Freewheeling Diode in Solenoids

What has allowed for a reduction in alternator size without decreasing output power?

Improved cooling features

What is the term used for the three electrical subassemblies that make up the generator portion of the IDG?

Brushless Alternators

What is the normal operating temperature for the cooling oil in most constant-speed drives?

93 °C (200 °F)

What mechanism is typically activated in most constant-speed drive units in case of an in-flight oil loss or an over temperature condition?

Electrically activated generator-drive disconnect mechanism Signup and view all the answers

What voltage and frequency does the IDG on the Boeing 747 produce for aircraft electrical systems?

115 volts 400 Hz Signup and view all the answers

Why is the term 'generator' still used even though brushless alternators are in use?

Historical convention Signup and view all the answers

What is the part of the relay attracted by the electromagnet to close the contact points called?

Armature Signup and view all the answers

How does the movement of the armature affect the contact points in a relay?

Closes the contact points Signup and view all the answers

What is the function of the main contacts in a Bus Tie Breaker (BTB)?

Connect three-phase power to generator bus bars Signup and view all the answers

Which component in a Bus Tie Breaker (BTB) remains in a closed position even after power is removed from the close coil?

Main contacts Signup and view all the answers

What causes the main contacts in a Bus Tie Breaker (BTB) to open?

Release of mechanical lock by trip coil Signup and view all the answers

What happens to the auxiliary contacts in a Bus Tie Breaker (BTB) when the main contacts are mechanically locked in a closed position?

They remain closed Signup and view all the answers

What is the purpose of a freewheeling diode installed across the coil of a solenoid?

To eliminate spikes when the master switch is opened Signup and view all the answers

Why would voltage spikes be harmful in a system without a freewheeling diode?

Cause damage to sensitive electronic components Signup and view all the answers

How does a freewheeling diode prevent damage to electronic components when the master switch is opened?

By allowing the induced EMF to feed back into itself Signup and view all the answers

What is the function of a battery in an aircraft system?

Used for starting an aircraft Signup and view all the answers

Why do some aircraft isolate the battery when external DC power is applied?

To prevent thermal runaway of a Nickel-Cadmium battery Signup and view all the answers

What feature do aircraft without battery isolation incorporate to prevent thermal runaway?

Battery charger units that automatically disconnect charging current above a pre-set battery temperature Signup and view all the answers

Why are circuit breakers and fuses placed close to the power supply?

To protect the wiring run from short circuits Signup and view all the answers

What does a tripped circuit breaker indicate?

An overload and possible fire Signup and view all the answers

What does a small white band show on a tripped circuit breaker?

That the circuit breaker has been tripped or activated Signup and view all the answers

What is a trip-free circuit breaker characterized by?

It will trip regardless of the switch position Signup and view all the answers

When are non-trip-free circuit breakers typically used?

In emergency lighting and essential equipment circuits Signup and view all the answers

What distinguishes non-trip-free circuit breakers from trip-free ones?

Non-trip-free breakers can be held on even during an overload condition Signup and view all the answers

What would happen if the cut-out relay or line contactor fails to open under reverse current conditions?

The reverse current would feed back to the generator and reverse the generator field polarity. Signup and view all the answers

What is a potential consequence of overvoltage in an aircraft system?

Equipment can be damaged due to higher voltages than they are designed for. Signup and view all the answers

How is overvoltage protection typically achieved in aircraft systems?

Using devices that protect against voltages higher than equipment is designed for. Signup and view all the answers

What effect does reverse current have on a generator under certain conditions?

It has a motoring effect on the generator and reverses the generator field polarity. Signup and view all the answers

Why is it important for a circuit breaker to release its contacts when reverse current reaches a certain value?

To protect the generator by isolating it from the busbar. Signup and view all the answers

What is the purpose of a latching mechanism in an overvoltage relay?

To maintain contact connections even under adverse conditions. Signup and view all the answers