TRAINING MANUAL ON INDUSTRIAL CONTROLS pptx

Training document on industrial control

1. INDUSTRIAL CONTROLS

2. COURSE OUTLINE INTRODUCTION TO INDUSTRIAL COMPONENTS OVERVIEW OF PRODUCT RANGE ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS STARTERS TIMERS EMERGENCY CIRCUITS ELECTRICAL PROTECTION ELECTRICAL SAFETY

3. DAY 1 OUTLINE INTRODUCTION TO INDUSTRIAL COMPONENTS OVERVIEW OF PRODUCT RANGE ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS

4. Control and Signaling Units

5. CONTROL SWITCHES Switches are commonly employed as input devices to indicate the presence or absence of a particular condition in a system or process that is being monitored and/or controlled. In motorized electromechanical systems, limit switches provide the function of making and breaking electrical contacts and consequently electrical circuits. A switch has two pieces of metal called contacts that touch to make a circuit, and separate to break the circuit.

6. PUSHBUTTONS AND SELECTOR SWITCHES They are manually ( or operator) actuated switches which communicate the intentions or desired conditions from the operator to the machine or process. They are either latching or non-latching switches. Their switch contacts are either normally open (NO) or Normally closed (NC). Typical applications include : Starting and stopping motors Opening and closing solenoid valves Turning lamps and sirens on and off Emergency interruption of processes CONTROL

7. PROXIMITY SWITCHES Proximity switches open or close an electrical circuit when they make contact with or come within a certain distance of an object. They are used to determine the condition that an object is present or absent. Proximity switches are most commonly used in manufacturing equipment (P.E.T. machines, packaging, palletizing, filling, etc), robotics, and security systems. CONTROL

8. CONTROL PROXIMITY SWITCHES There are four basic types of proximity switches based on the different principles of operation. They are: Infrared (photoelectric) Acoustic Capacitive Inductive Different proximity sensor targets demand different sensors. For example: A capacitive or photoelectric sensor might be suitable for a plastic target; An inductive proximity sensor requires a metal target. The maximum distance that this sensor can detect is defined "nominal range". Some sensors have adjustments of the nominal range or means to report a graduated detection distance. Their switch contacts are either normally open (NO) or Normally closed (NC).

9. CONTROL PROXIMITY SWITCHES – WIRING CONCEPTS WIRING DC CIRCUITS - SINKING AND SOURCING CONCEPT Sinking and Sourcing are terms used to define the control of direct current (DC) flow in a load. The concept of sourcing and sinking is independent of the component (transistor, mechanical relay) that implements the operation. While this concept applies to any DC circuitry, the component that implements the circuitry may vary.

10. SOURCING DEVICES A sourcing device provides the power or a positive potential. Sourcing devices 'push' the current through the load. Terms used to describe sourcing devices include PNP, Open Emitter, Normally Low, and IEC Positive Logic. PROXIMITY SWITCHES – WIRING CONCEPTS WIRING DC CIRCUITS - SINKING AND SOURCING CONCEPT CONTROL

11. SINKING DEVICES A sinking device provides a path for the current to ground and is not responsible for powering the device. Terms used to describe sinking devices include NPN, Open Collector, Normally High, and IEC Negative Logic. PROXIMITY SWITCHES – WIRING CONCEPTS WIRING DC CIRCUITS - SINKING AND SOURCING CONCEPT CONTROL

12. +VDC PROXIMITY SWITCHES – WIRING CONCEPTS WIRING DC CIRCUITS - SINKING AND SOURCING CONCEPT CONTROL

13. Field devices on the positive side (+VDC) of the field power supply are sourcing field devices. Field devices on the negative side (DC COM) of the field power supply are sinking field devices. Sourcing field devices must be connected to sinking I/O cards and vice versa. Sinking field devices must be connected to sourcing I/O cards and vice versa. RULES PROXIMITY SWITCHES – WIRING CONCEPTS WIRING DC CIRCUITS - SINKING AND SOURCING CONCEPT CONTROL

14. CONTROL PROXIMITY SWITCHES – WIRING CONCEPTS Wiring Diagrams for AC

15. CONTROL LIMIT SWITCHES A limit switch is configured to detect when a system's element has moved to a certain position. A system operation is triggered when a limit switch is tripped. Limit switches are widely used in various industrial applications, and they can detect a limit of movement of an article and passage of an article by displacement of an actuating part such as a pivotally supported arm or a linear plunger.

16. CONTROL LIMIT SWITCHES The limit switches are designed to control the movement of a mechanical part. Limit switches are typically utilized in industrial control applications to automatically monitor and indicate whether the travel limits of a particular device have been reached or exceeded.

17. CONTROL LIMIT SWITCHES- WIRING EXAMPLES Lamp connected to NO contact Lamp connected to NC contact

18. APPLICATIONS

19. Description of application: To detect six (6) jars with white metallic lids inside of an open cardboard box. Applicable industries: Bottling; Food industries Material(s) to be sensed : White metallic lids Solution: Detect the front edge of the cardboard box with a transmitted-beam sensor pair. Detect the jars with six (6) standard diffuse sensors (one sensor per jar) . The transmitted beam pair acts as a gating sensor, letting the six diffuse sensors know when to look for caps. Capping and Case Packaging APPLICATIONS

20. Filling Description of application: Filling Bottles Applicable industries: Bottling & Brewing Material(s) to be sensed: Beer / Water / Soda Solution: Sensing the presence of the bottle can be achieved through the use of a clear object detector such as ClearSight . A capacitive proximity sensor used at the filling station ensures the glass beer bottles are filled to the designated “Fill Level” every time. The advantage of using the capacitive proximity sensor is that it will ignore the glass while sensing the presence of the beer. APPLICATIONS

21. Pre-Sorting Description of application: To sort yogurt containers (strawberry, blueberry and lime) based on the color of the cap. Applicable industries: Food packaging Material(s) to be sensed: Plastic, Foil Solution: Three (3) color sensors are used, each programmed for a specific color: Red, blue and green. The fiber optic heads are mounted right next to each other so that all three sensors look at the same target simultaneously. The containers are then sorted according to the color of the lids. APPLICATIONS

22. Description of application: Sense the position of the ram press. Safety issues might include two-hand control and pinch point. Applicable industries: machine tool, automotive, manufacturing Material(s) to be sensed: Metal Solution: Sense the home and down positions of the ram using limit switches or proximity switches. A point of operation light curtain could be used to prevent injury. Two hand control to keep the operators hands out of the press during stamping cycle. Press and Fabrication Plant APPLICATIONS

23. In industry it is essential to know the current status of a process or machine. Information is made readily available by employing signaling devices. Examples include Lamps Horns Buzzers SIGNALING

24. CIRCUIT BREAKERS

25. CIRCUIT BREAKERS The circuit breaker is a mechanical switching device Capable of protecting the circuit wiring, Capable of making, carrying and breaking currents under normal circuit conditions , Capable of making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short circuit. CIRCUIT BREAKERS

26. All circuit breakers have common features in their operation, although details vary substantially depending on the voltage class, current rating and type of the circuit breaker. The circuit breaker, fulfils the following functions : Short-circuit protection Motor protection Protection of connecting leads Protection of installations Signalization of the switching state Tripping indication Switching under normal service conditions Remote switching Disconnecting Locking out with padlock (mandatory for main switch) CIRCUIT BREAKERS

27. CIRCUIT BREAKER FOR THE PROTECTION OF INSTALLATIONS AND CONNECTING LEADS The requirements for the circuit breakers for the protection of installations and connecting leads are somewhat less demanding : • The current range is often fixed • The thermal release is less precise • The ambient air temperature compensation is absent • The tripping threshold of the magnetic short-circuit tripping is mostly lower (as for example 3..4 x In) In some cases, they interrupt the short-circuit with a time delay. These time-staggered circuit breakers are suitable for the so called selective (or discriminating) load feeders. CIRCUIT BREAKERS

28. CIRCUIT BREAKER FOR THE PROTECTION OF INSTALLATIONS AND CONNECTING LEADS The integrated tripping device, mostly electronic, permits the inclusion of an OFF-time-delay of a few half-cycles, in addition to the setting of the overload and the short-circuit tripping threshold. These circuit breakers are used for the protection of installations (back-up protection, protection of the connecting wiring, switching in cascade (series) of circuit breakers, selective feeders) and not for the protection of individual load feeders like motors. The protection of the connecting wiring can be realised with thermal (bimetallic) releases without ambient air temperature compensation or with relatively simple electronic protective devices. The protection of a motor with the above mentioned circuit breaker is possible together with an additional motor protective device only. CIRCUIT BREAKERS

29. CIRCUIT BREAKER WITH MOTOR PROTECTIVE CHARACTERISTICS The inclusion of thermal, time-delayed overcurrent release is no sure indication that the particular circuit breaker is suitable for motor protection. Circuit breakers for motor protection are characterised by at least the following features : • Adjustable thermal (bimetallic) release setting equal to the motor current (or electronic release) • Ambient air temperature compensation (in the case of bimetal) • Reliable arrangement for the protection of the motor in the case of phase loss (as for example: electronic phase-loss detector. CIRCUIT BREAKERS

30. CIRCUIT BREAKERS THE CURRENT PATH OF THE CIRCUIT BREAKER The normal rated current as well as the short-circuit or the overload current flows from the incoming to the outgoing terminal of the circuit breaker through the magnetic and the thermal overload releases in series with the main contacts. Exactly the same current flows through all the functional modules. Unequal amplitude and duration of the currents in the different releases will obviously cause different individual reactions. CIRCUIT BREAKERS

31. THERMAL OVERLOAD RELEASE Normal service overloads do not immediately cause any dangerous unbearable stress to the equipment. The built-in thermally delayed bimetallic motor protective release is sufficient for the usual and simple overload protective tasks. In the circuit breakers also, the current flows through the thermally delayed bimetallic release. The bimetal bends, the amount of bending depends on its temperature, and presses against the release latch of the operating mechanism. CIRCUIT BREAKERS

32. THERMAL OVERLOAD RELEASE The temperature-rise of the bimetal depends on the heating energy generated by the current flowing through the circuit breaker. The release threshold, in other words the travel of the tip of the bimetallic strip necessary for tripping the release latch, is adjusted with the help of the current setting dial. If the release latch is pressed, it trips the operating mechanism thereby opens the main contacts and the overcurrent is interrupted before it can cause any damage to the motor winding, the connecting wiring or similar parts. CIRCUIT BREAKERS

33. ELECTROMAGNETIC OVERCURRENT RELEASE In the case of circuit breakers with motor protective characteristic, the electromagnetic overcurrent release is activated almost instantaneously when an overcurrent of 10…16 times of the maximum current-setting flows through the device. The exact operating threshold is either adjustable (depending on whether selectivity is desired or on the different inrush peak current of transformers or if the device is to be employed for the protection of generators) or is fixed through its design. The threshold is lower for circuit breakers used for the protection of installations and the connecting wiring. CIRCUIT BREAKERS

34. ELECTROMAGNETIC OVERCURRENT RELEASE In the case of smaller circuit breakers (mostly <100A), a small coil is introduced in the main current path. As a high current (overcurrent) flows through the windings of the coil, an electromagnetic force acts on the armature enclosed inside the coil and accelerates it. This armature or the striker hits the springloaded releasing latch of the operating mechanism, the main contacts spring back to the position "OPEN" and the overcurrent is interrupted. CIRCUIT BREAKERS

35. ACB: Air Circuit Breaker. Large, open type circuit breakers for the protection of installations in the current range of approximately >100A (typical value). MCB: Miniature Circuit Breaker. Small circuit breakers meant for the protection of the wiring, single or multiple pole, especially in building installations. MCCB: Moulded Case Circuit Breakers. A compact type of circuit breakers. A circuit breaker having a supporting housing of moulded insulating material forming an integral part of the circuit breaker. CIRCUIT BREAKERS

36. Desired operation Input voltage and current Motor name plate ratings Number of Poles Rated Operational Current Ie [A] Thermal release Adjustment Range [A] Magnetic Release Operation Current [A] SELECTING A CIRCUIT BREAKER

37. RELAYS

38. A relay is an electrical switch that uses an electromagnet to move the switch from the off to on position It takes a relatively small amount of power to turn on a relay but the relay can control something that draws much more power. When current is passed through the coil it creates a magnetic field that pulls the switch closed. Usually a spring will pull the switch open again once the power is removed from the coil. RELAYS

39. RELAYS

40. TYPES OF RELAY TUBE BASE RELAY ICE CUBE RELAY HOCKEY PUCK RELAY CONTROL RELAY INTERPOSING /ISOLATION RELAY GENERAL PURPOSE RELAY

41. Relays are categorized based on their structure. There are four basic types. SPST – Single Pole Single Throw Relay SPDT – Single Pole Double Throw Relay DPST – Double Pole Single Throw Relay DPDT – Double Pole Double Throw Relay 4PDT – Four Pole Double Throw Relay TYPES OF RELAY

42. This is a Single Pole Single Throw relay. Current will only flow through the contacts when the relay coil is energized. This is a Single Pole Double Throw relay. Current will flow between the movable contact and one fixed contact when the coil is DEenergized and between the movable contact and the alternate fixed contact when the relay coil is energized. TYPES OF RELAY

43. TYPES OF RELAY This is a Double Pole Single Throw relay. When the relay coil is energized, two separate and electrically isolated sets of contacts are pulled down to make contact with their stationary counterparts. There is no complete circuit path when the relay is De- energized. This relay is a Double Pole Double Throw relay. It operates like the SPDT relay but has twice as many contacts. There are two completely isolated sets of contacts. TYPES OF RELAY

44. This is a 4 Pole Double Throw relay. It operates like the SPDT relay but it has 4 sets of isolated contacts. TYPES OF RELAY TYPES OF RELAY

45. Relays are also designed for specific applications. Examples are Control Relays Interposing Relays Solid State Relays Terminal block Relays Timer Relays Etc. TYPES OF RELAY

46. Relay Selection Generally the following factors are considered when selecting a relay. Contact Ratings Contact Form : SPST, DPST, SPDT, DPDT, 4PDT Maximum operating current under resistive load. Coil Ratings Coil Voltage Other factors are considered when selecting relays for specific applications such as timing Currently many control devices have relays incorporate in their fabrication. Examples include: liquid level controllers, phase monitoring relays, PLCs, Drives, etc.

47. Testing A Relay Make sure there is no voltage at the coil terminals Test for continuity between the NO contacts. Observe that there is no continuity. Test for continuity between the NC contacts. Observe that there is continuity. Apply voltage to the coil terminals, A1 and A2. Measure the voltage across the terminals Test for continuity between the NO contacts. Observe that there is continuity. Test for continuity between the NC contacts. Observe that there is no continuity.

48. CONTACTORS

49. CONTACTORS

50. Relays and Contactors use the same basic principle of operation, but the way they achieve the end result is mechanically different. Relays usually have a hinged armature whereas contactors usually have a stronger solenoid action, which allows them to have larger contacts. CONTACTORS

51. Generally, a contactor is used to switch higher powers than a relay and needs more current to operate. Electrically, contactors consist of two main parts, the operating coil and the switching contacts. A contactor will have a number of contacts (or poles), usually three normally open contacts for power switching and a set of auxiliary contacts for use at lower current in the control circuit. CONTACTORS

52. Their basic electrical specifications are mainly concerned with: the voltage required to operate the coil; whether the coil needs AC or DC; the current-carrying capacity of the contacts; the maximum voltage the contacts can switch. The type of operation they will be used for further complicates the specification – for example, how often they will make and break in an hour and whether the load is inductive (an electric motor) or resistive (a heater element). CONTACTOR SELECTION

53. The choice of contactor depends upon: the type of voltage and mains supply; the load power; the load characteristics; the duty requirements. These are combined into several categories. Briefly they are as follows CONTACTOR SELECTION

54. CONTACTOR SELECTION For AC loads: AC1 – resistive load switching. Least severe conditions. AC2 – slip ring motor control switching. AC3 – squirrel cage motor starting and breaking during normal running. AC4 – as for AC3 but with higher operating frequency and also where the contactor may be required to break the motor starting current. Most severe conditions. For DC loads: DC1 – mainly resistive loads. Least severe conditions. DC2 – starting and stopping shunt motors. DC3 – as DC2 but allowing inching and plugging control. DC4 – starting and stopping series motors. DC5 – as DC4 but allowing inching and plugging control functions. Most severe conditions.

55. The use of a contactor – or relay – that is not up to the conditions in the circuit will rapidly fail in service. The contacts may weld or stick together causing power to be applied to a circuit after the contactor has been switched off. Too much current can cause the contact to melt and disintegrate like a fuse. CONTACTOR SELECTION

56. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS

57. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS TIMER ON DELAY NO CONTACTS TIMER OFF DELAY NO CONTACTS NC PUSHBUTTON NO PUSHBUTTON EMERGENCY PUSHBUTTON

58. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS 3 POLE POWER CIRCUIT BREAKER WITH MAGNETIC TRIPPING 2 POLE POWER CIRCUIT BREAKER WITH THERMAL TRIPPING 1 POLE POWER CIRCUIT BREAKER WITH THERMAL AND MAGNETIC TRIPPING

59. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS RELAY/ CONTACTOR COIL ON DELAY TIMER COIL OFF DELAY TIMER COIL TIMER COIL WITH ON AND OFF DELAY

60. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS LAMP EARTH 3 POLE FUSE 3 PHASE MOTOR

61. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS

62. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS

63. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS

64. ELECTRICAL CIRCUIT DIAGRAMS AND SYMBOLS

65. ASSIGNMENT Design a control circuit to detect the presence and absence of an object. Use lamps for indication.

66. DAY 2 OUTLINE STARTERS TIMERS

67. MOTOR STARTERS

68. Starting Electric Motors As we know, once a supply is connected to a three phase induction motor a rotating magnetic field will be set up in the stator, this will link and cut the rotor bars which in turn will induce rotor currents and create a rotor field which will interact with the stator field and produce rotation. Of course this means that the three phase induction motor is entirely capable of self starting. The need for a starter therefore is not, conversely enough, to provide starting but to reduce heavy starting currents and provide overload and no-voltage protection. There are a number of different types of starters, including ‘The Direct On-line Starter’ and ‘The Star-Delta Starter’. MOTOR STARTERS

69. Starting Electric Motors – STAR DELTA Due to their simplicity, robustness and cost-effectiveness, squirrel-cage motors are the preferred choice of industry. During start-up, they develop currents of up to approximately eight times the rated current with corresponding high starting torgue . These result in unwelcome voltage drops in the supply network. Therefore, the electricity companies determine limiting values for the motor starting currents in relation to the rated operational currents. The permissible values vary from network to network and depend on its load-bearing capacity. MOTOR STARTERS

70. Continuous rating: It is based on the maximum load which a motor can deliver for an indefinite period without its temperature exceeding the specified limits and also possessing the ability to take 25% overload for a period of time not exceeding two hours under the same conditions. Continuous maximum rating : It is the load capacity as given above but without overload capacity. Inferior to the continuous – rated motors. Intermittent rating : It is based on the output which a motor can deliver for a specified period without exceeding the temperat ure rise. Understanding motor ratings and component sizing MOTOR STARTERS

71. MOTOR STARTERS MOTOR WIRING CONFIGURATIONS STAR DELTA

72. MOTOR STARTERS IDENTIFYING MOTOR TERMINALS STAR CONNECTION DELTA CONNECTION

73. MOTOR STARTERS DOL STARTERS A DOL starter connects the motor terminals directly to the power supply. Hence, the motor is subjected to the full voltage of the power supply. The components consist of only a main contactor and thermal or electronic overload relay. The disadvantage with this method is that it gives the highest possible starting current. A normal value is between 6 to 7 times the rated motor current but values of up to 9 or 10 times the rated current exist. This starter is often used to start water pumps, compressors, fans and conveyor belts.

74. MOTOR STARTERS DOL STARTERS

75. MOTOR STARTERS So, the motor is first connected in star and after a few seconds when it has reached the required speed, it is converted to delta by means of a star-delta switch. This is the most common form of starter used for three phase induction motors. It achieves an effective reduction of starting current by initially connecting the stator windings in star configuration which effectively places any two phases in series across the supply. STAR-DELTASTARTERS

76. MOTOR STARTERS The components normally consist of three contactors, an overload relay and a timer for setting the time in the star-position (starting position). STAR-DELTASTARTERS

77. MOTOR STARTERS STAR-DELTA STARTERS

78. MOTOR STARTERS This starting method only works when the application is light loaded during the start. If the motor is too heavily loaded, there will not be enough torque to accelerate the motor up to speed before switching over to the delta position. Applications with a load torque higher than 50% of the motor rated torque will not be able to start using the star-delta starter. Motors with a power of 2.2kW and more should usually not be connected in delta directly ( the starting current will rise too much immediately after starting the motor). STAR-DELTA STARTERS

79. TIMERS Timers control operations based on the duration of an event. There are three basic types of timers: On-Delay Timer Off-Delay Timer One shot Timer Repeat Cycle Star-Delta

80. TIMERS

81. TIMERS ON DELAY TIMER It is a relay that accumulates time when turned on (when it’s coil is energized) and delays actuation of its contacts until the accumulated time is equal to the preset time.

82. TIMERS OFF DELAY It is a relay that actuates its contacts when the input signal (initiate contact) transitions from the OFF state to the ON state. It begins to accumulate time when the input signal transitions from the ON state to the OFF. It delays actuation of its contacts until the accumulated time is equal to the preset time.

83. TIMERS ONE SHOT The one shot timer actuates its contacts and accumulate time when the input is turned on. The contacts retain their new state until the accumulated time reaches the preset time. The process repeats itself when the input transitions from off to on.

84. TIMERS REPEAT CYCLE The Repeat Cycle timer actuates its contacts and accumulate time when the input is turned on. The contacts retain their new state until the accumulated time reaches the preset time. The Accumulator then resets and accumulates time until it is equal to the preset time. At this point the contacts are again actuated. This process creates an on-off sequence with an equal time interval.

85. TIMERS STAR-DELTA The star delta timer functions as a one-shot and on-delay timer combined as one. When its input is energised its star output is closed for a preset time. At the preset time it opens and the delta output is closed after a short delay ( tu ). All outputs drop when the timer input drops.

86. ASSIGNMENT Design a control circuit to start and stop a conveyor. A proximity sensor at the end of the conveyor detects the presence of an object and stops the conveyor. Run the conveyor using a STAR-DELTA STARTER

87. DAY 3 OUTLINE EMERGENCY CIRCUITS ELECTRICAL PROTECTION ELECTRICAL SAFETY

88. EMERGENCY CIRCUITS

89. EMERGENCY CIRCUITS When considering the design of any machine it is important to eliminate as many hazards as possible and by doing so negating the need for any additional safety measures. Having refined the design to reduce the risks to a practical minimum and provided all the safety information possible, the machine is safe for all the foreseen safety incidents. But what about the un-foreseen incidents? This is what the Emergency Stop button (Emergency Circuit) is for!

90. EMERGENCY CIRCUITS With the help of an emergency-stop device a machine or drive must be switched off as quickly as possible in the case of danger. There are two ways of doing this: An emergency-stop switch . Control circuits which are designed in such a way to allow all corresponding main circuits to be switched off by means of a single command. Emergency-stop devices can be activated as follows: Using the handle of the emergency-stop device one or more mushroom-head pushbuttons

91. EMERGENCY CIRCUITS THE EMERGENCY-STOP SWITCH It must be fed by the power supply of electrical circuits which can lead to dangerous movements in the system

92. EMERGENCY CIRCUITS

93. EMERGENCY CIRCUITS The emergency-stop switch can be activated by hand or remote control be provided with corresponding tripping devices for protection against overload and short-circuit simultaneously serve as the main switch if it additionally fulfils the requirements of a main switch. Restart after an emergency-stop After an emergency-stop a restart must be prevented. In addition to the emergency-stop device there must therefore also be other control circuits.

94. EMERGENCY CIRCUITS

95. EMERGENCY CIRCUITS SWITCHING OFF WITH A SINGLE COMMAND All main circuits can be switched off with a single command – if the control circuits are correspondingly constructed. This is the case if the control circuits are connected in series with an emergency-stop control device e.g. an emergency-stop mushroom-head pushbutton. As many emergency-stop control devices as desired can be connected in series. The only restriction is the length of the conductors. For direct current operation the voltage drop caused by the conductor and the number of contact elements must be taken into account. For alternating current operation there are restrictions due to the capacity of the conductor.

96. EMERGENCY CIRCUITS

97. EMERGENCY CIRCUITS EMERGENCY-STOP CIRCUITS WITH INCREASED RELIABILITY Faults can occur during the regular control procedure - with grave consequences for man and machine. Additional electric circuits which are only activated in the case of a fault provide greater safety. These special safety circuits are usually made up of contactor relays. In the literature a distinction is made between two basic circuits: Circuits made up of two contactor relays with overlapping contact elements Circuits made up of three contactor relays with positively driven contact elements

98. EMERGENCY CIRCUITS

99. EMERGENCY CIRCUITS

100. EMERGENCY CIRCUITS SAFETY RELAYS Safety relays are designed to provide a convenient and economical solution for incorporating control reliability into a safety circuit. They are used for the purpose of safely breaking a circuit, for instance the power supply circuit of presses, machine tools, or medical appliance. Safety relays are used in many industrial applications, for instance for ensuring safe operation of safety devices and actuators, for achieving safe stops for dangerous machines and processes, and for monitoring stop inputs and the internal safety of machines.

101. EMERGENCY CIRCUITS SAFETY RELAYS Power to the machine primary control elements (MPCE) is connected through the safety output contacts of the safety monitoring relay. Inputs to the monitoring relay are typically from safety devices such as emergency stop switches, limit switches, or safety interlock switches. The safety monitoring relay’s own output safety contacts are monitored internally. If a fault occurs in the operation of one of the monitoring relay contacts, the safety relay shuts down, removes power from the MPCE and prevents a start or successive cycle of the machine until the fault is cleared. In addition, the contacts of the MCPE or external safety relay can be monitored by the safety monitoring relay.

102. EMERGENCY CIRCUITS SAFETY RELAYS

103. EMERGENCY CIRCUITS SAFETY RELAYS

104. ELECTRICAL PROTECTION

105. High currents causes overheating. Unchecked, it eventually results in severe motor damage or even fire outbreaks. Over current is caused by: Excessive loads - Overheating may occur as a result of the motor doing work on very heavy or excessive loads. It may also be as a result of a jammed rotor. Low supply voltage- Low supply voltage can also cause overheating. It compels the motor to draw large currents in order to do work. ELECTRICAL PROTECTION

106. ELECTRICAL PROTECTION Single phasing – One or two phases may fail compelling the motor to run on single phase power, drawing excessive currents. High inertia load – the motor takes an abnormally long time to accelerate. Other causes include- Poor ventilation

107. ELECTRICAL SAFETY SURGE PROTECTION Transient (Surge) A high voltage transient is a high energy, short term (1...10 μs ) deviation or change from desired voltage levels. It is an unwanted bundle of high electrical energy in the AC power line or communications line. The transient can be noted as a single overvoltage spike or a burst of spikes, sometimes followed by a ringing waveform. Electrical Noise Interfering and unwanted voltage and current anomalies in an electrical device or system; consists of undesirable frequencies above 60 Hz. ELECTRICAL PROTECTION

108. Surge Protective Device (SPD) A general classification of a wide array of devices that are designed to react quickly to sudden and momentary overvoltage conditions, also referred to as a Transient Voltage Surge Suppressor (TVSS). The rating is dependent on the intended areas of usage and the corresponding magnitude of surge suppression capabilities. ELECTRICAL PROTECTION

109. A standard surge protector passes the electrical current along from the outlet to a number of electrical and electronic devices plugged into the power strip. If the voltage from the outlet surges or spikes -- rises above the accepted level -- the surge protector diverts the extra electricity into the outlet's grounding wire. In the most common type of surge protector, a component called a metal oxide varistor , or MOV , diverts the extra voltage. ELECTRICAL PROTECTION

110. In a motor control circuit, overload protective devices prevent damage caused by excessive current. The basic function of an overload protective device is to sense when the motor is drawing too much current over a specific period of time. Upon sensing this condition, the protective device cuts power to the motor. ELECTRICAL PROTECTION

111. RESIDUAL CURRENT DEVICE (RCD) It is a device that operates its contacts when it detects a difference between the amount of current in the live conductor and the neutral conductor. The RCD is also called a "ground fault circuit interrupter" (GFCI) or an "appliance leakage current interrupter" (ALCI). ELECTRICAL PROTECTION Residual current detection is complementary to over-current detection. Residual current detection cannot provide protection for overload or short-circuit currents.

112. ELECTRICAL SAFETY An MOV An MOV has three parts: a piece of metal oxide material in the middle, joined to the power and grounding line by two semiconductors . These semiconductors have a variable resistance that is dependent on voltage. When voltage is below a certain level, the electrons in the semiconductors flow in such a way as to create a very high resistance. When the voltage exceeds that level, the electrons behave differently, creating a much lower resistance. When the voltage is correct, an MOV does nothing. When voltage is too high, an MOV can conduct a lot of current to eliminate the extra voltage. ELECTRICAL SAFETY ELECTRICAL PROTECTION

113. ELECTRICAL SAFETY As soon as the extra current is diverted into the MOV and to ground, the voltage in the hot line returns to a normal level, so the MOV's resistance shoots up again. In this way, the MOV only diverts the surge current, while allowing the standard current to continue powering whatever machines are connected to the surge protector. Metaphorically speaking, the MOV acts as a pressure-sensitive valve that only opens when there is too much pressure. ELECTRICAL SAFETY ELECTRICAL PROTECTION

114. ELECTRICAL SAFETY

115. ELECTRICAL SAFETY You will receive an electrical shock if a part of your body completes an electrical circuit by touching a live wire and an electrical ground, or touching a live wire and another wire at a different voltage.

116. ELECTRICAL SAFETY High voltages cause additional injuries! Higher voltages can cause larger currents and more severe shocks. Some injuries from electrical shock cannot be seen. Power drills use 30 times as much current as what will kill.

117. ELECTRICAL SAFETY

118. ELECTRICAL SAFETY Currents greater than 75 mA cause ventricular fibrillation (very rapid, ineffective heartbeat). This condition will cause death within a few minutes unless a special device called a defibrillator is used to save the victim. Heart paralysis occurs at 4 Amps, which means the heart does not pump at all. Tissue is burned with currents greater than 5 amps2

119. ELECTRICAL SAFETY

120. ELECTRICAL SAFETY

121. ELECTRICAL SAFETY Damaged power tools and equipment are electrical hazards. Using the wrong PPE is dangerous. Using the wrong tool is dangerous. Some on-site chemicals are harmful. Defective ladders and scaffolding are dangerous. Ladders that conduct electricity are dangerous. Electrical hazards can be made worse if the worker, location, or equipment is wet.

122. ELECTRICAL SAFETY This hand-held device has exposed wires and should not be used. Watch out for exposed electrical wires around electronic equipment.

123. ELECTRICAL SAFETY Always test a circuit to make sure it is de-energized before working on it. Knowing where to look helps you to recognize hazards. Inadequate wiring is dangerous. Exposed electrical parts are dangerous. Overhead power lines are dangerous. Wires with bad insulation can give you a shock. Electrical systems and tools that are not grounded or double-insulated are dangerous. Overloaded circuits are dangerous.