Mr. Vex: Please tell me, Miss Ori!! I received an inquiry from a customer about DC motor. The customer directly inputs 24VDC without using a drive circuit. Is there such a motor?
Miss Ori: It might be the DC brush motor.
Mr. Vex: Wow!! There is such a motor?
Miss Ori: Have you ever seen a small rotating motor just connected by a battery before, when you were in elementary school?
Mr. Vex: Yes, I have. I also had an experience to connect the dry battery to the motor rotating.
Miss. Ori: The motor inquired by the customer is the same structure as the motor rotated by connecting the battery. Electrode which is called as brush and commutator are set inside of a motor. It is rotated by mechanically switching the current to touch these two commutators.
These kind of motors are called DC brush motor. (Figure 1)
Mr. Vex: Oh!! They are called "brush" and "commutator." Oriental Motor have motors which are called "Brushless Motor" using the word of "brush."Is there any relationship between them?
Miss. Ori: The structure of brushless motors is a bit different from brush motors.
It is not the mechanical connection such as "brush" and "commutator." The motor is rotated by electronically switching of current by using an electronic circuit (drive circuit) which is structured by a power element such as transistor.
Mr. Vex: I see!!! That's why it is called "brushless".
Miss. Ori: Exactly!!!
Mr. Vex:I could understand the difference between with/without brush from your explanation, but is there any difference for customers who are using?
Miss. Ori:Yes, the difference is maintenance. DC brush motors have the friction by rotating with touching electrodes which are "brush" and "commutator." As a result, it is necessary for replacement and maintenance. However, brushless motors are not necessary for maintenance because of the electric circuit (drive circuit).
Mr. Vex:I see!! Customers do not require maintenance for brushless motors.
Miss. Ori: Moreover, another difference is stability of rotational speed of motors. Rotational speed of motors with brush is changed depending on changing load.
Rotational speed of brushless motors can do stable speed control regardless of changing load. A condition of motor is confirmed by feedback control with mounted magnetic sensor which is called a Hall effect IC. Moreover, if there is occurred abnormal such as overload, connection error of cables and disconnection, the motor will stopped and alarm signal will be triggered . So, customers can use it safely. [Figure 2]
Mr. Vex:I understand. Brushless motors are filled with good points.
Miss. Ori: That's right!, the merits are wide range of speed limits, flat torque, slim type and high power. The product variation has increase thus do promote brushless motors to customers.
Mr. Vex:Of course! The inquiry from the customer was about replacement from DC motor with brush. So, I will do my best for replacement to the customer by explaining about the merits of brushless motors and the maintenance-free which you had just taught me.