BRUSHLESS MOTOR A DC Brushless Motor uses a permanent magnet external rotor, three phases of driving coils, one or more Hall effect devices to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors, they act as three-phase synchronous motors containing their own variable frequency drive electronics

CLOSED LOOP CONTROL A broadly applied term, relating to any system in which the output is measured and compared to the input. The output is then adjusted to reach the desired condition. In motion control, the term typically describes a system utilizing a velocity and/or position transducer to generate correction signals in relation to desired parameters.

COMMUTATION A term which refers to the action of steering currents or voltages to the proper motor phases so as to produce optimum motor torque. In brush type motors, commutation is done electromechanically via the brushes and commutator. In brushless motors, commutation is done by the switching electronics using rotor position information obtained by Hall sensors, a Tachsyn, or a resolver.

HALL EFFECTS refers to the potential difference (Hall voltage) on opposite sides of a thin sheet of conducting or semiconducting material in the form of a 'Hall bar' or a van der Pauw element through which an electric current is flowing, created by a magnetic field applied perpendicular to the Hall element. The ratio of the voltage created to the amount of current is known as the Hall resistance, and is a characteristic of the material in the element. Dr. Edwin Hall discovered this effect in 1879.

IGBTs (Insulated Gate Bipolar Transistor is a four-layer (n-p-n-p) device with an MOS-gated channel connecting the two n-type regions. In the normal mode of operation, a positive voltage is applied to the anode (A) relative to the cathode (K).

MOSFETs (Metal Oxide Silicon Field Effect Transistor a common type of transistor in which charge carriers, such as electrons, flow along channels. The width of the channel, which determines how well the device conducts, is controlled by an electrode called the gate, separated from channel by a thin layer of oxide insulation. The insulation keeps current from flowing between the gate and channel.

OPEN LOOP A system in which there is no feedback. Motor motion is expected to faithfully follow the input command. Stepping motor systems are an example of open-loop control.

POTENTIAL DIFFERENCE A potential difference between two points gives rise to a "force" called an electromotive force or emf that tends to push electrons or other charge-carriers from one point to the other. A potential difference is generated between the ends of an electrical conductor that moves perpendicular to a magnetic field. Between two points in an electrical circuit the potential difference is equal to the difference in their electrical potentials.

PULSE WIDTH MODULATION is a four-layer (n-p-n-p) device with an MOS-gated channel connecting the two n-type regions. In the normal mode of operation, a positive voltage is applied to the anode (A) relative to the cathode (K).

ROTOR The rotor is made of permanent magnet and can vary from two to eight pole pairs with alternate North (N) and South (S) poles.

TERMINAL RESISTANCE static line to line resistance @ 25 deg. C.

THREE-PHASE AC SYNCHRONOUS MOTORS As with single-phase motors, if the rotor coils of a three-phase motor are fed a separate field current to create a continuous magnetic field (or if the rotor consists of a permanent magnet), the result is a called a synchronous motor because the rotor will rotate in synchronism with the rotating magnetic field produced by the polyphase electrical supply.

VARIABLE FREQUENCY DRIVE (sometimes abbreviated VFD) is electronic equipment that allows an electric motor to be run at varying rotational speeds.
VFDs are frequently used to start large three-phase AC synchronous motors. These motors cannot be started simply by applying line frequency mains power; the rapidly rotating magnetic field would be unable to overcome the inertia of the rotor (and any connected load). Using a VFD provides one possible means to start these motors: the VFD will start using a low frequency that the rotor can follow, ramping up the frequency as the rotor accelerates. And unlike other starting methods, the VFD also allows very efficient speed control once the motor is running (simply by varying the ultimate frequency of the supplied power).