| 摘要 |
The stator terminals of an adjustable speed a-c induction motor are connected to a source of d-c electric power by means of an inverter, and a system is provided for blending both dynamic and regenerative electrical braking of the motor whenever it decelerates. The brake blending system comprises a plurality of braking resistors respectively coupled by a corresponding switch in parallel with the power source. The switches are controlled by a control circuit which responds to motor terminal voltage, motor angular velocity and the difference between the commanded and actual motor torques to determine the additional current which the motor could regenerate without exceeding commanded parameters. When the additional current corresponds to that current which can be absorbed by adding an additional stage of braking resistance, the control circuit actuates a switch to add a stage of dynamic brake resistance. The control circuit also monitors the voltage of the source and removes braking resistance in steps to maintain source voltage within selected limits in order to maximize the current fed to the power source and thus maximize regenerated energy. In an alternate embodiment the control circuit determines the admittance of the source and utilizes the admittance to maintain source voltage substantially constant by removal of dynamic brake resistance in order to force more regenerative current to the source.
|
