Electrical System; Power Generation - Cirrus DESIGN SR20 Information Manual

Cirrus Design Section 7
SR20 Airplane Description

Electrical System

The standard airplane is equipped with 28-volt direct current (VDC)
single alternator electrical system. The system provides uninterrupted
power for avionics, flight instruments, lighting and other electrically
operated and controlled systems during normal operation. The system
also allows load shedding in the event of an electrical system failure.
• Note •
An optional dual alternator system is installed in some airplanes. For a
complete description of the system, refer to 11934-S10, POH
Supplement for Dual Alternator System.

Power Generation

Primary power for the SR20 is supplied by a 28-VDC negative-ground
electrical system. The electrical power generation system consists of a
24-volt, 10-amp-hour battery, a 75-ampere alternator, a voltage
regulator and an over-voltage protection system. The battery is an
aviation grade, 12-cell lead-acid type with non-spill vent caps. The
battery is used for engine starting and as an emergency power source
in the event of alternator failure. The 75-ampere alternator provides
constant charging current for the battery and primary power to the
aircraft electrical system during normal system operation. The voltage
regulator provides transient suppression and constant voltage
regulation of the unfiltered alternator power. To protect sensitive
instruments, the over-voltage protection system monitors the primary
power bus and automatically limits the peak voltage to 28.5 volts.
During sustained over-voltage and under-voltage periods, the over-
voltage system provides a warning to the pilot.
P/N 13999-002 Info Manual 7-49
September 2011