Electrical control systems pdf

 

    In this chapter, we describe a general process for designing a control system. . A common example of an open-loop control system is an electric toaster in the. This section provides an introduction to control system design methods. P.A. . to the study of mechanical, thermal, fluid systems via convenient electric circuits. This is an example of a closed loop Control System. Control Systems output of the system is typically not an electrical signal. In the example.

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    Electrical Control Systems Pdf

    Chapter 1 covers the introduction of control systems engineering, basic however, are limited to the selected systems; electrical, mechanical. Feedback control systems. . current knowledge in feedback and control systems . .. by the generation and distribution of electrical power. In this lecture, we lead you through a study of the basics of control system. A control system is an interconnection of components forming a system.

    This system allows the user to set a desired temperature which is then compared to the room temperature measured by a temperature sensor. With the help of a microcontroller, the system responds by turning ON any of the two 2 loads Fan or a heater automatically depending on the temperature difference. The Fan is triggered ON when the room temperature is higher than the set temperature and the heater is triggered ON when the room temperature is lower than the set temperature. The system was designed and simulated using Proteus 8, circuit building software used for building electronics system. Proteus software was used to design and simulate the main circuit, and Micro-C hex file was loaded on the Proteus schematic design. A 5 V DC power supply was designed in order to provide a biasing voltage to most of the active devices used in the system design circuit. The DC power supply was designed and simulated using Multisim software. The system was simulated and simulation results were in accordance to the design specifications. Keyword: Electrical engineering 1. Introduction With the advancement of technology, automation has become part of our lives. Areas in the home that are usually occupied by people, such as the living room and bedrooms need to be maintained within habitable temperature ranges.

    If there is voltage at a-b on the coil, the coil is defective or the contactor has seized also note voltage level.

    Test power supply, fuses, thermal overload trips, measure voltage at motor terminals. Cage motors have a very low starting torque, and must not therefore start under heavy load1 lf there is voltage at the motor terminals, check the motor.

    Switch off the voltage, disconnect at the terminal board and check windings. Measure winding resistance with measuring bridge and compare: The insulation resistance between the windings, and between the windings and earth is measured with an insulation tester or insulation resistance bridge.

    A cage motor does not start in the star position of the star-delta switch, only on the delta stage: Motor torque in star connection is so low that it cannot operate the driven machine; too high a load. Reduce starting lad, use a starting V-belt or use a motor of higher rating - slipring motor. Motor starts in the operating position of the star-delta switch, speed greatly reduced under load: Motor has difficulty in starting, loud humming noise when switched on, motor heats up quickly: Measure phase currents; if they differ seriously from specification, the motor must be rewound.

    Disconnect cables from terminal board, and remove links from terminal board. Measure insulation between phases and to case; replace winding. Open circuit in stator 2. Open circuit in rotor 3. Brushes do not bed on slipring 4. Bearing seized. Test stator circuit: Test supply, fuses, switches, measure voltage at the stator terminals, check the windings as for the cage motor.

    Test rotor circuit: Disconnect rotor terminals and measure rotor stalled voltage with the stator switched on. Compare measured voltage with the voltage specified on the rating plate. If no voltage is measurable - open circuit in the rotor. If rotor voltage corresponds to value specified - switch off stator and test sliprings, carbon brushes and resistances for open circuit. After checking rated data on rating plate: Test plain bearings, ball bearings, shaft clearance; if necessary replace bearing bushes or ball bearings.

    Disconnect supply cables from the starter, insulate brushes from slip rings with piece of paper or wood, and test starter cable insulation; remove faults.

    Detach supply cables from terminal board, and remove links on terminal board; test insulation between phases and to earth; replace winding. Lift brushes from the sliprings; remove belt from pulley, motor will then idle; repair as required.

    Establish, by touching, whether the winding is heating irregularly, considerable heating at location of fault indicates rewinding. Test voltage supply, inspect starter and windings open or short-circuit or earth fault. Check type of motor, because different types have different characteristics. First establish whether armature and field voltage are present. Many motor control systems are provided with field monitoring devices to prevent the armature from taking too high a current or becoming damaged in the event of field failure.

    This point must also be given attention when faultfinding. Voltmeter at L2 and terminal t of field control element, then at terminal s, noting the position of the field control element. If voltage is present at F1 - F2, test armature circuit and winding FT - F2 for open circuit, turn-to-turn fault or earth fault. If voltage is present at F1 - F2 and A1 - A2, and if motor is still not running, check load and armature.

    Phase angle between high and low voltages is either 0 or If the phase angle is not the same, only the low voltage connections need be replaced. If measurement is carried out with a voltmeter, there must be no voltage between two winding terminals which are to be connected to a conductor on the output side. In the case of parallel connection of three-phase transformers, the following must be remembered: They must belong to the same switching group, with the possibility of equalising different characteristics by making suitable terminal connection.

    A voltmeter is installed between terminals phases of the same name. If this voltmeter does not indicate a voltage, the circuit is in order. The supply cable for the equipment to be protected is monitored by a total current converter for residual current. The equipment casings are earthed. If fault to frame occurs in equipment thus protected, a fault current flows via earth; the sum of the currents in the supply cables is no longer 0, and the residual current device operates.

    The switch also protects against contact of live-conductors to earth earth fault. Fault - Connection between neutral N and protective conductor PE after the residual current device.

    If the residual current device falls to trip despite exceeding the rated fault current, this leads to the conclusion that there is a fault between the neutral N and the protective conductor PE , after the residual current device. Most of the fault current flows back via the neutral conductor. In the event of fault to frame after rectifier circuits, the unidirectional fault current flow may lead to magnetisation of the core of the residual current device, so preventing tripping.

    Residual current devices FI safety switches bearing the symbol must cut out reliably even in the event of fault to frame after rectifier circuits pulsating direct fault currents. An insulation fault between the outer and protective conductor occurs before the residual current device. An earth leakage current flows via the earth electrode and an earth electrode voltage is generated.

    The residual current device does not trip. To avoid such faults in the area of the residual current device, the protective conductor before the residual current device should not installed together with the supply cable in one conduit.

    Safety switch trips: One reason for this might be a connection between neutral conductors in different residual current circuits behind the safety switch. In this case possible fault currents are distributed in any neutral conductors, and this may lead to undesirable tripping of a safety switch. Safety switch trips too early: This means that it trips before the permissible tripping range is reached.

    Either the protective conductor is defective, or the system already has a certain basic fault, producing a current below the release current. This occurs in measuring circuits where the basic leakage current is added to the test current supplied by the measuring instrument therefore the safety switch trips earlier. If the residual current device has tripped, all poles of the supply are disconnected. This means that the circuit in which the fault has occurred cannot be identified immediately.

    All the circuit breakers are now switched off or all the fuses are unscrewed, and the residual current device is reset. One of the circuit breakers is now switched in, or a fuse is screwed in until the residual current device trips again. The defective circuit is now identified. The main circuit breaker is now switched off or the fuse unscrewed, and the residual current device as well as the remaining circuits which have no faults are connected. In the defective circuit switch off all current using equipment, if plug-in pieces of equipment are being used, unplug them and reconnect the circuit.

    If the residual current device now holds, one of the pieces of equipment is defective. If the residual current device fails again, the circuit must be examined with insulation testers and the circuits sub-divided at the terminals to isolate the fault. The insulation of the N conductor must also be tested. Damp and wet areas are particular sources of faults. Sometimes faults occur where the residual current device trips irregularly. In this case install a device with a lower tripping current, these trips more easily and faultfinding is therefore simpler to carry out.

    If the residual current device repeatedly cuts out and all the circuit breakers are switched off; this indicates a fault between neutral and earth! WARNING The fault current release value of the residual current device may only be changed if permitted by the earthing condition of the system, i. In protective earthing, the casings of the equipment to be protected are connected via a protective conductor to a suitable earth electrode.

    Fault current flows back through the ground It must be remembered that the specific earth resistance varies due to seasonal climatic fluctuations dry weather, wet weather. Fault current flows back via a metal water pipe network to the electricity generator or transmitter e.

    If fault to frame takes place in protectively earthed equipment, a high current flows via the fault location and the protective earth electrode to the supply earth of the network, and the series-connected fuse cuts out.

    If several Current using units are protected by a single fuse, the fault must be located by measuring the insulation resistance to deter- mine which of the current using units is defective.

    The cases of the equipment to be protected are connected to the PEN conductor. Short circuits to frame on equipment employing PEN conductors causes the series-connected fuse to trip, for a large current flows through the fault and the PEN conductor. In cables having a cross section of less than 10mm2, the PEN conductor must be divided into an N and a PE conductor on the right in the diagram.

    The risk of conductor breakage is avoided by division in the case of small conductor cross-sections. The PE and N conductors must not be reconnected after the division. Example of PEN conductors in a three-phase four-wire network. The neutral and protective conductors are laid separately.

    No current normally in the PEN conductor. During installation the fuse in the defective circuit blows. It must then be checked whether the current using unit is short-circuiting or has an earth fault. If several current using units are protected by a single fuse, the fault must also be isolated between the units, i.

    A high degree of operational safety is achieved with the protective cable system e. If fault to frame occurs, a fault current flows due to the insulation and capacitance condition of the network. No contact voltage occurs due to the connections of the protective conductor to the numerous earth electrodes.

    For immediate location of the fault to frame the mains - earth insulation condition is monitored signal is received in the control room.

    The fault must then be removed as quickly as possible. The rise in voltage in fault-free conductors increases the possibility of a second fault to frame. This causes the equipment with the least protection to be disconnected.

    The double fault to frame earth short-circuiting then becomes a single fault again. The first fault is indicated by the monitoring system, but there is no indication of where the fault is located.

    Control System | Closed Loop Open Loop Control System

    The faultfinding is carried out by measuring the total current of the individual circuits from the supply transformer. Since an earth fault gives rise to a fault current albeit small , the sum of the currents in the outer conductors and the neutral conductor is no longer zero 1st law of Kirchhoff.

    The individual circuits are measured until the damaged circuit is found. A second possibility would be to switch off the individual circuits and observe the monitoring device until it no longer indicates a fault, but this procedure is not often possible because of operational breakdown. Testing of voltages U1, U2, U- with voltmeter and oscilloscope for open circuits. Compare the measured voltages U1, U2 with the data on the type plate. If the transformer voltages conform to the specifications, the fault lies in the diodes.

    Each diode must then be checked individually oscilloscope. If a pulsating d. Diodes and capacitors can only be replaced. In most cases the r. In most cases a defective power semiconductor can be checked with an ohmmeter 1. Disconnect to measure values. Apply a threshold voltage of approx. If the measurement is carried out so that the positive pole of the ohmmeter is located at the anode of the diode to be tested, the resistance value must be lower than that in the reverse direction.

    If the positive pole is located at the cathode, the instrument indicates a very high resistance value. If the diode is destroyed, a low resistance value is indicated in both directions. If the diode has a high resistance in both directions, there is an open circuit and the diode must be replaced. These can have a high resistance in both directions. If the thyristors are intact, the Instrument does not show any deflection in either direction, but if the thyristors are destroyed, 0 ohm can be indicated.

    In addition to the arithmetical mean value and r. This circuit is most frequently used for powers of up to 2 kW. Inductance opposes all variations in the current, and so smoothes it. The load current ia is continuous. What is the rescue procedure in the event of electrical accidents particularly for release from the circuit?

    In the sketch below, draw circuits to illustrate the following: With reference to insulation testing in an installation, name the individual insulation resistances which should be measured. Name three faults which could cause a motor overload to trip when a cage motor is switched on? State the range of voltages and currents which can be dangerous to man. In the sketch below, draw in the current and voltage paths which would be highly dangerous. Name five items of test and measuring equipment used for faultfinding, and state their uses.

    The following faults occur on fluorescent lamps: Lamp does not come on 2. Lamp does not come on, starter switches continuously 3. Lamp lights brightly and fails to come on again. State two possible faults if a cage motor with star-delta starting will only start in the delta connection.

    Switch off at all poles and on all sides. Protect against accidental switching on again. Test for freedom from voltage. Earth and short-circuit. Cover adjacent live parts and protect danger point. Switch off the supply. Remove the victim from the circuit. Apply first aid immediately.

    Inform doctor, rescue service and police. Open circuit, fault to frame, short-circuiting, earth fault, short circuit between turns, phases. Conductors to earth, conductor to conductor and system to earth should be measured.

    The following are tested: Connections to mains, load, remote Connection to mains, load, remote control system or control system Check whether the fault occurs when the current using units are disconnected. Mechanical faults bearings, chuck in drilling machines, gears Electrical faults conductor interrupted, etc Break in supply cable test fuses and motor safety switch Break in stator circuit After switching off, loosen connections on terminal board, and examine windings, replace stator winding if necessary.

    Break in rotor circuit inspect brushes and rotor resistances, test rotor winding, replace if necessary. Measurement in forward direction positive pole of measuring instrument connected to the anode - relatively low resistance. Measurement in reverse direction positive pole of the measuring Instrument connected to the cathode , a high resistance is indicated.

    If a low resistance is measured in both directions, the diode is destroyed. The fault to frame is caused by a conducting connection between a conducting part of the operating circuit and a conducting part which does not belong to the operating circuit.

    In short-circuiting there is a conducting connection between live operating parts. Conductor break - one strand is- broken Earth fault - Contact between winding and laminations or casing Turn-to-turn fault - Contact between two turns of a coil Phase-to-phase fault - Contact between two winding lines. Ohmmeter - Cable open circuit, examine power semiconductor Resistance measuring bridge Wheatstone bridge - measure winding resistance.

    This fault occurs in the supply cable motor safety switch has tripped , break in the stator and rotor circuit, or due to seized bearing. Either the star-delta contactor has a contact break, or the torque in the star connection is so low that the working machine cannot be started.

    Starter too small replace Starter has poor contact locate open circuit with test lamp; either bridge the contact or replace starter. Starter incorrectly connected - compare with wiring diagram. Break in the supply cable - test terminals and cables Brushes do not bed an commutator Replace brushes if necessary.

    Field winding interrupted - test Terminal voltage too low - measure Fault in starter - test contacts and connections Bearing seized. Brush sparking occurs where the commutator is out of round or if it is clogged with oil. Also when the motor is overloaded, displaced brushes, turn-to-turn fault in the field or inter-pole winding, and when the bearings are damaged. Transformer oil overheating - due to overloading or too high connection voltage high primary current - turn or earth fault low voltage - partial turn-to-turn fault.

    Flag for inappropriate content. Related titles. Jump to Page. Search inside document. EE Edition: Protect against reconnection. Test for no voltage. Earth and short-circuit remembering correct sequence. Cover adjacent live parts and enclose any danger points. Connection is carried out in the reverse order. The resistance of the human body depends on: Current over 50 mA and voltages from 50 V upwards can be fatal.

    Release the victim from circuit. Apply first aid. Inform doctor, rescue service. Report accident to police. Application If there is - no breathing a dilation of the pupil and no reaction at incidence of fight no pulse to feel at the carotid artery Performance - Place victim on a solid surface lying on the Back Press the lower half of the breastbone with the eminence of the hands put the second hand exactly on the first - the fingers don't touch the chest about 3 to 4 cm downward.

    Keep your arms stretched! The procedure always has to start with artificial respiration 5 times. Test lamp: Possible causes: Replace lamp. Single-phase V a. Two-way lamp circuit: Mains voltage too low Lamp defective Poor contact, open circuit, choke, capacitor Starter damaged. Mains voltage must be greater than V; Replace lamp Test connections, contacts and ballast Replace starter Lamp does not come on properly: Lamp does not come on; starter switch operates continuously - Starter is located in supply cable between lamp and ballast Lamp burning voltage too high; end of lamp life Remedy: The following must be tested: Switches and speed controls for open circuit and serviceability.

    Check motor windings for turn-to-turn fault and open circuits. Control circuit does not work: If possible carry out an operational test on the circuit remove main circuit fuses.

    Contactor remains actuated, although no voltage on coil: Clean magnet body. Voltage present on coil, contactor is not actuated. Coil interrupted, seized voltage too low. Testing the voltage. The machine is tested for mechanical damage: Motor terminal board for star and delta connections: Insulation resistance of windings relative to each other: Insulation resistance of windings to earth: Motor has difficulty starting; excessive speed reduction on load: One possibility the electrical contractor may decide upon is to supply the garage from a spare way in the consumer unit and make the small installation in the garage part of a TT system fig 3.

    For precise details on the fuse boxes, please refer to the electronic service information system ELSA. We respect copy right policy of principle of power system by vk mehta book grading system is to reinforce the importance of continuity of supply for the whole site and to help to assess the level of consequence of a power failure — that is, an increase in patient risk or business risk needs to have a corresponding increase in the integrity and resilience of the electrical distribution providing that service.

    The objective of the hours. Industrial building managers need the right wires, fittings and switches to make repairs. The baseline reports provide an overview of elements of the electricity system.

    We are fully stocked with over , square feet of electrical supply nyc to better serve all of our customers. We have the electrical supplies or solutions for your success. The distribution system can be divided in to: The vertical supply system rising mains.

    Hence, it is evitable that such community groups are aware about the basics of water supply system, operation maintenance of water and Distribution Feeder Principles. Secondary transmission in most countries is carried out by 3-phase, 4-wire system.

    Design the system in compliance with all applicable building and electrical codes. Square d: Gordon Electric Supply, Inc.

    Supply main is the end point of an electrical supply system. Charging is required as the capacity of a battery to supply current is limited to the energy stored in it in the form of chemical energy.

    Figures —12 and —13 2 Equipment Grounding. Electrical wire: We offer a wide range of electrical wires like wire with fire alarm, shielded and unshielded wire, thermostat wire and high temperature electrical wires at Gordon Electric Supply, Inc. This experience suggested there might be other people much like myself—outside the power industry, but vitally concerned with it— Earth Electrode: When a conductor or conductive plate buried in the earth for electrical earthing system.

    The subsystem represented in Figure 1 b could be one of a small power plant working as distributed generation DG.

    Understanding Access Control Systems

    Electrical Power Systems in Buildings We will discuss the general principles for how electricity is moved from the utility lines to a convenience outlet in a room. All matter is composed of atoms. Battery supplies the current to run the starting motor, various lights and horn, etc. The system components vary depending on the size of the building so we will address systems for small and large buildings.

    Service Equipment The equipment on the load customer end of the service conductors, which serve a customer, that make up the main control and shut off of the power supply. Cooper Electric provides exceptional electrical products and services for industrial contractors, commercial buildings, educational facilities, and more.

    Abstract: Residential, Commercial and Industrial Electrical Systems is a comprehensive coverage on every aspect of design, installation, testing and commissioning of electrical systems for residential, commercial and industrial buildings.

    Electrical distribution is the final stage in the delivery of electricity.

    Control System | Closed Loop Open Loop Control System | Electrical4U

    As an AE, you must know the electric power systems of these aircraft. However, the widespread use of electrical energy by modern civilisation has necessitated to produce bulk electrical energy economically and efficiently. Earth electrodes are in different shapes like, conductive plate, conductive rod, metal water pipe or any other conductor with low resistance. Handbook of Electrical Engineering stored in a retrieval system or transmitted in any form or by any means, 1. First we will consider the physics behind electricity.

    In medical locations of group 1 and group 2, a minimum of two lighting circuits shall be provided from separate sources of supply. We also offer consultation on commercial indoor and outdoor lighting applications.

    In early days, there was a little demand for electrical energy so that small power stations were built to supply lighting and heating loads. Service: The conductors and equipment for delivering electric energy from the serving utility to the wiring system of the premises served. It is at this beginning stage that the designer develops a general idea as to the nature of the distribution system.

    For worldwide implementations of the power management system, you can rely on engineering execution centers on every continent across the globe. Between the generating stations and the distribution stations, three different levels of voltage transmission, sub-transmission and distribution level of voltage are used.

    We provide The best distribution system is one that will, cost-effectively and safely, supply adequate electric service to both present and future probable loads. Distribution substations connect to the transmission system and lower the transmission voltage to medium voltage ranging between 2 kV and 35 kV with the use of transformers. The electric power requirements and the electric system components of aircraft vary widely Single Line Diagram of Power Supply System The electrical energy is produced at generating stations, and through the transmission network, it is transmitted to the consumers.

    Hussain Al-Mashat 1 Distribution Inside Large Buildings In large buildings the type of distribution depends on the building type, dimension, the length of supply cables, and the loads.

    Integral Energy, your local Network Operator or the Integral Energy Power Quality Centre can give Separately Derived System: A premises wiring system whose power is derived from a battery, a solar photovoltaic system, or from a generator, transformer, or converter windings, and that has no direct electrical connection, including solidly connected grounded circuit conductor, to supply conductors originating in another system.

    The essential electrical system will supply power for task illumination related to life safety which is necessary for safe cessation of procedures and all related anesthesia and resuscitation equipment. One of the sources shall be connected to the electrical supply system for safety services.

    One of the most common forms of AC Generator is an alternator. Figure 2 Converting wind power to electrical power in a wind turbine [17 ]. An electric supply system consists of three principal components viz.

    Johan Lundquist of the Chalmers University of Technology in Goteberg, dealers electrical supply is a privately held, employee-owned company engaged in the distribution and wholesale of electrical supplies to the commercial, residential, and industrial construction industries and electric utility companies. Total Harmonic Distortion and Effects in Electrical Power Systems Associated Power Technologies Introduction The power quality of distribution systems has a drastic effect on power regulation and consumption.

    It uses electromagnetism to change some of the engine's mechanical energy into electrical energy for powering the vehicle's loads and for charging the battery. Design the system with a minimum of electrical losses due to wiring, fuses, switches, and inverters. Metal parts of electrical raceways, cables, enclosures, and equipment must be connected to the supply source via the effective ground-fault current path. All Toyota alternators are rated by amps of current output from 40 to 80 amps.

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