Pictured in the animation is a conventional 4-pole brushless DC Motor. It consists of four magnets shown as yellow and blue arcs that are affixed to a rotor hub which in turn rotates in the center of the stator. The stator is depicted in the animation by the gray concentric circles with six "teeth" pointing inward toward the rotor. The stator consists of a stack of stamped, thin metal laminations. Once they have been stacked and insulated, magnet wire is wound around each of the six teeth. Electrically, this motor is conventionally known as a "Y" winding and is a three-phase design.  In this illustration Hall-Effect generators are used to sense the position of the rotor and are indicated by the three devices that are separated 120° apart and which change from black to red depending on their state.  For simplicity, the Halls are numbered and correspond to the inputs of the decoder circuit that are shown as boxes in the lower left hand part of the animation who's state changes correspondingly from transparent to red.  These signals from the Hall Effect sensors are decoded as indicated by the truth table shown in the upper left quadrant of the animation. The decoder circuit takes the inputs from the Halls and energizes the coils in the proper sequence.  An attempt has been made to indicate the state of the coils relative to the position of the rotor. In this three-phase motor, note that at any time two of the phases are energized while one is in a neutral state. Among the two phases that are energized, one phase which fires two opposing teeth is always positioned to maximize the magnetic flux relative to the magnets on the rotor thereby creating the most efficient force. The phases are fired in sequence is this rotational manner at up to extremely high speeds.

Copyright© Servo Magnetics Inc.

4.11.2006

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This animation is of a motor with a central rotor and peripheral stator.  The Torq motor is the opposite of this of course, but the electrical operation and sequencing are identical, the integral Hall switches being embedded in the Torq's stator to sense the rotor magnets.

Use the Step Through animation arrows below the animation to help with seeing the action sequence.