Hobart POWER MASTER Setup guide

OM-2065
110190
032993
Operation and Maintenance Manual
with Illustrated Parts List
for
POWER MASTER
Solid State Frequency Converter
Specification Number 7015-3
Rated Output: 90-kVA, 115/200-V, 3-PHASE, 400-Hz
415-V, 3-Phase, 50-Hz Input
Model Number 90SB51
Hobart Brothers Company
Airport Systems Group
Ground Power Equipment
Troy, Ohio 45373
U.S.A.

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Safety Instructions and Warnings for Electrical Power Equipment
ELECTRIC SHOCK can KILL. Do not touch live electrical parts.
ELECTRIC ARC FLASH can injure eyes, burn skin, cause equipment damage,
and ignite combustible material. DO NOT use power cables to break load and
prevent tools from causing short circuits.
IMPROPER PHASE CONNECTION, PARALLELING, OR USE can damage
this and attached equipment.
Important: Protect all operating personnel. Read, understand, and follow all instructions in the
Operating/Instruction Manual before installing, operating, or servicing the
equipment. Keep the manual available for future use by all operators.
1. General
Equipment that supplies electrical power can cause serious injury or death, or damage to other
equipment or property. The operator must strictly observe all safety rules and take precautionary
actions. Safe practices have been developed from past experience in the use of power source
equipment. While certain practices below apply only to electrically-powered equipment, other practices
apply to engine-driven equipment, and some practices to both.
2. Shock Prevention
Bare conductors, or terminals in the output circuit, or ungrounded, electrically-live equipment can fatally
shock a person. Have a certified electrician verify that the equipment is adequately grounded and learn
what terminals and parts are electrically HOT. Avoid hot spots on machine. Use proper safety clothing,
procedures, and test equipment.
The electrical resistance of the body is decreased when wet, permitting dangerous currents to flow
through it. When inspecting or servicing equipment, do not work in damp areas. Stand on a dry rubber
mat or dry wood, use insulating gloves when dampness or sweat cannot be avoided. Keep clothing
dry, and never work alone.
a. Installation and Grounding of Electrically Powered Equipment
Equipment driven by electric motors (rather than by diesel or gasoline engines) must be installed
and maintained in accordance with the National Electrical Code, ANSI/NFPA 70, or other applicable
codes. A power disconnect switch or circuit breaker must be located at the equipment. Check the
nameplate for voltage, frequency, and phase requirements. If only 3-phase power is available,
connect any single-phase rated equipment to only two wires of the 3-phase line. DO NOT
CONNECT the equipment grounding conductor (lead) to the third live wire of the 3-phase line, as
this makes the equipment frame electrically HOT, which can cause a fatal shock.
Always connect the grounding lead, if supplied in a power line cable, to the grounded switch box or
building ground. If not provided, use a separate grounding lead. Ensure that the current (amperage)
capacity of the grounding lead will be adequate for the worst fault current situation. Refer to the
National Electrical Code ANSI/NFPA 70 for details. Do not remove plug ground prongs. Use
correctly mating receptacles.
b. Output Cables and Terminals
Inspect cables frequently for damage to the insulation and the connectors. Replace or repair
cracked or worn cables immediately. Do not overload cables. Do not touch output terminal while
equipment is energized.
WARNING
Instructions 910082 Rev 1/90 Page i

c. Service and Maintenance
This equipment must be maintained in good electrical and mechanical condition to avoid hazards
stemming from disrepair. Report any equipment defect or safety hazard to the supervisor and
discontinue use of the equipment until its safety has been assured. Repairs should be made by
qualified personnel only.
Before inspecting or servicing electrically-powered equipment, take the following precautions:
Shut OFF all power at the disconnecting switch or line breaker before inspecting or servicing.
Lock switch OPEN
(or remove line fuses) so that power cannot be turned on accidentally.
Disconnect power to equipment if it is out of service.
Use suitable voltmeter to check for voltage on capacitors and be sure they are discharged before
touching any bare conductors.
If troubleshooting must be done with the unit energized, have another person present who is
trained in turning off the equipment and providing or calling for first aid.
3. Fire and Explosion Prevention
Fire and explosion are caused by electrical short circuits, combustible material near engine exhaust
piping, misuse of batteries and fuel, or unsafe operating or fueling conditions.
a. Electrical Short Circuits and Overloads
Overloaded or shorted equipment can become hot enough to cause fires by self destruction or by
causing nearby combustibles to ignite. For electrically-powered equipment, provide primary input
protection to remove short circuited or heavily overloaded equipment from the line.
b. Batteries
Batteries may explode and/or give off flammable hydrogen gas. Acid and arcing from a ruptured
battery can cause fires and additional failures. When servicing, do not smoke, cause sparking, or use
open flame near the battery.
c. Engine Fuel
Use only approved fuel container or fueling system. Fires and explosions can occur if the fuel tank is
not grounded prior to or during fuel transfer. Shut unit DOWN before removing fuel tank cap. DO NOT
completely fill tank, because heat from the equipment may cause fuel expansion overflow. Remove all
spilled fuel IMMEDIATELY, including any that penetrates the unit. After clean-up, open equipment
doors and blow fumes away with compressed air.
4. Toxic Fume Prevention
Carbon monoxide - Engine exhaust fumes can kill and cause health problems. Pipe or vent the exhaust
fumes to a suitable exhaust duct or outdoors. Never locate engine exhausts near intake ducts of air
conditioners.
5. Bodily Injury Prevention
Serious injury can result from contact with fans inside some equipment. Shut DOWN such equipment
for inspection and routine maintenance. When equipment is in operation, use extreme care in doing
necessary trouble-shooting and adjustment. Do not remove guards while equipment is operating.
6. Medical and First Aid Treatment
First aid facilities and a qualified first aid person should be available for each shift for immediate
treatment of all injury victims. Electric shock victims should be checked by a physician and taken to a
hospital immediately if any abnormal signs are observed.
Page ii Instructions 910082 Rev 1/90

Call physician immediately. Seek additional assistance. Use First Aid
techniques recommended by American Red Cross until medical help arrives. If
Breathing is Difficult, give oxygen, if available, and have victim lie down. For
Electrical Shock, turn off power. Remove victim; if not breathing, begin
artificial respiration, preferably mouth-to-mouth. If no detectable pulse, begin
external heart massage. CALL EMERGENCY RESCUE SQUAD
IMMEDIATELY.
7. Equipment Precautionary Labels
Inspect all precautionary labels on the equipment monthly. Order and replace all labels that cannot be
easily read.
EMERGENCY
FIRST AID
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Page iv Instructions 910082 Rev 1/90

Table of Contents
Chapter 1. Description/Operation
Section 1. Description 1-1.1
1. General 1-1.1
a. MountingsfortheSolidStateConverter.......................1-1.1
b. Advantages Offered by Solid State Converter. . . . . . . . . . . . . . . . . . . 1-1.1
2. Theory of Operation 1-1.3
a. Input Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1.3
b. Inverter...................................................1-1.4
c. Transformers..............................................1-1.4
d. OutputFilter...............................................1-1.4
e. ProtectiveCircuits .........................................1-1.4
f. Alarms...................................................1-1.5
3. Orientation 1-1.5
4. Detailed Description 1-1.5
a. ControlsandControlCircuits................................1-1.5
b. DescriptionofFrontPanelControls ..........................1-1.7
c. ConverterCabinet..........................................1-1.9
d. BridgeInterlockCircuit .....................................1-1.9
e. Remote Pushbutton Station Connection (Optional) . . . . . . . . . . . . . 1-1.10
Section 2. Preparation For Use 1-2.1
1. Receipt and Inspection of Equipment 1-2.1
2. Unpacking the Unit 1-2.1
3. Mounting the Unit 1-2.1
4. Preparation for Use 1-2.1
a. Select an Adequate source of Input Power . . . . . . . . . . . . . . . . . . . . . 1-2.2
b. Install Input Conductors in Converter. . . . . . . . . . . . . . . . . . . . . . . . . . 1-2.2
c. Install Cable for Remote Control START/STOP
PushbuttonStation(IfUsed)...............................1-2.2
d. Install Input Cable at Electrical Power Supply Service . . . . . . . . . . . . 1-2.2
e. OtherLocationsforCableEntrance...........................1-2.2
f. CheckConverterNo-LoadOperation..........................1-2.2
g. InstallOutputCable ........................................1-2.3
Chapter-Section . Page
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90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Table of Contents
Page iii

Section 3. Operation 1-3.1
1. Start-Up Procedure with No Load on Converter Unit 1-3.1
2. Start-Up Procedure with Converter Unit
Connected to an Aircraft 1-3.11
3. Door Interlock Switch 1-3.1
4. Turn-Off Procedure 1-3.1
Chapter 2. Servicing
Section 1. Maintenance 2-1.1
1. General 2-1.1
2. Field Maintenance Procedure 2-1.1
3. Service Information and Factory Repair 2-1.2
4. Component Torque Values 2-1.2
Chapter 3. Troubleshooting
Section 1. Procedures 3-1.1
1. General 3-1.1
2. Procedure for Restoring Unit to Operation After a Fault 3-1.2
a. UV- Undervoltage Fault. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1.2
b. OV-OvervoltageFault...................................... 3-1.2
c. OC(SH)-Overcurrent(Short)Fault........................... 3-1.2
d. OC(125%)-Overcurrent(125%Load)Fault.................... 3-1.3
e. OC (150%)- Overcurrent (150% Load) Fault . . . . . . . . . . . . . . . . . . . . 3-1.3
f. 0LOSS-Phase-Loss....................................... 3-1.3
g. IMB/GND................................................. 3-1.3
h. DCFuse ................................................. 3-1.4
i. A, B, C, D - Inverter Sections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1.4
Section 2. Troubleshooting Charts 3-2.1
Section 3. “SOFT-START” Instructions 3-3.1
1. General 3-3.1
2. Procedure for “SOFT-START” 3-3.1
Section 4. Transistor Module Test Procedure 3-4.1
1. Taking Resistance Measurements on the
Transistor Module 3-4.1
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Table of Contents Nov 01/90
Page iv

Section 5. Capacitor Test Procedure 3-5. 1
1. Taking Resistance Measurements on Capacitors 3-5. 1
Chapter 4. Illustrated Parts List
Section 1. Introduction 4-1. 1
1. General 4-1. 1
2. Purpose 4-1. 1
3. Explanation of Parts List 4-1. 1
a. Contents...................................................4-1. 1
b. PartsListForm.............................................4-1. 1
Section 2. Parts List 4-2. 1
1. Explanation of Parts List Arrangement 4-2. 1
2. Symbols and Abbreviations 4-2. 1
Section 3. Numerical Index 4-3. 1
1. Expalination of Numerical Index 4-3. 1
Section 4. Spare Parts 4-4. 1
1. Explanation of Spare Parts 4-4. 1
Chapter 5. Optional Equipment
Chapter 6. Manufacturer’s Literature
Unusual Service Conditions
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Table of Contents
Page v

List of Figures
Chapter 1. Description/Operation
FrequencyConverterUnit ................................... 1-1.2
Specifications and Capabilities ................................. 1-1.3
BlockDiagramofConverter .................................. 1-1.4
“H”InverterBridge....................................... 1-1.5
CardCage(FrontView) .................................... 1-1.7
ControlPanel.......................................... 1-1.8
BridgeInterlockandOptionalRemotePushbuttonStationConnections ........... 1-1.9
Chapter 2. Servicing
ComponentTorqueValues................................... 2-1.4
Chapter 3. Troubleshooting
AlarmBoards.......................................... 3-1.1
CardCage........................................... 3-1.2
ControlPanel.......................................... 3-1.3
BasePulseforTransistorSW1 ................................ 3-2.1
BasePulseforTransistorSW2 ................................ 3-2.1
UnfilteredOutputWaveform.................................. 3-2.2
FilteredOutputWaveform ................................... 3-2.2
TransistorModule ....................................... 3-4.1
TakingTransistorModuleResistanceMeasurements..................... 3-4.2
ResistanceValuesforTransistorModule ........................... 3-4.2
Chapter 4. Illustrated Parts List
AC/ACConverter........................................ 4-2.2
MainFrame&CoverAssembly ................................ 4-2.4
AC/AC Converter
(Front Components and Main Transformers) ................ 4-2.6
AC/AC Converter
(Rear Components) ............................ 4-2.8
FrontDoorAssembly...................................... 4-2.12
P.C.CardCageAssembly................................... 4-2.14
Chapter-Section . Page
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Table of Contents Nov 01/90
Page vi

Introduction
1. Scope
This manual contains operation and field maintenance instructions for a solid state frequency
converter, identified by Specification number 7015-3 and manufactured by Hobart Brothers
Company, Airport Systems Group, Ground Power Division, Troy, Ohio 45373, U.S.A.
2. Purpose
The purpose of this manual is to provide information and instructions to experienced operators and
maintenance personnel who have not previously been exposed to this equipment. This manual is not
intended to be a textbook on electricity or electronics.
3. Arrangement
This manual is divided into four chapters. Each chapter is divided into sections as required. Each
section starts with page 1. Each page is identified by chapter, section and page number in the lower
outside corner. Illustration numbering is also grouped by sections.
When a reference is made to material which is located in the same section, the material is identified by
paragraph location only. Example:
(Para. 1, A) . When referenced material appears in a different
section, it is identified by chapter, section, and paragraph location. Example,
(See 2-l; para. lA) .The
same method applies to illustrations which are identified by figure numbers. Examples:
(Fig. 8) ,or (2-l;
Fig. 8).
4. Service Information
If you have any questions concerning your Hobart Brothers Company, Power Systems Group
equipment, you are invited to contact our Service Department by mail, telephone, or FAX.
Write: Hobart Brothers Company
Airport Systems Group
Ground Power Division
1177 Trade Road East
Troy, Ohio 45373, U.S.A.
Phone: [phone] (Service Assistance)
[phone] (Parts Replacement)
FAX: [phone]
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Introduction
Page vii

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OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Introduction Nov 01/90
Page viii

Chapter 1. Description/Operation
Section 1. Description
1. General
The solid state converter covered by this manual is designed to provide power for maintenance and
starting of aircraft having 115/200-V AC, 3-phase, 400-Hz electrical systems. This converter unit is
identified by Specification Number 7015-3, and is manufactured by Hobart Brothers Company, Ground
Power Division, Power Systems Group, Troy, Ohio 45373. See Figure 2 for specifications and
capabilities for a basic, or stationary converter.
a. Mounting for the Solid State Converter
The Specification Number 7015-3 solid state frequency converter is designed to be mounted on a
passenger boarding bridge.
b. Advantages Offered by Solid State Converter
The solid state converter offers numerous advantages when compared to motor-generator type
power units. The main advantages are as follow:
(1) Energy Savings
Because the converter unit is a demand system, it consumes only the energy necessary and in
the amount required. If no aircraft is being serviced, no power is required, and thus none is
generated or consumed.
(2) Efficiency
The converter unit provides power to an aircraft at an efficiency of 94-95% or better, with +/-1%
voltage regulation at the aircraft. Since the unit is used in the vicinity of an aircraft being
serviced, expensive 400-Hz cabling is kept to a minimum and no external line drop
compensation is required.
(3) Longer Service
The solid state converter operates for longer periods of time without service than do
motor-generator units, as there are no parts to wear out and impair the unit’s operation.
(4) Space Requirement
The converter unit is much smaller in physical size than a motor-generator unit of comparable
power output, and thus requires less space when bridge-mounted or floor-stand mounted.
(5) Lower Noise Level
The converter unit, being solid state, is much less noisy in operation than motor-generator
(rotating) equipment.
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Chapter 1-1
Page 1

1. Control panel
2. Front Door Assembly
3. Cabinet
4. Rear Door
5. Card Cage Window
Frequency Converter Unit
Figure 1
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Chapter 1-1 Nov 01/90
Page 2

Physical
Weight
(approximate, w/out mounting) 1570 lbs. (713 Kg)
Width (front to back of unit) 46 inches (1168 mm)
Length 60-1/8 inches (1527 mm)
Height 19-9/16 inches (497 mm)
Electrical
Input
Volts
(AC Nominal) 415
Volts
(AC Range) 374 - 457
Amperes
(nominal input voltage/rated load) 123
Frequency
(Hz) 50
Conductor Sizes Recommended * #1 AWG
Grounding Wire Sizes Recommended * #6 AWG
Output
Volts (AC) /Frequency (Hz) 115/200V AC
(wye), 400 Hz
Output Power Rating
(kVA) 90
Amperes
(at rated load) 260
Output Cable Sizes Recommended * 2/0
Power factor
(PF) 0.8L
Duty cycle
(%) 100%
Overload shutdown 125% for 5 minutes, 150% for 10 seconds
Shorted output shutdown IMMEDIATE
*These sizes are taken from Tables 310-16 and 250-94, respectively, of the 1990 National Electrical Code,
for copper conductors rated at 75oC(167
oF). Before using conductors of the sizes above, however, refer to
and conform to your LOCAL electrical code, which may vary from the National Electrical Code.
Specifications and Capabilities
Figure 2
2. Theory of Operation
This Hobart converter is a state-of-the-art, solid-state 60 (or 50) Hz to 400 Hz frequency converter. It
employs all silicon semi-conductors and CMOS digital logic. This converter is specifically designed to
supply clean, reliable ground power to an aircraft, eliminating the costly need for operating the aircraft’s
auxiliary power unit. The block diagram in Figure 3 identifies major components of the system.
a. Input Rectifier
Theinputvoltageisfirstrectifiedina3phasebridgeconfigurationandthenfilteredtoprovidean
unregulated DC voltage of approximately 600-V. This DC voltage feeds a three phase inverter
which transforms the DC input into a 400-Hz regulated output voltage. The inverter output
transformers provide electrical isolation between the input and output.
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Chapter 1-1
Page 3

b. Inverter
The inverter employed in this system is a step wave-form inverter. This inverter uses harmonic
neutralization, which results in the elimination of all harmonic distortion below the eleventh harmonic
without filtering. The system consists of six identical bridge type inverters
(N=6) which are uniformly
staggered 30 electrical degrees apart
(180/N) . In this arrangement, the smallest harmonic is 2N-l. A
small filter is used to reduce the amplitude of eleventh and higher harmonics to the desired level.
The power level of each of the six inverters is total kVA output divided by six.
Component designations
(e.g. L2) 3refer to diagrams in this manual as well as markings on unit.
Each of the six individual inverters consists of a transistorized bridge and a snubber circuit. A
variable width square pulse is obtained on the bridge output terminals by turning on the transistors
S1 and S4 or S3 and S2. The snubber circuit consists of an air core inductor
(di/dt) and a printed
circuit board containing capacitors and resistors.
As the phase shift between the six inverters is digitally generated, no change - and consequently no
harmonic lower than the eleventh - appears when line or load is varied, regardless of pulse width
variation. Because of the elimination of the lower harmonics, the output filter is very simple.
c. Transformers
Each inverter transformer has three AC output windings. These windings are connected in series
with the windings from the other inverters to yield a low-distortion output. Each leg of the three
phase system is comprised of one winding from each of the six transformers.
d. Output Filter
The output filter consists of a series inductor and parallel capacitors
(L2, L3, L4, Cl7 to C34 on
Drawing in Chapter 6 )
. Output voltage is sensed and regulated through a negative feedback loop
which contains sensing transformers T7, T8, T9, and related circuitry in the amplifier board.
e. Protective Circuits
Current transformers T10, T11, and T12 provide an output current reading to the amplifier board,
which compares it with various thresholds on alarm board No. II. At about 150% of rated load, the
unit begins current limiting, and output voltage begins to drop off. The control circuits monitor output
voltage and output current, and sense various thresholds in voltage and load current to assure
protection of the system as well as the load.
When an overvoltage condition develops at the output
(voltage exceeding 132-V AC) , the unit will
shut down.
Block Diagram of Converter
Figure 3
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Chapter 1-1 Nov 01/90
Page 4

When an overload condition develops, wherein the load exceeds the unit’s power rating by 25%, the
unit will run for approximately 5 minutes before shutting down. For a 50% overload, the unit will turn
off after approximately 10 seconds. In case of a short circuit, the unit will turn off to avoid damage to
its components.
To prevent excessive current through the ground line, current transformer T13 senses ground line
current and constantly sends a signal to the ground protective circuit. When ground line current
exceeds approximately 25% of rated load, the ground protective circuit shuts the machine down.
f. Alarms
Protective devices and alarms are described in detail in the following paragraphs.
3. Orientation
To avoid confusion in the location of components, the control panel of the unit is located at the FRONT
of the unit. LEFT and RIGHT are determined by looking at the unit from the FRONT.
4. Detailed Description
a. Controls and Control Circuits
All control boards are concentrated in the card cage, a portion of which is visible from the front of
the unit through a small window located just beneath the control panel
(See 5, Fig. 1) . All control
circuits are solid state and employ CMOS technology for low power consumption and good noise
immunity. There are 13 boards in the card cage
(Fig. 5) which are divided into four groups: Alarm
boards
(3) ,Control boards (2) , driver boards (6), Power supply (2).
(1)
Alarm Cards
The alarm cards monitor a number of sensors and give signals indicating the nature of a fault
when a fault occurs. Faults in the unit are indicated by red lights
(LEDs) which may be observed
through a small window in the front door
(5,Fig.1)
“H” Inverter Bridge
Figure 4
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Chapter 1-1
Page 5

ALARM I monitors a series of current sensors. This device will sense a current in excess of
normal in the transistorized bridge and will turn the entire unit off. These sensors will react only
to an imminent failure of the transistors and not to an overload on the unit. A panel-mounted
three-position switch allows an operator to test if the alarm circuits are functioning. The RESET
position will bring the circuits back to normal.
ALARM II monitors output voltage for an over or under-voltage condition, for output current at
three levels of load
(125%, 150%, and 200%) , and for the loss of an input phase. The
undervoltage (UV) light will latch only if the undervoltage condition exists longer than 7 seconds
to allow for voltage transients when applying heavy loads. All thresholds are factory-set and
additional adjustment is not necessary. The potentiometer for these thresholds are in the alarm
cards and are not easily accessible. All of the lights on ALARM I and II cards are red and have a
latching circuit which allows for an investigation even after the cause of a fault has disappeared.
ALARM III has 3 green indicators signaling the presence of the internal voltages
( +6V and +12V )
and the integrity of the DC FUSE. When the +12V green light is on, the control circuits on all
cards are powered. The +6V light indicates the proper functioning of POWER SUPPLY I . There
isalsoared(IMB/GND) light which indicates a current flow through ground that will shut the
machine down.
(2) Control Cards
Amplifier (AMP) and comparator (COMP) cards generate the driving pulses for the power
transistors. The AMP card contains an oscillator, error amplifier, and voltage ramp-up circuit.
Card Cage (Front View)
Figure 5
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Chapter 1-1 Nov 01/90
Page 6

The AMPcard allows for adjustments to the output voltage as well as to the load compensation.
The VOLTAGE potentiometer allows an operator to adjust the output voltage in excess of +/-
15%. By setting the output voltage at a low of 100-V or a high of 132-V, the undervoltage (UV)
and overvoltage (OV) alarms should be triggered. In this way, the presence of the protective
thresholds is tested. A clockwise rotation will increase the output voltage.
Another adjustment on the AMP card is the LOAD COMPENSATION. At full load this
adjustment will increase the output voltage by up to 5%, to compensate for the voltage drop on
the cable connecting the load. A clockwise rotation on the potentiometer will bring the
compensation at full load from 0% to 5%.
Also on the AMP card front panel, a two-position toggle switch allows maintenance personnel to
operate the unit for test purposes without connecting the output cable to an aircraft. When this
switch is in the NORMAL position, the interlock circuit is activated and the unit will run only if the
output cable is connected to an aircraft, which is supplying 28VDC to the E/F interlock circuit in
the output cable. In the MAINT position, the unit will turn on and stay on even if the output cable
is not connected to an aircraft. A red light next to the switch will indicate that the aircraft is
disconnected and that the MAINT position on the toggle switch should be used in order to turn
the unit on. The CURRENT adjustment potentiometer determines the point at which the unit
goes into current limiting.
(3) Power Supply Cards
ThefunctionofPOWER SUPPLY I and POWER SUPPLY II is to generate the voltages
necessary to drive the power transistors. POWER SUPPLY NO. I is a high frequency DC to DC
converter which provides regulated +6V and -6V from an input of 70V. This output is used to
drive all of the transistors with the emitter connected to the -600V bus. To drive the rest of the
transistors, POWER SUPPLY II provides sets of floating +/- 6V sources.
(4) Driver Cards
The driver cards receive width modulated pulse signals from the comparator card, and amplify
these signals from logic power level to switch power modules on and off. Driver cards provide
necessary electrical isolation between control and power electronics.
b. Description of Front Panel Controls (See Figure 6)
The functions of each of the controls and indicators are as follows:
(1) START Button
After the unit input power is turned on and any of the alarms is reset, by pressing the START
button
(4) , the unit will turn on. (See start-up procedure) .
(2) STOP/RESET Button
The unit can be turned off by momentarily pressing the STOP/RESET button
(5). This button
permits the reset of alarms without opening the front door to access the card cage. This button is
especially useful when the phase loss (0 LOSS) alarm will latch due to a temporary failure in
input power.
(3) INPUT Indicator Light (Green)
This indicator light (3) will turn on upon application of input power.
(4) OUTPUT Indicator Light (Green)
This indicator light, (9) by turning on, indicates the presence of power at the output terminals.
(5) FAULT Indicator Light (Red)
This indicator light
(10) turns on whenever there is either an over-current, overvoltage,
undervoltage, ground, phase-loss fault, or inverter section fault. When this light comes on, it is
necessary to look into the front window of the converter unit and look at the ALARM cards I, II,
and III in the card cage to determine possible fault interrupted output power delivery. The
specific fault will be indicated by a fault light on ALARM card I, II, or III.
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Nov 01/90 Chapter 1-1
Page 7

(6) OUTPUT VOLTMETER
This meter
(7) , in conjunction with the VOLTAGE SELECTOR SWITCH, (7) measures output
voltage on all three phases, with an accuracy of +/-2%. Two test jacks
(8) are provided next to
the voltmeter for measuring voltage with a more accurate meter if that is required during service.
(7) VOLTAGE SELECTOR SWITCH
This switch
(6) permits the operator to check voltage output in each of the three phases, A, B, or
C, by turning the switch and observing the voltmeter.
(8) HOURMETER
The hourmeter
(1) measures and records converter running time, and will record up to 9999.9
hours on five revolving drums. The hourmeter operates whenever voltage is available at the
output terminals of the converter.
(9) KILOWATT-HOUR METER
The kilowatt-hour meter
(2) , as its name implies, measures total power usage from the
converter. The kilowatt-hour meter operates only when the converter is delivering power to a
load.
1. Hour meter 6. Meter Selector switch
2. Kilowatt-hour meter 7. Output voltage meter
3. Input power indicating light
(green) 8. Test jacks
4. Start button 9. Output power indicating light
(green)
5. Stop/reset button 10. Fault indicating light (red)
Control Panel
Figure 6
OM-2065 / Operation and Maintenance Manual
90SB51 / Spec. 7015-3 / Frequency Converter
Chapter 1-1 Nov 01/90
Page 8