Motor Control Fundamentals


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This slideshow is a presentation for IIEE-Bahrain technical seminar (AUTOMATION MOTOR CONTROL SYSTEMS) that was conducted on December 2, 2011 at Kingdom of Bahrain. Seminar was conducted by Celestino Cole

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Motor Control Fundamentals

  1. 1. by: Celestino A. Cole, Jr.2/5/2012 cole.celestino/motor control fundamentals 1
  2. 2. OBJECTIVE At the end of the presentation we will know the following: 1. Power circuit and control circuit 2. Ladder diagram and logic equivalent 3. Control components and motor control protection 4. Advance applications.2/5/2012 cole.celestino/motor control fundamentals 2
  3. 3. I. CONTROL CIRCUIT AND POWER CIRCUIT2/5/2012 cole.celestino/motor control fundamentals 3
  4. 4. POWER CIRCUIT AND CONTROL CIRCUIT POWER CIRCUIT- is a circuit used to supply electric energy to the motor.2/5/2012 cole.celestino/motor control fundamentals 4
  5. 5. POWER CIRCUIT AND CONTROL CIRCUIT CONTROL CIRCUIT- is a circuit used to supply control components in the motor control circuit. CONTROL CIRCUIT2/5/2012 cole.celestino/motor control fundamentals 5
  7. 7. II. LADDER DIAGRAM AND LOGIC EQUIVALENTS2/5/2012 cole.celestino/motor control fundamentals 7
  8. 8. LADDER DIAGRAMLADDER DIAGRAM- is a specialized schematics used todocument industrial logic system. They are called "ladder" diagrams because they resemble a ladder, with two vertical rails (supply power) and as many "rungs" (horizontal lines) as there are control circuits to represent.2/5/2012 cole.celestino/motor control fundamentals 8
  9. 9. LADDER DIAGRAMAdvantages:1. Capable of simplifying complicated motor control circuits compare to schematic diagrams. VS. = 2/5/2012 cole.celestino/motor control fundamentals 9
  10. 10. LADDER DIAGRAMAdvantages:2. Easy to trace faults. System start/stop Float control motor starter 2/5/2012 cole.celestino/motor control fundamentals 10
  11. 11. LADDER DIAGRAMAdvantages:3. Easy to translate with logical circuits for advance applications such as inPLC, process control automation, embedded intelligent systems andSCADA. PB1 PL = PB1* PB2 PL PB2 PB1 PL PL = PB1 + PB2 PB2 2/5/2012 cole.celestino/motor control fundamentals 11
  12. 12. LADDER DIAGRAMHOW TO CREATE A LADDER DIAGRAM +24VDC 0V VERTICAL RAILS COMPONENTS RUNG2/5/2012 cole.celestino/motor control fundamentals 12
  13. 13. RULES IN LADDER DIAGRAM Input Output Auxiliary contact  Input determines the initial state of the system.  Output functions either ON/OFF depending on the logic of the input combination.  Auxiliary contact is dependent to the state of the device that they are into. It changes its initial state from close to open or vice versa once the device is activated RUN SIMULATION2/5/2012 cole.celestino/motor control fundamentals 13
  14. 14. III. MOTOR CONTROL COMPONENTS AND PROTECTION2/5/2012 cole.celestino/motor control fundamentals 14
  15. 15. MOTOR CONTROL COMPONENTSSWITCH Switch is an electrical device that can break and connect an electrical circuit, as well as interrupting the flow of current or divert it from one conductor to the other. Types of switches typically used in motor control applications: 1. Pushbutton switch 2. Limit switch 3. Selector switch 4. Footswitch 5. Toggle switch2/5/2012 cole.celestino/motor control fundamentals 15
  16. 16. MOTOR CONTROL COMPONENTSMAGNETIC CONTACTOR main contacts Supply terminals Auxiliary A magnetic contactor is an contact(s) electrically controlled switch used for switching a power circuit. It has main contacts used for power circuit and auxiliary contact used for control circuit.2/5/2012 cole.celestino/motor control fundamentals 16
  17. 17. MAGNETIC CONTACTOR Control circuit RUN SIMULATION Power circuit2/5/2012 cole.celestino/motor control fundamentals 17
  18. 18. CONTROL RELAY A relay is an electrically operated switch. The principle of operation is similar to that of the contactor but differs in application. While contactor is used to control motors. Control relay on the other hand is used to control the operation of other control components particularly the magnetic contactor.2/5/2012 cole.celestino/motor control fundamentals 18
  19. 19. CONTROL RELAY Magnetic contactor B C In PLC application the voltage that activates V1 and V2 is coming from the PLC. The circuit is transitioned from PLC to When terminals V1 and V2 are magnetic contactor via energized the initial state of each control relays for safety purposes. Although contacts will change accordingly. possible, it is not From close to open and vice versa. technically practical to wire directly magnetic contactor to PLC since a large feedback AC current from the contactor circuit may harm the PLC unit.2/5/2012 cole.celestino/motor control fundamentals 19
  20. 20. TIMER  Relay timer contains an auxiliary contacts NO and NC that can be integrated into motor control circuits. The initial state of its contact will change when activated after pre-determined value.  The timer unit can be set into seconds or minutes depending on the application requirements.  For longer and iterative tasks, real time timers are available. RUN SIMULATION2/5/2012 cole.celestino/motor control fundamentals 20
  21. 21. THERMAL OVERLOAD RELAY Line terminals Thermal overload relay is an electrical component reset used in motor control Set value dial applications which provide protection for motor against excessive current. Auxiliary contact(s)2/5/2012 cole.celestino/motor control fundamentals 21
  22. 22. THERMAL OVERLOAD RELAY Principles of operation: This component has a bimetal strip As current rises, heat also rises. that is made of two dissimilar The hotter the bimetal strip metals bonded together. The two becomes, the more it bends. In an metals have different thermal overload condition, the heat expansion characteristics, so the generated from the heater will bimetal strip bends at a given rate cause the bimetal strip to bend when heated. until the mechanism is tripped, stopping the motor.2/5/2012 cole.celestino/motor control fundamentals 22
  23. 23. THERMAL OVERLOAD RELAY Typical set-up of contactor and overload relay2/5/2012 cole.celestino/motor control fundamentals 23
  24. 24. THERMAL OVERLOAD RELAY Characteristics: 1. Allow harmless temporary overloads (such as motor starting) without disrupting the circuit. 2. Trip and open a circuit if current is high enough to cause motor damage over a period of time. 3. Can be reset once the overload is removed.2/5/2012 cole.celestino/motor control fundamentals 24
  25. 25. ELECTRONIC OVERCURRENT RELAY (EOCR) Electronic overcurrent relay is used to protect the motor against overload. Unlike thermal overload Typical installation diagram for EOCR relay this component uses current to trigger once there is overload.2/5/2012 cole.celestino/motor control fundamentals 25
  26. 26. OVER/ UNDER VOLTAGE RELAY This component protects the motor against over voltage and under voltage situation. Typical installation diagram for over/under voltage protection2/5/2012 cole.celestino/motor control fundamentals 26
  27. 27. OVER/ UNDER VOLTAGE RELAY OPERATION Motor contactor 11 12 21 22 11 14 Over-voltage alarm 21 24 Under-voltage alarm2/5/2012 cole.celestino/motor control fundamentals 27
  28. 28. PHASE LOSS/ PHASE SEQUENCE RELAY In 3-phase system, phase loss Is the event when one or two phases is/are disconnected in the main supply. Phase sequence on the other hand is when two of the phases are interchanged resulting to a reverse rotation of a 3-phase motor. Phase control relays monitor: Phase loss is mandatory ■ Phase sequence protection to every motor ■ Loss of one or more phases operation. Phase sequence is for ■ Unbalance level selective purposes only such as pumps that reversing the motor direction may cause serious damage to the equipment.2/5/2012 cole.celestino/motor control fundamentals 28
  29. 29. PHASE LOSS/ PHASE SEQUENCE WIRING DIAGRAM Motor contactor PL/PS NC contacts PHASE PROTECTION RELAY2/5/2012 cole.celestino/motor control fundamentals 29
  30. 30. TRANSMITTER, TRANSDUCER AND SENSOR IN MOTOR CONTROL  Transmitter, transducer and sensor sometimes used interchangeably in industrial applications. It may simply called sensor, detector or switch. This devices can be integrated in motor control systems to facilitate the function of the motor in any industrial processes.  Depending upon the nature of requirements and device specification these components can be installed individually, composite or can be installed with the aid of the other.  Commonly integrated in motor control applications are: 1. Temperature controller 2. Pressure transmitter 3. Humidity sensor 4. Gas leak detector 5. Proximity switch 6. Light sensor2/5/2012 cole.celestino/motor control fundamentals 30
  31. 31. WORKING WITH TRANSMITTERS IN MOTOR CONTROL Example of composite system where two separate devices are integrated together to perform the desired function. Example: The specs indicate that the controller needs PT100 type thermocouple to operate Example of stand-alone unit. Example: A photo sensor that is commonly used in street lightings that can also be used in motor control applications can be installed stand alone.2/5/2012 cole.celestino/motor control fundamentals 31
  32. 32. TRANSMITTERS AND SENSORS IN MOTOR CONTROL Input in its raw form such as:- Temperature INPUT The controller will- Pressure Discrete output- Light process the OUTPUT- Color such as NO and NC- Moisture detected signal contacts INPUT and transformed it These inputs are detected by the sensor and to be into an output in Analogue output carried out as electrical the form of OUTPUT such as 4-20 mA signals: discrete or and 0-10 volts INPUT- Temperature sensor analogue.- Pressure transmitter- Gas leak detector- Smoke sensor Theoretical background2/5/2012 cole.celestino/motor control fundamentals 32
  34. 34. TRANSMITTER AND SENSORS IN MOTOR CONTROL APPLICATIONS  In motor control discrete output are characterized by normally close and normally open contacts. This contact output are to be integrated to control circuits. 15 162/5/2012 cole.celestino/motor control fundamentals 34
  35. 35. TRANSMITTER AND SENSORS IN MOTOR CONTROL APPLICATIONS In industrial control systems analog signals are commonly characterized by 4-20 mA or 0-10 volts. This is used when the application does not require fully activated or deactivated systems. This output signal is then integrated into other devices that directly controls the motor such as Variable Frequency Drive. <--- 4-20 mA or 0-10 volts feedback signal2/5/2012 cole.celestino/motor control fundamentals 35
  36. 36. IV. SOLID STATE MOTOR CONTROL AND PLC2/5/2012 cole.celestino/motor control fundamentals 36
  37. 37. Motor Control Using Solid State Relays Solid state relay- A solid state relay (SSR) is an electronic switching device in which a small control signal controls a larger load current or voltage. Small electronic 48 VAC supply signal input Control relay2/5/2012 cole.celestino/motor control fundamentals 37
  38. 38. PRINCIPLE OF SOLID STATE RELAY (optocoupler) Light from the source can change the initial state of a phototransistor The same with optocouplers when a small voltage signal is present it would activate the LED and change the state of phototransistor in the dual-in-line package2/5/2012 cole.celestino/motor control fundamentals 38
  39. 39. PRINCIPLE OF SOLID STATE RELAY (Silicon Controlled Rectifiers) AC supply In the normal "off" state, the device restricts current to the leakage current. When the gate-to-cathode voltage exceeds a certain threshold, the device turns "on" and conducts current. The device will remain in the "on" state even after gate current is removed so long as current through the device remains above the holding current. Once current falls below the holding current for an appropriate period of time, the device will switch "off". If the gate is pulsed and the current through the device is below the holding current, the device will remain in the "off" state. Control relay2/5/2012 cole.celestino/motor control fundamentals 39
  40. 40. PROGRAMMABE LOGIC CONTROLLERS (PLC) A PLC can receive supervisory information, such as production changes or scheduling information, from a host computer. A standard I/O system includes a variety of digital, analog, and special interface modules, which allow sophisticated control without the use of expensive, customized interface electronics.2/5/2012 cole.celestino/motor control fundamentals 40
  41. 41. SOLID STATE MOTOR CONTROL PROCESS FLOW The program is *SOFTWARE downloaded to PLC or *FIRMWARE microcontroller *PROGRAM The motor will operate based on the above MICRO- ELECTRIC The PLC or operations. CONTROLLER, MOTOR microcontroller PLC, will process the instructions received. The action of the relay will control the operation of MAGNETIC For every logic “true” a CONTROL RELAY the magnetic contactor. CONTACTOR small voltage signal is received by the control relay from the PLC. That signal will then control it’s action.2/5/2012 cole.celestino/motor control fundamentals 41
  42. 42. APPLICATION OF SOLID STATE MOTOR CONTROLProblem:From the headquarter to the pumping stationthe management wanted to have overridecontrol on the operation of their pumpmotor. The headquarter is 20 km away fromthe pumping station. Using copper wires istechnically impractical and using fiber opticsis financially unfeasible. FEEDBACK SIGNALS CONTROLLER, TRAN SDUCER AND TRANSMITTER SENSOR DETECTION2/5/2012 cole.celestino/motor control fundamentals 42
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  44. 44. 2/5/2012 cole.celestino/motor control fundamentals 44
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