Basler DECS-250 User manual

INSTRUCTION MANUAL
FOR
DIGITAL EXCITATION CONTROL SYSTEM
DECS-250
Publication: 9440300990
Revision: G 08/14
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9440300990 Rev G i
DECS-250 Preface
Preface
This instruction manual provides information about the installation and operation of the DECS-250 Digital
Excitation Control System. To accomplish this, the following information is provided:
•General Information
•Human-Machine Interface
•Functional Description
•Installation
•BESTCOMSPlus®Software
•Setup
•Communication Protocols
•Maintenance
•Specifications
•Expansion Modules
Warning!
To avoid personal injury or equipment damage, only qualified
personnel should perform the procedures in this manual.
NOTE
Be sure that the device is hard-wired to earth ground with no smaller
than 12 AWG (3.3 mm2) copper wire attached to the case ground
terminal. When the device is configured in a system with other
devices, a separate lead should be connected from the ground bus to
each device.
Current transformer (CT) grounding should be applied in accordance
with local codes and conventions.
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ii 9440300990 Rev G
Preface DECS-250
12570 State Route 143
Highland IL 62249-1074 USA
www.basler.com, [e-mail]
Tel: [phone], Fax: [phone]
© 2014 by Basler Electric
All rights reserved
First printing: October 2012
This publication contains confidential information of Basler Electric Company, an Illinois corporation. It is loaned for
confidential use, subject to return on request, and with the mutual understanding that it will not be used in any
manner detrimental to the interests of Basler Electric Company and used strictly for the purpose intended.
It is not the intention of this manual to cover all details and variations in equipment, nor does this manual provide data
for every possible contingency regarding installation or operation. The availability and design of all features and
options are subject to modification without notice. Over time, improvements and revisions may be made to this
publication. Visit www.basler.com to obtain the latest version. Should further information be required, contact Basler
Electric.
For terms of service relating to this product and software, see the Commercial Terms of Products and Services
document available at www.basler.com/terms.
The English-language version of this manual serves as the only approved manual version.
When distributed in electronic format:
Adobe® Reader®. Copyright © 1984-2008. Adobe Systems Incorporated. All Rights Reserved. Patents pending in
the United States and other countries. Adobe and Reader are either trademarks or registered trademarks in the
United States and/or other countries.
This product contains, in part, open source software (software licensed in a way that ensures freedom to run, copy,
distribute, study, change, and improve the software) and you are granted a license to that software under the terms of
either the GNU General Public License or GNU Lesser General Public License. The licenses, at the time of sale of
the product, allow you to freely copy, modify, and redistribute that software and no other statement or documentation
from us, including our End User License Agreement, places any additional restrictions on what you may do with that
software.
For at least three (3) years from the date of distribution of this product, a machine-readable copy of the complete
corresponding source code for the version of the programs distributed to you will be sent upon request (contact
information is provided above). A fee of no more than our cost of physically performing the source code distribution is
charged.
The source code is distributed in the hope that it will be useful, but WITHOUT ANY REPRESENTATION or
WARRANTY or even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Refer to the source code distribution for additional restrictions regarding warranty and copyrights.
For a complete copy of GNU GENERAL PUBLIC LICENSE Version 2, June 1991 or GNU LESSER GENERAL
PUBLIC LICENSE Version 2.1, February 1999 refer to www.gnu.org or contact Basler Electric. You, as a Basler
Electric Company customer, agree to abide by the terms and conditions of GNU GENERAL PUBLIC LICENSE
Version 2, June 1991 or GNU LESSER GENERAL PUBLIC LICENSE Version 2.1, February 1999, and as such hold
Basler Electric Company harmless related to any open source software incorporated in this product. Basler Electric
Company disclaims any and all liability associated with the open source software and the user agrees to defend and
indemnify Basler Electric Company, its directors, officers, and employees from and against any and all losses, claims,
attorneys' fees, and expenses arising from the use, sharing, or redistribution of the software. Review the software
website for the latest version of the software documentation.
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9440300990 Rev G iii
DECS-250 Preface
Contents
Introduction .................................................................................................................................................1
Features and Functions.............................................................................................................................1
Application.................................................................................................................................................2
Package.....................................................................................................................................................2
Optional Features and Capabilities ...........................................................................................................2
Storage......................................................................................................................................................3
Controls and Indicators..............................................................................................................................5
Front Panel Illustration and Description ....................................................................................................5
Menu Navigation........................................................................................................................................6
Adjusting Settings......................................................................................................................................7
Display Setup ............................................................................................................................................7
Power Inputs................................................................................................................................................9
Control Power............................................................................................................................................9
Operating Power........................................................................................................................................9
Power Stage...............................................................................................................................................11
Voltage and Current Sensing...................................................................................................................13
Generator Voltage...................................................................................................................................13
Generator Current ...................................................................................................................................13
Bus Voltage .............................................................................................................................................15
Synchronizer .............................................................................................................................................17
Generator Synchronization......................................................................................................................17
Voltage Matching.....................................................................................................................................19
Breaker Hardware Configuration.............................................................................................................19
Generator and Bus Condition Detection..................................................................................................20
Generator Governor Control....................................................................................................................23
Regulation..................................................................................................................................................25
Regulation Modes....................................................................................................................................25
Pre-Position Setpoints.............................................................................................................................27
Transient Boost .......................................................................................................................................28
Operation with Paralleled Generators .....................................................................................................29
Autotracking.............................................................................................................................................31
Setpoint Configure...................................................................................................................................32
Auxiliary Control .......................................................................................................................................33
Auxiliary Control Input Type ....................................................................................................................33
Auxiliary Control Input Function ..............................................................................................................33
Auxiliary Control Gains............................................................................................................................33
Summing Type ........................................................................................................................................34
Contact Inputs and Outputs.....................................................................................................................35
Contact Inputs .........................................................................................................................................35
Contact Outputs.......................................................................................................................................36
Protection...................................................................................................................................................39
Voltage Protection...................................................................................................................................39
Frequency Protection ..............................................................................................................................43
Power Protection.....................................................................................................................................44
Field Protection........................................................................................................................................47
Sync-Check Protection............................................................................................................................51
Generator Frequency Less Than 10 Hertz..............................................................................................52
Configurable Protection...........................................................................................................................52
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iv 9440300990 Rev G
Preface DECS-250
Limiters ......................................................................................................................................................55
Overexcitation Limiter..............................................................................................................................55
Underexcitation Limiter............................................................................................................................59
Stator Current Limiter..............................................................................................................................61
Var Limiter ...............................................................................................................................................62
Limiter Scaling.........................................................................................................................................63
Underfrequency Limiter...........................................................................................................................63
Metering .....................................................................................................................................................67
Metering Explorer ....................................................................................................................................67
Metered Parameters................................................................................................................................68
Status Indication......................................................................................................................................74
Auto Export Metering...............................................................................................................................82
Event Recorder..........................................................................................................................................83
Sequence-of-Events Recording ..............................................................................................................83
Data Logging...........................................................................................................................................83
Trending ..................................................................................................................................................87
Power System Stabilizer...........................................................................................................................89
Supervisory Function and Setting Groups...............................................................................................89
Theory of Operation.................................................................................................................................89
Stability Tuning .........................................................................................................................................99
AVR Mode ...............................................................................................................................................99
FCR and FVR Modes ............................................................................................................................103
Other Modes and Functions..................................................................................................................104
Mounting..................................................................................................................................................107
Mounting Considerations.......................................................................................................................107
Projection Mounting...............................................................................................................................107
Behind-the-Panel Mounting...................................................................................................................107
Terminals and Connectors.....................................................................................................................111
Overview................................................................................................................................................111
Terminal Types......................................................................................................................................115
Typical Connections...............................................................................................................................117
BESTCOMSPlus®Software.....................................................................................................................121
General Description...............................................................................................................................121
Installation .............................................................................................................................................122
Activation of the DECS-250 Plugin for BESTCOMSPlus®.....................................................................122
Menu Bars .............................................................................................................................................126
Settings Explorer...................................................................................................................................128
Metering Explorer ..................................................................................................................................129
Settings File Management.....................................................................................................................129
Automatic Metering Export....................................................................................................................131
Firmware Updates.................................................................................................................................132
BESTCOMSPlus®Updates....................................................................................................................135
BESTlogic™Plus.....................................................................................................................................137
Introduction............................................................................................................................................137
Overview of BESTlogic™Plus...............................................................................................................137
Logic Schemes......................................................................................................................................151
Programming BESTlogic™Plus ............................................................................................................156
BESTlogic™Plus File Management......................................................................................................158
BESTlogic™Plus Examples ..................................................................................................................159
Communication.......................................................................................................................................161
Local Communication............................................................................................................................161
Communication with a Second DECS...................................................................................................161
Modbus™Communication.....................................................................................................................162
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9440300990 Rev G v
DECS-250 Preface
CAN Communication.............................................................................................................................164
Ethernet Communication.......................................................................................................................165
PROFIBUS Communication..................................................................................................................168
Configuration...........................................................................................................................................169
Generator, Field, and Bus Ratings........................................................................................................169
Bridge ....................................................................................................................................................170
Sensing Transformer Ratings and Configuration..................................................................................170
Startup Functions ..................................................................................................................................171
Device Information.................................................................................................................................172
Display Units..........................................................................................................................................174
Security....................................................................................................................................................175
Password Access..................................................................................................................................175
Port Security..........................................................................................................................................176
Login and Access Controls....................................................................................................................177
Timekeeping ............................................................................................................................................179
Time and Date Format...........................................................................................................................179
Daylight Saving Time Adjustments........................................................................................................179
Network Time Protocol (NTP) ...............................................................................................................179
IRIG .......................................................................................................................................................179
Testing......................................................................................................................................................183
Real-Time Metering Analysis ................................................................................................................183
Frequency Response ............................................................................................................................185
Time Response .....................................................................................................................................186
Step Response Analysis........................................................................................................................188
Analysis Options....................................................................................................................................189
CAN Communication..............................................................................................................................191
Introduction............................................................................................................................................191
CAN Parameters ...................................................................................................................................191
Modbus™Communication......................................................................................................................195
Introduction............................................................................................................................................195
Modbus Modes of Operation.................................................................................................................196
Detailed Message Query and Response for RTU Transmission Mode ................................................199
Data Formats.........................................................................................................................................202
Secure DECS-250 Login via Modbus....................................................................................................204
Modbus Parameters ..............................................................................................................................205
PROFIBUS Communication ...................................................................................................................237
Data Types ............................................................................................................................................237
Setup .....................................................................................................................................................240
PROFIBUS Parameters.........................................................................................................................240
Maintenance ............................................................................................................................................287
Storage..................................................................................................................................................287
Preventive Maintenance........................................................................................................................287
Cleaning the Front Panel.......................................................................................................................288
Troubleshooting.....................................................................................................................................288
Support..................................................................................................................................................289
Specifications..........................................................................................................................................291
Operating Power....................................................................................................................................291
Control Power........................................................................................................................................291
Generator and Bus Voltage Sensing.....................................................................................................292
Generator Current Sensing ...................................................................................................................292
Accessory Inputs ...................................................................................................................................293
Contact Inputs .......................................................................................................................................293
Communication Ports ............................................................................................................................293
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vi 9440300990 Rev G
Preface DECS-250
IRIG Time Synchronization Input ..........................................................................................................294
Contact Outputs.....................................................................................................................................294
Field Power Output................................................................................................................................295
Regulation .............................................................................................................................................295
Parallel Compensation ..........................................................................................................................295
Generator Protection Functions ............................................................................................................296
Field Protection Functions.....................................................................................................................297
Synchronism Check (25) Protection......................................................................................................297
Startup...................................................................................................................................................298
Voltage Matching...................................................................................................................................298
On-Line Overexcitation Limiting ............................................................................................................298
Off-Line Overexcitation Limiting............................................................................................................299
Sequence of Events Recording (SER)..................................................................................................299
Data Logging (Oscillography)................................................................................................................299
Environment ..........................................................................................................................................299
Type Tests.............................................................................................................................................299
Patent ....................................................................................................................................................300
Physical .................................................................................................................................................300
Regulatory Standards............................................................................................................................300
Analog Expansion Module.....................................................................................................................303
General Information...............................................................................................................................303
Features ................................................................................................................................................303
Specifications ........................................................................................................................................303
Installation .............................................................................................................................................305
Communications....................................................................................................................................312
Functional Description...........................................................................................................................312
Metering.................................................................................................................................................316
Maintenance..........................................................................................................................................319
Contact Expansion Module....................................................................................................................321
General Information...............................................................................................................................321
Features ................................................................................................................................................321
Specifications ........................................................................................................................................321
Installation .............................................................................................................................................323
Communications....................................................................................................................................330
Functional Description...........................................................................................................................330
Metering.................................................................................................................................................332
Maintenance..........................................................................................................................................332
Revision History......................................................................................................................................333
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9440300990 Rev G 1
DECS-250 Introduction
Introduction
DECS-250 Digital Excitation Control Systems offer precise excitation control and machine protection in a
compact package. DECS-250 adaptability to many applications is assured through configurable contact
inputs and outputs, flexible communication capabilities, and programmable logic implemented with the
provided BESTCOMSPlus®software.
Features and Functions
DECS-250 features and functions include:
•Five excitation control modes:
oAutomatic Voltage Regulation (AVR)
oField Current Regulation (FCR)
oField Voltage Regulation (FVR)
oPower Factor Regulation (PF)
oVar Regulation (var)
•Three pre-position setpoints for each excitation control mode
•Internal tracking between operating mode setpoints and external tracking of a second DECS
excitation setpoint
•Two PID stability groups with Auto Tune feature
•Remote setpoint control input accepts analog voltage or current control signal
•Real-time metering
•Optional automatic synchronizer
•Optional integrated power system stabilizer (PSS)
oGenerator or motor control modes, accommodates phase rotation changes between
modes
oSpeed and power sensing or speed-only sensing
oTwo wattmeter or three-wattmeter methods of power measurement
•Soft start and voltage buildup control
•Five limiting functions:
oOverexcitation: summing point and takeover
oUnderexcitation
oStator current
oReactive power (var)
oUnderfrequency
•Twenty protection functions:
oGenerator undervoltage (27)
oGenerator overvoltage (59)
oLoss of sensing (LOS)
oOverfrequency (81O)
oUnderfrequency (81U)
oReverse power (32R)
oLoss of excitation (40Q)
oField overvoltage
oField overcurrent
oLoss of PMG
oExciter diode failure
oSync-check (25)
oEight configurable protection elements
•IRIG or network time synchronization
•Sixteen contact sensing inputs
oTwo fixed-function inputs: Start and Stop
oFourteen programmable inputs
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2 9440300990 Rev G
Introduction DECS-250
•Twelve contact outputs
oOne, fixed-function output: Watchdog (SPDT configuration)
oEleven programmable outputs
•Flexible communication
oSerial communication through front-panel USB port
oModbus communication through RS-485 port or Modbus TCP
oEthernet communication through an optional copper or fiber optic port
oCAN communication with an ECU (engine control unit), optional AEM-2020 Analog
Expansion Module, or optional CEM-2020 Contact Expansion Module
oOptional PROFIBUS communication protocol
•Data logging, sequence of events recording, and trending
•Optional CEM-2020 Contact Expansion Module provides:
oTen contact inputs
oEighteen contact outputs (CEM-2020H) or 24 contact outputs (CEM-2020)
oCustomizable input and output functions assigned through BESTlogic™Plus
programmable logic
oCommunication via CAN protocol
•Optional AEM-2020 Analog Expansion Module provides:
oEight analog inputs
oEight resistive thermocouple device (RTD) inputs
oTwo thermocouple inputs
oFour analog outputs
oCustomizable input and output functions assigned through BESTlogicPlus programmable
logic
oCommunication via CAN protocol
Application
The DECS-250 is intended for synchronous generator applications where the DECS-250 controls the
generator output through the application of regulated excitation power to the field. It provides regulated dc
excitation power based on the monitored generator voltage and current and a regulation setpoint
established by the user.
Excitation power is supplied from the DECS-250 by means of a filtered, switching power module that uses
pulse-width modulation. It is capable of supplying 15 Adc continuously at a nominal voltage of 32, 63, or
125 Vdc. With nominal operating power applied, it has a forcing capability of 30 Adc for 10 seconds.
Package
A single, compact package contains all excitation control and power components.
A front panel HMI provides local annunciation and control through a backlit liquid crystal display (LCD),
light-emitting diodes (LEDs), and pushbuttons. Remote annunciation and control is provided through a
flexible communication interface which accommodates Ethernet, Modbus, optional PROFIBUS, and the
optional Interactive Display Panel (IDP-800).
Optional Features and Capabilities
DECS-250 optional features and capabilities are defined by a combination of letters and numbers that
make up the style number. The model number and style number describe options and characteristics in a
specific device and appear on a label affixed to the device.
Style Number
The style number identification chart in Figure 1 defines the electrical characteristics and operational
features available in the DECS-250.
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9440300990 Rev G 3
DECS-250 Introduction
Figure 1. DECS-250 Style Chart
Storage
If a DECS-250 will not be placed in service right away, store it in the original shipping carton in a
moisture- and dust-free environment. The temperature of the storage environment must be within the
range of –40 to 85°C (–40 to 185°F).
Electrolytic Capacitor Considerations
The DECS-250 contains long-life aluminum electrolytic capacitors. For a DECS-250 kept in storage as a
spare, the life of these capacitors can be maximized by energizing the device for 30 minutes once per
year. Refer to the energizing procedures provided in Maintenance.
When energizing the DECS-250 from a low impedance source (such as a wall outlet), use of an Inrush
Current Reduction Module (ICRM) is recommended to prevent damage to the DECS-250. For a detailed
description of the Inrush Current Reduction Module, refer to Basler publication 9387900990. ICRM
connections are illustrated in Typical Connections.
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4 9440300990 Rev G
Introduction DECS-250
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Controls and Indicators
All controls and indicators are located on the front panel and consist of pushbuttons, LED indicators, and
a liquid-crystal display (LCD).
Front Panel Illustration and Description
DECS-250 controls and indicators are illustrated in Figure 2 and described in Table 1. The locators and
descriptions of Table 1 correspond to the locators shown in Figure 2.
Figure 2. Front Panel Controls and Indicators
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Table 1. Front Panel Control and Indicators Descriptions
Locator
Description
A
Display. The liquid crystal display (LCD) serves as a local source of information
provided by the DECS-250. The LCD displays operating setpoints, loop gains,
metering, protection functions, system parameters, and general settings. The 128 by
64 dot pixel, backlit LCD displays white characters on a blue background.
B
Pre-Position Indicator. This red light emitting diode (LED) lights when the active mode
setpoint is at any of the three pre-position (predefined) settings.
C
Limit Indicators. Two red LEDs indicate when the active mode setpoint reaches the
minimum or maximum value.
D
Scrolling Pushbuttons. These four buttons are used to scroll up, down, left, and right
through the menus displayed on the LCD (locator A). during an editing session, the left
and right scrolling pushbuttons select the variable to be changed and the up and down
scrolling pushbuttons change the value of the variable.
E
Reset Pushbutton. This button cancels editing sessions, resets alarm annunciations
and latched alarm relays, and can be used for quick access to the metering screen.
F
Communication Port. This type B USB jack connects the DECS-250 with a PC
operating BESTCOMSPlus®for local communication. BESTCOMSPlus is supplied with
the DECS-250.
Caution
In accordance with the guidelines defined in USB standards, the USB
port on this device is not isolated. To prevent damage to a connected
PC or laptop, the DECS-250 must be properly tied to ground.
G
Edit Pushbutton. Pressing this button starts an editing session and enables changes to
DECS-250 settings. At the conclusion of the editing session, the Edit pushbutton is
pressed to save the settings changes.
H
Null Balance Indicator. This green LED lights when the setpoint of the inactive
operating modes (AVR, FCR, FVR, var, and PF) match the setpoint of the active
mode.
I
PSS Active Indicator. This red LED lights when the integrated power system stabilizer
is enabled and can generate a stabilizing signal in response to a power system
disturbance.
J
Internal Tracking Indicator. This red LED lights when any inactive mode (AVR, FCR,
FVR, Var, or Power Factor) is tracking the setpoint of the active mode to achieve a
“bumpless” transfer when changing active modes.
Menu Navigation
The DECS-250 provides local access to DECS-250 settings and metering values through a menu
structure displayed on the front panel LCD. An overview of the menu structure is illustrated in Figure 3.
Movement through the menu structure is achieved by pressing the four scrolling pushbuttons.
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Figure 3. Menu Structure Overview
Adjusting Settings
A setting adjustment is made at the front panel by performing the following steps.
1. Navigate to the screen listing the setting to be changed.
2. Press the Edit button and enter the appropriate username and password to gain the needed level
of security access. (Information about implementing and using username and password
protection is provided in the Security section of this manual.)
3. Highlight the desired setting and press the Edit button to view the setting editing screen. This
screen lists the setting range or the permissible setting selection.
4. Use the scrolling pushbuttons to select the setting digits/selections and adjust/change the setting.
5. Press the Edit button to save the change.
Display Setup
BESTCOMSPlus®Navigation Path: Settings Explorer, General Settings, Front Panel HMI
HMI Navigation Path: Settings, General Settings, Front Panel HMI
Front panel display appearance and behavior can be customized to meet user preferences and site
conditions. These BESTCOMSPlus settings are illustrated in Figure 4.
LCD
LCD setup includes a contrast adjustmentAto suit the viewing angle used or compensate for
environmental conditions. The ability to reverse the display colorsBis provided to accommodate lighting
conditions and user preferences.
Sleep Mode
Sleep modeCreduces the demand on control power by turning off the LCD backlight when no pushbutton
activity is seen for the duration of the LCD Backlight Timeout settingD.
Language
Language modules are available for the DECS-250. Once a language module is implemented it can be
enabled via the Language Selection settingE.
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Screen Scrolling
The display can be set to automatically scroll through a user-selected listFof metered values. This feature
is enabled and disabled with the Enable Scroll settingG. The rate at which scrolling occurs is configured
with the Scroll Time Delay settingH.
Figure 4. Front Panel HMI Settings
AContrast Value (%): Adjustable from 0 to 100 in 1% increments.
BInvert display: Deselect for white characters on a blue background. Select for blue characters on a white
background.
CSleep Mode: Enable or disable.
DLCD Backlight Timeout: Adjustable from 0 to 120 seconds in 1 second increments.
ELanguage Selection: Select English, Russian, Spanish, or German.
FScrollable Metering Settings: Select from main categories of GV Primary, GC Primary, CC Primary,
Frequency, Power Primary, PF Primary, Energy Primary, BV Primary, Field Primary, PSS Primary,
Synchronization Primary, Aux Input, Tracking, Real Time Clock, Contact Inputs, Contact Outputs, or
Device ID. Follow this selection by the desired parameters within each category.
GEnable Scroll: Enable or disable.
HScroll Time Delay (s): Adjustable from 1 to 600 seconds in 1 second increments.
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Power Inputs
Power is applied to two separate inputs: control power and operating power. The control power input
supplies power to an internal power supply that provides power for logic, protection, and control functions.
The power stage uses the operating power input as the source for the converted excitation power that it
applies to the field.
Control Power
Two inputs supply the DECS-250 with control power. One input accepts dc control power and the other
input accepts ac control power. The level of acceptable control power voltage is determined by the style
number. One of two levels is possible. Style Lxxxxxx indicates a nominal voltage of 24 or 48 Vdc and
accepts a voltage range of 16 to 60 Vdc. Style Cxxxxxx indicates a nominal voltage of 125 Vac/Vdc and
accepts a voltage range of 90 to 150 Vdc and 82 to 132 Vac (50/60 Hz). One input (either dc or ac) is
sufficient for operation but two inputs provide redundancy (for style Cxxxxxx only). When both control
power inputs are used, an isolation transformer is required for the ac input. DC control power is applied at
terminals BATT+ and BATT–. AC control power is applied at terminals L and N.
Operating Power
Operating power is applied at terminals A, B, and C. To achieve the desired level of excitation, the
appropriate operating power input voltage must be applied. Table 2 lists the acceptable operating power
voltage ranges for the DECS-250. The operating power frequency range for the DECS-250 is 50 to 500
hertz for all voltages.
Table 2. DECS-250 Operating Power Specifications
Desired Nominal
Excitation Power Voltage
Applied Operating
Power Voltage Range
32 Vdc
56 to 70 Vac
63 Vdc
100 to 139 Vac, or 125 Vdc
125 Vdc
190 to 277 Vac, or 250 Vdc
Caution
If using 277 Vac operating power input, the connection must be
configured as L-N single-phase or equipment damage may result.
Inrush Current Reduction Module (ICRM)
During DECS-250 power-up, the optional ICRM prevents damage to the DECS-250 by limiting inrush
current to a safe level. When operating power is applied to the DECS-250, the ICRM limits the inrush
current by adding a high level of resistance between the DECS-250 and the power source. Once the
inrush current subsides, the series resistance diminishes quickly to allow nominal, steady-state current
flow.
Caution
To prevent damage to the DECS-250, the use of the ICRM is
recommended when using a low impedance source, such as a wall
outlet.
For a detailed description of the Inrush Current Reduction Module, refer to Basler publication
9387900990. ICRM connections are illustrated in Typical Connections.
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Power Stage
The power stage supplies regulated dc excitation power to the field of a brushless exciter. Excitation
power is supplied at terminals F+ and F–.
DECS-250 power stage operating power accepts single- or three-phase ac power from a transformer or
PMG. DC power from the station batteries or the armature of a dc exciter is also acceptable. Power Stage
operating power is applied at terminals A, B, and C. The GND terminal serves as a ground connection.
The DECS-250 power stage supplies excitation power by means of a filtered, switching power module
that uses pulse-width modulation. It is capable of supplying 15 Adc continuously at nominal voltages of
32, 63, or 125 Vdc. With nominal operating voltage applied, it has a forcing capability of 30 Adc for 10
seconds.
Nominal DECS-250 operating power levels include 60 Vac for a 32 Vdc continuous exciter field
requirement, 120 Vac or 125 Vdc for a 63 Vdc requirement, or 240 Vac or 250 Vdc for a 125 Vdc
requirement.
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