Glossary of Terms

Air-Cooled System: An air-cooled system is a system to cool generators. Generators while operating produce a lot of heat, requiring the interior of the generator to be cooled constantly to protect it from damage. Air circulation is used to bring the interior temperature down. Cool air is taken from the atmosphere and blown into the genset. Relatively smaller generators use an air-cooled system to keep the generator running efficiently.

AlternatorAn alternator is also known as a gen end or generator end. It is the component that converts mechanical energy into electrical power using electromagnetic induction. It can be a stand-alone unit, or it can be part of a genset.

Alternating Current (AC): Current flowing from zero to a positive maximum and then back to zero, flows down again to a negative maximum to return back to zero.

Amperage: Measurement of the strength or intensity of an electric current in ampere.

ATS: An automatic transfer switch, or ATS switch, connects your standby generator to your home. Normally, electricity flows from the utility to your home’s main electrical panel, where it powers all your circuits. Automatic transfer switches act as the “brain” of your entire electrical system.

BAAQMDBay Area Air Quality Management District.

Backup Generators: Used for fulfilling emergency load requirement during sudden shortage of power.

Battery Charger: The battery charger keeps the generator battery charged by supplying it with a precise ‘float’ voltage. If the float voltage is very low, the battery will remain undercharged.

Battery Charge Rectifier: This component changes AC voltage from the battery charge windings to DC voltage for charging a battery.

Block Heater: Reduces Engine Wear: With the temperatures maintained between 100 and 120 degrees, the oil pressure is elevated enough to provide sufficient lubrication on startup to limit the metal-on-metal contact associated with a cold start. Reduces Emissions: A cold engine does not run efficiently.

Brush: This graphite or copper made conducting element maintains sliding electrical contact between static and moving element.

Cam Loks: Cam-Lok® cables are essentially just a safe method of making proper electrical connections in the use of generator and tap-box (temporary) or major equipment connectivity such as motors and power distribution.

Continuous Power Rating: Continuous power rating is used when power load is constant (at 100%) for an unlimited period of time each year. The non-varying load factor is 70%-100% of the published continuous power rating. This power rating system is used when the power grid is inaccessible, especially for applications in the mining and agricultural industries.

CurrentThe flow of particles charged by electricity.

Diesel Engine: An internal combustion engine in which fuel oil is burnt by heat produced from air compression. The most commonly bought Industrial Diesel Engines are either Rebuilt Diesel Engine or Used Diesel Engine.

Diesel generator: A diesel generator generates electrical power through the use of a diesel engine and an alternator. Used most often as a backup generator, diesel generators are also used at locations with no access to a power grid. Diesel generators are quick and — if for backup purposes — start automatically during power outages.

Direct Current (DC): Current produced by storage battery or electromagnetic induction, with a unidirectional flow.

Distribution: Supply of lower voltage electric power from a centralized substation to the point of end use.

Docking Station: A docking station and switch is a system where a facility installs a docking station that can be connected to a mobile generator quickly and easily. In the event of utility power failure, a mobile generator can be deployed and hooked up to the docking station to provide power.

Dual Fuel System: A dual fuel system is sometimes referred to as a bi-fuel generator. It is a genset that can simultaneously operate on diesel and natural gas.

Emergency Standby Power (ESP) Rating: An ESP rating refers to a standby generator with a typical usage of 50 hours per year and maximum usage of 200 hours per year with varying loads. Average variable load factor is 70% of the ESP rating. No overload capability.

Emissions Rating: In the U.S., emissions ratings are used to confirm emission standards are met. There are certain legal requirements — most of which are regulated by the Environmental Protection Agency — that govern air pollutants (such as nitrogen oxides and carbon monoxide) released into the atmosphere via generators.

Enclosure: An enclosure is a housing of a genset. It is an assembly used to protect the genset from damage caused by weather, animals, and other harmful elements. Most enclosures are NEMA 3R-rated and are equipped with locks that prevent unauthorized persons from tampering with the genset.

Frequency: Frequency is the number of electrical waves that pass by per second. Frequency is measured in cycles per second known as Hertz (Hz). The US standard is 60 Hz.

Generator: A generator is a device that converts mechanical energy — a type of fuel using, for example, diesel or natural gas — into electrical energy used to power other machines and places. The electrical current results in either direct current (DC) or alternating current (AC). There are different types of generators with the primary difference being the fuel it uses to power units.

Generator End: A generator end is also referred to as an alternator or gen end. It is the component in a generator that converts mechanical energy into electrical energy.

Generator RPM: A generator’s revolutions per minute (RPM) is the number of turns in one minute needed to reach the required frequency of 60 Hz. Most generator engines must operate at 1800 or 3600 RPM to produce 60 Hz. Generally speaking, 1800 RPM sets are common for prime generators while 3600 RPM sets are for stationary units.

Generator Set Ratings: A generator set rating is a system of rating generators so that you can purchase or lease the generator that is best suited for your intended purpose. The ratings fit an application’s needs to optimum reliability, costs, and overall performance.

Genset: A genset is interchangeable with a generator (a less accurate term), generator set, or engine generator. A genset is an apparatus consisting of four main parts: (1) an engine, (2) alternator or generator end, (3) a control panel, and (4) a skid. It is used to convert energy to electric power.

Grid: In order to meet the power needs at the grids in different points, a system of power lines and generators, interconnected is used. This is a grid.

Hertz (Hz)unit of frequency that is equal to one cycle per second.

Kilowatt (KW)Kilowatt is power needed to do work at the rate of 1000 joules per second.

Kilowatt-hour (KWhr): Total number of kilowatts used per hour. Or 3,600,000 joules.

KVA: KVA is kilovolt-ampere and is the unit of apparent power. KVA is used for measuring the power consumption of non-resistive equipment such as motors, computers, and most non-incandescent lighting.

kW Rating: A kW rating is based on the horsepower of an engine and refers to the power output a generator is capable of supplying. A kW rating is determined by the horsepower rating of the engine times .746.

Liquid-Cooled System: A liquid-cooled system employs a radiator, water pump, and oil or a coolant to maintain the temperature of the generator’s interior. The pump distributes the cooling liquid to the generator’s engine. A liquid-cooled system is more durable but more expensive and is usually reserved for generators over 22 kilowatts.

Load: Load is that the amount of electric power used by devices associated to electricity generating system.

Load Bank: A load bank generator test puts a generator under varying load conditions and sees how the machine reacts to the power draw. While you can use other means of testing generators, load banks offer the most accurate means of testing the power equipment engine and electrical systems.

Mission Critical Standby: The mission critical standby rating means a generator’s typical usage is 200 hours per year and maximum usage is 500 hours per year with varying loads. Average variable load factor is 85% of the Standby rating. No overload capability. Typical applications are data centers and health care facilities.

MTS: A manual transfer switch connects the house’s electrical circuits to the generator. During a power outage, you can use it to switch on the backup power. Any appliance connected to the circuit will run on backup power till electricity is restored. The manual transfer switch can be installed both indoors and outdoors.

Natural Gas Generator: A natural gas generator is a generator that converts natural gas into electrical power. These generators are used both as portable generators and as backup generators.

Off-Peak: A specific period when power demand of a system is comparatively low. Counted from 10 p.m. until 6 a.m., from Monday through Saturday and during the whole day on Sunday by NERC.

Off-Peak Rate: This is the rate of cost for power used during Off-Peak periods.

PeakMeasurement of the maximum load that is consumed within a specified time period.

Phase: Phase measures the uniform periodic change in amplitude or magnitude of an alternating current.

Portable Generator: Portable generators are generators that can be moved from one location to another location with relative ease and are not meant for permanent use. Different models are fueled by different energy sources, like natural gas, diesel, or propane. These generators can provide power for up to 12 hours at a time and the power output is up to 17,500 watts.

Prime Power Rating: Prime power ratings provide the indefinite running time or the limited running time of generators under the prime power category. Average variable load factor is 70% of the prime power rating. There is a 10% overload availability. Prime power rated generators are used by persons who do not purchase electricity from a public utility but who provide their own electricity.

Prime Rated Generator: A prime generator set is any standard genset that is used as the primary power source for the equipment it is powering.

Rated Voltage: The specific voltage measurement at which an engine generator set can start functioning.

Rectifier: Rectifier is used for converting alternating current (AC) to direct current (DC).

Relay: Normally used in control circuits, relay is a switch driven by electricity and rules over contactor by virtue of low amperage contacts.

Rotor: Rotor is the element that on, which the rotating of a generator depends.

Rotor winding: Comprises of all the rotor pole windings and connections.

Single Point of Failure: Single point of failure is a location in a redundant system where a single powers failure results in loss of electrical power to the critical load.

Skid: A skid is a base used to mount the components of a genset.

Standby (Backup) Service: 1. Service through a permanent connection not normally used but available in lieu of, or as a supplement to, the usual source of supply.

Standby Generator: Used for power backup in home, Standby Generator is driven by gasoline or LP gas.

Standby Power: This is the backup source of electrical energy that remains dormant and starts functioning as soon as a control device instructs it to.

Standby Power Rating: A standby power rated generators are used during power outages to supply emergency power for a specific and limited period of time. Typical use is 200 hours per year and maximum use is 500 hours per year with varying loads. Average variable load factor is 70% of standby rating. There is no built-in overload capability.

Stationary Generator: Stationary generators are also known as standby or backup generators. They are usually permanently located to address business or industrial emergency needs. Stationary generators are usually connected to the main distribution panel and have the option of either being manually or automatically started when needed.

Stator: Stator is the static or unmovable element of a generator.

Stator winding: Comprises of stator coils with their interconnections.

Towable VS. Portable: A Towable Genset has a trailer towed behind a vehicle. Portable is something that can be moved by hand.

Transfer Switch: A transfer switch is a switch that either manually or automatically changes an electrical load from its regular and preferred source to an alternative and usually stationary or portable source. A transfer switch is most often used in emergency times when there has been a power outage. Transfer switches can also incorporate controls to do things like setting timers or activating/deactivating the backup generator.

UPS (Uninterruptible Power Supply): Supplies power automatically and instantly during shortage of power supply. UPS operation is dependent on a primary power source such as the electric utility grid, as it does generate power itself.

Utility Power: Power supplied from “the grid” i.e. PG&E or SMUD

Volt: Potential difference between two points.

Voltage: Measurement of electrical potential difference expressed in volts.

Voltage Regulator: By modulating the flow of DC to the rotor, Voltage regulator maintains optimum generator voltage, automatically.

Watt: Measurement of electrical power. One watt is equal to 1 joule of energy per second.

Windings: Windings are the coils of a generator. In other words, it is wire that has been turned one or more times to form a continuous coil to allow an electric current to pass through it. There are two main windings: stator and rotor.

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