Basler Electric DECS-250-LN1SN1N Digital Excitation Control System

Basler Electric DECS-250-LN1SN1N Digital Excitation Control System

The Basler Electric DECS-250-LN1SN1N is a Digital Excitation Control System engineered to regulate, monitor, and protect brushless or static-excited synchronous generators and synchronous motors. Built around a high-speed pulse-width-modulated (PWM) power stage rated at 15 Adc continuous (20 Adc continuous up to 55°C ambient) with a 30 Adc 10-second field forcing capability, this unit stabilizes terminal voltage, reactive power (var), and power factor during heavy marine and industrial load transients.

Housed in a ruggedized, vibration-tested chassis with conformal coating on critical internal circuit boards, the DECS-250-LN1SN1N integrates true-RMS 3-phase voltage and current sensing, 20 ANSI-standard generator protection elements, five operational limiters, and Ethernet-based load sharing into a single switchboard-mountable assembly.

Model Details

• Manufacturer: Basler Electric Company (Highland, IL, USA)
• Series / Model: DECS-250
• Manufacturer Part Number (MPN): DECS-250-LN1SN1N

Input / Output Ratings & Electrical Architecture

• Control Power Input (Style L): 16 to 60 Vdc (24 Vdc or 48 Vdc nominal), max burden 30 W / 50 VA.
• AC Operating Power Input (PWM Stage): 1-phase or 3-phase, 50 to 500 Hz. Accepts 60 Vac nominal (for 32 Vdc field output), 120 Vac nominal (for 63 Vdc field output), or 240 Vac nominal (for 125 Vdc field output). Also supports DC-fed power input.
• DC Exciter Field Output:
  • Continuous Rating: 15 Adc up to 70°C (158°F); 20 Adc up to 55°C (131°F).
  • Forcing Rating (10 Seconds): 30 Adc.
  • Nominal Output Voltages & Minimum Field Resistance: 32 Vdc (min. 2.13 Ω), 63 Vdc (min. 4.20 Ω), 125 Vdc (min. 8.33 Ω).
• Generator & Bus Voltage Sensing: 1-phase or 3-phase True RMS, 50/60 Hz nominal; selectable ranges of 100/120 Vac ±10%, 200/240 Vac ±10%, 400/480 Vac ±10%, and 600 Vac ±10%; burden < 1 VA per phase.
• Generator Current Sensing: 1-phase or 3-phase plus dedicated cross-current compensation (CCC) CT input; 1 Aac (< 5 VA burden) or 5 Aac (< 10 VA burden) nominal at 50/60 Hz.
• Discrete Contact Inputs: 16 dry-contact sensing inputs (12 Vdc, 4 mA nominal wetting current) — 2 fixed (Start/Stop) and 14 programmable via BESTlogic™Plus.
• Discrete Output Relays: 12 total — 11 programmable Form A (SPST-NO) relays and 1 dedicated Form C (SPDT) Watchdog relay; rated 7 A resistive make/break/carry at 24/48/125 Vdc and 120/240 Vac.
• Auxiliary Analog Input: 1 isolated input configurable for -10 to +10 Vdc or 4 to 20 mAdc remote setpoint/trim control.

Technical Details

Compatibility

• Excitation Topologies: Brushless permanent magnet generator (PMG) exciters, auxiliary winding (AREP) exciters, shunt-excited alternators, and DC-fed static exciter systems.
• Marine & Industrial Alternators: Leroy-Somer (LSA/LSAM series), Stamford / AvK (P7, P80, DIG/DSG series), Caterpillar / Olympian marine auxiliaries, Cummins Onan marine gensets, Wärtsilä, MAK, and Hyundai-Himsen auxiliary/propulsion alternators.
• Basler Expansion & Protection Modules:
  • AEM-2020 Analog Expansion Module (adds 8 analog inputs, 8 RTD inputs, 2 K-type thermocouple inputs, and 4 analog outputs over CAN).
  • CEM-2020 / CEM-2020H Contact Expansion Modules (adds 10 contact inputs and up to 24 contact outputs over CAN).
  • BE1-11g Generator Protection System and DGC-2020 / DGC-2020HD Digital Genset Controllers.
  • SGC-250 Synchronous Generator Controller assemblies (single or dual-redundant configurations).

Features

1. Five Closed-Loop Regulation Modes with Auto-Tuning: Supports Automatic Voltage Regulation (AVR), Field Current Regulation (FCR), Field Voltage Regulation (FVR), Power Factor (PF), and Reactive Power (var) control with two independent PID stability groups and automated pole-placement Auto Tune.
2. High-Response 15A/20A PWM Power Stage: Delivers rapid field forcing up to 30 Adc for 10 seconds across 32, 63, or 125 Vdc field windings, maintaining tight terminal voltage recovery during large marine thruster or cargo pump motor starts.
3. Integrated Machine Protection & Limiters: Built-in ANSI protection suite—including 27/59 (under/overvoltage), 81O/U (over/underfrequency), 32R (reverse power), 40Q (loss of excitation), 59F/51F (field overvoltage/overcurrent), Exciter Diode Monitor (EDM), Loss of PMG, and 25 Sync Check—paired with temperature-compensated Overexcitation (OEL) and Stator Current limiters.
4. Ethernet Digital Load Sharing: Enables zero-droop reactive load sharing across paralleled generators via 100Base-T Ethernet, eliminating complex analog cross-current compensation CT wiring errors.
5. BESTCOMSPlus® & BESTlogic™Plus Programmability: Simplifies commissioning with drag-and-drop programmable logic gates, real-time strip-chart oscillography, sequence-of-events recording (SER), and front-panel USB access.

Part Number Cross-References

• Direct Form/Fit Predecessor: Basler Electric DECS-200 series (identical panel cutout, rear mounting stud pattern, and external tracking compatibility).
• Style Variants in DECS-250 Family:
  • DECS-250-LN1CN1N (Identical electrical spec with screw-compression terminals instead of spring-clamp terminals).
  • DECS-250-CN1SN1N (High-voltage 120 Vac / 125 Vdc control power supply variant).
  • DECS-250-LN1SN1P (Adds PROFIBUS DP communication protocol).
• Packaged Assembly Equivalent: Basler Electric SGC-250 (pre-wired panel assembly incorporating the DECS-250).

Frequently Asked Questions

What does the style code LN1SN1N mean on the Basler DECS-250?

The LN1SN1N suffix defines the factory hardware and firmware configuration: L specifies a 16–60 Vdc (24/48 Vdc nominal) control power supply, N indicates no Power System Stabilizer, 1 denotes internal autotracking, S specifies spring-clamp compression terminals, N indicates no internal auto-synchronizer, 1 provides 100Base-T copper Ethernet, and N denotes no secondary PROFIBUS module.

Is the Basler DECS-250-LN1SN1N approved for marine classification society vessels?

Yes. The Basler DECS-250 holds marine type approvals from the American Bureau of Shipping (ABS), Det Norske Veritas / Germanischer Lloyd (DNV•GL), and Bureau Veritas (BV), and is salt-fog tested to MIL-STD-810E Method 509.3 for engine-room and switchboard environments.

Can the DECS-250-LN1SN1N replace an older Basler DECS-200 AVR?

Yes. The DECS-250 shares the exact same front-panel footprint, panel cutout dimensions, and rear mounting stud pattern as the legacy DECS-200 series, making it a direct mechanical and functional upgrade with enhanced metering, Ethernet load sharing, and USB programming.

What is the maximum continuous output current of the DECS-250-LN1SN1N?

The PWM power stage is rated for 15 Adc continuous at ambient temperatures up to 70°C (158°F), and up to 20 Adc continuous when ambient temperatures remain at or below 55°C (131°F). It also supports 30 Adc field forcing for up to 10 seconds during transient motor starting.

Which software is required to program and tune the DECS-250-LN1SN1N?

Configuration, PID auto-tuning, BESTlogic™Plus programmable I/O mapping, and real-time oscillography are performed using Basler Electric’s BESTCOMSPlus® PC software via the front-panel USB Type-B port or rear 100Base-T Ethernet port.