on Reddit this afternoon. Someone triggered a car-killing battery fire by short-circuiting lead-acid batteries together during a jump. http://imgur.com/a/JSntv Batteries have their risks just like anything else in life. Its just a matter of managing that risk. Just the same...

Scratch that. I made a mistake - this circuit is for wide common-mode range, but not CMRR. The CMRR will be dependent on how well you match RG2 to R1 and RF, R2, and RG1 together, making it somewhat poorer for this application.

There are a couple of other tricks too. The IR21771 and IR2177 avoid much of the switching noise by floating the differential amp and powering it off of the gate drive power supply caps. They provide a PWM output that you would route to a capture/compare unit on your microcontroller as well as...

The influence of the switching voltage on the current signal is represented by the Common Mode Rejection Ratio (CMRR) of the current sense amplifier. There should be some kind of amplifier IC that is amplifying the voltage difference across the shunt, and transforming it into a ground-reference...