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Motor basics

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What is a motor?

We, Igarashi Electric Works Ltd. develops, produces and sells small motors. What is a motor in the first place?
Simply put, a motor is that "a shaft rotates when electricity is applied." To put it a little more technically, it is a device that converts electrical energy into mechanical energy.
A motor is indispensable to move things with the power of electricity. It is no exaggeration to say that modern society would not be possible without a motor.
What is the principle of "a shaft rotates when electricity is applied"?

Motor principle

The principle of a motor is based on "Fleming's left-hand rule". Power is generated by passing an electric current through a magnetic field. This "magnetic field", "current" and "power" are related to the structure of a motor.

Basic structure of a motor

We will introduce the structure of the motor using a direct current (DC) brushed motor, which is the most frequently handled by us (Igarashi Electric Works Ltd.), as an example in this page. (Hereinafter, unless otherwise stated, a motor means a DC brushed motor.)

The motor is roughly divided into three parts: case, end cap and rotor.


A case has a built-in magnet that creates a magnetic field.

B)End Cap

An end cap has the role of passing electric current through a magnetic field. A motor is connected to a power supply from an end cap.


A rotor has the role of extracting power and transmitting it to connected parts. In some cases, the rotation of the rotor is transmitted directly to the part.
In many cases, parts such as gears are used to control the magnitude and speed of force and convert it into final power.

Where motors are used

Click here to see where motors are actually used.

Relationship between motor and generator

As explained earlier, a motor is that "a shaft rotates when electricity is applied." On the contrary, a generator is "a thing that generates electricity when the shaft is turned".
One uses electricity and the other produces electricity. The roles of motors and generators are different.
However, both are important in the sense that they move the world based on the same principle.

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