| dc.description.abstract | As the MOSFET switches off, Vds rises instantaneously. However, induc-tive load of motor keeps the current flowing through it. That is, Ids cannot immediately decay to zero. At this time, power loss is unavoidable. This kind of power loss increases the temperature of MOSFET. Then the device may be destroyed by excessive temperature rise. To reduce the power loss of switching off, this thesis proposes the current width modulation method.
Rotation of the motor relies on the excitation stator winding to make the internal rotor and the stator relative position to change, but the magnetic flux is related to the relative position of stator and rotor. It causes the equiv-alent inductance of the motor to change with the magnetic flux. That makes the current change rate inconsistent. Therefore, the current width modulation control is used to limit the current by adjust the conduction time. So that, the peak of switching current does not change with the angle, which can re-duce v*i value of the switching-off loss. On the other hand, shortening the off-time make the motor phase current continuous to provide energy. This paper compares the current value and the switching loss at turning-off of two control methods between CWM and PWM under the condition of the motor fixed load and the same rotational speed. Finally, Validate the method with experimental results. | en_US |