CRJ-700 Electrical System

What voltage does the AC system provide?

115 v

What voltage does the DC system provide?

28 v

What two components make up the engine driven generators?

IDG (integrated drive generator) and GCU (generator control unit)

What provides DC power?

The TRU's recitfy AC power into DC power. The aircraft also has two batteries, APU battery and main battery.

When can the pilot reset a circuit breaker in flight?

Under the direction of a QRH procedure or when in the judgement of the PIC it is necessary for the safe completion of the flight.

What two components compromise the IDG?

CSD (constant speed drive) and a generator

How does the CSD work?

It utilizes an internal oil system to hydr-mechanically to change variable input speed from the engine accessory gearbox to a constant speed output for the generator of 12,000 RPM.

To what altitude do the engine driven generators provide maximum output, what do they do above that?

40 KVA to 41,000'

What altitude does the APU provide maximum output?

40 KVA to 41,000'

What causes an automatic shutdown of an IDG?

High oil temperature or high oil pressure

What indications will the pilot recieve when the IDG shutdowns?

A caution message will be displayed on the EICAS and a fault message will be displayed on the cooresponding IDG switch on the electrical services panel.

What causes an automatic disconnect of the IDG?

A severe overtemp situation or overtorque will causes an automatic disconnect of the IDG.

Can a disconnected IDG be reconnected inflight?

No, a disconnected IDG must be reconnected by maintenance personal on the ground.

How many AC buses are there and what are they?

4 - BUS 1, BUS 2, SERV BUS, ESS BUS

What is the power priority for each of the main AC buses?

On side, Inside, Off side, Outsides (BUS 1 - Gen 1, APU, Gen 2, External AC)

Which AC bus normally provides power the ESS BUS? What causes an automatic transfer and can this be done manually?

The AC BUS 1 normally provides power to the ESS BUS. It will automatically transfer to the AC BUS 2 if the GCU determines there is a fault with AC BUS 1. It can also be manually transferred by pressing the AC ESS XFER button on the Electrical Power Services Panel.

How will the pilot know if the AC ESS BUS has been transferred to the AC BUS 2?

No matter how the transfer occurs the pilot will notice the AC ESS XFER switchlight is illuminated.

What causes an AC AUTOXFER caution message? What will occur as a result?

If a bus shorts the GCU will prevent the autotransfer of the bus to prevent losing all electrical power sources as they try to power a faulty bus. It can not be undone in flight.

Is it possible to manually isolate a BUS?

Yes, utilizing the QRH for smoke removal or other procedures will isolate an individual BUS. This will result in a AC AUTOXFER OFF status message.

In the SERVICE CONFIGURATION what buses are powered?

AC SERV BUS

How does the ADG operate?

The dry ADG utilizes springs and flyweights to adjust blade angles to maintain the required frequency.

What affect does the ADG have on flaps?

The flaps will move at halfspeed when the ADG is the only source of AC power.

What must the pilot do to restablish normal power after the ADG has deployed?

Stow the ADG handle and then press the PWR TXFR OVERRIDE button.

How many DC TRUs are there and where are they located?

There are 4 DC TRUs that rectify the AC power located in the nose compartment that distribute the power through two DC Power Centers (DCPC) located in the avionics compartment.

How many ties does the DC TRU system incorporate and how do they operate?

There are 5 ties, MAIN TIE, CROSS TIE, ESS TIE, DC ESS TRU 2, SERV TIE Contactor. They operate automatically.

How do the DC Bus Ties 1 and 2 work?

They should automatically close to transfer power but can be manually closed by depressing the cooresponding switchlight.

Which DC Bus Tie should never be closed if the SERV TRU is powering DC BUS 1or DC BUS 2?

The ESS Tie.

What is the power output from the ADG?

15 KVA

What causes the ADG to auto deploy?

When AC BUS 1 & 2 are not powered in flight.

What DC BUS is not normally displayed?

The EMER BUS is only displayed when faulted or not powered.

What is the power output from the TRUs?

28 V / 120 Amp

What controls the distribution of AC Power?

ACPC (AC Power Centers)

What controls the distribution of DC Power?

DCPC (DC Power Centers)

What is the purpose of the DC ESS TRU 2 tie?

It allows the powering of ESS and BATT DC BUS to be powered through the ESS TRU 2 if the ESS TRU 1 fails on emergency power. It will also allow the AC ESS BUS to power DC ESS TRU 2 which will then power the rest of the system.

What are the HOT battery buses?

APU BATT DIR BUS, MAIN BATT DIR BUS, DC EMER BUS

What does the DC SERV TIE do?

Powers the DC SERV BUS through the APU BATT DIR BUS

How will the pilot know that a TRU has failed?

Through a corresponding EICAS Caution Message when the voltage drops below 18 V