T-34C AIRCRAFT SYSTEMS FAMILIARIZATION
ELECTRICAL POWER SUPPLY SYSTEM
The electrical power supply system consists of a nominal 28-VDC system and a 26-volt/115-
VAC inverter system. The DC system is comprised of a battery and an engine-operated
generator. On the ground, the DC system can be powered by an external power unit. The AC
power is provided by two inverters which change DC power to AC power. Control of the
electrical system is provided through various circuit breakers, relays, buses, and switches.
BASIC CIRCUIT COMPONENTS
A circuit breaker protects an electrical circuit from overload. It is constructed of a bi-metallic
strip with each metal having a different expansion rate when exposed to heat. Should a piece of
electrical equipment malfunction causing the circuit to overheat, the bi-metallic strip bends and
causes the circuit breaker to "pop," thereby creating an "open" circuit and interrupting electrical
power to the faulty equipment.
A relay is used to control a large amount of current flow with a small amount of current flow.
Activated by a remotely controlled switch, it allows a small amount of current flow to the relay
electromagnetic coil. The relay "closes" and provides a complete circuit to the system component
requiring high current (for example, the engine starter). Relays, therefore, allow the use of small
switches in the cockpit to control large electrical loads. Interruption of current to the relay
"opens" the relay and current flow to the electrical load ceases.
A bus is an electrical power distribution point. A bus can receive electrical power from the
battery, generator, external power unit, or inverters. It then distributes the electrical power to
various electrical loads (i.e., lights, motors, instruments, etc).
DC POWER SYSTEM
The DC power is supplied by the battery, the generator, or an external power unit. Controls for
the DC system are located on the electrical control panel on the right console in both cockpits.
ELECTRICAL POWER SYSTEMS 9-3