AC CONTROL PANEL
1. EXTERNAL POWER SWITCH (two position)
EXT PWR
- connects AC external power to variable frequency buses
- is capable of powering all AC and DC buses on the aeroplane
- isolates the AC generators from the buses
- AC EXT PWR ON indication (green) is displayed on the MFD Electrical page when AC
external power is connected to the aeroplane
- an External Power Protection Unit (AC PPU) is installed in the right ACCB to ensure only
AC Power within specification is allowed on the bus
- the AC PPU checks for the following parameters:
• voltage level (under voltage trip point 106 VAC ±2%, over voltage trip
point 124 VAC ±2%)
• frequency (underfrequency trip point 370Hz ±2%, overfrequency trip
point 450Hz ±2%)
• phase rotation (A-B-C)
OFF
- disconnects AC external power from variable frequency buses
2. AC GEN 1 AND 2 SWITCHES (two position)
GEN 1 OR GEN 2
- arms respective GCU to activate, and connect its generator to the asso-
ciated variable frequency bus
- AC generators are inhibited with AC EXT PWR ON
OFF
- shuts respective generator down
- resets GCU for subsequent generator and circuit monitoring following shutdown of a
generator
- AC GEN 1 or 2 caution light turns on anytime the respective generator is not supplying
power
Dash8 - Q400 - Electrical
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