Chapter 3: Inverters

Function

Converts D.C. power supply to A.C. power during emergency

Operating critical equipment

Range on aircraft

Output: 26V to 115V, 400 Hz (a.c.)

Input: 24V or 26V (d.c.)

Types of inverters

Static

Rotary

Uses solid state technology

Looks like a motor or generator

26V or 115V 400Hz a.c.

Heavy

Noisy

Used in smaller or older aircrafts

D.C. (24V - 28V) to A.C. (115V 400Hz)

Produced in 2 stages:
Stage 1 - Step up the voltage level to that required
Stage 2 - Frequency generated to that required

Difference between older and newer static inverters

Older

Newer

Uses standard electric and electronic components like transformers, capacitors, transistors and crystal diodes.

Oscillator circuit is able to produce 400Hz

Bulky

Converts power in 2 stages

First stage converts low inverter input voltage D.C to 145V or 290 D.C.

Second stage converts the high voltage into a 115V single phase 400Hz A.C.

Provides A.C power to:


Attitude and directional gyro,
rate gyro,
autosyn indicators and transmitters, magnesyn indicators and transmitters,
radar

Static over Rotary

Uses solid stage technology

No rotary parts

Extremely accurate and reliable

Lighter than a rotary inverter

High efficiency

Low maintenance, longer life

No warming up period required

Capable of starting under load

Extremely quiet operation

Very little heat generated

Fast response to load changes

Principle of operation

Square waves --> Fourier series