Ques. What duty is performed by the spark?
Ans. It breaks down the negative electrode resistance.
Ques. What conditions are now necessary for continuous operation of the rectifier?
Ans. The rectifier will now operate indefinitely as long as the current supply is uninterrupted and the direct current load does not fall below the minimum required for the arc.
Fig. 2,101.—General Electric 50 light double tube combined unit series mercury arc rectifier outfit; front view. This unit consists of a constant current transformer, reactance, tube tank and exciting transformer mounted on a common base; also a static discharger and pilot lamp mounted on top of the transformer. This arrangement makes the rectifier outfit, with the exception of the switchboard panel, complete in itself.
Ques. Is the rectifier self-starting?
Ans. After the bulb has been started a few times, as described above, it becomes self-starting, so that under all ordinary operating conditions it will commence to operate when the switches connecting it with the load and the alternating current supply are closed.
Ques. What provision is made in the Westinghouse-Cooper Hewitt rectifier to render it self-starting?