ASEA AC90SVHE-3 User manual

Operations Manual
for the ASEA Power Systems
Model AC90SVHE-3 and AC100SVHE-3
3 Phase Yacht Power Converters
P/N 605059
Revision ~
Issued 7/16/14

AC90SVHE-3 / AC100SVHE-3 Operations Manual....2
CERTIFICATION
ASEA Power Systems certifies that this product was thoroughly tested and inspected and found to meet or
exceed its published specifications when shipped from the factory.
WARRANTY
ASEA Power Systems warrants each unit to be free from defects in material and workmanship. For a
period of 18 months after purchase or 12 months after installation (whichever is shorter), ASEA Power
Systems will repair or replace any defective module provided the unit has been installed and operated in a
manner according to this manual. A thorough inventory of spare parts & modules is maintained at our
factory. Our world-wide sales/support facilities also inventory a complement of spare parts and modules.
ASEA Power Systems is not responsible for consequential damage arising from the use of its equipment.
It does not apply to extensively modified or non-standard systems. Debit memos for returned units are
not accepted, and will cause return of the system without repair.
LIFE SUPPORT POLICY
ASEA Power Systems does not authorize the use of any of its products or systems for use an AC voltage
supply (source) for life support systems. Life support systems are devices which support or sustain life,
and whose failure to perform, when properly used in accordance with this Operations Manual, can be
reasonably expected to result in significant injury to the user.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....3
1 USING THIS MANUAL
This manual has been written as an Operations Manual. Installation, Operations, and
Preventative Maintenance are covered in detail. This manual will cover the following models:
AC90SVHE-3 90kVA 3 Phase Yacht Power Converter
AC100SVHE-3 100kVA 3 Phase Yacht Power Converter
Please note that these converters are capable of being paralleled for higher power applications.
The Model AC90SVHE-3 can be paralleled to produce the following models:
AC180SVHE-3/2 180kVA 3 Phase Yacht Power Converter
AC270SVHE-3/3 270kVA 3 Phase Yacht Power Converter
AC360SVHE-3/4 360kVA 3 Phase Yacht Power Converter
The Model AC100SVHE-3 can be paralleled to produce the following models:
AC200SVHE-3/2 200kVA 3 Phase Yacht Power Converter
AC300SVHE-3/3 300kVA 3 Phase Yacht Power Converter
AC400SVHE-3/4 400kVA 3 Phase Yacht Power Converter
It is important that the operator reads this manual prior to installing and operating the converter.
A thorough understanding of the information covered in this manual is required for proper
installation and operation.
If any questions arise while reading this manual, the user is encouraged to call ASEA Power
Systems. ASEA Power Systems is located at:
ASEA Power Systems
15602 Commerce Lane
Huntington Beach, CA. 92649
Phone [phone]
FAX [phone]
Web http://www.aseapower.com

AC90SVHE-3 / AC100SVHE-3 Operations Manual....4
TABLE OF CONTENTS
CERTIFICATION ...........................................................................................................................2
WARRANTY ..................................................................................................................................2
1 USING THIS MANUAL.....................................................................................................3
2 SAFETY NOTICES.............................................................................................................6
3 INTRODUCTION TO THE AC90SVHE-3 / AC100SVHE-3 ...........................................8
4 SPECIFICATIONS............................................................................................................10
4.1 ELECTRICAL SPECIFICATIONS ......................................................................10
4.1.1 Input Service..............................................................................................10
4.1.2 Output Service ...........................................................................................10
4.1.3 Control, Metering, and Status....................................................................11
4.1.4 Output Derating: Coolant Temperature.....................................................12
4.2 PHYSICAL SPECIFICATIONS ...........................................................................13
4.2.1 Mechanical.................................................................................................13
4.2.2 Environmental............................................................................................13
4.2.3 Coolant Requirements................................................................................13
5 INSTALLATION ..............................................................................................................14
5.1 MECHANICAL INSTALLATION.......................................................................15
5.1.1 General.......................................................................................................15
5.1.2 Clearances..................................................................................................15
5.1.3 Coolant Connections..................................................................................18
5.2 ELECTRICAL INSTALLATION.........................................................................19
5.2.1 Input Power Connections...........................................................................20
5.2.2 Output Power Connections........................................................................20
5.2.3 Grounding..................................................................................................22
5.2.4 Multi-Cabinet Connections........................................................................22
5.2.5 Seamless Transfer Connections.................................................................23
5.2.6 Other Option Connections .........................................................................24
6 OPERATION.....................................................................................................................25
6.1 POWER TURN-ON PROCEDURE......................................................................25
6.1.1 Systems Not Equipped With The Seamless Transfer Option....................27
6.1.2 Systems Equipped With The With Seamless Transfer Option..................28
6.2 MULTI-CABINET TURN-ON PROCEDURE ....................................................30
6.3 AUTO-RESTART FEATURE ..............................................................................31
6.3.1 Operation....................................................................................................32
6.4 TURN-OFF PROCEDURE...................................................................................33
6.4.1 Systems Not Equipped With The Seamless Transfer Option....................33
6.4.2 Systems Equipped With The Seamless Transfer Option...........................34
6.5 REMOTE COMMUNICATION...........................................................................35
6.5.1 RS-232C/SCPI...........................................................................................36
6.5.2 RS-485/Modbus.........................................................................................37

AC90SVHE-3 / AC100SVHE-3 Operations Manual....5
7 SOFTWARE FEATURES.................................................................................................39
7.1 GENERAL.............................................................................................................39
7.2 LOAD MANAGEMENT.......................................................................................39
7.3 LOAD MANAGEMENT OPERATION...............................................................41
7.3.1 Shore Cord Alarm, Single, Master, and Slave converters .........................41
7.3.2 Shore Cord Setup, Single, Master, or Slave Converters............................42
7.3.3 Voltage Droop, Single or Master Converters ............................................43
7.3.4 Automatic Transfer to Generator, Single or Master Converters (Seamless
Transfer installed)......................................................................................44
7.3.5 Quick Setup of Shore Cord Alarm, Single, Master, or Slave Converters..45
7.4 GENERATOR FREQUENCY ANALYSIS .........................................................46
7.5 CONVERTER OUTPUT IMPEDANCE CONTROL...........................................46
7.6 AGC CONTROL...................................................................................................47
7.7 kW-HOUR METER AND MAXIMUM POWER LEVEL DISPLAY.................48
7.8 CONVERTER OUTPUT VOLTAGE CONTROL...............................................49
7.9 EVENT LOG.........................................................................................................50
8 TROUBLE-SHOOTING AND DIAGNOSTICS..............................................................52
8.1 COMMON PROBLEMS.......................................................................................52
8.2 FAILURE AND WARNING MESSAGES...........................................................53
8.3 INFO DISPLAY ....................................................................................................53
8.4 STATUS WORDS.................................................................................................54
8.5 GATHERING DATA............................................................................................54
8.6 SOFTWARE TOOLS............................................................................................54
9 CALIBRATION ................................................................................................................56
10 MAINTENANCE..............................................................................................................58
11 INTERNATIONAL POWER FORM REFERENCE........................................................59
12 INDEX...............................................................................................................................64
FIGURES
1 SYSTEM BLOCK DIAGRAM...........................................................................................8
2 OUTPUT DERATING: COOLANT TEMPERATURE...................................................12
3 N/A.........................................................................................................................................
4 MECHANICAL OUTLINE AND CONTROLS...............................................................16
5 MECHANICAL OUTLINE...............................................................................................17
6 INPUT AND OUTPUT CONNECTIONS........................................................................21
7 FRONT PANEL CONTROLS ..........................................................................................25
8 RS-232C PINOUT.............................................................................................................36
9 RS-485 CONNECTIONS..................................................................................................37
10 STATUS WORD BIT DEFINITIONS..............................................................................55

AC90SVHE-3 / AC100SVHE-3 Operations Manual....6
2 SAFETY NOTICES
Each shore power converter is capable of transferring large amounts of electrical energy very
quickly. This quality is fundamental to a high performance power converter. International
symbols are used throughout this manual to stress important information. Read the text below
each symbol carefully and use professional skills and prudent care when performing the actions
described by the text.
THE CAUTION SYMBOL (TRIANGLE ENCLOSING AN EXCLAMATION POINT)
INDICATES A CONDITION THAT COULD SERIOUSLY DAMAGE EQUIPMENT AND
POSSIBLY INJURE PERSONNEL. CAUTIONS WILL BE PRESENTED IN THIS
FORM. ALL CAUTIONS SHOULD BE RIGOROUSLY OBSERVED.
THE WARNING SYMBOL (TRIANGLE WITH A LIGHTNING BOLT) IS USED TO
SIGNAL THE PRESENCE OF A POSSIBLE SERIOUS, LIFE THREATENING
CONDITION. A CONDITION THAT IS HAZARDOUS TO BOTH PERSONNEL AND
EQUIPMENT WILL BE ISSUED AS A WARNING. ALL WARNINGS WILL BE
PRESENTED IN THIS FORM.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....7
THIS EQUIPMENT CONTAINS HIGH ENERGY, LOW IMPEDANCE
CIRCUITS! LETHAL POTENTIALS ARE CONTAINED WITHIN THE
SYSTEM EVEN WHEN IT APPEARS NON-OPERATIONAL.
CARE MUST BE EXERCISED WHEN SERVICING THIS EQUIPMENT IN
ORDER TO PREVENT SERIOUS OPERATOR INJURY OR EQUIPMENT
DAMAGE.
DO NOT WORK ON OR OPERATE THIS EQUIPMENT UNLESS YOU ARE
FULLY QUALIFIED TO DO SO. NEVER WORK ALONE.
THE EQUIPMENT IS NOT IGNITION RATED; IT MUST NOT BE OPERATED
IN AREAS WHERE COMBUSTIBLE GASES MAY ACCUMULATE.
DO NOT REMOVE THE SHORE CORD FROM THE DOCK PEDESTAL
WITHOUT FIRST OPENING THE DOCK OR YACHT BREAKER. FAILURE
TO DO SO MAY RESULT IN DAMAGE TO THE CONVERTER AND
PEDESTAL.
OBSERVE THE FOLLOWING WHEN SERVICE AND MAINTENANCE ARE
REQUIRED:
REMOVE ALL JEWELRY FROM ARMS AND NECK WHEN SERVICING THIS
EQUIPMENT. THIS PREVENTS THE POSSIBILITY OF SHORTING
THROUGH THE JEWELRY, OR ELECTROCUTION OF THE OPERATOR.
WEAR SAFETY GLASSES WHEN SERVICING THIS EQUIPMENT TO
PREVENT EYE INJURY DUE TO FLYING PARTICLES CAUSED BY
ACCIDENTAL SHORT CIRCUIT CONDITIONS.
DO NOT REMOVE ANY PANELS OR COVERS WITHOUT FIRST OPENING
ALL SHORE POWER AND SWITCHGEAR CIRCUIT BREAKERS
DISTRIBUTING POWER TO AND FROM THE CONVERTER, AND THEN
REMOVING THE INPUT SERVICE.
SERVICE SHOULD BE REFERRED TO PERSONNEL AUTHORIZED BY THE
FACTORY TO SERVICE THIS EQUIPMENT.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....8
3 INTRODUCTION TO THE AC90SVHE-3 / AC100VHE-3
The AC90SVHE-3 and AC100SVHE-3 are high performance Yacht Power Converters utilizing
dual-conversion technology. The system will accept any three phase input service with a
frequency between 40-70Hertz, and a voltage between 170-520VAC.
The output power form has been programmed at the factory for the voltage and frequency required
by your yacht.
FIGURE 1 SYSTEM BLOCK DIAGRAM
Dual-conversion technology is the preferred technique for AC power conversion, and was chosen
for these systems. In this technology, the shore power service is isolated by an input transformer,
then, converted to DC power by an input rectifier. The output inverters then convert the DC
power back to the required AC power form (both voltage and frequency) required by the yacht.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....9
3INTRODUCTION TO THE AC90SVHE-3 / AC100VHE-3,
cont.
Being converters designed from the ground up specifically for the yachting industry, all efforts
have been made to produce systems capable of withstanding the marine environment. All system
components are packaged in one drip-proof, dust-resistant stainless steel enclosure. Major
components are internally modular, allowing a simple exchange in the unlikely event of failure.
Complete electrical maintenance and service can be provided with only top and front access to the
system. Three lightweight power modules can be removed and replaced through the front panel
for repair or power level upgrade.
System operation is managed through two basic operators: A safety disconnect on the front of the
enclosure is used for securing input service during maintenance and service, and three membrane
switch groups in the control console—SHORE POWER, CONVERTER POWER, and SHIP’S
POWER—provide normal operation of the system. Each switch group contains an ON and OFF
switch with associated LED indicators.
In addition to the basic function of power conversion, the converter provides the user with a
sophisticated power analysis and monitoring capacity. All parameters for input and output
power, along with operations and status information, are available on the front panel display
console. Various displays are selected through a long life, sealed membrane switch panel.
This converter is designed to have the heat it introduces into its own internal atmosphere cooled
via a side-mounted, air-to-liquid heat exchanger. The heat-exchanger is designed for use with
chilled water or coolant (not seawater).
For additional information on controls and indicators, please refer to Section 6.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....10
4 SPECIFICATIONS
4.1 ELECTRICAL SPECIFICATIONS
Parameter AC90SVHE-3 AC100SVHE-3
4.1.1 Input Service
Input Power Form Three Phase Three Phase
Input Voltage Range 170-520VAC 170-520VAC
Input Frequency Range 40-70 Hertz 40-70 Hertz
Input Current, Max. Three Phase 250 ARMS 278 ARMS
Input Current, Soft Start, Max. 63 ARMS 63 ARM
Input Current Distortion <8% THD @ rated load <8% THD @ rated load
Input Power Factor >0.98 @ rated load >0.98 @ rated load
4.1.2 Output Service
Output Power Rating 90kVA @ 0.85 p.f. 100kVA @ 0.85 p.f.
Output Power Form Three-Phase 120/208 VAC, 127/220 VAC, 220/380 VAC, 230/400 VAC,
240/416 VAC, 254/440 VAC, 277/480 VAC
Output Frequency 50 or 60 Hertz 50 or 60 Hertz
Output Frequency Accuracy 0.01% 0.01%
Output Voltage Distortion < 1% THD < 1% THD
Output Voltage Line Regulation 0.50% 0.50%
Output Voltage Load Regulation 1.0% 1.0%
Output Voltage Response Time 0.20 msec. 0.20 msec.
Output Current, Continuous Refer to Table 1 on page 11 for basic ratings
Output Current, Peak 380% of cont. rating 350% of cont. rating
Output Current, Surge 270% of cont. rating 250% of cont. rating
Conversion Efficiency 94% @ rated load 94% @ rated load

AC90SVHE-3 / AC100SVHE-3 Operations Manual....11
4 SPECIFICATIONS, cont.
4.1 ELECTRICAL SPECIFICATIONS,cont.
4.1.2 Output Service, cont.
Table 1 - Output Current (Rated Continuous RMS)
Output Form
AC90SVHE-3
Output Current
AC100SVHE-3
Output Current
3Ø, 277/480VRMS
108ARMS/Ø
120ARMS/Ø
3Ø, 254/440VRMS
118ARMS/Ø
131ARMS/Ø
3Ø, 240/416VRMS
125ARMS/Ø
139ARMS/Ø
3Ø, 230/400VRMS
131ARMS/Ø
145ARMS/Ø
3Ø, 220/380VRMS
136ARMS/Ø
156ARMS/Ø
3Ø, 127/220VRMS
237ARMS/Ø
263ARMS/Ø
3Ø, 120/208VRMS
250ARMS/Ø
278ARMS/Ø
4.1.3 Control, Metering, and Status
Input Power Control Input Service Disconnect Switch, 2 pos.
Shore Power Control Membrane Switch, Input ON/OFF Control
Ship’s Power Control Membrane Switch, Output ON/OFF Control,
Converter Power Control Generator/Shore Power Transfer Control
Shore Power Metering Voltage, Current, Frequency, kVA, kW, %Load
Converter Power Metering Voltage, Current, Frequency, kVA, kW, %Load
Generator Power Metering Generator 1 & 2 Voltage, Frequency
(Optional) Current, kVA, kW, %Load
System Status Operational status, Diagnostics, Software Calibration

AC90SVHE-3 / AC100SVHE-3 Operations Manual....12
4 SPECIFICATIONS, cont.
4.1 ELECTRICAL SPECIFICATIONS, cont.
4.1.4 Output Derating: Coolant Temperature
FIGURE 2 OUTPUT DERATING: COOLANT TEMPERATURE

AC90SVHE-3 / AC100SVHE-3 Operations Manual....13
4 SPECIFICATIONS, cont.
4.2 PHYSICAL SPECIFICATIONS
Parameter AC90SVHE-3 AC100SVHE-3
4.2.1 Mechanical
Height 55.6"/141cm 55.6"/141cm
Width, Enclosure 30.6"/77.8cm 30.6"/77.8cm
Depth * 28.5"/72.4cm * 28.5"/72.4cm
Weight 1,475lbs/669kg 1,475lbs/669kg
* There are two copper water lines that face backwards which are an additional 2”/5.1cm in length (see
Figure 4 on page 16).
4.2.2 Environmental
Ambient Temperature Range 0-50C non-condensing
Internal Air Exchange Rate 900CFM (ft3/min) / 1,530 m3/hour
4.2.3 Coolant Requirements
Water Flow Rate 4-10 GPM range (minimum and maximum, respectively)
Coolant Flow Rate 8-10 GPM range (minimum and maximum, respectively)
Water/Coolant Flow Min. Rate 4 + (4 * Percent Coolant)
e.g. 100% coolant mix, 4 + (4 *1.00) = 8 GPM
50% coolant mix, 4 + (4 *0.50) = 6 GPM
Water/Coolant Temperature 4-10°C for full output power capability. See derating chart on
the previous page for operation at other temperatures.
Water/Coolant Pressure 4 bar maximum

AC90SVHE-3 / AC100SVHE-3 Operations Manual....14
5 INSTALLATION
The installation section is divided into two parts. The first will cover mechanical installation, the
second, electrical installation.
Read this manual thoroughly prior to attempting the installation. Improper installation is the most
significant cause of system start-up problems and service issues over the product’s life. Upon
receipt of the equipment, perform an external visual inspection. Verify that nameplate
information is consistent with the ship’s power requirements (required form, voltage, and
frequency).
Proper planning will speed up installation, location, and connection of the equipment. Follow the
suggested minimum clearances provided in Table 2. While operating in the air-cooled mode
with the designated covers removed: ensure the room/compartment has adequate
ventilation and cooling. The thermal load presented by the converter will be substantial
and approximately 18,282BTU/Hr at maximum continuous load for the AC90SVHE-3, and
approximately 20,313BTU/Hr for the AC100SVHE-3.
THE CONVERTERS ARE HEAVY, WEIGHING 1,475lbs. (669kg)
EXTREME CAUTION MUST BE EXERCISED IN HANDLING AND
INSTALLATION TO AVOID EQUIPMENT DAMAGE OR INJURY TO
PERSONNEL. AN ADEQUATE MATERIAL HANDLING DEVICE
SHOULD BE USED FOR UNLOADING, MOVING, AND POSITIONING
THE SYSTEM.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....15
5.1 MECHANICAL INSTALLATION
5.1.1 General
The converters were designed for deck mount installations and as such are provided with six
mounting holes. Mounting holes have been provided with ½” (12.7mm) diameters; stainless steel
hardware in the range of 3/8” to 7/16” (10-11mm) diameter is required.
The mounting surface should be flat and dimensionally stable to within 1/16” (1.5mm) to prevent
torsional stresses being applied to the structure of the converter. Spacers (shim stock) may be
added between the mounting surface and the converter mounting flanges to adjust the mounting
plane. If the system is to be mounted in a high vibration/shock environment, then the factory
must be consulted concerning the application. Drawings for approved shock mounting
assemblies will be supplied.
5.1.2 Clearances
The following recommended clearances must be considered during installation for proper
operation:
TABLE 2 FOR PROPER:
Operation Service
Front 0”24” min
Lower Rear Sides 0”0”
Top Rear 0”0”
Rear 0” 0”
Please contact factory engineers for review of the installation plan if unsure on any specification or
requirement.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....16
5.1 MECHANICAL INSTALLATION, cont.
FIGURE 4 MECHANICAL OUTLINE AND CONTROLS

AC90SVHE-3 / AC100SVHE-3 Operations Manual....17
5.1 MECHANICAL INSTALLATION, cont.
FIGURE 5 MECHANICAL OUTLINE

AC90SVHE-3 / AC100SVHE-3 Operations Manual....18
5.1 MECHANICAL INSTALLATION, cont.
5.1.3 Coolant Connections
The two coolant line connections are made using 1/2" NPT fittings. Use Teflon sealant to ensure
no leakage will occur.
The left-side bottom condensation drip line connection is made using a 3/8" NPT fitting. Use
Teflon sealant to ensure no leakage will occur.
Isolation valves must be installed locally so that shutoff can occur in the event of a leak.
A flow control solenoid must be installed to halt coolant flow when the converters are not in use.
Without such, condensation can be created within the converter.
No maintenance need be performed on the heat exchange unit when it is used in a chilled, fresh
water or ethylene glycol system.
A coolant flow rate greater than 10 GPM (Gallons Per Minute) is wasteful and can accelerate water
erosion of the heat exchange unit’s copper piping and sweated junctions.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....19
5.2 ELECTRICAL INSTALLATION
This procedure assumes the physical installation of the converter has been completed.
It is the installer’s responsibility to provide input service over-current protection and disconnect
means.
It is recommended that connection be made to the distribution bus through a manually operated
disconnect device such as a molded case switch or circuit breaker (rated for the total system
amperage) to ease disconnection and provide a safe servicing environment in the event of
converter failure.
Follow the table below when considering shore power input cabling.
MAXIMUM CURRENTS UNDER LOW-LINE CONDITIONS:
Model AC90SVHE-3 AC100SVHE-3
Input Current
Three Phase, 170-290V 275A 306A
Three Phase, 330-520V 150A 167A
Output Current: Refer to Table 1, page 11
All power wiring requires the removal of the lower front panel (behind the front door) and the
power cable access cover (cabinet bottom). This cover is secured with 6 each 1/4-20” x ½”
stainless steel screws. Drill or punch the appropriate holes for the selected strain reliefs.
Re-install the input service panel using the removed hardware. Place the disconnect switch in the
OFF position.

AC90SVHE-3 / AC100SVHE-3 Operations Manual....20
5.2 ELECTRICAL INSTALLATION, cont.
INPUT WIRING MUST BE PERFORMED BY A QUALIFIED ELECTRICIAN
FAMILIAR WITH STANDARD SAFEGUARDS AND PROCEDURES REQUIRED BY
THE INSTALLATION OF THIS TYPE OF EQUIPMENT. POWER MUST BE
REMOVED FROM THE INPUT DISTRIBUTION SYSTEMS SUPPLYING POWER TO
THE AC90SVHE-3 / AC100SVHE-3 PRIOR TO THE START OF THE FOLLOWING
STEPS. INPUT POWER MUST BE SECURED (LOCKED) IN THE OFF
(DE-ENERGIZED) STATE UNTIL INSTRUCTED OTHERWISE BY THIS
DOCUMENT. ALSO SECURE IN THE OFF STATE ANY CIRCUIT BREAKER(S) IN
THE SWITCHGEAR PANEL THAT MAY BE SUPPLYING SHIP’S BUS POWER TO
THE CONVERTER OUTPUT TERMINAL BLOCK. FAILURE TO FOLLOW THESE
PROCEDURES CAN RESULT IN DAMAGE TO THE EQUIPMENT, AND CAN
PRESENT THE RISK OF INJURY OR DEATH TO THE INSTALLER OR THE
OPERATOR.
5.2.1 Input Power Connections
The converter is supplied with compression type terminal blocks for input power connections.
These terminal blocks accept wires in the range of 350MCM to 6AWG. Refer to the applicable
standards for selection of required wire gauge and type.
In two or more cabinet systems, one shore cord is connected to each converter shore power
terminal block.
5.2.2 Output Power Connections
The converter is supplied with compression type terminal blocks for output power connections.
These terminal blocks accept wires in the range of 350MCM to 6AWG. Refer to the applicable
standards for selection of required wire gauge and type.
The output ground wire is to be connected to a 3/8-16 UNC stud. Please refer to the Figure 6 on
page 21 for additional detail.