Glossary of Terms

We have compiled a list of commonly used terms for used diesel generators and surplus diesel generators.
We hope you find this information useful and if you have any questions give us a call at 208-262-9875.

Vital Power & Equipment your home for generators.  We sell Used Generators and New Surplus Generators.  Diesel and Natural Gas Generators. Emergency Standby and Portable Generators.




  • Alternating Current (AC)
    • An electric current which changes direction with a regular frequency



  • Alternator
    • An electric generator that produces an alternating current, which uses rotating parts to change the magnetic field to the alternating current.



  • Ambient Temperature:
    • The surrounding air temperature of the diesel generator in any giving area



  • Amperage
    • Is the strength (intensity) of an electrical current, which is measured in amperes, commonly referred to as (AMPS)



  • Ampere
    • Named after the French physicist Andre M. Ampere.  An ampere is a type of electric current produced by one volt applied across a resistance of one ohm.



  • Apparent Power
    • Measured in “volt amperes” and is often express in “kilovolt amperes” (kVA).  It is the product of voltage, (volts) and the current (amperes), it is both active and reactive power.



  • Backup Generator or Genset
    • A generator used as emergency power back up.  The best line of defense for a power outage.



  • Battery
    • Is a group of usually two or more cells that are connected together to provide an electrical current.



  • Battery Charger
    • A generator battery charger is different than the battery charger in your vehicle.  A generator battery charger is designed to maintain and supply a constant float voltage to the battery to optimize the life of the battery.



  • Battery Charge Rectifier
    • The rectifier converts AC voltage to DC voltage to charge the battery.



  • Blackout
    • Refers to the sudden loss of all electrical power.



  • Black Start
    • This refers to the starting of the generator by way of its own power source with out any external power supply.



  • Brownout
    • Is the commonly used term in the industry, which refers to the reduction of voltage or power when the demand for the electricity exceeds capacity.



  • Brush
    • Consists of either graphite or copper conducting elements, which maintains the sliding electrical contact between the static and moving element.



  • Commutator
    • Is a device used in a generator to convert or “switch” the alternating current that the generator produces into a direct current before the current is sent to an external circuit.



  • Contactor
    • A device that uses a small control current to energize or de-energize the load.  The contactor is designed to handle high amounts of current and are combined with overload relays
  • Core
    • Is comprised of laminations in the generator that constitute the magnetic structure.



  • Cradle
    • Is often revered to the metal frame or cover enclosing the generator or engine, to provide protection from external interferences.



  • Current
    • The rate that electricity flow





  • DC Generator
    • A generator that transforms mechanical energy into D-C electric energy



  • Decibel Level (DB)
    • Used in the industry to define noise level



  • Delta Connection
    • Delta connection is a three-phase connection where the beginning of each phase is connected to the end of the next phase.





  • Diode
    • It is an electrical component with two active terminals called an anode and a cathode.  It allows the current to pass in only one direction.  In addition it converts AC power to DC power.



  • Direct Current
    • Is an electrical current that flows only in one direction.



  • Dynamo
    • Is simply an electric generator that produces a direct current.





  •  Emergency Power
    • Commonly referred to as the “generator”.  Emergency power is needed when there is a loss of electricity to a building or facility.  The generator(s) supplies the “emergency power” to maintain operations which could potentially save companies millions of dollars and save the lives of those involved with a power outage, for example the patients and personnel in a hospital.



  • Enclosure (AKA Housing)
    • There are two common types of enclosures

1)    Sound Attenuated – A sound attenuated enclosure or is an enclosure that is baffled or insulated to reduce the noise made from the generator.


2)    Weather Enclosure – A metal enclosure that is not sound- proofed but is used to keep the outside elements from interfering with the normal operations of the generator.




  • Exciter
    • Is known as an auxiliary generator, that provides power or electrical current to a larger generator.







  • Frequency
    • Is the number of complete cycles of the alternating voltage per second.  Typically referred to as hertz (Hz)



  • Frequency Regulation
    • Measures the difference between a non-load and a full-load frequency as a percentage of the full-load frequency.



  • Fuel Cell
    • A non-combustible device that converts the energy of a fuel to electricity or heat.



  • Full Load
    • Is the maximum load of a generator of circuit.  Any additional load would be considered an overload.





  • Generator
    • A machine that converts mechanical energy into electrical energy.



  • Genset
    • A commonly used term for generator (see Generator)



  • Green Energy
    • Is the production of electricity from renewable resource such as solar, wind and geothermal. Green electricity is non-polluting.



  • Grid
    • The Commercial Utility’s electrical system used for supplying power.





  • Hertz (Hz)
    • Cycles per second commonly referred to as frequency.  North America runs 60 Hz.





  • Idle Control
    • A device that the controls the idle speed of an engine in direct relation to an electrical load.



  • Ignition Coil
    • The ignition coil is device that supplies DC voltage to the spark plugs.



  • Inrush Current
    • Is the immediate input current by a power supply when it is first turned on.



  • Insulation
    • The non-conductive material used to prevent the escape of the electric current from a conductor.



  • Inverter
    • Changes DC power to AC power. Also known as a power converter.





  • Kilo-volt-amperes (kVA)
    • kVA is an electrical term used to rate electrical devices. 1,000 Volt Amperes.



  • Kilowatt (kW)
    • An alternate term for rating electrical devices. 1,000 watts







  • Leg
    • Is the phase winding of a generator.



  • Load
    • Is the amount of electric power that various devices demand from the electricity generator system.



  • Load Factor
    • The ratio derived from the average load to the generator power rating.





  • Main Breaker
    • Is the main circuit breaker at either the input or output of the bus, of which all the bus power must flow.



  • Manual Bypass Switch
    • Is a switch that is manually operated to bypass electrical components in an Uninterruptible Power Supply (UPS), so work can be done with out power interruption.



  • Megawatt (MW)
    • One million watts of power or electricity.





  • N.E.C
    • National Electrical Code (NEC)



  • N.E.C.A
    • Is the National Electrical Contractors Association. (NECA)



  • N.E.M.A
    • Is the National Electrical manufactures Association (NEMA)
  • Natural Gas Generator:  A generator that runs on Natural Gas and/or Propane
  • Used Natural Gas Generators:  A used natural gas generator can save our clients time and a lot of money.





  • Ohm
    • Is a unit of electrical resistance.



  • Ohmmeter
    • Is the device used to measure electrical reistance.



  • On Set Paralleling
    • Manuel paralleling systems that is built onto the generator.



  • Overcrank
    • A feature with most generators that displays an alarm when the generator fails to start.





  • Power Distribution Unit (PDU)
    • A device that monitors and controls the distribution of power to other loads.



  • Peak Load
    • Is the maximum kW demand of a facility.



  • Peak Shaving
    • Is when a facility reduces it’s electrical demand from the utility by using the back up generator during high demand times.



  • Power Factor
    • The ratio between the real power, kW and the apparent power, kVA in a circuit.  The standard power factor is shown as a percentage (.8) or 80%.







  • Reactive Power
    • Is the energy movement in an Alternating Current (AC) arising from the production of electric and magnetic fields.



  • Rectifier
    • Is and electrical device that converts AC power to DC power.



  • Rotor
    • Is the rotating element of a generator or motor.



  • RPM
    • Is Revolutions Per Minute (RPM)





  • Single Phase
    • Is an Alternating Current having two input terminals and two output terminals.  Single phase is often referred to as 110/220 volt or120/240 volt.



  • Stator
    • Is the stationary part of a generator or motor.  The direct opposite of a Rotor (see rotor)



  • Surge
    • A sudden variation in frequency, current or voltage



  • Synchronized
    • The matching of one wave to the other by adjusting the phase angle and frequency until the two coincide.





  • Synchronous Generator
    • Is an AC generator having a DC exciter.





  • Tachometer
    • An instrument that measures rotational speeds of a shaft or disk, usually displayed as RPM’s.



  • Transfer Switch
    • Transfers the load from the original source, usually the utility, to the back up generator if the original source has failed.



  • Transformer
    • A device commonly used to decrease or increase the voltage from the generator to match the facilities voltage.





  • Underwriters Laboratories (UL listed)
    • A non-profit, independent testing and certification organization.



  • Utility
    • Your commercial power source.  Your local “Utility” company.


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  • Watt
    • The unit used for measuring the true total electric power.



  • Winding
    • Represents all the coils of a generator.