PCC Type Controllers
PCC type controllers work using the same principle except that the circuits are opened and closed automatically (similar controllers exist on the Gothenburg M28, older Düwag built trams, some later British tram designs and Melbourne's Z1/Z2 class). This is controlled by a spring-loaded "governor" on the armature shaft of the motor. In this system, the accelerator (pedal) or controller (handle) controls the rate of acceleration, and since full series and full parallel are still the normal operating positions, speed is controlled by automatically cutting power above a speed which depends on the position of the accelerator/controller and then automatically coasting and braking as above.
Read more about this topic: Tram Controls
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