AUTHOR : Ki-Yong Nam, Woo-Taik Lee, Jung-Pyo Hong
ORGANIZATION : International Compumag Society
JOURNAL : COMPUMAG
YEAR : 2005.6.26
VOL : I
ISSUE :
PAGE : 176 ~ 177
The Blushless Direct Current(BLDC) motor has of high
torque, compact size, and high efficiency. Therefore, the
BLDC motor is widely used from computers, household and
industrial products, and automobiles. However, the BLDC
motor has a disadvantage that is high cost compared with DC
motor because it is necessary to use an inverter and controller
to remove brush of DC motor[1],[3].
The ideal BLDC motor has a trapezoidal back-EMF and
the constant source voltage is inputted. And then the current
made by source voltage instantly rise to steady state.
Therefore, the torque is produced without torque ripple.
However, the current characteristic of the actual BLDC motor
is different from the ideal case, because current is influenced
by the inductance and it can not rise or fall to the stead state
directly as Fig. 1. Also, the current ripple is produced by
difference between the rising and falling current in the
freewheeling region and rising current continuously increases
because of rising time that is longer than the commutation
time in high speed. Therefore, the current ripple is produced
by influence of the inductance and the torque ripple is affected
by current ripple directly[2].
In this paper, the method of reducing torque ripple is
proposed by varying the source voltage to flow the current
continuously after analyzing circuit for acquiring the current.