Hi Michael.
I find your conclusion interesting. Perhaps it is a matter of personal preference.
Here's an article that discusses the differences between PMAC and BLDC.
http://www.appliancedesign.com/CDA/Articles/Motors/BNP_GUID_9-5-2006_A_10000000000000292917
The two types of motors are similar enough that a PMAC controller can drive a BLDC motor and vice versa (they both take PWM 3-phase AC current at the motor), but the " difference is in the "torque function" of each motor type, and how current is driven into the windings. If each motor type is spun, and the resulting back EMF examined on an oscilloscope, it would be seen that the BLDC motor has a flat-topped trapezoidal voltage, and the PMAC motor has a sinusoidal shape. In order to derive smooth torque from these motors, the applied current should be the same shape as the back EMF."
I personally prefer the PMAC over the BLDC "because of the smooth torque and lack of commutation noise". However, "trapezoidal control is simpler to implement than sinusoidal control. This added complexity must be considered in the decision of which motor and control type is best for an application." Because there are a number of very good PMAC controllers available, like the Sevcon Gen4 (which is now used by many of the marine drive system vendors), I don't think that controller complexity is an issue for us. I do know that the Gen4 is significantly more efficient than the older Millipak, at least it runs much cooler at the same power throughputs.
Fair winds,
Eric
Marina del Rey, CA
PS. You don't have to figure this all out this week. I can tell that much of this is brand new to you. There is a lot of information to absorb. Take your time and give all this info a chance to sink in. But you can see why many people choose to go with a complete system rather than trying to reinvent the wheel.
--- In electricboats@yahoogroups.com, Michael Mccomb <mccomb.michael@...> wrote:
>
> thank you for pointing me toward clarifying the differences between the PMAC and BLDC motors... i probably was reading them as interchangeably the same and they most definitely are not... i would not be interested in PMACs but only BLDCs and will read carefully from here on out to make certain i understand which of these i am looking at
>
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