Application Engineering

Please read the Warranty Statement carefully before proceeding with any design or ordering materials or labor.

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Understanding the operation of various components of the generator is vital for making the correct choice of equipment. Brushless alternators and transient performance are discussed together with the various excitation systems and their effects on the generator performance.

The chapter describes engine governing and starting systems and relay and microprocessor-based generator set control systems.

Accessories such as control annunciators, circuit breakers, batteries and chargers, exhaust systems, canopies, lubrication oil level maintenance, standby heating devices, fuel tanks, vibration isolators and power switching equipment are also discussed.

Requirements and Recommendations:

• Alternator winding temperature rises are classified in degrees Celsius over an ambient temperature of 40°C. Temperature rises of 80°C, 105°C or 125°C are termed Class B, F and H respectively for continuous ratings. Alternator air intake temperatures greater than 40°C will result in higher temperature rises, requiring derate of the alternator output to avoid damage.
• A winding temperature rise of 150°C above 40°C is allowed for machines rated for standby duty, while lower temperature rise alternators are appropriate for long-hour duty generator sets.
• Separately-excited generators using a Permanent Magnet Generator will sustain fault current for a specified time and will be more robust to non-linear loads.
• Self-excited generators are a lower-cost option that is suitable for less arduous electrical applications where short circuit coordination, motor starting and non-linear load performance are not critical factors.
• Most Cummins Power Generation products incorporate electronic governing systems that permit isochronous speed control. Some smaller products below 250 kVA rated output may be fitted with mechanical governing systems.
• The PowerCommand control system integrates engine and alternator control and monitoring functions with protection. Full authority electronic control is available on some engines giving enhanced performance and emission control.
• The PowerCommand paralleling system provides the same level of integrated control with active paralleling and active and reactive load sharing.
• Starting batteries must be located as close as possible to the starter motor to minimize starting circuit resistance.
• Battery enclosures must be properly ventilated.
• Batteries must be sized appropriately for the ambient conditions. Extremely cold conditions may require a significantly larger battery capacity.
• Do not site enclosed generators within buildings unless this has been approved by the Cummins Power Generation distributor.
• Coolant heaters will enable engines to start immediately at low temperatures. Alternator and control enclosure anti-condensation heaters may be required even in tropical conditions. These will require a separate auxiliary electrical supply.
• Observe data sheet limits for fuel pressures and temperatures, particularly when using a remote fuel tank.
• For remote cooled generators, ensure that the cooling system chosen is suitable for the duty required and the ambient conditions. Observe data sheet limits for coolant temperatures and pressures, including static head.

For information regarding your application contact your nearest distributor.

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