Electric motors have been vastly improved in recent years, especially for applications that require high efficiency and torque at a wide range of speeds - such as your EA sailboat. The big advance is what is known as the PMAC (permanent magnet alternating current) or BLDC (brushless direct current) motor. These two names refer to the same motor design, a confusion caused by the fact that these motors are designed to get their power from a direct current source - such as batteries - but require that this dc be converted by a “motor controller” into a three-phase alternating current in which the voltage and frequency, and even the wave form, is custom made for the immediate demands of the motor. To do this, the motor controller receives its instructions both from the throttle control, and from sensors in the motor itself, which signal its needs of the instant. The process is entirely reversible, so moving between forward and reverse is purely electronic and requires no gears.

PMAC/BLDC motors offer several advantages over brushed DC motors, including more torque per weight, more torque per watt (increased efficiency), increased reliability, reduced noise, longer lifetime (no brush and commutator erosion), elimination of ionizing sparks from the commutator, and overall reduction of electromagnetic interference (EMI). With no windings on the rotor, they are not subjected to centrifugal forces, and because the windings are supported by the housing, they can be cooled by conduction, requiring no airflow inside the motor for cooling. This in turn means that the motor's internals can be entirely enclosed and protected from dirt or other foreign matter.

The motor used in the EA system takes full advantage of this by being totally enclosed, a big plus in the marine environment. This motor was designed especially for marine propulsion by John Fiorenza, an icon in the field, and is beautifully manufactured to his exacting specifications. You can learn more about this motor (model ME0201013601) at his website:
www.motenergy.com/

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