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Volts
= Amperes X Ohms Amperes = Volts/Ohms Ohms = Volts/Amperes Watts = Volts X Amperes Watts = (Volts X Volts) / Ohms Watts = Amperes X Amperes X Ohms Ohms = Watts / (Amperes X Amperes) |
| Volts are the force that push amps (current of
electrons) through the matrix (atomic structure) of a conductor (wire). Volts x amps = watts (power). Volts do not change on the grid except for brief spikes due to lightning or surge. The number of amps rises and falls depending on power consumption. The conductor has natural resistance (measured in ohms) to the flow of current (amperage). When more amps are required for power consumption, the wires get hot because the voltage keeps pushing more and more amps against the matrix of the wire. If too many amps are getting pushed down the conductor, the conductor can overheat and cause fire. The grid is a balance of these factors in constant effort to maximize safety, efficiency, supply and reliability, plus the added dynamic of cost. |
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| Buy Best basic electric book Electric book series Basic electric book/ very detailed House wiring Resource: My simple illustrations and wiring: Do it yourself electric Email and I'll make illustration geno03245w@gmail.com |
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Circuit breakersResources:Water heater is tripping breaker How to replace circuit breaker How to wire gfci Can AC breaker be used for DC breaker How to reset circuit breaker Not enough space for circuit breakers Circuit breakers How to install subpanel Why you need ground wire Match breaker and wire size How to wire subpanel See inside breaker box How to wire safety switch How to wire whole house surge protector |
| Terminology for wiring Load = light bulb, motor, fan, heater, pump etc; Total load = add up wattage on all Loads. Resistive Load: incandescent light bulb, heating element have uniform voltage and amp draw; Inductive load: motor, pump etc. Inductive loads pull more amps during start up. Load rating... light bulb shows wattage, label on water heater shows volts-watts, timer labels show rating for inductive or resistive etc Figure volts amps watts Volts x amps = watts Water heater formulas .pdf Hot wire = wire or wires that carry voltage potential and would shock you if breaker was on Image residential breaker box Neutral wire = Grounded Conductor = A system or circuit conductor that is intentionally grounded. By code, a white wire used for 120V and 277V circuits to complete circuit along with a Hot wire. Ground = NEC (national electric code) defines ground: A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to some conducting body that serves in place of the earth. Grounded = Effectively. Intentionally connected to earth through a ground connection or connections of sufficiently low impedance (resistance) and having sufficient current-carrying capacity to prevent the buildup of voltages that may result in undue hazards to connected equipment or to persons. Ground wire = green or bare copper wire that connects to ground busbar in breaker box Why ground is needed Grounding electrode = earthing electrode (ground rod) Ground resistance = resistance due to the resistivity of the soil in the vicinity of the grounding electrode 208 and 240 volt single-phase circuits have 2 Hot wires. (US electric) Image residential breaker box Some countries have 230-240Volt circuits with 1 Hot and 1 Neutral (instead of 2 Hot wires). What is 208 volt 120 and 277 volt circuits have 1 Hot and 1 Neutral / Usually 277volt is found in commercial applications (US) What is 277 volt Standard voltages in US and Americas include 12V 24V 120V 208V 240V 277V 480V 600V etc found in various applications Voltages around the world vary depending on country. Standard voltages make it possible to mass produce wires, breakers, appliances etc. 60Hz or 60 cycle = number of times AC generator rotates each second. Americas use 60 Hz power, while other countries use 50Hz. Read more DC direct current is generated by solar panels and batteries. Large arc when switching high voltage DC is fire hazard. Device must show DC rating. Read about DC vrs AC AC alternating current produced by power plant, windmill, or portable generator. More Single-phase = residential electrical systems are single phase AC, requiring 2 wires to complete circuit More Three-phase = commercial wiring requiring 3 Hot wires to complete circuit More Wire gauge = diameter of wire. The wire size and load rating and breaker must match Select wire and breaker Breaker: circuit breaker is overcurrent protection that will trip when amp draw from Load or short circuit overheats wire. Turn breaker fully off and then fully on. Jumper = short wire used to connect 2 electrical points together. Fuse: A piece of metal, connected in the circuit, that melts and interrupts the circuit when excess current flows. Transformer = converts voltage and amperage ratio on a line. Cell phone charger, doorbell transformer, LED driver are examples of changing 120 volt into safe, low voltage applications. On the grid, transformers are used to supply 120-240 to household, and other voltage combinations to local business and industry. Insulation = Common usage: electric wires are coated with insulation to isolate each wire from coming into contact with other wires. Removing the insulation is necessary when connecting wires. Professional usage: The action of isolating sources of electricity from coming into contact with other wires, boxes, earth, people, appliances, etc is referred to as insulation. A fault, where electricity has reached earth unexpectedly or breeched a layer of containment, is known as an insulation failure. In motors: motor insulation is classified by maximum allowable operating temperature. |
| Thermal trip The breaker has detected an overload. Resolution: Remove excessive loads from the circuit. The breaker has detected a short circuit. Resolution: Identify the location of the short circuit and resolve. The breaker was manually turned off. |
| Series arc Description: A low current arc typically found in worn or degraded appliance and extension cords, poor connections in appliances or fixtures, or in contacts within equipment. Identify the equipment causing the tripping, and repair or replace. |
| Parallel arc Description: High current arc between two conductors, usually found in installed wiring where the wire has been compromised by a nail or screw, tight staple, and damaged insulation. Resolution: Replace wire. |
| Ground fault Description: Current has found an alternate path to ground, which could cause harm to people or property. |
| Electrical terminology Ampacity: The current in Amperes that a conductor can carry continuously under the conditions of use without exceeding the conductor’s temperature rating. Ampere: The measurement of the rate of flow of current in an electrical circuit. One Ampere is the measurement of the rate at which current that will flow through a resistance of 1 Ohm when an electrical potential of 1 Volt is applied across that resistance. Sometimes this term is shortened to the word “Amp.” Arc-Fault Circuit Interrupter (AFCI): A device that is able to sense when an electrical arc occurs somewhere in a circuit and acts to de-energize the circuit connected to it. AWG (American Wire Gauge): This is the industry standard used to specify the size of electrical conductors. There are 40 different electrical conductor sizes ranging from 36 AGW (smallest) to 0000 AWG (largest). Each consecutive AGW size is 1.26 times smaller or bigger in diameter than the next. The larger the diameter, the greater the conductor’s current carrying capacity (ampacity). Ballast: A device that is an integral part of a fluorescent light. It is used to regulate the amount of current which is allowed to flow though the light. Bonding: Connecting the metal parts of electrical components together to assure electrical conductivity between them. It is the practice of intentionally electrically connecting all exposed metallic items not designed to carry electricity in a room or building as protection from electric shock. Bonding Jumper, Main: This is a connection made between the grounded circuit conductor (Neutral) and the equipment grounding conductor inside the service entrance panel. Branch Circuit: Consists of the circuit conductors that are between the final overcurrent device (fuse/circuit breaker) protecting the circuit and the outlet(s) which are part of that circuit. There are three types of branch circuits – General Purpose (to supply ordianry lights and outlets), Small Appliance (for kitchens and locations where appliances are used), and Individual (or dedicated to clothes dryer, water pump, microwave etc). Circuit Breaker: A circuit protection device that is designed to either be 1) manually operated to open or close a circuit; or 2) automatically open a circuit when a predetermined overcurrent flows through the circuit. These are most often used inside the service entrance panel. Continuous Load: An electrical load where the maximum current in a circuit is expected to continue for a period of 3 hours or longer. A continuous load shall not exceed 80% of the rating of the branch circuit. CU: a marking on wire connectors, lugs and device terminals that indicates they are suitable for use with Copper conductors only. Current: The flow of electricity (electrons) through an electrical circuit. Current is measured in Amperes. AL is marking used for Aluminum. Dedicated Circuit: See Individual Branch Circuit. A branch circuit that supplies only one piece of utilization equipment (such as an electric range). Typically, a single receptacle (not a Duplex receptacle). Duplex Receptacle: An electrical outlet that allows two plug-and-cord-connected devices to be connected to the house wiring system and receive power at the same time. Floor Plan: A scale diagram of a room or building drawn as if seen from above. Floor plans show construction details such as placement of plumbing, the electrical system, and doors and windows. Fuse: An overcurrent protection device with a fusible link which melts during an overcurrent condition in a circuit in order to stop the flow of electricity. Fuses can often be found in older service entrances panels and come in various ratings and form-factors. Ground: The earth. It is used as the “common reference point” for measuring electrical potential (voltages) within an electrical system. Grounded (Grounding): Connected to the ground or connected to an electrically conductive item that physically extends the connection to the ground. Grounded Conductor: (Not to be confused with Grounding conductor.) For residential wiring, this is the “Neutral” wire which is the one with the white insulation. Ground Fault: An unintentional, connection between a current carrying conductor and non-current carrying (grounded) parts of an electrical system (other conductors, metal enclosures, conduit, earth, etc.) causing current to flow on an unintended path (Ground-Fault Current Path). Ground Fault Circuit-Interrupter (GFCI): A device used to protect persons from the risk of bodily injury by deenergizing a circuit within a very short period of time when the current flowing to ground exceeds .006 amperes. Ground-Fault Current Path: The path on which fault current flows beginning at the point of the ground fault and flowing through normally non-current carrying parts of the electrical system back to the electrical supply source. Grounding Conductor: A conductor that is used to connect equipment or the grounded circuit of a wiring system to the grounding electrode or electrodes. In residential wiring, this is typically a 4 AWG – 8 AWG bare copper wire. Grounding Electrode: A conducting material making a direct connection to the earth. This could be a metal water pipe, concrete-encased bare copper conductor, or a ground rod. Ground rods must be at least 0.5” in diameter and at least 8’ long. Individual Branch Circuit: A branch circuit that supplies only one piece of utilization equipment (such as an electric range). Typically, a single receptacle (not a Duplex receptacle). Insulated/Insulation: A non-conductive covering applied to wires or placed between conductive materials to prevent current from leaving a conductor and flowing on an unintended path. Lighting Outlet: An outlet intended for the direct connection of a lamp holder or luminaire. Load: The electrical power (wattage) consumed by the devices attached to an electrical system. Loads can be of several types, the main ones being – Continuous, Non-Continuous, and Intermittent. Load Balancing: The arrangement or sequence of attaching conductors to the panelboard (service entrance panel) in order to balance the anticipated loads on the phase conductors. With a balanced load, the connected equipment would draw an equal current through each 120-volt leg of a 120V/240V electrical system. Generally speaking, the simplest way to balance the load on a panelboard is to connect an equal number of branch circuits to each phase conductor. Load Center: Also known as a Service Entrance Panel or Residential Panel Board, circuit breaker box, subpanel. Circuit breakers typically “plug-in” to load centers whereas they “bolt-in” to panel boards. Location Damp: An exterior or interior location that is normal ly or periodically subject to condensation of moisture in, on, or adjacent to, electrical equipment, and includes partially protected locations. Location Dry: A location not normally subject to dampness, but may include a location subject to temporary dampness, as in the case of a building under construction, provided ventilation is adequate to prevent an accumulation of moisture. Location Wet: A location in which water or other liquid can drip, splash, or flow on or against electrical equipment. Luminaire: Light fixture. A complete lighting unit consisting of a light source such as a lamp or lamps, together with the parts designed to position the light source and connect in to a power supply. Prior to the National Electrical Code adopting this term, “lighting fixture” was the commonly used term. This term is still used more often than luminaire. Maximum Continuous Load: Safe maximum. Defined to be 80% of the circuit rating (protection device). Any electrical load that operates for a period of 3 hours or more on a branch circuit shall not exceed 80% of the circuit rating (protection device). National Electrical Code (NEC): The electrical code published by the National Fire Protection Association. This code provides for practical safeguarding of persons and property from hazards arising from the use of electricity. It does not become law until adopted by federal, state, and local laws and regulations. Neutral Conductor: The conductor connected to the neutral point of an electrical system that is intended to carry current under normal conditions. Ohm: A unit of measure for electrical resistance. One Ohm is the amount of resistance that will permit one Ampere of current to flow when one Volt is applied across the resistance. Open Circuit: A circuit that does not have a continuous path over which current can flow. A circuit that is turned OFF. Turning off a switch creates an open circuit (good), while a loose connection also can create an open circuit (bad). Closed circuit: a circuit that is turned ON. Outlet: A point on the wiring system at which current is taken to supply utilization equipment. Overcurrent: Any current is excess of the rated current of the equipment or the ampacity of a conductor. Overcurrent Device: Also referred to as an Overcurrent Protection Device and is a form of protection that operates when current exceeds a pre-determined value. These devices are primarily consist of circuit breakers and fuses. Overload: Operation of equipment in excess of the normal full -load rating, or of a conductor in excess of its rated ampacity, that over time, would cause damage or dangerous overheating. Receptacle: A receptacle is a contact device at the outlet for the connection of an attachment plug. Receptacle Outlet: An outlet where one or more receptacles are attached. Romex: A trade name for Nonmetallic Sheathed Cable (NM). Service: The conductors and equipment for delivering energy from the servicing utility to the wiring system of the premises served. Service Conductors: The conductors running from the service point to the service disconnecting device. Service Drop: The overhead service conductors from the last pole or other aerial support that connect to the service-entrance conductors at the building. Service Entrance Panel (SEP): A metal enclosure that houses circuit protection devices (circuit breakers or fuses) and provides the means by which power is divided up to be distributed to the individual circuits. It contains a “Main” breaker that allows the power from the utility company to be disconnected from the entire building. Service Equipment: The equipment intended to be the main control and means of cutting off of the supply of electricity to a building. This usually consists of a circuit breaker or switch and fuse and their accessories. Short Circuit: A connection between any two or more conductors of an electrical system in such a way as to significantly reduce the resistance of the circuit. This situation causes the currently to flow outside of the intended path, hence the term “Short Circuit.” A short circuit is referred to as a “Fault.” Split-Circuit Receptacle: A standard duplex receptacle whose “break-away” tabs have been removed and is connected such that one half of the receptacle supplies power all the time while power to the other half is controlled by a switch. Surface-Mounted Luminaire: A luminaire mount directly on (surface of) the ceiling or a wall. Switch: A device use to control (enable or disable) the flow of electricity in a circuit or portion of a circuit. Terminal: A screw or quick-connect device where a conductor is intended to be connected. Three-way Switch: A type of switch that is used in pairs to allow you to control the power supplied to a light or receptacle from two different locations. UL: Underwriters Laboratories (UL) is an independent not-for-profit organization that develops standards and tests electrical equipment to those standards. UL-Listed: Indicates that an item has been tested and approved to the standards established by the UL for that particular item. Ungrounded: Not connected to ground or a conductive body that extends to the ground connect ion. Volt: A measurement of electrical potential energy. It is the difference in electrical potential between two points of a conductor carrying one Ampere when the power being dissipated between those two points is one Watt. Voltage (nominal): A value assigned to a circuit or system for the purpose of specifying its (nominal) operating voltage. In residential systems the nominal voltage would be specified as 120/240 Volts. In practice, the actual voltages can vary slightly around the specified nominal voltages. Voltage Drop: A reduction in voltage (difference in electrical potential energy) at a given point in a circuit due to current flowing through a resistance (typically the conductors in a circuit). The voltage drop across any given length of conductor can be calculated by “Ohm’s Law”: E (voltage) = I (current) x R (resistance). Watt: A unit of power. It is equal to: W (wattage) = E (voltage) x I (current). |
| Motor
terminology/ source: Leeason eBusiness Center www. lesson.com Actuator: A device that creates mechanical motion by converting various forms of energy to rotating or linear mechanical energy. Adjustable Speed Drive: A mechanical, fluid or electrical device that variably changes an input speed to an output speed matching operating requirements. AGMA (American Gear Manufacturers Association): Standards setting organization composed of gear products manufacturers and users. AGMA standards help bring uniformity to the design and application of gear products. Air-Over (AO): Motors for fan or blower service that are cooled by the air stream from the fan or blower. Alternating Current (AC): The standard power supply available from electric utilities. Ambient Temperature: The temperature of the air which, when coming into contact with the heated parts of a motor, carries off its heat. Ambient temperature is commonly known as room temperature. Ampere (Amp): The standard unit of electric current. The current produced by a pressure of one volt in a circuit having a resistance of one ohm. Armature: • The rotating part of a brush-type direct current motor. • In an induction motor, the squirrel cage rotor. Axial Movement: Often called “endplay.” The endwise movement of motor or gear shafts. Usually expressed in thousandths of an inch. Back Driving: Driving the output shaft of a gear reducer – using it to increase speed rather than reduce speed. Worm gear reducers are not suitable for service as speed increasers. Backlash: Rotational movement of a gear reducer’s output shaft clockwise and counter clockwise, while holding the input shaft stationary. Usually expressed in thousandths of an inch and measure at a specific radius at the output shaft. Bearings: Sleeve: Common in home-appliance motors. Ball: Used when high shaft load capacity is required. Ball bearings are usually used in industrial and agricultural motors. Roller: Use on output shafts of heavy-duty gear reducers and on some high-horsepower motors for maximum overhung andthrust load capacities. Breakdown Torque: The maximum torque a motor can achieve with rated voltage applied at rated frequency, without a sudden drop in speed or stalling. Brush: Current-conducting material in a DC motor, usually graphite, or a combination of graphite and other materials. The brush rides on the commutator of a motor and forms an electrical connection between the armature and the power source. Canadian Standards Association (CSA): The agency that sets safety standards for motors and other electrical equipment used in Canada. Capacitance: As the measure of electrical storage potential of a capacitor, the unit of capacitance is the farad, but typical values are expressed in microfarads. Capacitor: A device that stores electrical energy. Used on single-phase motors, a capacitor can provide a starting “boost” or allow lower current during operation. Center Distance: A basic measurement or size reference for worm gear reducers, measured from the centerline of the worm to the centerline of the worm wheel. Centrifugal Starting Switch: A mechanism that disconnects the starting circuit of a motor when the rotor reaches approximately 75% of operating speed. Cogging: Non-uniform or erratic rotation of a direct current motor. It usually occurs at low speeds and may be a function of the adjustable speed control or of the motor design. Commutator: The part of a DC motor armature that causes the electrical current to be switched to various armature windings. Properly sequenced switching creates the motor torque. The commutator also provides the means to transmit electrical current to the moving armature through brushes that ride on the commutator. Counter Electromotive Force: Voltage that opposes line voltage caused by induced magnetic field in a motor armature or rotor. Current, AC: The power supply usually available from the electric utility company or alternators. Current, DC: The power supply available from batteries, generators (not alternators), or a rectified source used for special applications. Duty Cycle: The relationship between the operating time and the resting time of an electric motor. Motor ratings according to duty are: • Continuous duty, the operation of loads for over one hour. • Intermittent duty, the operation during alternate periods of load and rest. Intermittent duty is usually expressed as 5 minutes, 30 minutes or one hour. Efficiency: A ratio of the input power compared to the output, usually expressed as a percentage. Enclosure: The term used to describe the motor housing. The most common industrial types are: Open Drip Proof (ODP), Totally Enclosed Fan Cooled (TEFC), Totally Enclosed Non-Ventilated (TENV), Totally Enclosed Air Over (TEAO). Endshield: The part of a motor that houses the bearing supporting the rotor and acts as a protective guard to the internal parts of the motor; sometimes called endbell, endplate or end bracket. Excitation: The act of creating magnetic lines of force from a motor winding by applying voltage. Explosion-Proof Motors: These motors meet Underwriters Laboratories and Canadian Standards Association standards for use in hazardous (explosive) locations, as indicated by the UL label affixed to the motor. Locations are considered hazardous because the atmosphere does or may contain gas, vapor, or dust in explosive quantities. Field: The stationary part of a DC motor, commonly consisting of permanent magnets. Sometimes used also to describe the stator of an AC motor. Flanged Reducer: Usually used to refer to a gear reducer having provisions for close coupling of a motor either via a hollow (quill) shaft or flexible coupling. Most often a NEMA C face motor is used. Foot-Pound: Energy required to raise a one-pound weight against the force of gravity the distance of one foot. A measure of torque. Inch-pound is also commonly used on smaller motors and gear reducers. An inchpound represents the energy needed to lift one pound one inch; an inchounce represents the energy needed to lift one ounce one inch. Form Factor: Indicates how much AC component is present in the DC output from a rectified AC supply. Unfiltered SCR (thyristor) drives have a form factor (FF) of 1.40. Pure DC, as from a battery, has a form factor of 1.0. Filtered thyristor and pulse width modulated drives often have a form factor of 1.05. Frame: Standardized motor mounting and shaft dimensions as established by NEMA or IEC. Frequency: Alternating electric current frequency is an expression of how often a complete cycle occurs. Cycles per second describe how many complete cycles occur in a given time increment. Hertz (hz) has been adopted to describe cycles per second so that time as well as number of cycles is specified. The standard power supply in North America is 60 hz. Most of the rest of the world has 50 hz power. Full Load Amperes (FLA): Line current (amperage) drawn by a motor when operating at rated load and voltage on motor nameplate. Important for proper wire size selection, and motor starter or drive selection. Also called full load current. Full Load Torque: The torque a motor produces at its rated horsepower and full-load speed. Fuse: A piece of metal, connected in the circuit to be protected, that melts and interrupts the circuit when excess current flows. Generator: Any machine that converts mechanical energy into electrical energy. Grounded Circuit: • An electrical circuit coupled to earth ground to establish a reference point. • A malfunction caused by insulation breakdown, allowing current flow to ground rather than through the intended circuit. Hertz: Frequency, in cycles per second, of AC power; usually 60 hz in North America, 50 hz in the rest of the world. Named after H. R. Hertz, the German scientist who discovered electrical oscillations. High Voltage Test: Application of a voltage greater than the working voltage to test the adequacy of motor insulation; often referred to as high potential test or “hi-pot.” Horsepower: A measure of the rate of work. 33,000 pounds lifted one foot in one minute, or 550 pounds lifted one foot in one second. Exactly 746 watts of electrical power equals one horsepower. Torque and RPM may be used in relating to the horsepower of a motor. For fractional horsepower motors, the following formula may be used. HP = T (in.-oz) x 9.917 x N x 107 where, HP = horsepower T = Torque N = revolutions per minute Hysteresis: The lagging of magnetism in a magnetic metal, behind the magnetizing flux which produces it. IEC (International Electrotechnical Commission): The worldwide organization that promotes international unification of standards or norms. Its formal decisions on technical matters express, as nearly as possible, an international consensus. IGBT: Stands for isolated gate bipolar transistor. The most common and fastest-acting semiconductor switch used in pulse width modulated (PWM) AC drives. Impedance: The total opposition in an electric circuit to the flow of an alternating current. Expressed in ohms. Induction Motor: The simplest and most rugged electric motor, it consists of a wound stator and a rotor assembly. The AC induction motor is named because the electric current flowing in its secondary member (the rotor) is induced by the alternating current flowing in its primary member (the stator). The power supply is connected only to the stator. The combined electromagnetic effects of the two currents produce the force to create rotation. Insulation: In motors, classified by maximum allowable operating temperature. NEMA classifications include: Class A = 105°C, Class B = 130°C, Class F = 155°C and Class H = 180°C. Input Horsepower: The power applied to the input shaft of a gear reducer. The input horsepower rating of a reducer is the maximum horsepower the reducer can safely handle. Integral Horsepower Motor: A motor rated one horsepower or larger at 1800 RPM. By NEMA definitions, this is any motor having a three digit frame number, for example, 143T. Inverter: An electronic device that changes direct current to alternating current; in common usage, an AC drive. Kilowatt: A unit of power equal to 1000 watts and approximately equal to 1.34 horsepower. Load: The work required of a motor to drive attached equipment. Expressed in horsepower or torque at a certain motor speed. Locked Rotor Current: Measured current with the rotor locked and with rated voltage and frequency applied to the motor. Locked Rotor Torque: Measured torque with the rotor locked and with rated voltage and frequency applied to the motor. Magnetic Polarity: Distinguishes the location of north and south poles of a magnet. Magnetic lines of force emanate from the north pole of a magnet and terminate at the south pole. Mechanical Rating: The maximum power or torque a gear reducer can transmit. Many industrial reducers have a safety margin equal to 200% or more of their mechanical rating, allowing momentary overloads during start-up or other transient overloads. Motor Types: Classified by operating characteristics and/or type of power required. The AC induction motor is the most common. There are several kinds of AC (alternating current) induction motors, including, for singlephase operation: shaded pole, permanent split capacitor (PSC), split phase, capacitor start/induction run and capacitor start/capacitor run. Polyphase or three-phase motors are used in larger applications. Direct current (DC) motors are also common in industry as are gearmotors, brakemotors and other types. Mounting: The most common motor mounts include: rigid base, resilient base C face or D flange, and extended through bolts. Gear reducers are similarly base-mounted, flangemounted, or shaft-mounted. National Electric Code (NEC): A safety code regarding the use of electricity. The NEC is sponsored by the National Fire Protection Institute. It is also used by insurance inspectors and by many government bodies regulating building codes. NEMA (National Electrical Manufacturers Association): A non-profit trade organization, supported by manufacturers of electrical apparatus and supplies in the United States. Its standards alleviate misunderstanding and help buyers select the proper products. NEMA standards for motors cover frame sizes and dimensions, horsepower ratings, service factors, temperature rises and various performance characteristics. Open Circuit: A break in an electrical circuit that prevents normal current flow. Output Horsepower: The amount of horsepower available at the output shaft of a gear reducer. Output horsepower is always less than the input horsepower due to the efficiency of the reducer. Output Shaft: The shaft of a speed reducer assembly that is connected to the load. This may also be called the drive shaft or the slow speed shaft. Overhung Load: A force applied at right angles to a shaft beyond the shaft’s outermost bearing. This shaft-bending load must be supported by the bearing. Phase: The number of individual voltages applied to an AC motor. A single-phase motor has one voltage in the shape of a sine wave applied to it. A three-phase motor has three individual voltages applied to it. The three phases are at 120 degrees with respect to each other so that peaks of voltage occur at even time intervals to balance the power received and delivered by the motor throughout its 360 degrees of rotation. Plugging: A method of braking a motor that involves applying partial or full voltage in reverse to bring the motor to zero speed. Polarity: As applied to electric circuits, polarity indicates which terminal is positive and which is negative. As applied to magnets, it indicates which pole is north and which pole is south. Poles: Magnetic devices set up inside the motor by the placement and connection of the windings. Divide the number of poles into 7200 to determine the motor’s normal speed. For example, 7200 divided by 2 poles equals 3600 RPM. Power Factor: The ratio of “apparent power” (expressed in kVA) and true or “real power” (expressed in kW). Power Factor = Real Power Apparent Power Apparent power is calculated by a formula involving the “real power,” that which is supplied by the power system to actually turn the motor, and “reactive power,” which is used strictly to develop a magnetic field within the motor. Electric utilities prefer power factors as close to 100% as possible, and sometimes charge penalties for power factors below 90%. Power factor is often improved or “corrected” using capacitors. Power factor does not necessarily relate to motor efficiency, but is a component of total energy consumption. Prime Mover: In industry, the prime mover is most often an electric motor. Occasionally engines, hydraulic or air motors are used. Special application considerations are called for when other than an electric motor is the prime mover. Pull Out Torque: Also called breakdown torque or maximum torque, this is the maximum torque a motor can deliver without stalling. Pull Up Torque: The minimum torque delivered by a motor between zero and the rated RPM, equal to the maximum load a motor can accelerate to rated RPM. Pulse Width Modulation: Abbreviated PWM, the most common frequency synthesizing system in AC drives; also used in some DC drives for voltage control. Reactance: The opposition to a flow of current other than pure resistance. Inductive reactance is the opposition to change of current in an inductance (coil of wire). Capacitive reactance is the opposition to change of voltage in a capacitor. Rectifier: A device or circuit for changing alternating current (AC) to direct current (DC). Regenerative Drive: A drive that allows a motor to provide both motoring and braking torque. Most common with DC drives. Relay: A device having two separate circuits, it is constructed so that a small current in one of the circuits controls a large current in the other circuit. A motor starting relay opens or closes the starting circuit under predetermined electrical conditions in the main circuit (run winding). Reluctance: The characteristics of a magnetic field which resist the flow of magnetic lines of force through it. Resistor: A device that resists the flow of electrical current for the purpose of operation, protection or control. There are two types of resistors - fixed and variable. A fixed resistor has a fixed value of ohms while a variable resistor is adjustable. Rotation: The direction in which a shaft turns is either clockwise (CW) or counter clockwise (CCW). When specifying rotation, also state if viewed from the shaft or opposite shaft end of motor. Rotor: The rotating component of an induction AC motor. It is typically constructed of a laminated, cylindrical iron core with slots for cast-aluminum conductors. Short-circuiting end rings complete the “squirrel cage,” which rotates when the moving magnetic field induces a current in the shorted conductors. SCR Drive: Named after the silicon controlled rectifiers that are at the heart of these controls, an SCR drive is the most common type of generalpurpose drive for direct current motors. Self-Locking: The inability of a gear reducer to be driven backwards by its load. Most general purpose reducers are not self-locking. Service Factor for Gearing: A method of adjusting a reducer’s load carrying characteristics to reflect the application’s load characteristics. AGMA (American Gear Manufacturers Association) has established standardized service factor information. Service Factor for Motors: A measure of the overload capacity built into a motor. A 1.15 SF means the motor can deliver 15% more than the rated horsepower without injurious overheating. A 1.0 SF motor should not be loaded beyond its rated horsepower. Service factors will vary for different horsepower motors and for different speeds. Short Circuit: A fault or defect in a winding causing part of the normal electrical circuit to be bypassed, frequently resulting in overheating of the winding and burnout. Slip: The difference between RPM of the rotating magnetic field and RPM of the rotor in an induction motor. Slip is expressed in percentage and may be calculated by the following formula: Speed Regulation: In adjustable speed drive systems, speed regulation measures the motor and control’s ability to maintain a constant preset speed despite changes in load from zero to 100%. It is expressed as a percentage of the drive system’s rated full load speed. Stator: The fixed part of an AC motor, consisting of copper windings within steel laminations. Temperature Rise: The amount by which a motor, operating under rated conditions, is hotter than its surrounding ambient temperature. Temperature Tests: These determine the temperature of certain parts of a motor, above the ambient temperature, while operating under specific environmental conditions. Thermal Protector: A device, sensitive to current and heat, which protects the motor against overheating due to overload or failure to start. Basic types include automatic rest, manual reset and resistance temperature detectors. Thermal Rating: The power or torque a gear reducer can transmit continuously. This rating is based upon the reducer’s ability to dissipate the heat caused by friction. Thermostat: A protector, which is temperature-sensing only, that is mounted on the stator winding. Two leads from the device must be connected to a control circuit, which initiates corrective action. The customer must specify if the thermostats are to be normally closed or normally open. Thermocouple: A pair of dissimilar conductors joined to produce a thermoelectric effect and used to accurately determine temperature. Thermocouples are used in laboratory testing of motors to determine the internal temperature of the motor winding. Thrust Load: Force imposed on a shaft parallel to a shaft’s axis. Thrust loads are often induced by the driven machine. Be sure the thrust load rating of a gear reducer is sufficient so that its shafts and bearings can absorb the load without premature failure. Torque: The turning effort or force applied to a shaft, usually expressed in inch-pounds or inch-ounces for fractional and sub-fractional HP motors. Starting Torque: Force produced by a motor as it begins to turn from standstill and accelerate (sometimes called locked rotor torque). Full-Load Torque: The force produced by a motor running at rated fullload speed at rated horsepower. Breakdown Torque: The maximum torque a motor will develop under increasing load conditions without an abrupt drop in speed and power. Sometimes called pull-out torque. Pull-Up Torque: The minimum torque delivered by a motor between zero and the rated RPM, equal to the maximum load a motor can accelerate to rated RPM. Transformer: Used to isolate line voltage from a circuit or to change voltage and current to lower or higher values. Constructed of primary and secondary windings around a common magnetic core. Underwriters Laboratories (UL): Independent United States testing organization that sets safety standards for motors and other electrical equipment. Vector Drive: An AC drive with enhanced processing capability that provides positioning accuracy and fast response to speed and torque changes. Often used with feedback devices in a closed-loop system. Voltage: A unit of electromotive force that, when applied to conductors, will produce current in the conductors. Watt: The amount of power required to maintain a current of 1 ampere at a pressure of one volt when the two are in phase with each other. One horsepower is equal to 746 watts. Winding: Typically refers to the process of wrapping coils of copper wire around a core. In an AC induction motor, the primary winding is a stator consisting of wire coils inserted into slots within steel laminations. The secondary winding of an AC induction motor is usually not a winding at all, but rather a cast rotor assembly. In a permanent magnet DC motor, the winding is the rotating armature. Motor-driven-countdown-timer Delay-timer-for-motor-or-pump How-to-wire-motor-control-contactor Motor-driven-countdown-timer How-to-control-motor-with-two-switches wire-size-for-motor calculate-inrush-for-3-phase-motor |
Ohm's lawNobody can say exactly what electricity is.We can describe what it does... it is the force that moves electrons across the surface of a conductor. For example a copper wire is a conductor, and electricity can be used to move electrons down the wire. When the electrons arrive at a light bulb, electricity pushes the electrons across a narrow filament inside the bulb. The filament is also a type of wire, except smaller than regular electric wire. When electrons are pushed across the small wire, the wire becomes hot, and begins to glow. The glowing wire becomes the light from the light bulb. How do we know what size wire and how much electricity is needed to cause the light bulb to give off light without also causing the larger wire to get hot? That's where ohm's laws is used. While we can't say exactly what electricity is, we can predict what it will do using ohm's law. Ohm's laws are a series of formulas that help electricians and engineers design functional electrical and electronic systems. The basic formulas are shown in the ohms law wheel. Ohms laws have been used in common practice for many decades. Over time, reports arise about the peculiar things electricity can do... such as jump across wires and cause shorts and fires. The practical experience over time, plus application of ohms laws has given rise to the National Electric Code. The code is a guideline that standardizes wire and breaker sizes, and establishes best practices. The practical application of ohm's law and the code lets electricians safely wire a house or a business. |
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