12.5.7.2 AC External Power
Location of the AC Ground Power Connection
A GPU can be connected to the AC external power receptacle on the forward right hand fuselage
near the nose cone (Figure 12.5-19), to supply AC power to the aeroplane.
An external power switch on the overhead AC CONTROL panel (Figure 12.5-5) connects power
directly to the left and right variable-frequency buses, supplying power to all AC and DC buses.
The External Power Protection Unit monitors the qualities of the incoming power. The external
power must be within acceptable limits, otherwise the external power is rejected.
12.5.7.3 External Power Protection
An External Power Protection Unit (AC PPU) is installed on the right ACCB to make sure the
external ground power is within specified limits before supplying power to the aeroplane busses.
The AC PPU monitors the following parameters:
• Undervoltage
• Overvoltage
• Underfrequency
• Overfrequency
• Phase Rotation (A-B-C)
12.5.8 Circuit Breakers
The EPGDS utilizes passive protections in the form of circuit breakers and current limiters. Cir-
cuit breakers are protection devices that open the circuit in case of excess current flow. Circuit
breakers protect electrical system power sources, component control circuits and bus distribu-
tion.
There are circuit breakers on:
• Four flight deck circuit breaker panels
• DC Contactor box in the nose compartment
• AC contactor boxes in the left and right main landing gear wheel wells
Two wardrobe circuit breaker panels
Each circuit breaker is identified by the:
• Circuit breaker panel
• Electrical bus
• Identification label
• Alphanumeric location.
Dash8 - Q400 - Electrical
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