Figure 1-38.-Simplified block diagram of a static inverter.

operated with a controlled 90 phase difference. Pulse

width modulation is used for control of the output volt-

able pulse width generator, two drive subassemblies, a

step change adjustment circuit, and two silicon control

age of each static inverter. The outputs of the two

rectifier power stages.

inverters are fed into two Scott "T''-connected

transformers to provide a 3-phase output from a 2-phase

The power stage assembly contains capacitors,

input.

transformers, and filters associated with the power stage

of the inverters.

The 4345A static inverter is enclosed in an alum-

inum cabinet (fig. 1-37), divided into three sections.

FUNCTIONAL DESCRIPTION

These are the meter panel assembly, the inverter module

assembly, and the power stage assembly. A resistor

A simplified functional block diagram of the model

subassembly is located on the back of the cabinet.

4345A static inverter is shown in figure 1-38. A brief

The meter panel assembly contains the instruments

discussion of the various components and circuits

and controls necessary for the operation of the equip

contained in the unit follows.

ment.

The inverter module assembly contains a control

Oscillator Assembly

circuit +30-volt dc power supply, a drive circuit

+30-volt dc power supply, an input sensing circuit, a

The oscillator (fig. 1-38) consists of a 1600-Hz

synchronizing subassembly, two variable pulse width

tuning fork controlled oscillator and a binary frequency

Figure 1-38.-Simplified block diagram of a static inverter.

1-31