ABSTRACT :
This paper
describes the reduction in torque ripple due to phase commutation of brushless
dc motors. With two-phase 1200 electrical conduction for the
inverter connected to the conventional three-phase BLDC machine, the
commutation torque ripple occurs at every 60 electrical degrees when a change
over from one phase to another occurs. This effect increases the commutation time
at higher speeds which increases the torque ripple. The torque ripple is
reduced by changing the switching mode from 1200 to a dual switching
mode with 1200 switching at lower speeds and 1800
electrical for the inverter at higher speeds.
KEYWORDS:
1. Brushless dc motor
2. Current commutation
3.
Torque ripple
4.
Electric
vehicle
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1. PWM inverter and equivalent circuit of BLDC motor
EXPECTED SIMULATION RESULTS:
Fig.2.
(a) Relative torque ripple amplitude and (b) The duration of
commutation
time
CONCLUSION:
This paper has presented an analytical
study of torque ripple comparison due to commutation of phase currents in a
brushless dc motor for both 1200 and 1800 conduction modes. The results have
been validated by simulation and experimental verification. In three-phase switching
mode at high speeds the torque ripple and losses are minimized and therefore
the efficiency of the machine is increased. But the same cannot be achieved at low
speed in this mode. On the other hand, the 1200 situation is exactly opposite.
Thus a composite switching scheme is proposed for satisfactory operation of the
machine at all speeds. The effectiveness of the method is validated by suitable
experiments.
REFERENCES:
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