Electrical System Protection - Cirrus SR22 Pilot Operating Handbook

C D
IRRUS ESIGN
SR22
Constant Power Bus (CONV)
The Constant Power Bus (CONV) is fed by BAT 1 in the MCU through one
5-amp fuse located on top of the MCU.

Electrical System Protection

Circuit Breakers, Fuses and Voltage Suppressors
Individual electrical circuits connected to the Main, Essential, and
Non-Essential Buses in the airplane are protected by re-settable circuit
breakers mounted in the circuit breaker panel on the left side of the center
console. Loads on circuit breaker panel buses are shed by pulling the indi-
vidual circuit breakers.
Transient Voltage Suppressors
Transient Voltage Suppressors (TVS) are installed in key areas of the elec-
trical system to protect the system from lightning strikes. During lightning
strikes, enormous energy spikes can be induced within the airplane elec-
trical system. In the absence of any transient protection, this unwanted
energy would typically be dissipated in the form of high-voltage discharge
across the avionics and electrical systems of the airplane. By adding a high
power TVS at key power entry points on the electrical buses, unwanted
energy from electrical transients is allowed to dissipate through a
semi-conducting pathway to ground.
If smoke and/or fumes are detected in the cabin and it is suspected
that this event was caused by a TVS failure, the operator should
confirm that there is no fire and perform the
Essential Buses
The circuit breaker panel ESS BUS 1 and ESS BUS 2 are powered directly
by ALT 1 and ALT 2 from the MCU Essential Distribution Bus through
30-amp fuses inside the MCU and also by BAT 2 through the 20-amp BAT
2 circuit breaker.
In the event of ALT 1 or ALT 2 failure, the Essential Buses in the circuit
breaker panel will be powered by the remaining alternator through the
Main Distribution Bus 1 or Main Distribution Bus 2 in the MCU. In the
case of both alternators failing, BAT 1 is connected directly to the Essential
Distribution Bus in the MCU and will power ESS BUS 1 and ESS BUS 2. In
the event of both alternators and BAT 1 failing, BAT 2 is connected directly
to ESS BUS 1.
P/N 13772-006
Reissue A
• CAUTION •
Elimination Checklist.
S 7: A
ECTION IRPLANE AND
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LECTRICAL
Smoke and Fume
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