Generators

Question 1

The NEC provides key design requirements for a generator system. Where are these design requirements found?

Answer 1

Article 445 Generators
Article 700 Emergency Systems
Article 701 Legally Required Standby Systems
Article 702 Optional Standby Systems
Article 705 Interconnected Electrical Power Production Sources
Article 708 Critical Operations Power Systems

Question 2

If a generator is installed indoors what are potential concerns?

Answer 2

• The generator set and ancillary equipment is accessible for operation and maintenance
• The load bearing capacity of the building to house the generator
• construction must comply with applicable codes and regulations (noise, emissions, vibrations, etc)
• room layout must satisfy manufacturer’s requirements for combustion air-intake, exhaust, ventilation, fuel supply
• all equipment being co-located with generator will need to be evaluated to ensure they can operate in the same environmental conditions

Question 3

If a generator is installed outdoors, what must be provided?

Answer 3

-weatherproof enclosure

May also need:

• acoustical lining and silencer grade
• fuel storage

Question 4

True or False

Load characteristics and generator system response capabilities are important design parameters that must be considered.

Answer 4

True

Question 5

How does nonlinear loads impact generators?

Answer 5

Nonlinear loads include computers, UPSs, electronic lighting ballasts, electronic equipment, and VFDs.
Nonlinear loads typically introduce harmonics in the electrical system, and depending on the magnitude of harmonics and the total harmonic distortion present, the generator set will be derated to reliably support the loads.

Question 6

How does linear loads impact generators?

Answer 6

Linear loads include heaters, motors, and transformers.
Linear loads, such as large motors, have a high starting current that require the generator set to be oversized in some cases to overcome the demand.

Question 7

Before selecting a fuel type, what factors should a design engineer consider?

Answer 7

• availability of physical space onsite
• reliability of fuel supply
• onsite storage limitations and associated hazards
• compliance with codes and regulations
• cost
• driven-generator performance

Question 8

What is a paralleled generator system?

Answer 8

A paralleled generator system uses multiple generators to form a large-capacity generator system. Paralleling multiple generators is achieved by synchronizing the output of the generators and connecting them to a paralleling switchgear common bus. Synchronizing the output of the generators requires all of the paralleled generators to have the same voltage, frequency and phase rotation.

Question 9

What are the advantages of a paralleled generator system?

Answer 9

• Reliability
• availability
• expandability
• fuel cost savings

Question 10

To perform manual generator-sizing calculations, what information is required for each load?

Answer 10

• Load starting information : starting kilowatts (SkW), starting kilovolt-amperes (SkVA), and starting power factor (PF)
• Load running information: running kilowatts (RkW), running kilovolt-amperes (RkVA), and running power factor (PF)