Relays


Not only can the inclination (relative to vertical) of a well be changed, but also the azimuth at which it is being drilled. The azimuth refers to the compass bearing relative to magnetic north. The well path can be turned to the right or to the left . Obviously it is essential to know at all times were the bit is. Therefore a number of directional surveying techniques are employed to monitor the progress of the hole. Essentially compass readings and inclination measurements are taken at intervals and relayed to the drill floor either via surface read outs or on film to be retrieved by wireline.  [c.49]

Whenever functional groups are connected with a C=C double bond, their reactivity is often relayed through that double bond. Analogous rules can be applied to the corresponding cyclopropane derivatives.  [c.16]

Relative viscosity Relaxation Relaxation spectrometry Relays  [c.847]

Circuit Brea.kers, Current iatermption is essential ia high voltage equipment when overloads or other emergencies occur. Circuit breakers consist of relays having contacts equipped with SF jets and high voltage transformers hoi ding fault-sensiag cods that can activate a relay contact for each phase of current (61). At 60 Hs, a 765 kV root-mean-square (rms) breaker can have a rating of 50,000 MVA (31). High (1.7 MPa (17 atm)) pressure SF jets extinguish the arcs generated on opening the contacts. Designs of circuit breakers called puffer breakers have encouraged the design of smaller devices, which has extended the use of these types of units (62,63). Sulfur hexafluoride can also act as the iasulation for the sensing transformer and supply pressure to activate the relay contacts. At higher pressures and wiater temperatures, heaters serve to prevent SF condensation.  [c.243]

Core-Loss Limits. In the United States, flat-roUed, electrical steel is available in the following classes (12) nonoriented, fiiUy processed nonoriented, semiprocessed nonoriented, fiiU-hard and grain-oriented, fiiUy processed. Loss limits are quoted at 1.5 T (1.5 x lO" G). The loss limits at 1.7 T (1.7 X ICf G) of the fourth class and of the high induction grades are shown in Table 2. Typical appHcations include use for transformers, generators, stators, motors, ballasts, and relays.  [c.370]

The 50% Ni alloys generally range from 45—50 wt % Ni and may contain up to 0.5 wt % Mn and 0.35 wt % Si The carbon level generally is kept below 0.03 wt %. Most alloys contain 48 wt % Ni, and some are available iu two grades rotor grade, P40 = ca 6000, useful for rotors and stators iu which the magnetic properties must be nondirectional and transformer grade, P40 = ca 10,000, where high permeabihty is achieved iu directions parallel and perpendicular to the rolling direction. These latter generally are used iu audio and instmment transformers, instmment relays, for rotor and stator laminations, and for magnetic shielding. Typical permeabihty—flux density curves for a 0.35-mm thick, transformer-grade lamination at various frequencies are given iu Figure 5, and the magnetic properties of thin-gauge (0.1 mm) material suitable for cut-cores and tape-wound cores are ihustrated iu Figure 6. A three- to fourfold iucrease iu initial and maximum permeabihty can be achieved by annealing alloys of ca 56—58 wt % Ni iu the presence of a magnetic field after the usual high temperature anneal. The 56 wt % ahoy hsted iu Table 4 is so treated.  [c.372]

Much work has been done on exploration and development of redox polymers that can rapidly and efftciendy shutde electrons. In several instances an enzyme has been attached to the electrode using a long-chain polymer having a dense array of electron relays. The polymer which penetrates and binds the enzyme is also bound to the electrode.  [c.45]

A third group includes silver—nickel, silver—cadmium oxide, and silver—graphite combinations. These materials are characterized by low contact resistance, some resistance to arc erosion, and excellent non sticking characteristics. They can be considered intermediate in overall properties between silver alloys and silver or copper—refractory compositions. Silver—cadmium oxide compositions, the most popular of this class, have wide appHcation in aircraft relays, motor controllers, and line starters and controls.  [c.190]

The nonoriented steels are subdivided into low, intermediate, and high siUcon steels. The first contain about 0.5—1.5% siUcon, used mainly in rotors and stators of motors and generators. Steels containing ca 1% siUcon are used for reactors, relays, and small intermittent-duty transformers.  [c.400]

Eor switch and motor housings, engineering resins such as thermoplastic poly(phenylene oxide) that has high impact strength, allowing thin walls, is used. With its low moisture absorption, it is a good electric insulator. It is also corrosion-, heat-, and fire-resistant. Polycarbonate is used for switches and outdoor electrical plugs because of its good low temperature impact strength and fire resistance. Eor lighting fixtures, polycarbonate is useful not only as a sheet glazing material for electrical lighting, based on its transparency, but also for mol ding housings and outdoor fixtures. Thermoplastic polyesters, eg, PBT, PET, and PCT (poly(cyclohexane-1,4-dimethanol terephthalate)), are playing increasingly important roles in such electrical appHcations as switches, wiring devices, connectors, and relays. Reinforced polyesters (thermoset) also play a role in power boxes based on their composite stmctural integrity and dimensional stabiUty. Epoxies play an important role in electrical laminates, eg, printed circuit boards, whereas high heat thermoplastics, eg, polyetherimide (PEI), polyethersulfone (PES), and polysulfone (PSO), are now penetrating this market via injection molding technologies. Overall, the superior performance of engineering thermoplastics will allow them to continue to grow in electronic appHcations as spaces become more confined and heat requirements increase. However, for the foreseeable future, workhorse resins such as PVC, LDPE, HDPE, ABS, and phenoHc will continue to dominate (12,40-42).  [c.333]

The semiconducting properties of sihcon carbide have led to its use in thermistors (temperature-sensitive devices) and in varistors (voltage-sensitive devices). Thermistors are used for measuring and controlling temperature, as compensating devices for induction coils in electronic circuitry, and for time-delay apphcations. Varistors protect the coils or contacts in relays and solenoids against high voltage surges, limit the inductive kick in oil burner ignition circuits, and stabilize circuits supphed by rectifiers.  [c.468]

London forces are caused by the electrons in nonpolar molecules circulating with extremely high frequency. This causes nonpolar molecules to be polar at any given instant, even though the polarity changes with high frequency. As with tme dipoles, attractive alignments are more favored because the molecules are free to rotate. Two nonpolar molecules begin to oscillate as they approach each other, and the attraction between them becomes stronger as the distance decreases. The first oscillator relays its orientation to the second at the speed of electromagnetic waves. Thus, when the molecules are far apart, there is a delay in the response of the second oscillator to the first, leading to weaker attraction at larger distances. The term dispersion forces comes from their effect on the index of refraction, which is frequency dependent. Hamaker (10) appHed London s expression for the attraction between two isolated molecules to calculate the energy of attraction for all the molecules in two separate particles. The result is the Hamaker constant, which is used for calculating the attractive force between particles. A further refinement is to include terms for the effect of solvent such as water. Hamaker constants for representative particles are shown in Table 2 (higher constants indicate greater attraction).  [c.148]

Electrical. The plant electrical system is sometimes more important than the steam system. The electrical system consists of the utihty company s entry substation, any ia-plant generating equipment, primary distribution feeders, secondary substations and transformers, final distribution cables, and various items of switch-gear, protective relays, motor starters, motors, lighting control panels, and capacitors to adjust power factor.  [c.227]

The Coulomb integral (ac) of the carbon atoms adjacent to the heteroatom (more electronegative than the carbon atoms in benzene because of the inductive effect of the heteroatom as relayed through the cr-bonds) is accommodated by making the appropriate Coulomb integrals more negative than a. This increases the agreement between the simple MO calculations and those based on elaborate, non-empirical treatments. It is convenient to express the value of ac in terms of a and /3, and so the Coulomb integrals used for the heteroatom and for the adjacent carbon atoms may be defined by two parameters h and h according to equations (1) and (2),  [c.5]

Figure 8>-58>b is the ladder logic diagram for the same mixing process. It involves rungs of parallel circuits containing relays (the circles) and contacts. Parallel oars on the rungs represent contacts. A slashed pair of bars depict a normally closed contact. A normally open momentary contact is shown on rung I in Fig. 8>-58>b. The ladder logic and diagram builder in PLCs can be programmed easily because there are only a limited number of symbols required in ladder logic diagrams.  [c.754]

Developed to replace hard-wired relay logic, the early PLCs were programmed using the same ladder logic diagrams used to represent logic implemented with hard-wired relays. As the initial target market was electrical, programming in ladder logic was a definite  [c.774]

Undervoltage Protection If a power outage occurs, it is necessary to remove motors from the line to prevent excessive starting current surges on the electrical system when voltage is reestablished. It is also unsafe to have drives starting indiscriminately when electrical service is reestablished. Conversely, it may be desirable to leave the motors connected during short voltage dips this is time-delay under-voltage protection. Instantaneous undervoltage protec tion disconnects the motor as soon as the voltage drops appreciably. This is satisfactoiy if continuity of operation is relatively unimportant. It is inherent in low-voltage magnetic starters when a power loss drops out all contactors as soon as a voltage dip occurs. If time-delay undei volt-age protec tion is desired for these controls, time-delay relays must be added to the standard control circuit. Because circuit breakers do not drop out on a voltage dip, undei voltage relays are necessary.  [c.2490]

Reverse-Phase Protection Reverse-phase relays are used on some large motors to prevent their starting when the electrical-system phase rotation is reversed because of improper wiring or maintenance. They are also used as undei voltage and voltage-b ance relays. Individual relays may be applied to each motor in place of the under-voltage relay, or one relay may be operated off a bus for several motors. Individual relays are more expensive but more rehable, particularly when motor circuits are changed frequently. This type of pro-tec tion is normally supphed only on high-voltage switch-gear-type starters.  [c.2490]

Adequate single-phase protection is provided on low-voltage ac motor starters by three overload relays, which are now standard. Rotor heating is not particularly a problem on smaller motors which have more thermal capacity, but it is important to protect the stator windings of these machines against burnout.  [c.2490]

Both differential and ground relaying detect ground faults. Ground-fault protection is located at the starter and protects the cable and the motor differential CTs are located at the motor and protect the motor only. Economic priorities indicate ground-fault protec tion first, adding differential protection when justified by potential savings in downtime and repair costs.  [c.2491]

Programmable Logic Controller (PLC) A microcomputer-based solid-state control system which receives inputs from user-supplied control devices such as switches and sensors, implements them in a precise pattern determined by instructions stored in the PLC memory, and provides outputs for control or user-supplied devices such as relays and motor starters.  [c.165]

This is also known as safe stall time or the locked rotor withstand capacity of the motor. This is the time during which the motor can safely withstand electromagnetic effects and consequent heating in a locked condition. These are drawn for the cold and hot conditions of the motor in Figure 2.16. Evidently, the motor must come to speed within this time, irrespective of type of load or method of switching. In a reduced voltage start-up or slip-ring motors the starting current would be low and these curves would signify that for any reason if the rotor becomes locked during start or run, or takes a prolonged time to come up to speed, the protective device must operate within the safe stall time. Generally, these curves are drawn for the stator to monitor the actual running condition and not the condition during start-up. The rotor can withstand much higher temperatures during a run. With the help of these curves, knowing the starting time and the starting current of the motor, one can ascertain the number of starts and stops the motor would be capable of undertaking. These curves also help in the selection of the protective relays and their setting as discussed in Chapter 12.  [c.44]

These can be started by adopting either a current limiting method or a definite time control method. In a current limiting method the closing of contactors at each step is governed by the current limiting relays which permit the accelerating contactor of each step to close when the motor current has fallen from its first peak value to the second pre-set lower value. The relays determine the closing time by sensing the motor data between each step and close only when the current has fallen to a predetermined value of the current relays. The closing sequence is automatic and adjusts against varying loads.  [c.83]

Scales can be coimected with printers, remote displays, bar code scanners, keyboards, relays, computers, and various controllers such as programmable logic controllers (PLCs). Scales typically have one or more simplex or duplex serial ports that can be current loop, RS-232, RS-422, or RS-485. Erequendy ports are programmable for on-demand or continuous data output, eg, for periodically transmitting weight data to a printer or continuously to a remote display. RS-422 and RS-485 are typically used in multidrop systems where a single computer may be used to communicate with several scales. Scales can be part of a local area network such as ARCnet, together with other devices such as printers, controllers, and computers. Scales often have an analogue output such as 4-20mA or 0-10 VE)C for communication with controllers such as PLCs. Some weight indicators have digital inputs and outputs (1/O) the inputs, for example, could be used for remote operation of scale buttons such as print or tare, whereas the outputs could be used to activate alarms when a particular weight is achieved. Weight indicators designed specifically for batching appHcations are also discussed herein.  [c.335]

Electrical ndNuclea.r Properties. Rare earths are often used as additives to modify the performance of several electronic components. Neodymium stabilizes the thermal variation of the dielectric constant of barium titanate, BaTiO, over a large temperature range (NPO-type capacitors). Doping by trivalent rare earths gives BaTiO semiconducting properties useful for appHcations involving electromagnetic wave absorption or to obtain the positive temperature coefficient (PTC) effects used in the realization of sensors or thermal relays. The discovery of one of the most famous high superconductors that works using Hquid nitrogen involving rare earths is YBa2Cu20y g (38) which has a critical temperature over 90 K. These materials are not, however, ready for industrialization.  [c.548]

Uses of Soft Magnetic Materials. Because of low resistivity, iron and low carbon steels tend to be used in static apphcations, eg, pole pieces for electromagnets and cores for d-c magnets or relays. Low carbon steels and the lower grade Fe—Si alloys are used in small motors and generators. The higher grade Fe—Si alloys have traditionally been used in power distribution transformers and large rotating machinery, but certain amorphous iron—metalloid alloys are increasingly being used in the manufacture of distribution transformers by General Electric, Westinghouse, and Osaka, for example. Fe—A1 and Fe—Al—Si alloys are used primarily as recording head materials because of their high hardness, resistivity, and saturation magneti2ation. Ni—Fe alloys used widely in high quahty relays, transformers, converters, and inverters in the electronics industry, have much higher permeabihty and lower loss than Fe—Si alloys. The Co—Fe alloys are used because of their higher saturation polari2ation (fiux density) and Curie temperature, but have the disadvantage of poorer workabiUty and higher cost. Because of their exceptionally higher resistivities, ferrites are particularly suitable for high frequency apphcations.  [c.377]

Uses. Hard ferrites are used widely in electromechanical devices, eg, generators, relays, motors, and magnetos electronic appHcations, eg, loudspeakers, traveling-wave tubes, and telephone ringers and receivers antitheft tags, hoi ding devices such as door closers, seals, and latches and are perennial favorites in various toy designs. Loudspeakers are the largest use of permanent magnets (ca 50%). Strontum ferrites exhibit higher coercivities and are increasingly being produced.  [c.381]

Programmable Logic Controllers. Initially, programmable logic controllers (PLCs) were dedicated, stand-alone, microprocessor-based devices executing straightforward binary logic for sequencing and interlocks. These were originally intended for appHcations which, prior to that time, had been implemented with hardwired electromechanical and electrical relays, switches, pushbuttons, timers, etc (8). PLCs significantly improved the ease with which modifications and changes could be implemented to such logic. Although many of the early appHcations were in the discrete manufacturing industries, the use of PLC quickly spread to the process-related industries. From the time of their introduction in the late 1960s, PLCs have become increasingly more powerful in terms of calculational capabiHties, eg, PID algorithms data highways to connect multiple PLCs improved operator interfaces and interfaces with personal computers and DCSs. In processes where control is dominated by logic-type controls, PLCs are a preferred  [c.61]

PLCs allow the connection of combinations of software relays, switches, etc, and do not require the hardwiring of physical devices. The more complex and interconnected the logic and the greater the number of devices, the greater the benefits of the PLCs in terms of flexibiUty in implementing, changing the logic, and saving physical space. As digital technology has improved, the use of PLCs in these appHcations has also increased. Various approaches have been devised to increase rehabiUty (8—10). Dynamically redundant PLCs may be hooked up in series (Fig. 4a) or in parallel (Fig. 4b). The series configuration minimises the chance that a triac failing to turn on causes the solenoid to energize when it should not, because now the triacs in both systems would have to fail. However, the series hookup also increases the possibiUty of shutdown owing to the failure of a single triac failing open. The parallel hookup reduces the possibiUty of a shutdown owing to a single triac failing open but, in turn, increases the probabiUty of an unsafe condition owing to a triac failing closed. Whereas redundant PLCs increase rehabiUty, they still requite regular checking.  [c.62]

A bone is classified according to shape as flat, long, short, or irregular. A living bone consists of three layers the periosteum, the hard cortical bone, and the bone marrow or cancellous bone. The periosteum is a thin coUagenous layer, filled with nerves and blood vessels, that suppHes nutrients and removes cell wastes. Because of the extensive nerve supply, normal periosteum is very sensitive. When a bone is broken, the injured nerves send electrochemical neural messages relaying pain to the brain.  [c.185]

Another potential use of redox enzymes ia biosensiag involves the conversion of enzymes from electrical insulators to electrical conductors (8—12). An electrically conductive redox enzyme is expected to have greatiy enhanced efficacy in electrochemicaHy transduced biosensors. In the native, ie, unmodified, enzyme the active site is generally surrounded by insulating polypeptide regions, representing a formidable barrier to electron transfer from the enzyme to the electrode. Chemical modification of these protein regions can, however, render the regions conductive, imparting facile electrical accessibility to the active site. A typical modification involves the covalent bonding of redox moieties to several sites on the enzyme, usually at the lysine residues. Glucose oxidase [9001 -37-OJ, for example, has been modified using ferrocene [101 -54-5] C QH QFe, groups, which act as electron relays, mediating conduction to the electrode. Another approach has become known as electrical wiring of redox enzymes. In this method, the redox enzyme is electrostatically complexed to a synthetic polymer that contains a high concentration of redox sites. The polymer provides a conduction pathway or molecular wire between the enzyme and the electrode.  [c.108]

Electrical connectors are mechanical devices that connect wires, cables, printed circuit boards, and electronic components to each other and to related equipment. Connector designs include miniature units for microelectronic applications specialized cable tack and panel designs for incorporating combinations of a-c, d-c, and radio-frequency conducting contacts and high current connectors for industrial application and for transmission and distribution of electrical power in overhead and underground networks. Further categorization of connectors can be made according to application, whether connectors permanently join conductors and components or permit separation and rejoining the means used to effect connection, whether by fusion (welding, soldering) or by pressure, the values of which can be small or great enough to severely deform metal the distribution type, whether of power or of low (signal) levels of current and the conductor size. The term electrical contact describes the junction between two or mote curtent-carrying members that provide electrical continuity at their interfaces. Connector contacts ordinarily remain stationary in active circuits, eg, they ate not mated or separated. Components having electrical contacts other than connectors include circuit breakers, switches, relays, and contactors that ate designed to intermpt or to establish current flow in active circuits, and slip rings and bmshes that transmit current from a stationary to a moving frame of reference.  [c.23]

Electrical and electronics are the largest end uses for PPS. Principal advantages of PPS are strength at high temperature, dimensional stabiUty, flame and arc resistance, and precision moldabiUty. Products are coimectors, cod bobbins, relays, and switches. The growth of electrical and electronic end uses is 10%. Apphances are the second largest ends uses for PPS resins as a replacement for phenoHc, but also for metal parts.  [c.274]

Limit Switches and Stem-Position Transmitters Travel-limit switches, position switches, and valve-position transmitters are devices that, when mounted on the valve, actuator, damper, louver, or other throtthng element, detect the component s relative position. The switches are used to operate alarms, signal hghts, relays, solenoid valves, or discrete inputs into the control system. The valve-position transmitter generates a 4-20-mA output that is proportional to the position of the valve.  [c.786]

It is essential for proper design to have the data for refrigerant-oil miscibility under all operating conditions. Some refrigerant-oil combinations will always be miscible, some always immiscible, but some will have both charac teristics, depending on temperatures and pressures apphed. Defrosting is the important issue for evaporators which are cooling air below freeziug. Defrosting is done periodically, ac tuated predominantly by time relays, but other frost indicators are used (temperature, visual, or pressure-drop sensors). Defrost technique is determined mostly by fluids available and tolerable complexity of the system. Defrosting is done by the following mechanisms when the system is off  [c.1115]

Package-Handling Systems The control of packagehandling systems may depend on simple motor starters, on interlocked relays with photocell control, or on computers. Sohd-state controls are finding much application in the last two systems.  [c.1975]

Line Starters and Combination Starters A line starter consists of a contactor (motor-starting switch) and motor-overload relays, (Contactors are capable of canving and interrupting normal motor-starting and -running currents they are not, hovv ever, normally capable of interrupting short-circuit currents. They must be backed up by fuses or a circuit breaker for this function,  [c.2488]

Centralized Control As mentioned previously, motor starters rnav be located either at the motor or at some remote point. Frequently they are grouped at a location convenient to the source ol powder. The leeders radiate Irorn this point to the individual motor loads, A convenient method is the control-center modular structure lor lovv -voltage control, into which are assembled motor starters and other control devices. The individual starters can be drawn out ol the structure lor rapid, easy maintenance and adjustment. With this construction it is easy to change starter size or add additional starters. All the starters are in one location, so that intenviring is simple and easy to check, Aiixiliaiv relays, control translorrners, and other special control devices can also be included. See Fig, 29-7,  [c.2489]

Overload Protection Overload relays lor protecting motor insulation against excessive temperature are located either in the motor control or in the motor itsell. The most common method is to use thermal overciirrent relays in the starter. These relays have heating characteristics similar to those ol the motor which they are intended to protect. Either motor current or a current proportional to motorline current passes through the relays so that relay heating is comparable to motor heating.  [c.2489]

High-voltage contactor-type motor controls depend on power fuses for short-circuit protection. The fuses are coordinated with the overload relays to protect the motor circuit over the full range of fault conditions from overload conditions to solid maximum-current short circmts.  [c.2490]

FIG. 29-8 Typical high-voltage ac motor starter illiistrating several protective schemes fuses, overload relays, ground-fault relays, and differential relays with the associated current transformer that act as fault-current sensors. In practice, the differential protection current transformers are located at the motor, hut the relays are part of the starter.  [c.2490]

Ground-Fault Protection High-voltage motors (2300 V and above) should be protected with ground-fault relays if the power source is grounded (see Fig. 29-8). This scheme includes a large-diameter current transformer (CT) encircling all three motor leads. Short-circuit current to ground flows through the CT to ground and returns to the power source external to the CT this unbalance induces current in the CT and ground relay to shut down the motor. With this protection only two overload relays and two line CTs (rather than the standard three) are required, so the additional protection is very economical. It cannot be used, however, unless the power source is grounded.  [c.2491]

In a fast bus transfer scheme, the phase angle is monitored through special relays (Section 16.11) which initiate the changeover, so that the self-induced e.m.f. of the motor does not slip too far in the phase angle, A6, between the two voltages and the motor is not exposed to excessive overvoltages. At higher A6 the relays will block the transfer and protect the system from excessive voltages. If the fast bus transfer fails to change over automatically, slow changeover takes place and the motor-induced e.m.f. is allowed to decay by up to 40-20% before the bus transfer lakes place. For insulating and braeing the windings, such bus transfers may occur up to 500 limes in the total lifespan of the motor.  [c.188]


See pages that mention the term Relays : [c.296]    [c.167]    [c.45]    [c.366]    [c.785]    [c.2489]    [c.2490]    [c.157]   
Surface production operations Ч.2 (1999) -- [ c.525 ]