1. Definition of the motor

Motor refers to a device that converts electricity into power or electrical energy into mechanical energy.

Sometimes electrical input is abbreviated to input, and mechanical output is abbreviated to output. In the process of energy conversion, part of the input does not become power, but becomes heat, which is called loss.

a. The relationship between input power, output (also called power) and loss is as follows:

Input power = mechanical output + loss  The unit of expressing these quantities is watt (W)

b. The definition formula of input power and mechanical output is expressed as follows:

Input power (W) = voltage (V) x current (A)

Mechanical output (W) = speed (rad / s) x torque (Nm)

c. The efficiency of the motor refers to the ratio of the mechanical output to the input power expressed in percentage (%).

Motor efficiency = output / input × 100%

Some of the losses are caused by mechanical reasons like friction, but the larger proportion is the loss in the copper wire and the loss in the iron core. The former is called copper loss, and the latter is called iron loss.

2. Components of the motor

2.1 The components of the motor mainly include five parts as shown in the below figure ① ～ ⑤

①Rotor or rotating body: the rotating part
②Bearing: the part that supports the rotor shaft (the shaft)
③ Stator: the part that generates the force that rotates the rotor
④Bracket or end plate: supports the bearing and becomes an integral part with the stator
⑤Wire: the stator of the wire connected to the drive circuit or power supply for the motor

2.2 Among the above constituent elements, the stator and rotor are more closely related to the basic classification of motor. The typical structure of the stator can be listed in the following four types.
A. Distributed winding stator
B. Concentrated winding stator
C. Induction stator
D. Permanent magnet stator

2.3 The rotor can be divided into 10 types.
A. Squirrel cage rotor
B. Salient pole cage rotor
C. Semi-hard magnetic steel rotor
D. Mild steel rotor
E. Salient pole type silicon steel rotor
F. Fine rack type mild steel rotor
G. Permanent magnet rotor
H. Induction rotor
I. Coil rotor
J. Commutator rotor

2.4 The main component material of the motor

A. Enameled wire

The material is generally copper, but aluminum is also used sometimes.

The wire is divided into a wire that supplies power from the power source to the motor and a coil formed inside the motor. From the point of view of the wire that generates a magnetic field, the part corresponding to the coil is also called enameled wire.

B. Iron core

The so-called iron core is a magnetic channel, as the literal meaning is, the material is iron. In addition, iron used to join two magnets by magnetic flux is generally called a yoke.

The iron used for the mechanism structure and the iron used for the core are different in the types of auxiliary components. The iron used for the mechanism structure contains carbon (C), and the iron used for the iron core is added with silicon (Si), which is also called silicon steel. In the motor, the iron core is divided into a stator iron core and a rotor iron core, and the magnetic circuit is formed by the gap between the two. The magnetic poles of the stator core constituting the excitation circuit of the electromagnet excitation type DC motor are excited by direct current. Therefore, the iron core does not need to have a laminated structure and use mild steel.

On the other hand, the magnetic flux of the rotor core constituting the armature circuit changes when it rotates, so a laminated core is used. In addition, permanent magnets are generally used for the magnetic poles of small DC motors. Since the excitation is performed by alternating current, the stator core of the synchronous motor, the stator of the induction motor and the iron core of the rotor are preferably laminated iron cores.

C. Insulator (material)

An insulator that interrupts the current to prevent the current from flowing outside the specified location. The material is an insulating material. Generally, rubber and polymer compounds called enamel / resin, paper, mica, glass fiber, etc. are used.

D. Permanent magnet

The most important material of the motor is the permanent magnet as the source of the magnetic field. It can also be called an alloy or oxide with iron as the main component.

3. Classification of motors (each category includes: definition, principle and structure, wiring, characteristics)

3.1. Shaded pole motor
3.2. Universal motor
3.3. Brushless DC motor
3.4. Hybrid stepper motor
3.5. Servo motor (servo system)
3.6. Pump motor