Alternating Current (AC) is electric current that alternates between a positive maximum value and a negative maximum value at a characteristic frequency, usually 50 or 60 cycles per second (Hertz).
American National Standards Institute.
Acoustic material is any material considered in terms of its acoustic properties, especially its properties of absorbing or deadening sound.
Active power is the real power (kW) supplied by the generator set to the electrical load. Active power creates a load on the generator set's engine and is limited by the horsepower of the engine. Active power does the work of heating, turning motor shafts, etc.
Air Circuit Breaker
An air circuit breaker automatically interrupts the current flowing through it when the current exceeds the trip rating of the breaker. Air is the medium of electrical insulation between electrically live parts and grounded (earthed) metal parts.
Alternator is another term for AC generator.
The amortisseur windings of a synchronous AC generator are the conductors embedded in the pole faces of the rotor. They are connected together at both ends of the poles by end rings or end plates. Their function is to dampen waveform distortion during load changes.
Ampacity is the safe current-carrying capacity of an electrical conductor in amperes as defined by code.
The ampere is a unit of electric current flow. One ampere of current will flow when a potential of one volt is applied across a resistance of one ohm.
An annunciator is an accessory device used to give remote indication of the status of an operating component in a system. Annunciators are typically used in applications where the equipment monitored is not located in a portion of the facility that is normally attended. The NFPA has specific requirements for remote annunciators used in some applications, such as hospitals.
Apparent power is the product of current and voltage, expressed as kVA. It is real power (kW) divided by the power factor (PF).
The armature of an AC generator is the assembly of windings and metal core laminations in which the output voltage is induced. It is the stationary part (stator) in a revolving-field generator.
Backup protection consists of protective devices, which are intended to operate only after other protective devices have failed to operate or detect a fault.
The amount of data that can be transmitted in a fixed amount of time. For digital devices, it is expressed as bits per second, or bytes per second. For analog devices, it is usually expressed as cycles per second, or Hertz.
Base load is that portion of a building load demand which is constant. It is the "base" of the building demand curve.
The speed of data transmission in serial data communications approximately equal to the number of code elements (bits) per second (BPS). Bits per second are also termed BPS, with the prefix (k) denoting thousands.
The process of making the logical connections to the network (also called connecting). This involves connecting network variable outputs to network variable inputs using LonWorks software.
Black Start refers to the starting of a power system with its own power sources, without the assistance from external power supplies.
A logical system used to express one of two states, such as on or off (yes or no, 1 or 0, etc.)
Bus capacity is the maximum load that can be carried on a system without causing degradation of the generator frequency to less than a prescribed level (usually 59 Hz in a 60 Hz system).
CT (Current Transformer)
Current transformers are instrument transformers used in conjunction with ammeters, control circuits and protective relaying. They usually have 5 ampere secondaries.
A circuit is a path for an electric current across a potential (voltage).
A circuit breaker is a protective device that automatically interrupts the current flowing through it when that current exceeds a certain value for a specified period of time. See Air Circuit Breaker, Main Breaker, Molded Case Circuit Breaker and Power Circuit Breaker.
Circulating Harmonic Currents
Circulating Harmonic Currents are currents that flow because of differences in voltage waveforms between paralleled power sources, or induced by operation of non-linear loads.
A continuous load is a load where the maximum current is expected to continue for three hours or more (as defined by the NEC for design calculations).
Current is the flow of electric charge. Its unit of measure is the ampere.
A cycle is one complete reversal of an alternating current or voltage from zero to a positive maximum to zero again and then from zero to a negative maximum to zero again. The number of cycles per second is the frequency.
Dead Bus refers to the de-energized state of the power connections between outputs of paralleled generator sets. The term bus in this usage can either be rigid solid bus bars or insulated flexible cables.
Delta connection refers to a three phase connection in which the start of each phase is connected to the end of the next phase, forming the triangle-shaped Greek letter Delta. The load lines are connected to the corners of the triangle.
A differential relay is a protective device that is fed by current transformers located at two different series points in the electrical system. The differential relay compares the currents and picks up when there is a difference in the two, which signifies a fault in the zone of protection. These devices are typically used to protect windings in generators or transformers.
Digital Master Control (DMC)
This device is designed to control the power systems in a facility. It is offered as an option on Cummins switchgear.
Direct Current (DC)
Direct current is current with no reversals in polarity.
Distributed Control System
A collection of nodes that interact to control a system whose components are spread out over some distance. Each node has intelligence for operating its own particular component of the system. Different parts of the system communicate status and control information with one another to form a distributed control system. Typically, they communicate on a peer-to-peer level. This is different from a type of system where all control and interaction between components is dictated by one central control. This is a common master/slave arrangement.
Distribution Circuit Breaker
A distribution circuit breaker is a device used for overload and short current protection of loads connected to a main distribution device.
Droop Load Sharing
Droop load sharing is a method of making two or more parallel generator sets share a system kW load. This is accomplished by having each governor control adjusted so that the sets have the same droop (reduction of speed). Typical droop is two cycles in frequency from no load to full load.
Efficiency is the ratio of energy output to energy input, such as the ratio between the electrical energy input to a motor and the mechanical energy output at the shaft of the motor.
An emergency system is independent power generation equipment that is legally required to feed equipment or systems whose failure may present a life safety hazard to persons or property.
Energy is manifest in forms such as electricity, heat, light and the capacity to do work. It is convertible from one form to another, such as in a generator set, which converts rotating mechanical energy into electrical energy. Typical units of energy are kW/h, Btu (British thermal unit), Hp/h, ft/lbf, joule and calorie.
A fault is any unintended flow of current outside its intended circuit path in an electrical system.
Feeder Circuit Breaker
See Distribution Circuit Breaker.
Fiber Optic Cable
A technology using glass or plastic threads (fibers) to transmit data. A fiber optic cable is a bundle of either glass or plastic threads capable of transmitting messages modulated into light waves. Typically, fiber optic cable has greater bandwidth allowing them to carry more data than metal wires. Fiber optic cable is lighter and less susceptible to interference than metal wires. Also, data can be transmitted digitally rather being transformed into analog data for transmission as is the case with metal wires when used for computer data transmission. Fiber optics are becoming increasingly more common for use with Local-Area Networks (LANs).
First Start Sensor
A first start sensor is an electronic device within some paralleling equipment that senses generator set and bus voltage and frequency, and determines whether or not a generator set is the first unit ready to close to the bus following a call to start under "black start" conditions.
Frequency is the number of complete cycles per unit of time of any periodically varying quantity, such as alternating voltage or current. It is usually expressed as (Hz) Hertz or CPS (cycles per second).
Frequency Adjust Potentiometer
A frequency adjust potentiometer is used to manually bring the frequency (speed) of the incoming set to that of the bus for synchronizing purposes. When the generator set is paralleled, operation of this potentiometer will adjust the kW load assumed by the generator set.
Frequency regulation is a measure that states the difference between no-load and full-load frequency as a percentage of full-load frequency.
A device that acts as an interface between two different communication protocols. The Network Gateway Module (NGM) provides a communication protocol that a PC can understand. Other gateway devices may be used to interface between our Lontalk protocol and other systems such as a SCADA or Building Automation System. Typically, a gateway becomes necessary when a SCADA or BAS does not have a driver developed for Lontalk.
A generator is a machine which converts rotating mechanical energy into electrical energy.
Genset Communication Module (GCM)
The GCM provides a communication gateway between the Model 3100 PowerCommand Control (PCCI) and the network. The GCM communicates with the PCCI control over a serial data link. The GCM gets data from the PCCI controls such as voltage, current, engine speed, oil temperature, etc. and then sends it out on the network if another network node is bound to it or requesting data.
机组通讯板(GCM)是 PCC3100 控制器和网络之间的通讯接口。GCM与PCC通过串行数据连接。GCM从PCC得到如电压、电流、发动机转速、油温等，再把它们发送给需要这些信息的网络节点。
A governor is a device on the engine which controls fuel to maintain a constant engine speed under various load conditions. The governor must have provision for adjusting speed (generator frequency) and speed droop (no load to full load).
The utility-owned power distribution system.
A ground is a connection, either intentional or accidental, between an electrical circuit and the earth or some conducting body serving in place of the earth.
Ground Fault Protection
This function trips (opens) a circuit breaker or sounds an alarm in the event that there is an electrical fault between one or more of the phase conductors and ground (earth). This ground fault protection function may be incorporated into a circuit breaker.