Generator Terminology

Glossary Entries

4-Stroke

Cycle commonly used in internal combustion engines which comprise of intake, compression, combustion and exhaust strokes that occur during 2 crankshaft rotations.

AC

A current which reverses in regularly recurring intervals of time and which has alternative positive and negative values, and occurring a specified number of times per second. (See frequency.)

Alternating Current

A current which reverses in regularly recurring intervals of time and which has alternative positive and negative values, and occurring a specified number of times per second. (See frequency.)

Ampere

The unit of electric current flow. One ampere will flow when one volt is applied across a resistance of one ohm.

Amps

The unit of electric current flow. One ampere will flow when one volt is applied across a resistance of one ohm.

Atmospheric Pressure

The force exerted by the atmosphere on the earth's surface, which allows a centrifugal pump to operate. At sea level, the atmospheric pressure equals 14.7 PSI. As elevation increases, atmospheric pressure decreases, therefore pump performance also decreases.

Auto Light Controller

A device used to program the starting and stopping operations of light towers.

Automatic Decompression

Eliminates the compression in the engine to reduce the force required for the recoil start engines.

Ballast

A device used to provide the proper starting and operating electrical condition to power HID lamps.

Brake Horsepower

Pump performance can be expressed in horsepower using the following formula: Brake HP = GPM x Ft./Head / 3940

Capacitance

The property of a circuit or body that permits it to store an electrical charge equal to the accumulated charge divided by the voltage. Capacitance is expressed in farads.

Cavitation

Status in which the pump impeller is not receiving a full supply of material. This can be due to reduced flow or over rotation. Excessive pump RPM can cause a vortex in the eye of the impeller. Air bubbles attach to the metal surfaces and, under extreme pressure, implode, taking tiny bits of metal away with each implosion, pitting the impeller and volute surfaces. Excessive cavitation can cause severe, permanent damage to the pump components, resulting in poor performance.

Centrifugal Force

The action that causes something to move away from its center of rotation.

Centrifugal Pump

Uses centrifugal force to move water or other liquids. Centrifugal pumps use an impeller and a volute to create the partial vacuum and discharge pressure necessary to move water through the casing. The impeller and volute form the heart

Check Valve

A device used in a suction or discharge line that allows flow in only one direction to prevent reverse flow, thus isolating the material being pumped.

Circuit

A complete or partial path over which electric current may flow.

Circuit Breaker

A mechanical switching device capable of making, carrying, and breaking currents under normal conditions. Also making, carrying for a specific time, and automatically breaking currents under specified abnormal circuit conditions, such as those of short circuit. Circuit breakers have an ampere trip rating for normal overload protection and a maximum magnetic ampere interrupting capacity (AIC) for short circuit protection.

Commercial Power

The term applied to power furnished by an electric power utility.

Conductor

A wire, cable, or bus bar designed for the passage of electrical current.

Contactor

An electro-mechanical device operated by an electric coil; it allows automatic or remote operation to repeatedly establish or interrupt an electrical power circuit.

Critical Lifts

Suction lifts greater than 25'.

Current

The amount of electricity flowing in a circuit, measured in amperes.

Cycle

A given length of time (see Alternating Current). In the U.S., most electric current is 60 cycle (60 Hz).

DC

An electric current flowing in one direction.

Delta Connection

A common three-phase connection shaped schematically like the Greek delta. The end of one phase is connected to the beginning of the next phase, or vice versa.

Dewatering Pump

Designed for clear water applications (agricultural, industrial, and residential). As a general rule, dewatering pumps are limited to a 10% solids concentration and a solids size of one-fourth the diameter of the suction inlet. For applications requiring greater solids handling capability, trash pumps should be used.

Diaphragm Pump

Uses a positive displacement design rather than centrifugal force to move water through the casing, delivering a specific amount of flow per stroke, revolution, or cycle. Due to their great air handling capabilities, diaphragm pumps are ideal for applications involving slow seepage at the point of suction.

Dielectric

Insulating material, such as air or glass, that has a high resistance to the conductance of electric current; a non-conductor.

Direct Current

An electric current flowing in one direction.

Distribution Panel

A device that provides multiple power outlets from a 208V 3-phase or 240V single-phase power source for operating power tools, work lights, and other electrical equipment.

DOT Running Lights

The lights on the exterior of the vehicle approved by the Department of Transportation per the application.

Duty Point

The point on a performance curve that plots flow (GPM) and head (feet).

Dynamic Discharge Head

The sum of the static discharge head and the discharge friction loss in the discharge line. Also referred to as Total Discharge Head.

Dynamic Suction Head

The sum of the static suction lift and the suction friction loss in the suction line. Also referred to as Total Suction Head.

EEF

Output power to input power ratio in an electric motor.

Efficiency Factor

Output power to input power ratio in an electric motor.

Electric Utilities

All enterprises engaged in the production and/or distribution of electricity for use by the public.

Electrical Contact

Device for making and breaking electrical circuits, which are a part of all electrical switching devices.

Electromotive Force

The force or electric pressure that causes or tends to cause a current to flow in a circuit, equivalent to the potential difference between the terminals and commonly measured in volts.

Float Switch

A device used to start and stop a pump based on preset water levels.

Flow Rate

How many gallons per minute (GPM) of pump flow are required. Flow can also be expressed in gallons per hour (GPH) and in million gallons per day (MGD). 1 MGD = 700 GPM.

Fluid Type

Whether the fluid being pumped is clean or dirty, contains any solids or abrasives, or is a hazardous material.

Frequency

The number of complete cycles of an alternating voltage or current per unit of time, usually expressed in cycles per second or Hertz (Hz).

Friction Loss

Reductions in flow due to turbulence as water passes through hoses, pipes, valves, and fittings. This includes both suction and discharge friction losses.

Full Load Current

The greatest current that a motor or other device is designed to carry under specific conditions: when rated voltage is applied at rated frequency with rated horsepower. Any additional current is an overload.

Fuse

An over-current protective device that consists of a conductor that melts and breaks when current exceeds rated value beyond a predetermined time.

Fuseable Disconnect Switch

A switching device that provides a safe way to distribute power for operating electrical equipment.

Galvanized

A corrosion resistant coating for iron and steel.

Generator Receptacle

A contact device installed for the connection of a plug and flexible cord to supply emergency power from a portable generator or other alternate source of power. Receptacles are rated in voltage, amps, number of wires, and by enclosure type.

GFCI

A receptacle with a built in circuit that will detect leakage current to ground on the load side of the device. When the GFCI detects leakage current to ground, it will interrupt power to the load side of the device, preventing a hazardous ground fault condition. GFCI receptacles must conform to UL Standard 943 Class A requirements, and their use is required by the National Electric Code NFPA-70 in a variety of indoor and outdoor locations.

Ground

A connection, either intentional or accidental, between an electric circuit and the earth or some conducting body serving in place of the earth.

Ground Fault Circuit Interrupter

A receptacle with a built in circuit that will detect leakage current to ground on the load side of the device. When the GFCI detects leakage current to ground, it will interrupt power to the load side of the device, preventing a hazardous ground fault condition. GFCI receptacles must conform to UL Standard 943 Class A requirements, and their use is required by the National Electric Code NFPA-70 in a variety of indoor and outdoor locations.

Grounded Neutral

The common neutral conductor of an electrical system, which is intentionally connected to ground to provide a current carrying path for the line to neutral load devices.

Grounding Conductor

The conductor that is used to establish a ground and that connects equipment, a device, a wiring system, or another conductor (usually the neutral conductor) with the grounding electrode.

Head

Gains or losses in pressure caused by gravity and friction as water moves through a system. It can be measured in lbs. per square inch (PSI) or feet of water. A pump must produce 1 PSI to push a column of water vertically 2.31 feet. Use the following formulas to convert: Max. pressure x 2.31 = Max. Head RatingMax. Head Rating ÷ 2.31 = Max. Pressure

Hertz

A unit of frequency equal to one cycle per second.

High Head Pump

Capable of handling flows at significantly higher total dynamic head ratings (TDH). They utilize a closed design impeller and a compact volute called a diffuser to generate the high discharge pressure needed and cannot handle large solids.

High Pressure Sodium

A gas discharge lamp which uses sodium in an excited state to produce light.

Horsepower

The amount of energy required to lift 33,000 lbs., one foot, in one minute. The electrical equivalent of one horsepower is 745.6 watts.

Hose Length

The suction and discharge hose or pipe lengths required for a given application. Longer hoses increase friction loss, thereby reducing pump performance. Therefore, hose lengths should be kept as short as possible.

HP

The amount of energy required to lift 33,000 lbs., one foot, in one minute. The electrical equivalent of one horsepower is 745.6 watts.

Hz

A unit of frequency equal to one cycle per second.

Impedance

A characteristic of an electric circuit that determines its hindrance to the flow of electricity. The higher the impedance, the lower the current. The unit of measure is the same as resistance (ohms).

Impeller

A rotating disk with a set of vanes coupled to the engine or drive shaft that produces centrifugal force within the pump casing of a centrifugal pump.

Inductance

The property of an electric circuit that causes it to store energy in the form of a magnetic field and because of which a varying current in a circuit induces an electromotive force (voltage) in that circuit or a neighboring circuit.

Kilovolt-Amperes

A rating of apparent power before being used, such as the rating of a transformer.

Kilowatt

A unit of measure of electrical power, equal to 1000 watts. Used where larger units of electrical power are measured.

kVA

A rating of apparent power before being used, such as the rating of a transformer.

kW

A unit of measure of electrical power, equal to 1000 watts. Used where larger units of electrical power are measured.

Liquid Containment

A system designed to be capable of holding the accidental release of fluids and prevent the release of those fluids.

Lumens

A unit equal to the amount of light given out through a solid angle by a source of one candela intensity radiating equally in all directions.

Manual Transfer Switch

A switch designed to disconnect the load from one power source and reconnect it to another source, while at no time allowing both sources to be connected to the load simultaneously.

Maximum Suction Lift

The height (approx. 25') that water can be lifted by a centrifugal pump in actual conditions, taking into consideration altitude, friction loss, temperature, suspended particles, and the inability to create a perfect vacuum. The 25' suction lift is attainable for cold water (60°F) at sea level. Suction lift diminishes as elevation increases, due to the reduction in atmospheric pressure. In addition, suction lift decreases as the water temperature increases since warm water contains more entrained air.

Mechanical Seal

A spring-loaded pump component that forms a seal between the pump and the engine or motor. Pumps designed for working in harsh environments require a more abrasive resistant seal.

Megohm

A unit of resistance equal to one million ohms.

Metal Halide

A gas discharge lamp which produces light by passing an electric arc through a mixture of gases.

NEC

The National Electrical Code, which is the standard of the National Board of Fire Underwriters for electric wiring and apparatus, as recommended by the National Fire Protection Association.

NEMA

National Electrical Manufacturers Association, a non-profit trade association supported by the manufacturers of electrical apparatus and supplies. NEMA promulgates standards to facilitate understanding between manufacturers and users of electrical products.

Net Positive Suction Head

Positive flow of water to suction part of pump.

Neutral

The point common to all phases of a polyphase circuit, conductor to that point, or return conductor in a single phase circuit. The neutral in most systems is grounded at or near point of service entrance only and becomes the grounded neutral.

NPSH

Positive flow of water to suction part of pump.

Ohm

Unit of electrical resistance. One volt will cause a current of one ampere to flow through a resistance of one ohm.

Ohm'S Law

The rate of the flow of the current is equal to the electromotive force divided by the resistance. The three basic Ohm's law formulas are: Amperes = Volts ÷ OhmsOhms = Volts ÷ AmperesVolts = Amperes x Ohms

Outrigger

A projecting beam extending beyond the main structure of the unit to stabilize and support the extending part.

Overload Protection

The effect of a device operative on excessive current, but not necessarily on short circuit, to cause and maintain the interruption of current flow to the device being governed.

Parallel Circuit

An electrical circuit that has more than one path though which electrons may flow.

Performance Curve

A chart or graph that illustrates pump performance by plotting the total head and flow rate at various suction lifts. Performance curves for diesel-driven pumps also show pump performance at various engine RPMs.

PF

The ratio of true power to volt-amperes in an alternating current circuit. Power factor is expressed in a percent of unity either lagging for inductive loads or leading for capacitive loads. Resistive loads produce a unity power factor.

Pin and Sleeve

A receptacle with cylindrical sleeve-type contacts.

Pintle Hitch

A means of connecting two things using a pin or bolt to allow the other item to rotate using a lunette ring.

Powder Coated

Method of applying a decorative and protective finish by spraying charged particles of pigment and resin to electrically grounded surfaces and then heated and fused in a curing oven.

Power Factor

The ratio of true power to volt-amperes in an alternating current circuit. Power factor is expressed in a percent of unity either lagging for inductive loads or leading for capacitive loads. Resistive loads produce a unity power factor.

Prime

The creation of a partial vacuum inside the pump casing, which allows water to flow into the pump.

Quick Disconnect

Connecting devises that permit easy and immediate connection and separation of two or more components.

Reactance

The component of impedance that does not dissipate energy. Inductive reactance stores magnetic energy and hinders the flow of alternating current. Capacitive reactance stores electric energy.

Relay

An electric device that is designed to interpret input conditions in a prescribed manner and, after specified conditions are met, to respond and cause contact operation or similar abrupt changes in associated electric control circuits.

Resistance

The non-reactive opposition that a device or material offers to the flow of direct or alternating current. Usually measured in ohms. The larger the resistance the lower the current for a given source (driving) voltage.

Resistive Load Bank

A device that provides temporary electrical loads for field testing power sources such as generators and uninterruptible power supplies.

Seepage

The rate at which the fluid being pumped accumulates at the point of suction. Slow seepage allows air into the pump suction, which causes some types of pump to lose their prime.

Self-Priming

The ability of a pump to purge air from its casing and suction hose, creating a partial vacuum and allowing water to flow freely into the pump. Most smaller portable centrifugal pumps (2" to 4" diameter) require an initial manual priming before operation is begun and then operate as self-priming.

Series Circuit

Electrical circuit with only one path though which electrons may flow.

Single-Phase

A circuit that differs in phase by 180°. Single-phase circuits have two conductors, one of which may be a neutral or three conductors, and one of which is neutral.

Solids Concentration

Ratio of solids to liquid in the overall volume of the material being pumped, which is helpful in determining the proper pump for the application. Hydraulic submersible pumps handle higher solids concentrations than diesel-driven trash pumps.

Solids Size

Average diameter of individual particles in the material being pumped, which is important to know when specifying a pump. Large solids can be filtered with strainers or rock guards.

Stand-By Power

An independent reserve source of electric power that provides stand-by electric power upon failure or outage of normal power source.

Star Connection

A three-phase connection, so called because, schematically, the joint of the "Y" points looks like a star (same as a "Y" or "Wye" connection).

Starting Amps

The maximum current drawn by a motor during the starting period.

Static Discharge Head

The vertical distance from the centerline of the pump impeller to the point of discharge. (See definition for dynamic discharge head.)

Static Suction Lift

The vertical distance from the lowest suction point to the centerline of the pump impeller. This distance should be kept to a minimum for maximum pump performance. (See definitions for theoretical and maximum suction lift.)

Step-Down Transformer

A transformer that provides one or more electrical outlets at reduced voltage and current from the main power source.

Strainer

A fitting at the end of a suction hose that prevents solids larger than its solids handling capability from entering the pump.

Submersible Pump

A centrifugal pump designed to operate within the water source being pumped, thereby eliminating the suction lift limitations common to other types.

Surge Arrestor

A protective device for limiting surge voltages on equipment by discharging or bypassing surge current; it prevents continued flow of follow current to ground, and is capable of repeating these functions as specified.

TDH

The sum of the dynamic suction head and the dynamic discharge head. Also referred to as Total Head.

Terminal Block

An insulating base equipped with terminals for connecting wires.

Theoretical Suction Lift

The maximum height (33.9') that water can be lifted inside a tube under perfect conditions (perfect vacuum) at sea level. At this point, the water inside exerts a pressure equal to the weight of the atmosphere pushing down on the ocean's surface. Theoretical suction lift is calculated by dividing the atmospheric pressure at sea level (14.7 lbs. per square inch) by the weight of one cubic inch of water (.0361 lbs.). This equals 407.2" or 33.9'.

Three-Phase

A combination of circuits energized by alternating electromotive sources that differ in phase by one third of a cycle, that is, 120°. A three-phase circuit may be three wire or four wire with the fourth wire being connected to the neutral point of the circuit that may be grounded.

Total Dynamic Head

The sum of the dynamic suction head and the dynamic discharge head. Also referred to as Total Head.

Transformer

A static electric device consisting of a single winding, or two or more coupled windings, used to transfer power by electromagnetic induction between circuits at the same frequency, usually with changed values of voltage and current.

UL

An independent, non-profit U.S. organization that tests products for safety.

Underwriters Laboratories

An independent, non-profit U.S. organization that tests products for safety.

Viscosity

The resistance to flow of a liquid at a given temperature. Highly viscous liquids are thick and tend to flow slower than liquids of low viscosity.

Volt

A unit of measure of electric potential and electromotive force, equal to the difference of electric potential between 2 points on a conducting wire carrying a constant current of one ampere when the power dissipated between the points is one watt.

Voltage

Electromotive force, or difference in electric potential, expressed in volts.

Volute

The casing surrounding the impeller in a centrifugal pump that collects the liquid discharged from the impeller.

Watt

A unit of measure of electrical power, equal to the power used when one volt causes one ampere to flow in a circuit.

Winch

A machine for lifting loads by means of a rope, chain or wire that is wound around a cylinder turned by an engine or by hand.

Wye Connection

A three-phase connection, so called because, schematically, the joint of the "Y" points looks like a star (same as a "Y" or "Wye" connection).