| 摘要 |
<p>PURPOSE:To prevent the current of an armature from rising above a necessary level and prevent a braking force from greatly fluctuating, by controlling a field current in accordance with an instructed braking force pattern instructed from a motorman's seat. CONSTITUTION:When initial braking is performed, the output of an instruction pattern circuit 11 for instructing a prescribed braking force is reduced at a predetermined ratio by a braking force pattern change circuit 12 depending on a signal from a cam shaft controller 10. A braking force comparison amplifier 13 compares the outputs of a dynamic braking force detector 8 and the instruction pattern circuit 11 with each other to control the output of a separate excitation controller 5 to the prescribed level. When a field current IF reaches an upper limit level dependent upon the capacity of a field coil 3 and the capability of the separate excitation controller 5, a maximum field current detector 9 generates an output so that the cam shaft controller 10 short-circuits a resistance section of a main resistor 2 and advances a cam shaft to the second step.</p> |
