Maintopik5

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dc motor control

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Maintopik5

  1. 1. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM E4102- DC MOTOR CONTROLLED (KAWALAN MOTOR AT) TOPIK 5 – ELECTRIC BRAKING LECTURER : FADZILAH BT HASHIM 012-5469607
  2. 2. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING REGENERATIVE DYNAMIC PLUGGING ELECTRIC BRAKING
  3. 3. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.0 Introduction Slow or stop a motor and load pacuannya as important as the beginning of many applications such as cranes and traction(tarikan) on a slope to prevent excessive speed. Method based on friction braking, electromechanical response, eddy currents and so forth. It does not depend on the motor, but sometimes electric braking (electrical braking) is better, especially in terms of economy and the absence of wear on the brakes (brake wear). DC motors are widely used as a means of holding or braking. TOPIK 5 – ELECTRIC BRAKING
  4. 4. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.0 Introduction DC motors are widely used as a means of holding or braking. One reason for this is a good braking characteristics and the ability to change (transition) the motor current from the generator mode (mod penjana) and vice versa. During the period of braking, the motor berkendali sbg generator and energy (potential energy) the kinetic (kinetik) or gravity (Gravitational) degenerative (dissipated) to the resistance (plugging) or returned to the supply (regenerative braking). Electromechanical braking is a process to stop the motor. Braking can be done to stop the rotation of the motor armature. For larger motors there is inertia load (armature rotates) on the motor. Therefore it can not be dismissed so quickly. TOPIK 5 – ELECTRIC BRAKING
  5. 5. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM There are three types of braking method; Dynamic braking. Plugging braking. Regeneration braking. TOPIK 5 – ELECTRIC BRAKING
  6. 6. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.1 Dynamic braking Braking is more popular. It is a way to stop the rotation of the motor armature where armature disconnected from the supply source but connected to the external resistance. When the external resistance is connected, the current,Ia will change direction, the torque will happen with the fight against the direction of rotation. The opposite direction of this torque causes the motor to stop. In this way also the armature current can be limited during the braking process. This method can be briefly described as figure 5.1 TOPIK 5 – ELECTRIC BRAKING
  7. 7. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Figure 5.1 The block diagram of the dynamic braking method Referring to figure 5.1 before the braking output voltage dynamics are as follows; Eo = Va - IaRa After the dynamic braking??? 5.1 Dynamic braking TOPIK 5 – ELECTRIC BRAKING
  8. 8. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Selepas pembrekan dinamik. Power during the initial braking is ; 5.1 Dynamic braking TOPIK 5 – ELECTRIC BRAKING
  9. 9. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Referring to figure 5.2 the armature is separated from the supply and a braking resistor, Rb directly connected merintanginya. In this way the motor acts as a generator, driven by the stored kinetic energy to generate power to the Rb . 5.1 Dynamic braking TOPIK 5 – ELECTRIC BRAKING
  10. 10. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM This is a simple method of bringing the motor close to stop conditions. Braking time is dependent on the system inertia, load torque and motor rating. When the braking circuit is connected to left field to supply the input. One danger is that if supply fails, the braking will also fail. If the field is left connected across the armature, resulting in braking torque is the same but start falling with the the high rate of slope which propotional to speed, then the problem arises once the speed falls below the critical imperative of self (self-excitation). For the series motor, it is necessary to reverse the continued braking whether the field winding or armature winding to produce the emf in the armature. Rb values must be (Rb + Ra + RSE) is less than the critical resistance to the speed at which braking is made. 5.1 Dynamic braking TOPIK 5 – ELECTRIC BRAKING
  11. 11. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Example calculation of dynamic braking: 1. A DC series motor with the supply 240V using a chopper with a duty cycle 75% motor speed in the eddy current 15A and armature resistance 0.15Ω is 1000rpm. If the motor stopped by dynamic braking of the external resistance 0.35Ω and moment of inertia 95kgm2 . Calculate: - Initial braking power - Mechanical time constant -Time the motor to reach 25% initial speed . TOPIK 5 – ELECTRIC BRAKING
  12. 12. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  13. 13. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  14. 14. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  15. 15. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.2 Plugging braking In this method of supply to the armature will be disconnected from the supply source and reconnected to the opposite polarity. Change of polarity will cause the torque generated in opposite directions, and against the direction of rotation. These changes cause the motor to stop immediately. This method is shown in Figure 5.3. Faster than the dynamics of 2Tm. TOPIK 5 – ELECTRIC BRAKING
  16. 16. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.2 Plugging braking TOPIK 5 – ELECTRIC BRAKING
  17. 17. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Power when Initial braking, P = (Va + Eo)Ia. Time to stop the motor Tb = 2Tm. 5.2 Plugging braking TOPIK 5 – ELECTRIC BRAKING
  18. 18. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.2 Plugging braking Referring to figure 5.4 this braking method involves the exchange and at the same connection on the field winding (field) or the armature coil (armature) while the motor is berkendali. A powerful braking torque is obtained by setting the same voltage supply with armature while the connections is inverted. TOPIK 5 – ELECTRIC BRAKING
  19. 19. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.2 Plugging braking Armature voltage is used (Ea + V) is in ≈ 2V, thus the limiting braking resistor (also can resistor starters) should be placed on the circuit. Kinetic energy caused by the movement of the system is removed (dissipated) to the armature and braking resistance Whichever method is electrical braking will become less effective as speed is reduced due to a reduction in braking torque of the supply shall be disconnected at a speed close to 0 (except to change the motor rotation direction) by means of a current relay or router speed and wear a mechanical or hydraulic brakes for cause the motor is stationary. High starting currents and mechanical stress could limit the application of the method of plugging, especially to a small motor. TOPIK 5 – ELECTRIC BRAKING
  20. 20. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  21. 21. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Tm = time for the motor speed decreased by 50% of actual speed. J - moment of inertia at the motor shaft rotation (kg/m2 ) W1 - the actual speed when you start braking (rpm) P1 = the actual power received by the braking resistance of the armature TOPIK 5 – ELECTRIC BRAKING
  22. 22. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM Contoh pengiraan Pembrekan plugging: 1 A series of DC motor with a 240V supply using the chopper 75% duty cycle in the 15A eddy current motor and 0.15Ω armature resistance when speed is 1000rpm. If the motor stopped by braking plugging using a series resistance of 2.23Ω. Calculate; - Current and power during the initial braking. - Time to stop the motor. TOPIK 5 – ELECTRIC BRAKING
  23. 23. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  24. 24. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  25. 25. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.3 Regenerative Braking(Pembrekan penjanaan semula) In this process of braking the motor will function as a generator. Motor is fed energy from the supply. Chopper is used to rise and reduce the voltage. Referring to figure 5.5 : TOPIK 5 – ELECTRIC BRAKING
  26. 26. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.3 Regenerative Braking(Pembrekan penjanaan semula) When the chopper Ch1 work, the machine will function as a motor and the chopper Ch2 off, the energy stored in the motor will be discharged through the diode D1, thereby reducing current flow. When the chopper CH2 work, the motor voltage to be generated. Opposite currents will flow through the chopper and the energy stored in the motor. When the chopper CH2 off, energy will be released in the form of current through the diode D2 to supply. TOPIK 5 – ELECTRIC BRAKING
  27. 27. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM 5.3 Regenerative Braking(Pembrekan penjanaan semula) Referring to figure 5.4 chopper voltage; Vch = (I – D)Vs (where D is the duty cycle ) Power generated Pg = IaVs(I - D) = IaVch The voltage generated when the motor acts as generator Eo = Kv.IaW Eo = Vch + IaRm = (I – D)Vs + IaRm TOPIK 5 – ELECTRIC BRAKING
  28. 28. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM TOPIK 5 – ELECTRIC BRAKING
  29. 29. E4102- DC MOTOR CONTROL FADZILAH BINTI HASHIM THANK YOU……THANK YOU…… TOPIK 5 – ELECTRIC BRAKING

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