On the Characteristics of the 180°―type Transistor Commutatorless Motor (Compared with the 120°―type transistor― commutatorless motor)

摘要

For the 180°-type thyristor-commutatorless motor, reactors and capacitors are needed to obtain commutation energy, and the setting angle must be held leading and therefore the armature current circulates through the feedback diodes and armature windings. For these reasons the 180°-type thyristor-commutatorless motor has low efficiency and is considered to be impractical. While the transistor-commutatorless motor does not depend on the induced voltage during the commutation and needs neither reactors nor capacitors for commutation, and therefore its circuit configuration is simple and the system is economical. Furthermore the transistor-commutatorless motor has the advantage that its setting angle can be made zero or negative (lagging) for steady operation as well as starting. In this paper, based on the experiments, the characteristics of the 180°-type transistor-commutatorless motor, which has neither feedback diodes nor commutation reactors and capacitors, are discussed compared with the 120°-type transistor-commutatorless motor. Also the effect of the cumulative- and differential -compound field windings over the load characteristics of the 180°-type transistor- commutatorless motor are discussed. The results are as follows. 1) For the 120°-type, the positive torque is generated for the setting angle in the range, -60°≤γ₀≤60°, while for the 180°-type the positive torque is obtained only in the range, -30°≤γ₀≤30°. 2) In the case of the 120°-type, the input voltage is always higher than the induced voltage and therefore the transistor is ON during the entire period (120°) for which the base voltage is applied to the transistor. In the case of the 180°-type there exists the period of 60°during which the induced voltage is higher than the input voltage and therefore the transistor is ON only in the time interval of 120°while the base voltage is applied for 180°. 3) For the identical setting angle and load current, the 180°-type has a higher induced voltage (or motor speed) than the 120°-type, namely, the former has a larger torque pulsation than the latter. 4) With the differential-compound field winding and for a negative setting angle (lagging), the motor efficiency is low (about 50%) due to the increase of commutation- surge loss and decrease of power factor.