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EE4503 Electrical Systems Design

EE4503 Electrical Systems Design. Branch circuit and Feeder (Motor). Topics. Motor Branch Circuit Protection & Controller Feeder. Motor Branch Circuit.

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EE4503 Electrical Systems Design

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  1. EE4503Electrical Systems Design Branch circuit and Feeder (Motor)

  2. Topics • Motor Branch Circuit • Protection & Controller • Feeder

  3. Motor Branch Circuit http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/Solution%20Center/technical_library/BUS_Ele_Tech_Lib_Motor_Circuit_Notes.pdf

  4. Motor Branch Circuit • Motor Branch Circuit Conductors • Motor Branch Circuit Short Circuit Protection • Overload Protection • Motor Controller • Motor Disconnect • Motor Control Circuits

  5. Motor Branch Circuit Conductor http://www.1on1tutoringlive.com/files/ocp2.htm Disconnect Short Circuit Protection Overload Protection Controller & Control Circuit

  6. Motor Branch CircuitType of Motor • Induction Motor • 1 phase and 3 phase • Synchronous Motor (only 3 phase) • Armature & Field (DC) • DC Motor • Armature & Field

  7. Motor Branch CircuitRatings of Motor • Power: HP or kW • # of phase • Voltage • Current () Check Manufacturer for Data

  8. Motor Branch CircuitRatings of Motor http://www.stmaustralia.com.au/images/TecoLVTEFC.pdf

  9. Motor Branch CircuitCurrent (cable) Calculation • Normal Operation: • Multi-speed Motor: maximum current • On-Off Operation: when is the multiplier

  10. Motor Branch CircuitCurrent (CB) Calculation

  11. Motor Branch CircuitCurrent Calculation Ground Cable • 115% of the rated current

  12. Short Circuit Protection Able to handle the starting current • Fuse • Non Time-Delay Fuse • Time-Delay Fuse • Circuit Breaker • Inverse Time Circuit Breaker (normal) • Instantaneous Circuit Breaker

  13. Short Circuit ProtectionCircuit Breaker

  14. Overload Protection • To protect overheat of the motor • Circuit Breaker cannot function well for overload because of the starting current • Three methods of detecting temperature • Bimetal Thermal Overload Relay • Electronic Overload Relay • Thermistor Protective Relay

  15. Motor Controller • Starter • DOL: usually less than 7.5kW • Reduced Voltage Starter • Inverter

  16. Motor Controller • Reduced Voltage Starter • Star-Delta Starting • Autotransformer Starting • Resistant Starting • Part-Winding Starting • Elecronics Starting

  17. Motor ControllerContactor • Turn on-off the motor • The rating of Contactor needs to be higher than the rating of Motor • Utilization Category • AC2: handle 2-5 times the nominal current • AC3: handle 5-7 times, but stop at nominal • AC4: handle high amount of on-off operation

  18. Motor Controller • Reduced Voltage Starter • Star-Delta Starting • Autotransformer Starting • Resistant Starting • Part-Winding Starting • Elecronics Starting

  19. Motor Controllercomponents • Power Circuit • Usually 3 phase power circuit • Control Circuit • Single phase or DC circuit

  20. Motor ControllerDirect On Line Starting http://www.scslow.co.uk/WEG%20MANUAL%20STARTERS.htm

  21. Motor ControllerStar-Delta Starting http://myelectrical.com/notes/entryid/83/motor-starting-star-delta

  22. Disconnecting Means • Disconnect when circuit is live • Design for inductive load • Install “within sight” and less than 15m • Rating is higher than 115% of motor rating

  23. Feeder • All motor: • Combination of Motor and other loads: • is continuous load • Neutral can be a lot smaller but not smaller than Ground

  24. Reference • Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์

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