UM-YROTATE-IT-RX62T datasheet(17/54 Pages) RENESAS

17 / 54 page

RX62T

YROTATE-IT-RX62T Motor Control Kit

UM-YROTATE-IT-RX62T Rev.1.00

Page 17 of 51

Jan 15, 2014

10. Permanent magnets AC Brushless motor model

The synchronous permanent magnets motor (e.g. sinusoidal Brushless motor) is widely used in the industry. More

and more home appliance makers are now using such AC Brushless motor, mainly because of the intrinsic motor

efficiency.

The permanent magnet motor is made with few components:

1. A stator formed by stacking sheared metal plates where internally the copper wiring is wound, constructing

the stator winding

2. A rotor in which permanent magnets are fixed

3. Two covers with ball bearings that keep together the stator and the rotor; the rotor is free to rotate inside

the stator

The working principle is quite simple: if we supply the motor with a three-phase system of sinusoidal voltages, at

constant frequency, in the stator windings flow sinusoidal currents, which create a rotating magnetic field.

The permanent magnets in the rotor tend to stay aligned with the rotating field, so the rotor rotates at synchronous

speed.

The main challenge in driving this type of motor is to know the rotor position in real-time, so mainly implementation

are using a position sensor or a speed sensor.

In our implementation, the system is using either one or three shunts to detect the rotor position in real-time.

Let’s analyse the motor from a mathematic point of view.

If we apply three voltages va(t), vb(t), vc(t) to the stator windings, the relations between phase voltages and currents

are:

“a” winding

How current flows

into “a” winding

“a” winding

magnetic axis

“b” winding

“c” winding

Motor axis

(shaft)

UM-YROTATE-IT-RX62T Datasheet(PDF) 17 Page - Renesas Technology Corp