The rectifying action is as follows: - The ends of the secondary of the transformer are alternately positive and negative with respect to the center tap. When one end is positive with respect to the center tap, the other end is negative with respect to the center tap. Therefore during each half cycle of alternating voltage, the plate of one or the other of the Tungar bulbs is positive with respect to the filament, and a current will flow during each half cycle first through one tube and then through the other.

The current always flows out of the center tap of the transformer secondary into the positive side of the storage battery, through the battery, through the ammeter, and then through one or the other of the Tungar bulbs. This current is not the steady direct current which can be obtained from a battery, but a pulsating current which flows always in the same direction. It is satisfactory for charging storage batteries but is not suitable for use where a steady direct current is required.

The Rectigon and the other Tungar chargers are similar in principle to the one just described but differ considerably in their construction. These chargers are made up of two half-wave chargers connected together electrically so as to make a full-wave rectifier. They have two transformers, two ammeters and two current control, tap switches. The secondaries of the transformers are tapped for various voltages so that the charging rate can be varied by means of the tap-switches.

58. Method of Operation of Chargers. -To operate the Tungar charger shown in Figure 42, connect the charger to the battery to be charged by means of the four-pole battery switch. Turn the Tungar snap-switch "On". The ammeter should show a charging rate of about 12 amperes. Two of these units are always included in an installation, and when operated in parallel give a charging rate of 24 amperes.

The primaries of the transformers are tapped for primary voltages of 105, 115, and 125, and the line lead to these taps from the tumbler switch should be connected to the tap corresponding to the line voltage. If the line voltage is between 100 and 110 volts it should be connected on the 105 volt tap. If the voltage is between 110 volts and 120 volts it should be connected to the 115 volt tap, and if the voltage is between 120 volts and 130 volts it should be connected on the 125 volt tap. If the line voltage is low and the charging rate too high, the lead may be connected to a tap corresponding to a higher line voltage. This lead should never be connected to a tap of a lower rating than the line voltage, that is, the charging rate should not be increased by changing the tap connection to one which is below the line voltage.

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