Sensored & Sensorless

Last Reviewed: Mon, 27/Mar/2017


Sensorless versus Sensored
In most brushless motors there are Hall effect sensors - one per motor winding - that tell the controller where the "hot" winding is in relation to the center of the magnet it is trying to reach. Just before the center is reached (maximum pull), the controller switches the current to the next (lagging) winding until it almost reaches the center of the magnet. There are a lot of magnets around the circumference of the motor, so each full revolution of the motor requires firing each winding many times. Hall-effect sensor feedback is analog and continuous whether motor is turning or not, so when starting, the controller can choose the correct winding to power based on the sensor feedback. A sensorless motor works the same way, but the controller is a bit smarter. Some means of determining the powered winding's position relative to the next magnet is still required. A sensorless controller determines this by looking at the amount of energy being "reflected" by the windings themselves. When the "reflection" begins to peak, the controller switches power next winding. This works great when the wheel is turning, but if it's stopped (stalled) the controller has to make a guess as to where to apply power to start the wheel turning. You will hear a clicking sound as the controller switches from one winding to another trying to get the motor to start in the correct direction. Any motion at all enables the feedback process to start working so efficient operation can begin within an inch or less of travel. ElectricRider's revision F controllers will power sensored and sensorless three-phase brushless motors.


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