Gearmotors

Gearmotors of all types and sizes including single / multiphase, universal, servo, induction and synchronous types. An AC gearmotor consists of a series of three windings in the stator section with a simple rotating section and an integral gearbox or gearhead. The changing field caused by 50 or 60 Hertz AC line voltage causes the rotor to rotate about the axis of the motor. AC motors are the most common and simple type of motor manufactured.  DC gearmotors are configured in many types and sizes, including brushless and servo. A DC gearmotor consists of a rotor and a permanent magnetic field stator and an integral gearbox or gearhead. The magnetic field is maintained using either permanent magnets or electromagnetic windings. DC motors are most commonly used in variable speed and torque applications.  A DC servomotor has an output shaft that can be positioned by sending a coded signal to the motor.  As the input to the motor changes, the angular position of the output shaft changes as well.  Servomotors are generally small and powerful for their size, and easy to control.  Common types of DC servomotors include brushless or gearmotor types.  Stepper motors are a class of motors that provide incremental motion, or steps, in response to pulses of current that alternately change the polarity of the stator poles; step motors do not require feedback and are sometimes used in "Open Loop," or no-feedback applications.

Important performance specifications to consider when searching for gearmotors include shaft speed, continuous torque, continuous current, and continuous output power.  The terminal voltage is the design DC motor voltage.  The continuous torque is the output torque capability of the motor under constant running conditions.  Continuous current is the maximum rated current that can be supplied to the motor windings without overheating.  Continuous output power is the mechanical power provided by the motor output.

Important AC motor specifications to consider when searching for gearmotors include voltage and frequency, phase, and motor construction.  Voltages and frequencies include 115 / 120V 60 Hz, 208-230 / 240V 60 Hz, 460 / 480V 60 Hz, 575 / 600V 60 Hz, 50 Hz / International Power, and 400 Hz / Aerospace.  Phase choices include single or three-phase.  Motor construction choices include induction, synchronous, AC servo, and universal.  Important DC motor specifications to consider include terminal voltage, motor construction and commutation.  The terminal voltage is the design DC motor voltage.  Motor construction choices include permanent magnet, shunt wound, series wound, compound wound, disc armature, and coreless or slotless.  Commutation choices include brush or brushless. 

Important gearing specifications to consider for gearmotors and gearheads include the gearing arrangement, gearbox ratio, and gearbox efficiency.  Gearing arrangement choices for gearmotors or gearheads include spur, planetary, harmonic, worm, and bevel.  Gearbox ratio is the ratio of input speed to output speed.  A ratio greater than one, therefore, indicates speed reduction, while a ratio less than one indicates speed increase.  Efficiency is the percentage of power or torque that is transferred through the gearbox.  Losses occur due to factors such as friction and slippage inside the gearbox. 

Feedback choices for gearmotors include integral encoder, integral resolver, and integral tachometer.  Other important parameters to consider when specifying gearmotors include shaft orientation or type and number of shafts, design units, motor shape, diameter or width, housing length, NEMA frame size, enclosure options and special or extreme environment construction.  Common features include multi-speed, reversible, integral driver electronics, integral brake, integral clutch, and brake and clutch combination.

• 10 Things Everyone Ought to Know About Custom Gearmotors (.pdf)
  A custom gearmotor is one that meets your particular application specifications. It has the correct mechanical and electrical interfaces, fits within the envelope available, meets your performance,...
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• Cartridge Brush Design For DC Motors and Gearmotors
  The traditional method for mounting copper or silver graphite brushes in brush-commutated DC motor and gearmotor assemblies has been to solder the brushes onto standard cantilever springs to enable...
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• New Gearmotor Sizing Guide from Bison Gear and Engineering Corp.
  Selecting the proper gearmotor is a matter of matching output speed and torque to an application's needs. RPM is determined by the driven machine's requirements and should be known. That leaves torque...
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Part Numbers for Gearmotors