6 Pole operation on the MMM - Long term effects?
 

Some people have mentioned that running a 6 pole motor might stress the ESC beyond what is was designed as far as phase clock frequency goes. I currently run a Mega 2100kv 6 pole motor on 6S with my MMM V2. Are there any extra precautions I should take? The settings are all pretty much stock, braking and reverse are at 50%, startup is low, timing is 0, and LVC is on Auto. I've been running it like this since August. Also, I'm one of the "lucky" few to have received F/W 1.18 preloaded into mine, and I upgraded to 1.20 only in November I think.

According to CC no. Your settings look fine to me and the MMM was built to run 6 pole as well. I was very pleased with how smooth my MMM ran the Align 600XL I had.

Well, a 4 pole motor will work the esc twice as hard as a 2 pole motor. So a 6 pole motor will work the esc harder still than a 4 pole. The fets are rated for a certain number of cycles, so it may last longer with a 2 pole motor. However as long as the temps are good, the esc should last just fine with either motor.

Ah well my cooling obsession from my pre-millennium days of overclocking still exists somewhat, as such I've mounted the big novak heatsink on it along with a couple 5V high cfm 40x20 fans. The ESC always behaves itself. Thanks for the verification!

i have been running an 8 pole motor for about 6months on my v2 and the only problem i have has is going from full brake to full throtle i will get alittle coging

No, FET life has nothing to do with the number of poles.

The FETs keeps switching on/off in a certain frequency(eg. 8kHz or 16kHz) no matter how hard or soft you pull your throttle, no matter how fast the ESC commutates(changing motor current directions ). The only difference is the FET on-state time width---so callled Pulse Width Modulation. There are 3 phase coils, so each FET works(switch on/off) only during 1/3 active time, in the other 2/3 dead time it just keeps shut off, no matter how many poles the rotor has.

And, the FET switching in the ESC is just NOTHING. Your computer's CPU power supply converter is also based on FET components, they keep swithing about 100 times faster than your ESC, year after year.

So, as I understand it the esc has a certain rpm limit on 2 pole, why would it have half that limit on 4poles?

The phases much switch more often on a higher pole motor per rotation than on a lower pole count motor. How else does the esc do it?

I've often thought about this.

I think you have to consider the winds you are dealing with and the physics of what is going on inside the motor.

If you use the same wind in two different motors, only one is a 2 pole motor and the other is a 4 pole motor. The 4 pole motor is going to be half the kv rating of the 2 pole.

As pole count increases, kv decreases for the same wind.

Take a look at some of the available winds and their kv's for various motors.

You can buy a 9000kv 2 pole motor, but you will never see even a 4000kv 12 pole outrunner.

It's a trade off though. Watts is Watts of power.

Lower kv means less rotational speed but more torque.

There is a limit on how many times a minute a ESC can phase shift for a 2 pole motor, but I believe the actual limit is the same with higher pole counts. There is just alot more phase shifts per revolution.

This goes along with what you said, "The phases much switch more often on a higher pole motor per rotation than on a lower pole count motor."

Yes, you're right, a high pole count motor requres the ESC to commutate faster than a low Pole motor, but that adds no more stress to the MOSFETs. Most ESC has fixed working frequency, MOSFETs are switching on/off according to this frequency. Faster phase changing results fewer switching times in a single commutation cycle. View from a longer period, say one second, the MOSFETs turn on/off the same times as slow phase changing situation.

An ESC's RPM limit comes from the phase detect circuitry, and how fast the MCU can safely process the detected phase information, not the FETs.

Actually higher pole motor make the ESC more relex during starting. A 4 pole motor has twice phase shifting speed than a 2 pole motor under same RPM, making the phase detect circuitry work comfortably much earlier. I experienced some cogging with MMM + Feigao XL combination, after switched to Castle/Neu 2200KV, that cogging goes away completely, the motor starts up amazingly smooth.

Every ESC has a maximum commutation limit (the speed at which it can switch phases), but it's down to the ESC's CPU. The faster the motor spins, the more phase switches it requires, and the harder the ESC's CPU has to work in order to process this. This used to be a potential problem on older ESCs where it'd be entirely possible to exceed what their CPUs could handle, but within modern ESCs (at least, good modern ESCs like the MMM), this limit is extremely high. So much so, that nobody really states the maximum commutation rating anymore.

So yup, your MMM will handle a 6-pole 2100kv motor with total ease.

You'd be surprised at some of the smaller heli motors you can buy; I have a 4000kv 9-pole outrunner in my heli which I run on 3S. Even then, the Hyperion ESC I run it on doesn't have a problem with it...but it must be on the borders of what it can handle. And Lutach has some crazy 9000kv 6-pole, or something lol.

Dagger is right, but there are other limitations as well.

Don't confuse PWM frequency with commutation frequency, they are asynchronous.

We have successfully run 14 pole motors over 60,000 RPM on the MMM software without significant timing changes, and the MOSFET switching times on the MMM are in the order of 70ns -- so there will be NO ISSUE running higher pole count motors on the MMM.

The MMM uses a very high processing power microprocessor (25 MIPS) -- more than 4 times faster than competing ESCs. We also have the fastest timing calculations and loops in the industry -- often faster than competitors by an order of magnitude or more.

So the MMM will run high pole count motors better than anything else on the market. And it will keep timing tighter and efficiency higher than any other ESC, especially at high RPMs and power levels.

Patrick

That's nice to know Patrick. Too bad my Big Maxx didn't like the MMM though, bad commutation according to Plettenberg.

Weird, plett and neu construction are not much (if any) different... And the MMM seems to work well wwith a neu.

I have heard that Plett will blame everything other than their motors when a warranty or repair claim comes up...

I don't know if this fits in the conversation, but, can you use the MMM with the MM motors, like say the 7700kv or the 6900kv. If so will it hurt anything? Thanks in advance and sorry if this is the wrong spot for the question.

Jon