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Jargon Buster

Diesel Generator Jargon Buster

Confused by all the technical jargon when looking to buy a diesel generator? Let our jargon buster help you. Our jargon buster aims to give simple, plain English explanations of typical words and phrases used across the power generation industry, specifically when dealing with diesel generators. We hope it helps! 


AC generator – Electrical generator that produces alternating current (e.g. alternator)

Active power
 – AC power with a unity power factor. Measured in watts.

Alternator – Electrical generator that produces alternating current

Ampere – The unit for electrical current (Amp).

Analogue controls – Controls using variable voltage

Apparent power – The produce of current and voltage in an alternating current circuit which has a reactive element.

Asynchronous – Motors or generators which operate at a speed not fixed by supply frequency or poleage

Attenuators – Also known as silencers, attenuators are large structural devices built for the reduction of the emission of sound

Automatic transfer switch – An item of equipment that automatically switches a power supply from regular to emergency mode in the event of a power outage.

Base load – The portion of load of a generator or building which is constant.

Biofuel – More environmentally friendly diesel fuel with all or part of its content derived from vegetable oils.

Black start – The starting of a power system without an external power source

Brown out – A voltage decrease in the utility mains power supply that is either deliberate or unintended.

Bulk tank – A large fuel storage tank from which the generator may take its supply of fuel for immediate use

Bunding – This relates to the provision for containing fuel, water and oil leakage.

Busbar – Interconnecting high current circuits in a switchboard or building with copper or aluminium (typically stiff) conductors of rectangle, square, round, or hollow form.

Circuit – An electrical circuit is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, switches etc. with a power source and a closed loop return path for the current.

Circuit breaker – When the current level in a circuit surpasses a specified amount, this protective device immediately interrupts the flow of electricity.

Close-fit – A generic word for a canopy enclosure meant to fit onto the generating set’s base frame; these can be sound proofed or just weather protected.

Combined Heat and Power (CHP) – Utilization of a generating set or sets for the aim of using the heat produced (through the exhaust and radiator) while also producing energy.

Contactor – An electrically operated heavy current switching device.

Day tank – A tiny fuel storage tank from which the generator draws its immediate fuel supply. Usually contains 6-10 hours of fuel supply and is built into the generating set’s base frame.

Decibels – the unit for both sound pressure and sound power level. Abbreviated as dB and DbA

Deviation factor – Deviation factor indicates the percentage deviation in the value of performance measure with respect to its minimum value.

Direct current – Current flow in one direction

Double skin – The extra layer inside a fuel tank and piping that helps to reduce the chance of a leak. This also applies to any poisonous liquid in the vicinity of a producing set.

Dump Line – When a potential fire risk exists, the safety approach of using a pipe work system to ‘dump’ fuel away from a day tank is used.

Duty assist – An arrangement in which multiple generating sets are structured to give mutual support in the event that one element fails to operate or requires aid in meeting a certain goal: If one of the generating sets ceases to operate or fails to meet a target, the second producing sets will take over.

Duty standby – An arrangement where two (or more) generating sets are configured to provide mutual support in case of one piece failing to operate: If one generating set fails to operate, the other one will operate. One unit is duty, the other(s) is standby to the duty unit.

Electronic governor – An electronic device that controls and maintains an engine’s speed.

Engine governing –Mechanic, hydraulic or electronic engine speed control

Exhaust silencer – A device that reduces the amount of noise produced by an engine exhaust system.

Fillpoint cabinet – A cabinet which connects to the generators fuel tank, used to allow remove filling of a fuel, or other fluid such as oil.

Frequency – The number of cycles of alternating signal


Fuel lines – Pipelines from an engine to a fuel tank or from one fuel tank to another fuel tank.

Fuel polishing – The removal of water, sediment, matter and microbial contamination back down to defined levels.

Gas powered – A gas fuelled generator

Governor – A device on the engine for maintain speed under varying load.

Hertz – The unit of frequency measurement equal to one cycle per second.

Insulation – To avoid current leakage, non-conductive material is employed between phases or between phases and the earth.

IP rating – Ingress Protection.

Kilo-volt-ampere kVA – 1000VA. The product of the circuit’s maximum current and voltage rating is referred to as the rating of an electrical circuit.

Kilo-watt kW – 1000 watts. Unit used for power rating of electrical devices.

Load acceptance – % of the generators rated load that can be applied to a generator set and is capable of accepting in one step

Load bank – A device that can be connected to a generator either for test purposes to simulate a real load

Load factor – The ratio of average load to the generating set power rating.

Load step – Normally a percentage load applied to a generating set.

Noise pollution – A term that refers to the typical noise of any machine that is close to buildings, people, or other objects, and which may require treatment to mitigate its impact, as well as being a major design factor.

Overload – Term referring to the amount by which an electrical circuit is exceeding its rating.

Parallel operation – Operating two or more generating sets together to supply an electrical load.

Power factor – The power factor is the ratio of real power flowing through a circuit

Prime power – The greatest power that a generator is capable of continually delivering while supplying a varied load for an endless number of hours per year.

Short term operating reserve (STOR) – Is a contracted service where a service provider delivers a contracted level of power to the National Grid.

Sound pressure level – Sound level in dB or dBA

Starting current – Current drawn by an electronic motor during starting.

Surge – A high increase in the quantity over a very short time.

Thermostat – Device which switches at a designed temperature, used to control temperature.

Transformer – May be alternating current or voltage related, the transformer is a device for changing the value of the quantity from one level to another.

Volt – The unit of electrical potential.

Voltage dip – When a load is attached, a temporary dip in generator voltage occurs before the AVR control system responds and corrects it.

Voltage regulation – As a percentage of the nominal voltage, the permitted difference between maximum and minimum steady state voltage.

Watt – A unit of power.