Glossary

actuate:

To put into motion.

anode:

The positive end of a diode or rectifier.

blocking rectifier:

Permits current flow in only one direction. This keeps the polarity of the exciter in the correct direction.

bolted:

Use of a bolt to hold two or more parts together.

breaker:

An automatic switch used to open a circuit.

bridge:

A circuit used to change AC to DC and to measure small quantities of current, voltage or resistance.

build-up:

(Voltage) A gradual increase.

cathode:

The negative end of a diode or rectifier.

capacitance:

The measure of a capacitors ability to take and hold a charge.

circulating current:

The flow of current between two generators working in parallel.

conduct:

Give path for current flow.

consideration:

factor.

continuity:

A circuit that is not open.

control:

One that controls.

damping:

To smooth out.

de-energize:

To stop current from going to a component.

distribution winding:

An arrangement of windings, in groups that are in several slots, that go from one end of the core to the other end.

droop:

decrease.

effective:

Gives the desired effect.

elementary:

simple.

excitation:

DC current (controlled) used to make a magnetic field.

energize:

To cause current to go to a component.

electrostatic charges:

Electricity caused by friction.

exciter:

Gives DC current to the field windings of the generator.

field:

Magnetic lines of force around a conductor caused by current flow.

field windings:

Many turns of wire wrapped around an iron core. When a DC current flows through the field windings it causes a magnetic field (like that of a bar magnet).

flashing:

A process of putting DC current, from an outside source, into the field windings to get residual magnetism.

fluctuate:

change.

flux:

Magnetic lines of force.

full wave rectifier:

Changes AC to DC current.

gain:

A change in quantity of voltage.

gate:

An electronic part of a controlled rectifier (thyristor).

generate:

To make electricity.

grounded:

To make a connection to ground or to a component with similar effect.

impedance:

A combination of resistances.

impulse modulated:

To vary the amplitude, frequency or phase of a wave by impressing one wave on another wave of constant properties.

induced:

caused.

interference:

Mixture of signals.

instrumentation:

Group of instruments.

insulated:

A component with insulation.

induce (to):

To send DC current to a coil and make a magnetic field.

lead:

wire.

line voltage:

The output voltage of the generator.

lock in:

When a contact closes to keep a solenoid energized.

lock out:

When a contact opens to keep a solenoid de-energized.

magnetic:

Having the characteristics of a magnet.

magnification:

Make larger.

module:

An assembly of electronic components and circuits.

moisture:

The water content in the air.

oscillation:

A flow of electricity that periodically changes direction.

phase winding:

Group of generator stator coils in which electric power for the load is induced.

polarity:

The positive or negative characteristics of two poles.

pulsating:

Characteristics of rectified current similar to mechanical vibration.

radio suppression:

Reduce the cause of radio frequency interference.

reciprocating:

Movement in a straight line first one direction then the other.

regenerative power:

Power that works against the primary power.

reset:

To put a switch in a ready condition.

residual magnetism:

The characteristic of a magnet after removal of excitation.

saturable reactor:

Acts as a valve, as load changes, valve opens or closes to give more or less current to the rectifier.

saturated:

Magnetized to the point where an increase in current will give no increase in magnetic force.

satisfactorily:

correctly.

SCR:

Silicone Controlled Rectifier (semiconductor).

selinium (Se):

A metallic (like metal) element with electrical characteristic of being a semiconductor.

semiconductor:

Components like, transistors, diodes, thyristors, etc. Has electrical characteristics between a conductor and insulation.

short:

Any connection between two or more components that is not desired.

shutdown:

When the engine is stopped either automatically or manually.

simultaneous:

At the same time.

solid-state:

An electronic component with no moving parts.

surge:

A sudden increase in voltage or current.

tap:

Connection to get power from a circuit.

tested:

When a test has been made.

transfer:

change.

transient peak voltage:

A high voltage condition for a short time period.

turn-on:

To start, as current flow through the controlled rectifier; to activate.

voltage droop resistor:

Variable resistor for control of voltage change from full load to no load.

voltage level resistor:

Gives wide range of voltage control.

voltage level rheostat:

Control for adjusting voltage output level.

voltage spike:

Temporary high voltage, lasts only a moment.

windings:

Layers of wire on a core.

wiring:

The wires of a circuit.

wound:

circled.

Identification

IDENTIFICATION PLATES (Typical)
1. Generator voltage location. 2. Generator group part number. 3. Sequence number location. 4. Serial No. Plate. 5. Caterpillar serial number location. 6. Caterpillar nameplate.

A sequence number (3) is stamped on the upper right hand side of the generator stator assembly located between the generator drive adapter face and the terminal box. This number will be stamped in a position below the generator voltage (1) and the generator group part number (2). These are stamped at the time of manufacture.

Caterpillar Tractor Co. will assign the Caterpillar serial number at the time of the generator use.

A serial number plate (4) will be attached to the generator by Caterpillar. This plate will be stamped with the generator model number, Caterpillar serial number, and the generator arrangement number.

Below the serial number plate, Caterpillar will stamp the Caterpillar serial number (5).

A Caterpillar data nameplate (6) is located below the stamped serial number.

3 Phase 4 Pole Generator

3 Phase 6 Pole Generator

Generator And Regulator Components

FIG. 1. SR 4 BIG BRUSHLESS GENERATOR

FIG. 2 GENERATOR REGULATOR HOUSING (SELF-EXCITED)
AVR Automatic Voltage Regulator. ETTS Excitation transformer terminal strip. RL501 Voltage build-up relay (self-excited only). T5 Excitation transformer (self-excited only). T6 Excitation transformer (self-excited only).

FIG. 3 GENERATOR REGULATOR HOUSING (PERMANET MAGNET EXCITED)
AVR Automatic voltage regulator. RTS Regulator terminal strip.

FIG. 4. AUTOMATIC VOLTAGE REGULATOR (AVR)
1. AVR control panel (hinged). M3 Trip/alarm board. A5 Card cage assembly. F1 Fuse. P7 4-pin connector plug. TP Thermal protector.

FIG. 5. AUTOMATIC VOLTAGE REGULATOR (AVR)
C1 Filter capacitor. R1 Droop potentiometer. R2 Voltage level potentiometer. R3 Voltage gain potentiometer. M5 Power supply & interconnection printed circuit board. T3 AVR power supply transformer. CR9 Rectifier package. CR10 Rectifier package.

FIG. 6. AUTOMATIC VOLTAGE REGULATOR (AVR)
M1 Sensing and control board. M2 Overcurrent protection board. M3 Alarm/trip switch board. M4 Excitation output board. RTS Regulator terminal strip.

FIG. 7. AUTOMATIC VOLTAGE REGULATOR (AVR)
T1 Sensing transformer. T2 Sensing transformer. CR9 Rectifier package. CR10 Rectifier package.

FIG. 8. PRINTED CIRCUIT (PC) CARDS AND PIN SOCKET LOCATIONS
M1 Sensing and control board and socket. M2 Overcurren protection board and socket. M3 Trip/alarm switch board and socket. M4 Excitation output board and socket. M5 Power supply and interconnection board.

AUTOMATIC VOLTAGE REGULATOR (Later 589, 685 and 689 frame generators only)

FIG. 9. ROTATING FIELD ASSEMBLY (RFA) (SELF-EXCITED)
1. Rotating rectifier bridge. 2. Bearing. L3 Exciter armature. L4 Rotating field.

FIG. 10. ROTATING FIELD ASSEMBLY (RFA) (PERMANENT MAGNET)
1. Bearing. 2. Rotating permanent magnet. L3 Exciter armature. L4 Rotating field.

FIG. 11. EXCITER AND RECTIFIER ASSEMBLIES
1. Rotating rectifier bridge. L2 Main exciter field. L3 Exciter armature. CR(7 & 8) Varistor assemblies (surge suppression diodes). R6 Suppression resistor.

FIG. 12. PM ASSEMBLY
PMG Rotating permanent magnet. L1 PM stator.

FIG. 13. ROTATING BRIDGE RECTIFIER
1. Rotating field (L4) leads. CR1 Rectifying diodes. CR2 Rectifying diodes. CR3 Rectifying diodes. CR4 Rectifying diodes. CR5 Rectifying diodes. CR6 Rectifying diodes. CR(7 & 8) Varistor assemblies (surge suppression diodes). E1 Positive heat sink. E2 Negative heat sink. R6 Suppression resistor.

FIG. 14. STATOR
L5 Stator Winding.

FIG. 15. DROOP TRANSFORMER (Regulator Housing and Regulator Removed for Illustration)
1. Droop Transformer (T4).

Introduction

Generator Introduction

SR-4 GENERATOR

This SR-4 brushless generator family (different from the smaller SR-4 generator family covered in Service Manual, Form No. SENR7968) is available in both six and four-pole versions. Installation is on:

the low speed 3412 and 6.25 inch bore Vee Engines.

the 3500 series low and high speed engines.

This brushless generator has replaced the SRCR generator family.

The SR-4 generator can have either a self-excited or a permanent magnet exciter design. The permanent magnet pilot exciter (PMPE) provides 300% short circuit sustaining capability for approximately 10 seconds. The PMPE also makes sure there is voltage build-up and constant excitation during large load application. Both the PMPE and self-excited SR-4 generators have the exciter and bridge rectifier mounted outboard of the bearing for service accessibility.

Generator Components

Stationary Components

1. Regulator (see following section).

2. Stator (alternator coils-L5).

STATOR (L5)

3. Field Coil (L1).

Used only in permanent magnet excited generator.

PMG EXCITER
L1 Field coil. PMG Permanent magnet.

4. Exciter field (L2).

EXCITER FIELD
2. Bridge rectifier. L2 Exciter field. L3 Exciter armature.

Rotating Components

1. Main field (L4).

2. Exciter armature (L3).

3. Permanent magnet (PMG). Used only in permanent magnet excited generator.

4. Bridge rectifier (2).

ROTATING FIELD ASSEMBLY
2. Bridge rectifier. 3. Bearing. L3 Main exciter armature. L4 Rotating field. PMG Permanent magnet (Used only on PMG excited generator.)

The rotor is supported between the pilot bore of the engine flywheel and a single generator bearing. The rotor is driven by a flexible steel disc coupling which is bolted to the flywheel and to the generator drive flange (4).

PILOT
4. Generator drive flange. 5. Pilot.

Regulators

The SR-4 generator uses two types of regulators that are shock mounted and enclosed on top of the generator housing. These regulators regulate output voltage automatically according to volts per hertz. (See IDENTIFICATION section, NOTE column of this manual).

Card Cage (printed circuit board) Type Regulator

AUTOMATIC VOLTAGE REGULATOR (AVR) (Used on all frame sizes)
1. Card cage. 2. RL501 Build-up relay socket. (Used on self-excited only).

This regulator is used on all frame sizes, self-excited and PMPE versions. The card cage (1) consists of four printed circuit boards which are plugged into a fifth printed circuit board. The only moving part in the regulator is a sealed voltage build-up relay (self-excited version only) which plugs into a socket (2).

Epoxy module (A1) type Regulator

AUTOMATIC VOLTAGE REGULATOR (AVR) (Used on 589, 685 and 689 frames - self-excited only)
A1 Regulator module.

This regulator is used on later frame sizes (589, 685 and 689) of the self-excited generators.

NOTE: A small module has been added to the regulator for the 689 frame generator so the regulator can accommodate the higher voltage.

With exception of the slight modification for the 689 frame generator regulator, this type of regulator is the same as used on the smaller framed SR-4 generator family covered in Form No. SENR7968.

For Systems Operation/Testing and Adjusting of the regulator for the large frame (589, 685 and 689) SR-4 generator family, make reference to Service Manual, SR-4 Generator, Form No. SENR7968. For identification, make reference to the IDENTIFICATION section, NOTE column of this manual.

Voltage Generation

Permanent Magnet Pilot Exciter (PMPE) (Optional)

Excitation Circuit

When the engine starts turning the Rotating Field Assembly (RFA), the permanent magnet (P.M.) rotor induces alternating current (AC) voltage in the stationary P.M. exciter armature (L1). The resulting AC current flows to the six Regulator Terminal Strip terminals (11 thru 16).

REGULATOR TERMINAL STRIP - TERMINAL IDENTIFICATION
F1 & F2 Exciter terminals. G Ground. 5-8 Voltage level, droop and gain control terminals. 20-24 Sensing terminals to T1 & T2. 26 Not Used. 11-16 P.M. stator output terminals.

If manual control of the voltage is used, make reference to the electrical schematics in the section, MANUAL CONTROL.

From terminals (14 thru 16), current flows through wires (14 thru 16) to and from the thermal protector (TP). This places the thermal protector in the excitation circuit to protect against overloads.

Terminals (11 thru 13) are the connecting terminals to the bridge rectifier (CR9 and CR10). Three-phase, full wave AC voltage appears across these three terminals.

From terminals (11 thru 13), AC flows through wires (11 thru 13) to the three-phase full wave bridge rectifier (CR9 and CR10).

EXCITER CIRCUIT RECTIFIER PACKAGES
CR9 Rectifier package. CR10 Rectifier package. C1 Filter capacitor.

From (CR9 and CR10), DC flows through wire (4) to the 15 amp fuse (F1).

From (F1), DC flows through wire (1) to the printed circuit (PC) board (M4), terminal number (1). Also from fuse (F1), AC flows through wire (1) to charge filter capacitor (C1). (Used to reduce the AC ripple on the DC level.)

From terminal number (1) on (M4), DC flows through wire (1) to the Regulator Terminal Strip, terminal (F1).

M-4 TERMINAL CONNECTIONS (TS400)
#1 Terminal. #2 Terminal. #3 Terminal.

From terminal (F1), DC flows through wire (F1) to the stationary exciter field (L2).

From the main exciter field (L2) through wire (F2) to the Regulator Terminal Strip, terminal (F2).

From terminal (F2), DC flows through wire (2) to PC board (M4), terminal number (2).

From terminal (2), one path through board (M4) to terminal (1) of board (M4) involves the flyback circuit explained in the Voltage Regulation Section, Excitation Output Board (M4).

From terminal (2), the other path through board (M4) is to terminal (3) on board (M4).

From PC board (M4) terminal (3), current flows through wire (3) to the three-phase full wave bridge rectifier (CR9 and CR10).

NOTE: Terminal (3) is also connected (through the ground terminal (G) on the Regulator Terminal Strip) to the stator (L5) frame.

From the bridge rectifier (CR9 and CR10), current returns through wires (11 thru 13) to Regulator Terminal Strip terminals (11 thru 13).

From terminals (11 thru 13), the circuit is complete on current return to the P.M. exciter armature (L1).

Output Circuit

ROTATING FIELD ASSEMBLY (RFA) (PERMANENT MAGNET)
L3 Exciter armature. L4 Main field coils. PMG Permanent Magnet.

DC current flow to exciter field (L2) causes a magnetic field in which the exciter armature (L3) is turning. With (L2) energized, AC voltage is induced in the exciter armature (L3). This AC voltage from the exciter armature (L3) causes AC current to flow. AC is rectified in the three-phase full wave bridge rectifier circuit (CR1 thru CR6) on heat sinks (E1) and (E2). The DC output from the bridge rectifier is carried to the main field coils (L4) by conductors routed through a passage in the rotor shaft. Current through main field coils (L4) makes the magnetic field of the generator. As rotating field (L4) turns it induces a three-phase AC voltage in stator (L5) that is sent to terminals (T0), (T1), (T2) and (T3) which are connections for a load. To keep the output voltage constant with changing loads, it is necessary to control the excitation current. This control is the function of the Automatic Voltage Regulator (AVR).

ROTATING BRIDGE RECTIFIER
CR1-6 Rotating rectifier diodes. E1 Positive heat sink. E2 Negative heat sink.

OUTPUT BUS BARS
T0-3 Output bus bars.

SR-4 GENERATOR (PERMANENT-MAGNET EXCITED)

Self-Excited (Standard)

ROTATING FIELD ASSEMBLY (SELF-EXCITED)
L3 Main exciter armature. L4 Rotating main field.

When the engine starts turning the Rotating Field Assembly (RFA), the residual magnetism in the exciter field (L2) causes a small amount of AC voltage to be generated in the exciter armature (L3). This induced voltage in (L3) causes AC current to flow. This AC current flows through the three-phase full wave bridge rectifier circuit (CR1 thru CR6) on heat sinks (E1 and E2). DC then flows through the rotating field (L4) of the alternator. The resulting field adds to the residual magnetism of the rotating field (L4). With (L4) turning, an AC voltage is generated in stator (L5) which causes a current to flow to the output terminals (T1), (T2) and (T3). Part of this AC output is tapped off at terminals (T7), (T8) and (T9) (T1, T2 and T3 in high voltage, 800 frame system).

STATOR (L5)

From terminals (T7), (T8) and (T9) (or T1, T2 and T3), AC current flows to the Regulator Terminal Strip terminals (22, 24 and 20).

Show/hide table

Up to 600 volts is present at Regulator Terminal Strip terminals 20, 22 and 24. Do not short these terminals to ground with any part of the body or any conductive material. Loss of life from electrical shock or injury from molten metal may result.

From terminals (22, 24 and 20), the AC flows through wires (6, 5 and 7) to the Excitation Transformer Terminal Strip (ETTS) terminals (5, 6 and 7).

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Up to 600 volts is present at Excitation Transformer Terminal Strip terminals 5, 6 and 7. Do not short these terminals to ground with any part of the body or any electrical conducting material. Loss of life from electrical shock or injury from molten metal may result.

EXCITATION TRANSFORMERS & TERMINAL STRIP
1-7 Terminals 1 thru 7. T5-6 Excitation transformers.

From terminals (5, 6 and 7), AC flows to excitation transformers (T5 and T6).

Make reference to the chart below for primary and secondary connections of transformers (T5 and T6).

SELF-EXCITED EXCITATION SYSTEM
1-7 Terminals 1 thru 7. T5,6 Exciter transformers.

Besides providing excitation power, transformers (T5 and T6) isolate the exciter field circuit from the stator windings.

From (T5 and T6) secondaries. AC returns through the four secondary wires (identified above) to the 7-terminal ETTS.

From ETTS terminals (1 thru 4), current flows to the Regulator Terminal Strip, terminals (11, 13, 14, and 15).

REGULATOR TERMINAL STRIP - TERMINAL IDENTIFICATION
F1, F2 Exciter terminals. 5-8 Voltage level, droop & gain control terminals. 20-24 Sensing terminals to T1 & T2. 11-16 Excitation transformer output terminals.

NOTE: If manual control of the voltage is used, make reference to the electrical schematics in the section, MANUAL CONTROL.

From ETTS terminal (1), wire (1) connects to terminal (15) of the Regulator Terminal Strip (RTS).

From ETTS terminal (2), wire (2) connects to terminal (14) of the RTS.

From ETTS terminal (3), wire (3) connects to terminal (13) of the RTS.

From ETTS terminal (4), wire (4) connects to terminal (11) of the RTS.

AC current flows from the Regulator Terminal Strip terminals (11 thru 16) to the three-phase full wave bridge rectifier (CR9 and CR10) in the following manner:

From terminals (14 thru 16), current flows through wires (14 thru 16) to and from the thermal protector (TP). This places the thermal protector in the excitation circuit to protect against overloads.

THERMAL PROTECTOR (TP) AND FUSE (F1)
TP Thermal protector. F1 15 amp fuse.

Terminals (11 thru 13) are the connecting terminals to the bridge rectifier (CR9 and CR10). Three-phase, full wave AC voltage appears across these three terminals.

From terminals (11 thru 13), AC flows through wires (11 thru 13) to the three-phase full wave bridge rectifier (CR9 and CR10).

From (CR9 and CR10), DC flows through wire (4) to the 15 amp fuse (F1).

From (F1), DC flows through wire (1) to the printed circuit (PC) board (M4), terminal number (1). Also from fuse (F1), stray AC flows through wire (1) to charge filter capacitor (C1). (Used to reduce the AC ripple on the DC level).

EXCITER CIRCUIT BRIDGE RECTIFIER
CR9 rectifier. CR10 rectifier. C1 Filter capacitor.

From terminal number (1) on (M4), DC flows through wire (1) to the Regulator Terminal Strip, terminal (F1).

M-4 TERMINAL CONNECTIONS
1. Terminal #1. 2. Terminal #2. 3. Terminal #3.

From terminal (F1), DC flows through wire (F1) to the stationary exciter field (L2).

The magnetic field created in the stationary exciter field (L2) adds to the residual magnetic field that was used for initial start-up.

From the main exciter field (L2) through wire (F2) to the Regulator Terminal Strip, terminal (F2).

From terminal (F2), DC flows through wire (2) to PC board (M4), terminal number (2).

From terminal number (2), one path through board (M4) to terminal (1) of board (M4) involves the flyback circuit explained in the Voltage Regulation Section, Excitation Output Board (M4).

From terminal (2), the other path through board (M4) outputs at terminal (3) on board (M4).

NOTE: During start-up, the part of the excitation circuit through (M4) to terminal (3) on (M4) is kept close circuit by a plug-in start-up relay-contact on PC board (M5). This is covered in the sub-sections "Excitation Output Board" and "Power Supply & Interconnection Board" covered under the main section "Voltage Regulation."

From PC board (M4) terminal (3) current flows through wire (3) to the three-phase full wave bridge rectifier (CR9 and CR10).

NOTE: Terminal (3) is also connected [through the ground terminal (G) on the Regulator Terminal Strip] to the stator (L5) frame.

From the bridge rectifier (CR9 and CR10), current returns through wires (11 thru 13) to Regulator Terminal Strip terminals (11 thru 13).

From terminals (11 thru 16), current flows to Excitation Transformer Terminal Strip terminals (1 thru 4).

From terminals (1 thru 4) current returns to the secondaries of transformers (T5 and T6) through the color wires mentioned previously. This completes the self-excited excitation circuit.

ROTATING FIELD ASSEMBLY (RFA) (SELF-EXCITED)
L3 Exciter armature. L4 Main field coils.

With the DC current flow through exciter field (L2), the (L2) magnetic field increases. The increased magnetic field in (L2) increases the AC voltage induced in the exciter armature (L3). This AC voltage from the exciter rotor (L3) causes AC current to flow. The AC is rectified in the three-phase full wave bridge rectifier circuit (CR1 thru CR6) on heat sink (E1 and E2). The DC output from the bridge rectifier is carried to the main field coils (L4) by conductors routed through a passage in the rotor shaft. Current through main field coils (L4) makes the magnetic field of the generator. As rotating field (L4) turns it induces a three-phase AC voltage in stator (L5) that is sent to terminals (T0), (T1), (T2) and (T3). To keep the output voltage constant with changing loads, it is necessary to control the excitation current. This control is the function of the Automatic Voltage Regulator (AVR).

ROTATING BRIDGE RECTIFIER
CR1-6 Rotating rectifier diodes. E1 Positive heat sink. E2 Negative heat sink.

OUTPUT BUS BARS
T0-3 Output bus bars.

SR 4 GENERATOR (Self-Excited)

Voltage Regulation

Introduction

The SR 4 Automatic Voltage Regulator (AVR) is the same unit for the self-excited and permanent magnet exciter types. However, the self-excited version does add a plug-in build-up relay (RL501) to the Power Supply & Interconnection PC board (M5). Without the relay, the regulator is used for permanent magnet excitation.

AUTOMATIC VOLTAGE REGULATOR (AVR)
M5 Power Supply & Interconnection PC board. RL501 Build-up relay. T1-2 Sensing transformers.

Sensing Voltage

For regulating purposes, voltage is tapped off at the center of each of the dual voltage generator phase coils. For regulation purposes on single voltage generators, the voltage is tapped off the T1, T2 and T3 phase leads.

Show/hide table

Up to 600 volts is present at Regulator Terminal Strip terminals 20, 22 and 24. Do not short these terminals to ground with any part of the body or any conductive material. Loss of life from electrical shock or injury from molten metal may result.

From the generator phase leads (T7, T8 and T9) or (T1, T2 and T3) the AC current flows to terminals (22, 24 and 20) on the seventeen terminal - Regulator Terminal Strip (RTS).

From terminals (24) and (20) on the RTS, AC current flows through wire (20) and common wire (24) to potential transformer (T1).

From terminals (24) and (22) on the Regulator Terminal Strip, AC current flows through wire (22) and common wire (24) to potential transformer (T2).

From the secondary of transformer (T1), the AC signal flows through wires (1) and (2) to pins (1) and (2) on the four pin connector (P7).

AVR FOUR PIN CONNECTOR (P7)

From secondary of transformer (T2), the AC signal flows through wires (3) and (4) to pins (3) and (4) on the four pin connector (P7).

The four pin connector plugs into a socket on the PC board (M5). This voltage represents the output of the generator and one of the inputs to the regulator.

Reference Voltage (Voltage Level Control)

Another input to the regulator is a DC reference level voltage which is adjusted by the Voltage Level Control (R2) located on the front of the regulator panel. This voltage is taken off the regulator PC board (M5) and outputted to the regulator control panel. It then returns to the PC board (M5) as an input.

AVR - VOLTAGE LEVEL CONTROL
P6 Connector plug. R2 Voltage level control.

From the Power Supply and Interconnection PC board (M5), a DC reference level voltage occurs at pin (3) of the six pin connector (P6).

From pin (3), DC flows through wire (8) to the voltage level control (R2), then to terminal (8) of the RTS.

From terminal (7), DC flows through wire (7) to pin (2) of the six pin connector plug (P6).

NOTE: For remote voltage level adjustments, disconnect R2 from regulator assembly. Use terminals (7) and (8) on RTS to reconnect the wires for the remote R2.

This DC reference voltage is taken from pin (2) and compared to the sensed generator output voltage. This function is performed by the sensing and control PC board (M1).

Voltage Droop And Gain

AVR - DROOP AND GAIN CONTROLS
R1 Droop potentiometer. R3 Gain potentiometer.

The Droop and Voltage Gain controls are located on the front of the regulator panel. The droop potentiometer (R1) is used in paralleling operations with other generators. The voltage gain potentiometer is an adjustment to compensate for voltage droop caused by generator load or governor speed droop.

CURRENT TRANSFORMER (T4)

A current transformer (T4) takes the output off lead (T8) for dual voltage generators or (T2) for single voltage generators.

The AC current travels through wire (5 and 6) from the transformer (T4), to terminals (5 and 6) on the RTS. From terminals (5 and 6), AC current takes the following paths:

From terminal (5) through wire (5) to pin (1) of the six pin connector plug (P6).

From terminal (5) through wire (5) to (depending on setting) variable droop resistor (R1) to wire (9) to pin (4) of the six pin connector plug (P6).

From terminal (5) through wire (5) to (depending on setting) variable droop resistor (R1) to variable voltage gain resistor (R3) through wire (10) to pin (5) of the six pin connector plug (P6).

From terminal (6) through wire (6) to pin (6) of the six pin connector plug (P6).

From terminal (6) to gain diode (CR11) to variable voltage gain resistor (R3) through wire (9) to pin (4) of the six pin connector plug (P6).

From terminal (6) to gain diode (CR11) to variable voltage gain resistor (R3) through wire (10) to pin (5) of the six pin connector plug (P6).

From terminal (6) to gain diode (CR11) to variable voltage gain resistor (R3) to variable voltage droop resistor (R1) (depending on setting) through wire (5) to pin (1).

Regulator Power Supply

At the 17 terminal Regulator Terminal Strip, AC current is taken off at the two terminals (12) and (13). From terminals (12 and 13), AC current flows through wires (12) and (13) to the primary of power transformer (T3). The secondary of (T3) provides the "Power Supply and Interconnection" PC board (M5) with two voltages. Power transformer (T3) to PC board (M5) connections are as follows:

AUTOMATIC VOLTAGE REGULATOR (AVR)
#13 terminal. #12 terminal. M5 Power supply and interconnection board. P5 Six pin connector. T3 Power transformer.

1. Secondary voltage (small transistor power supply and low excitation cutout reference voltage).

From (T3) through two red wires (1 and 4) to pins (1) and (4) of six pin connector (P5).

From (T3) through a yellow wire (2) (common) to pin (2) of the six pin connector (P5).

2. Secondary voltage [main regulator power supply and reference level voltage for PC board (M1)].

From (T3) through two blue wires (3 and 5) to pins (3) and (5) of the six pin connector (P5).

From (T3) through an orange wire (6) (common) to pin (6) of the six pin connector (P5).

The six pin connector (P5) plugs into the power supply and interconnection board (M5). The PC board (M5) is covered in the following section.

Regulator Printed Circuit (PC) Boards

The intelligence of the regulator is contained in a printed circuit (PC) board assembly (A5). The assembly (A5) is comprised of a main PC board (M5) to which four smaller PC boards are plugged. All five boards are grouped in a metal cage. Each of the two outside boards (M3) and (M4) are held in place by two screws. The two middle boards (M1) and (M2) are held in position by the plastic tracks. (M1) and (M2) use extraction levers for removal.

The boards are identified as follows:

M1 Sensing and control board

M2 Overcurrent Protection Board

M3 Trip/Alarm Switch Board (held in place by two screws)

M4 Excitation Output Board (held in place by two screws)

M5 Power Supply & Interconnection (Host) Board

A-5 ASSEMBLY View #1
Cage (metal) - M1 Sensing and control board. M2 Overcurrent protection board. M3 Trip/alarm switch board. M4 Excitation output board. M5 Power supply and interconnection board.

A-5 ASSEMBLY View #2
Cage (metal) - M1 Sensing and control board. M2 Overcurrent protection board. M3 Trip/alarm switch board. M4 Excitation output board. M5 Power supply and interconnection board.

PRINTED CIRCUIT BOARD ARRANGEMENT
M1 Sensing and control board and socket. M2 Overcurrent protection board and socket. M3 Trip/alarm switch board and socket. M4 Excitation output board and socket. M5 Power supply and interconnection board.

Power Supply & Interconnection Board (M5)

POWER SUPPLY & INTERCONNECTION BOARD (M5)
P7 SOCKET Socket for plug (P7). M3 SOCKET Pin sockets for PC board (M3). M2 SOCKET Pin sockets for PC board (M2). M1 SOCKET Pin sockets for PC board (M1). M4 SOCKET Pin sockets for PC board (M4). P6 SOCKET Socket for plug (P6). 1. Thermistor terminals (Earlier M5 boards only) P5 SOCKET Socket for plug (P5). RL501 Socket for start-up relay (RL501).

This PC board handles the following functions:

1. Provides operating DC power for the regulator assembly. AC power enters through the six pin socket for plug (P5).

2. Provides a reference DC voltage for low excitation cutoff protection on PC board (M2). The AC voltage for this reference DC voltage also enters through plug (P5).

3. Provides a reference DC voltage used [by PC board (M1)] to compare with "sensed" generator output voltage from transformers (T1 and T2). Sensed AC output voltage enters through the four pin socket for plug (P7).

4. Provides the interconnecting circuitry between the other four PC boards (M1 thru M4).

5. Provides pin sockets for boards (M1 thru M4).

6. Contains a socket for the voltage build-up relay (RL501) (self-excited generator). This relay and relay contact are used to keep the exciter circuit (located on PC board M4) "on" until operating voltages open the normally closed (NC) contacts. When the contacts open this allows the M4 board to regulate the exciter circuit and generator output. The start-up relay functions only during start-up.

7. Provides a means by which regulator control panel signals (Voltage Level, Voltage Droop and Voltage Gain) enter the Sensing and Control Board (M1). These signals enter (M5) through the six pin socket for plug (P6).

8. On earlier M5 boards, provision was made through two terminals (1) for connecting one to three positive temperature coefficient (P.T.C.) thermistors. However, this type of winding temperature circuit was never implemented and the two terminals (1) are not on later M5 boards.

NOTE: If the M5 board has these two terminals (1), they must be connected together with a jumper for proper operation of the regulator.

Sensing and Control Board (M1)

The PC board (M1) slides into the cage assembly (A5), second from the righthand side. It plugs into the PC board (M5). Removal from the cage and the host board (M5) is accomplished by use of two extraction levers.

SENSING & CONTROL BOARD (M1)
1. Extraction levers. 2. Plug.

The function of the regulator sensing and control board is to:

1. Receive "sensed" AC output voltage from the PC host board (M5) as an input. Rectify and filter this input to obtain a DC voltage.

2. Take a reference voltage from the PC board (M5) (as adjusted by the voltage gain and level controls) as another input.

3. Compare the rectified and filtered generator output voltage to the adjusted reference voltage. (Reference level can be adjusted -10 +5% of rated voltage.)

4. Use the resulting electrical imbalance between the two DC voltages to provide a controlling signal as an output from (M1) and input to (M4). This signal is a pulse width modulated signal which eventually controls the power "on" and "off" the exciter field. The on-off rate is two times line frequency (120 times/sec. at 60 Hz). The ratio [as determined by (M1)] of on/off time controls the average value of the exciter field voltage.

5. Provide a "volts per hertz" control. This feature gages the output of the generator to the output of the engine. This prevents stalls under extraordinary heavy loads.

6. Receives a protective shut-off signal voltage from PC board (M2) in situations where too low excitation current or too high excitation current exists.

Excitation Output Board (M4)

EXCITATION OUTPUT BOARD (M4)
1. Retaining screws (two). 2. Heat sink. 3. Power transistor. 4. Diode. 5. Plug. 6. Terminal #3. 7. Terminal #2. 8. Terminal #1.

The Excitation Output Board (M4) is located on the right side of the cage assembly (A5) - as viewed from the front of the regulator. The (M4) board plugs into the main board (M5). It is held in the cage assembly (A5) by two screws.

The Excitation Output Board's function is to control generator output by turning "on" and "off" the exciter circuit. The (M4) board receives the controlling impulse modulated signal from PC board (M1) as an input. According to this signal, the (M4) board switches "open" and "close" the excitation circuit.

"Closed" Excitation Circuit (Field "on")

From bridge rectifier (CR9 and CR10) and capacitor (C1) current flows through wire (1) to PC board (M4), terminal #1 (8).

From (M4), terminal #1, current flows through wire (1) to Regulator Terminal Strip, terminal (F1).

From terminal (F1) current flows to exciter field (L2).

From exciter field (L2) to Regulator Terminal Strip, terminal (F2).

From terminal (F2) through wire (2) to PC board (M4), terminal #2 (7).

From terminal #2 through a switching power transistor (3) on (M4) to terminal #3 (6) on (M4).

NOTE: On the self-excited generator the switching power transistor on (M4) is turned "on" during start-up by interconnecting circuitry on (M4 and M5) and by a plug-in relay - relay contact on (M5). During normal operation, a signal from the sensing and control board (M1) to PC board (M4) controls the switching transistor (3).

BUILD-UP RELAY RL501 (Self-Excited Generator)

From terminal #3 through wire (3) to bridge rectifier (CR9 and CR10) and capacitor (C1).

"Open" Excitation Circuit (Field "off")

The PC board (M4) also contains the intelligence part of a "Flyback" circuit which comes into play when the (M4) board switches open the excitation circuit.

NOTE: A flyback circuit from the negative (-) end to the positive (+) end of the exciter field (L2) permits a current flow when (M4) has switched open the excitation circuit.

When the current flows through exciter field (L2) it causes a magnetic field around the coils of the field. The strength of the magnetic field is in relation to the current going through the exciter field. An increase in current flow makes the magnetic field stronger, and a decrease in current flow makes the magnetic field weaker.

When the current through the exciter field (L2) stops because PC board (M4) has cut off the flow, the magnetic field strength is maximum. The field now starts to collapse (grow weaker) back into the conductors of the coil. As a result of this, a voltage is induced in the coil which is where the "flyback" circuit comes in.

From the negative (-) end of the exciter field (L2) through wire (F2) to terminal (F2).

From terminal (F2) through wire (2) to (M4), terminal #2.

From PC board (M4), terminal #2 through a diode on board (M4) to terminal #1 on board (M4).

From terminal #1 through wire (1) to Regulator Terminal Strip, terminal (F1).

From terminal (F1) through wire (F1) to the positive (+) end of the exciter field (L2).

The PC board (M4) also provides reference excitation current to the Overcurrent Protection Board (M2).

On the self-excited generator, part of the voltage build-up circuitry is located on the PC board (M4). This circuitry allows the excitation circuit to remain in the "on" mode to allow voltage to increase from residual magnetism.

NOTE: As mentioned in this section and the section on PC board (M5), the main portion of the excitation voltage build-up circuitry is located on PC board (M5).

Overcurrent Protection Board (M2)

The Overcurrent Protection Board (M2) is located second card from the left in the cage assembly (A5) - as viewed from the front of the regulator. It plugs into the PC board (M5). The PC board (M2) performs the following functions:

OVERCURRENT PROTECTION BOARD (M2)
1. Extraction lever. 2. Spring connectors.

Overcurrent Limiting

The PC board (M2) contains current limit circuitry that limits the exciter field current while allowing full forcing voltage. PC board (M2) senses overcurrent from the excitation circuit on the PC board (M4).

When the current limit is reached, the PC board (M2) activates an "alarm" light [light emitting diode (LED)] on the PC board (M3). It also acts to restrict the excitation drive signal on PC board (M1) so that the overcurrent limit is not exceeded.

The current limit condition occurs during motor start-up or as a result of a fault or severe overload on the generator. If the overcurrent condition is maintained, then the Time-Delay Cutout function comes into play.

Time Delay Cutout

At the moment the current limit is reached, a time delay circuit on PC board (M2) senses the current limiting operation and starts timing. If the overcurrent condition has not subsided in approximately 10 seconds, the PC board (M2) performs the following:

1. Initiates a cutoff signal to the drive output on PC board (M1).

2. Lights a trip indicator lamp (LED) on PC board (M3).

The delay period of 10 seconds allows time for large motor starting or for circuit breakers to clear a fault before damage occurs to the generator due to excessive current. Excitation will remain cutoff until the trip/reset switch on the PC board (M3) is moved to the reset position. Operation can also be restored by shutdown and restarting of the engine.

On later self-excited generator regulators, a magnetic circuit breaker (K1) has been added to physically open the excitation circuit in a field overcurrent fault. The K1 breaker is energized through the trip circuit on the Alarm/Trip board (M3).

Low-Excitation Cutout

This circuit on the PC board (M2) will cutoff field current if the excitation power [as sensed from the secondary of the power transformer (T3)] drops below a safe level. This circuit prevents damage to the switching power transistor on the PC board (M4) due to low base current. As in the overcurrent situation, PC board (M2) sends a signal to the PC board (M1) which in turn cuts off the drive signal to the PC board (M4). This cuts off field excitation. Operation of the low-excitation protection system occurs at engine speed of less than half-speed or in the case of a fault in the optional PMPE exciter.

Alarm/Trip Board (M3)

The Alarm/Trip Board (M3) is located in the leftside of the cage assembly (A5) - as viewed from the front of the regulator. It plugs into the host PC board (M5) and is secured to the cage assembly by two screws.

ALARM/TRIP BOARD (M3) (EARLIER TYPE)
1. Winding temperature alarm/trip switch. 2. Terminals for remote switches (3). 3. Terminals (3) "common". 4. Retaining screws (2). 5. Plug. 6. Trip/Reset switch (overcurrent). 7. Alarm lamp. 8. Trip indicator lamp. 9. DC voltage test points.

As covered under the section for the PC board (M2), the Alarm/Trip Board (M3) contains:

Overcurrent trip/reset switch (6).

Alarm lamp (7) - glows when excitation field current is at the overcurrent limit.

Trip lamp (8) - glows the moment the exciter field circuit is tripped out (after approximately 10 seconds of overcurrent).

Winding Temperature Switch (1) - this switch has no function and appears only on earlier M3 boards. Later boards do not have this switch.

Six-terminal Terminal Strip (TS301)

a) earlier M3 boards - terminals four thru six (3) can be used for remote alarm and trip lights. Terminals one thru three (2) can be used for a remote trip/reset switch.

b) later M3 boards - A magnetic circuit breaker is connected to terminals three (10) and four (11). The K1 breaker opens the exciter circuit after approximately a ten second field overcurrent. The K1 breaker is located on the voltage regulator panel. The switch (S301) electrically opens the exciter circuit at the same time.

ALARM/TRIP BOARD (M3) (LATER TYPE)
10. Terminal three. 11. Terminal four.

Manual Control

SELF-EXCITED GENERATOR

PMG-EXCITED GENERATOR

NOTE: The manual control is shipped loose (not installed). Operating instructions will be sent with the control.

The manual voltage control can be used to control generator voltage when there is a failure in the generator regulator assembly. The location of the manual voltage control panel can be up to 35 m (115 ft) from the generator. Make reference to the chart.

NOTE: Shielding is needed to reduce EMI (electromagnetic interference) radiation from the wires during automatic operation.

CIRCUITS EXTERNAL TO REGULATOR (PERMANENT-MAGNET EXCITED GENERATOR)

CIRCUITS EXTERNAL TO REGULATOR (SELF-EXCITED GENERATOR)

REGULATOR CIRCUITS