Figure 6-32.Block diagram of constant-current regulator.
The output voltage is applied to the input of the gate
pulse generator that determines the condition angle of
the SCRs and changes it to bring the system to
equilibrium. Transient overload protection is provided
for the semiconductor element of the Hall unit. Open-
circuit protection is provided when no current is drawn
by the load and the brightness potentiometer output
voltage is any value other than zero. Under these con-
ditions, the SCRs will be prevented from conducting,
and the output voltage to the load will be zero.
The airfield lighting systems may be operated
completely by the remote control panel assembly. The
only operation required at the electrical distribution
vault is to ensure that all circuit breakers are engaged,
the regulators are set for remote operation, and the load
switches are in the ON position. The electrician must
ensure that the unit is installed properly and that the
different levels of light intensity desired can be
achieved. Figure 6-33 is a typical view of a remote
control unit that you may encounter in the installation
of a contingency airfield lighting system.
The unit uses 120 volts as the control voltage with
low-burden pilot relays to compensate for the voltage
drop caused by the long distances usually found
between the control tower and the vault. In this type of
control system, the switches on the control panel
actuate low-burden relays; these, in turn, actuate the
power switches, contactors, and the relays controlling
the regulators that supply the airfield lighting circuits.
Figure 6-33.Typical remote control panel operating controls.