Figure 1-43.-Voltage regulator, block diagram.

GAP when the input frequency drops below 56 Hz or

energized. When the delay relay energizes (relay #2), it

applies normal power to the ac field rectifier, via the ac

the input voltage falls below an adjustable limit (330 to

voltage regulator, for application as field excitation to

380 volts).

the ac motor to allow synchronous motor operation. At

The voltage monitor circuitry is basically the same

the same time, the dc generator is rerouted to the dc

as the voltage-sensing and error voltage detector circuit

supply (relay #3) to prevent starting the motor-generator

of the voltage regulator. The frequency monitor is

set on dc and to charge the batteries. The system is now

basically the same as the frequency discriminator and

operating in NORMAL mode.

error voltage detector circuits. These circuits will be

If the normal supply falls out of its limits in either

discussed later in this chapter. The big difference in the

voltage or frequency, the respective monitor will sense

circuits is the output application. The output of the

it, and relay action (relay #4) will shut down the motor-

monitors is used for relay switching, since the other

generator set. At the same time, the dc generator field is

disconnected from the dc field rectifier #2 and con-

circuit's output is for regulation of either voltage or

nected directly to the battery supply (relay #5). The dc

frequency.

motor speed regulator and the ac generator voltage

regulator are energized (relay #6 and #7) to maintain the

VOLTAGE REGULATOR

required motor speed and control the load voltage. The

system is now in the STOP GAP mode.

The function of the voltage regulator is to maintain

If the reason for switching modes had been a voltage

the output voltage at the preset value (2 percent) regard-

drop, the voltage would not have dropped below 317

less of temperature or load variations. The basic cir-

volts, and the transition would have been accomplished

cuitry for both the ac and dc regulators is similar except

within 1 second. In the case of a frequency drop, the

that the dc regulator does not use the 6-phase rectifiers

change is made within 2 seconds and the frequency does

in the sensing circuit. Constant generator voltage output

not drop below 54 Hz.

is obtained by having the regulating circuit change the

When the ship's power returns to the specified

voltage feed in response to an error signal.

limits, the synchronizer will have the normal power at

one side and the ac generator power at the other. It will

A differential amplifier is used in the error voltage

automatically adjust the speed regulator to match the

detector circuit (fig. 1-43) to compare the generator

generator frequency to the normal power. The matching

output voltage, with a reference voltage, to produce the

is accomplished in less than 1 minute, and the system is

error signal. The error signal, acting through the

transferred back to ac motor drive and battery charge

modulator, modifies the timing of the pulse repetition

(NORMAL mode).

frequency of the unijunction trigger circuits. The

controlled pulses are fed to the respective field rectifier

MONITOR CIRCUITS

to control the average power to the generator field. The

rate circuit modifies the error signal to stabilize the

The frequency and voltage monitoring circuits are

designed to switch and set from NORMAL to STOP

voltage regulator.

Figure 1-43.-Voltage regulator, block diagram.

1-39