Cummins 4BTA3.9G2 Diesel Generator Set – 66 kVA, Turbocharged, Leroy Somer/Stamford Alternator

The Cummins 4BTA3.9G2 Diesel Generator Set offers compact and efficient power generation for commercial and light industrial operations. Driven by a rugged 4-cylinder Cummins engine, this set utilizes a turbocharged and aftercooled air system for improved combustion and performance, while maintaining low emissions and fuel consumption.

The 3.9-liter engine runs on a 4-stroke cycle with a bore and stroke of 102 mm × 120 mm. A BYC PB electronic governor ensures precise speed regulation, and the fuel system includes spin-on fuel filters and water separators for enhanced reliability and maintenance efficiency. The starting voltage is 12V, supported by a 37A alternator for battery charging, with SAE 3 / 11.5 flywheel configuration for generator coupling.

The alternator is the AQT TAL-042-E, available from Leroy Somer or Stamford, delivering 66 kVA (53 kW) output with 4-pole construction and 2/3 winding pitch. Class H insulation ensures high thermal durability, while self-excitation and the R220 AVR provide stable voltage control within ±1%. The alternator is IP23 protected, with THF < 3.5% and TIF < 50, making it suitable for both general-purpose loads and sensitive equipment. Cooling is facilitated by a 0.25 m³/sec airflow.

Specifications:

– Engine Make: Cummins
– Engine Model: 4BTA3.9G2
– Engine Type: 4-Cylinder, In-line, Diesel
– Aspiration: Turbocharged & Aftercooled
– Cycle: 4 Stroke
– Bore x Stroke: 102 mm × 120 mm
– Displacement: 3.9 Litres
– Governing Type: BYC PB / Electronic Governor
– Flywheel Dimensions: SAE 3 / 11.5
– Battery Charging Alternator: 37 AMP, 12V
– Starting Voltage: 12V
– Fuel System: BYC PB with spin-on fuel filters and water separators
– Fuel Filter: Spin-on with water separator
– Lubrication System: Spin-on lube oil filter
– Lube Oil Capacity: Approx. 10–12 litres (see engine manual)

– Alternator Make: AQT | Leroy Somer / Stamford
– Alternator Model: TAL-042-E
– Output Rating: 66 kVA
– Rated Output: 53 kW
– Number of Poles: 4
– Winding Pitch: 2/3
– Insulation Class: H
– Temperature Rise: 125°C @ 40°C ambient
– Ingress Protection Rating: IP23
– Excitation System: Self-Excited
– AVR Model: R220
– Voltage Regulation: ±1%
– Harmonic Distortion (THF): < 3.5%
– Telephone Influence Factor (TIF): < 50
– Cooling Air Flow: 0.25 m³/sec
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