The electron beam power supplies incorporate a proven series tube regulator design with a modern integrated circuit control.

The output of the "Main Power" circuit breaker is also applied to the high-voltage contactor which provides on/off control. The output of the contactor is applied to the delta-connected primary of the rectifier transformer. This winding is tapped so that a range of input voltages may be accommodated. The transformer is also designed for either 50 or 60 Hz operation.

The rectifier transformer secondary is terminated so that its connection can be easily changed from wye to delta. This provides a convenient means of obtaining increased current output at lower voltage settings. The output of the transformer is rectified and its negative output provides the accelerating voltage for the electron beam gun. The positive output is connected to the plate of a high-power tetrode tube.

Tetrode Control Circuits
A power tetrode is used as the control element in a conventional series tube regulator configuration and is connected between the power supply positive output and ground. Variation of the voltage drop across the tube results in a variation of the power supply output.

A voltage divider is connected across the output and its ground-referenced signal is compared to a reference signal by a summing amplifier, the output of which provides the error signal for the voltage regulating loop. This signal is applied to the base of the control grid drive transistor. This circuit drives the control grid of the tetrode. The output of the power supply is then held constant by action of the regulating loop.

The tetrode also provides a means of interrupting the short-circuit, which results from high-voltage arcs to ground. A shunt resistor connected in series with the cathode develops a signal which is proportional to the current passing through it. This signal is applied to the current cutback circuit and if it is greater than a preset maximum, the cutback circuit takes control and will bias the tetrode off for a short time. At the end of this period, the regulator assumes control, and the high voltage short still exists, the cutback circuit takes control and the tube is biased off. In this manner, the system is completely protected from the numerous high voltage arcs which occur in electron beam systems.

Gun Filament Power Supply
The gun filaments are operated temperature limited, therefore emission current is directly proportional to the AC power applied to the filament transformer. Tight control of this power provides the required regulated emission control. Following is a description of this operation.

On/off control is provided by an AC contactor, the output of which provides power to phase proportioning SCRs. Their output provides the required AC control to the primary of the gun filament transformer. its secondary is connected to the gun filaments and the center tap is connected to the negative output of the high voltage power supply.

Closed Loop System Operation
The power supply is designed so that it will operate several guns at the same time. In this event, the current passing through the shunt resistor in the ground return is the summation of the currents of all the guns. Therefore its signal cannot be used as the feedback signal for the emission controllers. A DC current transformer is used to provide this signal when used in conjunction with its amplifier, this device provides a ground referenced DC signal that is proportional to the DC current passing through the single turn primary. One of these devices is provided for each gun in the system and its output provides the feedback signal for the emission regulator. It is compared with the reference signal provided by either the control panel potentiometer or a conventional evaporation rate controller and the result is the error signal. This signal is the applied to the SCR control circuit and the AC power applied to the primary of the filament transformer is adjusted accordingly.

When a high voltage arc occurs, the tetrode removes power to the gun and the arc is extinguished. While the high voltage is turned off, the emission current regulator is disengaged and filament current is reduced to a quiescent level. When high voltage is again applied. The emission current regulator again becomes active and normal operation resumes.