A gear motor is a single component that integrates a gear reducer with an electric motor. Depending on their design and purpose, such geared-motor units can produce high torque even at low speeds or with low horsepower.
They are able to achieve this because the gearhead acts as a torque multiplier, meaning smaller geared motors generate relatively high torque.
AC or DC Motors
Gear-motors can be designed for use with either AC or DC motors, with each serving the same purpose of converting electrical energy into mechanical energy even though they are built and controlled differently. The biggest difference is their source of power, with AC motors powered by an alternating current and DC motors powered by a direct current (hence their abbreviated names).
Geared-motor units also come with a variety of gearing styles such as bevel, helical, hypoid, spur or worm gears, with each having their own advantages and disadvantages. The most important ratings when identifying the ideal gear-motor for a particular application are usually input horsepower, output speed and output torque.
Types of DC Motor
DC motors generally all have the same type of rotor, featuring windings that generate an electromagnetic field when they receive an electrical current. The major differences come in the form of the stator, which are made of permanent magnets or coil windings.
Permanent magnet DC motors are the simplest design and are thus less costly than wound DC motors, though their construction style means their torque output will be significantly limited compared to a wound DC motor. The magnets will also degrade with use, making the longer lasting wound DC motor the more commonly used in industrial applications.
There are two definitive types of wound DC motor designs that will be preferred for different applications, with the difference being how the rotor and stator windings are connected. The two types are Series Wound and Shunt (or Parallel) Wound, with a third option being a Compound Wound DC motor that is a combination of the main two types.
Series Wound DC Gear-Motors for High Torque
The Series Wound DC geared-motor units feature the rotor and stator windings connected in sequence, or a series, with the electrical current running through each of them equally. The stator windings will have a thicker diameter and have fewer turns than those in a Shunt gearboxes and geared-motors, which makes the resistance of the windings lower compared to the Shunt type and allows the Series Wound motor to extract large amounts of electrical current to produce high torque.
Shunt Wound DC Gear-Motors for High Torque
In shunt wound DC motors, the rotor and stator windings are connected parallel to each other, hence the alternative name of Parallel Wound DC motor. This type of connection splits the motor current in two with one going through the rotor and another through the stator. With a smaller wire diameter and more turns compared to the Series Wound windings, the Shunt stator has a very high resistance with the initial drawn current relatively low.