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soft starer


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provide brief description of soft starter

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soft starer

  1. 1. SOFT-STARTER <ul><li>BY: RAVI SHANKAR SINGH </li></ul>
  2. 2. Soft Starter <ul><li>Soft-Starter is an electronic starter designed to accelerate, deaccelerate three-phase induction motors and to control the voltage applied on the motor during start and stop. </li></ul>
  3. 3. Starting of Induction Motor <ul><li>For induction motors, the starting torque (LRT) is approximately proportional to the square of the starting current (LRA) drawn from the line. LRT ∝ I 2 </li></ul><ul><li>This starting current is proportional to the applied voltage (V) </li></ul><ul><li>Torque can also be considered to be approximately proportional to the applied voltage. LRT ∝ V 2 </li></ul><ul><li>An induction motor will develop far too much torque when connected directly to the supply. </li></ul><ul><li>At the instant of start-up, there are some un-necessary effect on electrical and the mechanical components. </li></ul>
  4. 4. Un-Necessary Mechanical Effects <ul><li>The sudden impact at start up on the load, followed by the rapid acceleration to full speed causes excessive wear on :- </li></ul><ul><ul><li>Belts and pulleys </li></ul></ul><ul><ul><li>Gears and chains </li></ul></ul><ul><ul><li>Couplings and bearings </li></ul></ul><ul><ul><li>Cavitation in pumps etc. </li></ul></ul>
  5. 5. Un-Necessary Electrical Effects <ul><li>A heavy current surge on the electrical supply which can be severe enough to cause voltage dips and flickering lights. </li></ul><ul><li>Burning of contacts due to high currents which are many times the motor full-load current. </li></ul>
  6. 6. Problems Arises by these Effects <ul><li>Continuous maintenance. </li></ul><ul><li>Greater chance of unscheduled shutdowns </li></ul><ul><li>Oversized mechanical and electrical components to cater for the power surge on start up. </li></ul><ul><li>Short component life. </li></ul>
  7. 7. Solution of the problems….. <ul><li> Soft Starter </li></ul><ul><li>By Adjusting voltage during starting, the current drawn by the motor and the torque produced by the motor can be reduced and controlled. </li></ul>
  8. 8. Block Diagram I M THYRs Protective Devices Firing Pulse Generator µ- Controller Control Signal Power Signal Soft Starter 3- ø Supply
  9. 9. <ul><li>By using six SCR’s in a back to back configuration , the soft starter is able to regulate the voltage applied to the motor during starting from 0 volts up to line voltage. </li></ul><ul><li>Feedback from the motor to the logic circuit used to control the SCR firing for stabilization of motor acceleration </li></ul><ul><ul><li>Frequency do not change as in VFD </li></ul></ul><ul><ul><li>Only the voltage and current changes. </li></ul></ul>Fig.1 Fig.2 Starting Principle of Soft Starter
  10. 10. Characteristics of soft starter Current/speed curve with Soft start DOL Soft start Torque/speed curve with Soft start DOL Soft start Load Torque
  11. 11. Features of soft starter <ul><ul><ul><ul><li>Soft start and soft stop </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pulse (kick) start </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Current Control ramps </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pump Control characteristics </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Tacho/Encoder feedback </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Dual Adjust - start/stop characteristics for varying loads </li></ul></ul></ul></ul>
  12. 12. Soft starting feature <ul><li>Adjustable initial voltage = 10 – 50% V Rated . </li></ul><ul><li>Adjustable ramp time = 1– 30 seconds (can be extended ) </li></ul>Current/speed curve with soft starter Soft start DOL
  13. 13. Kick starting feature <ul><li>When require breakaway torque </li></ul><ul><li>Voltage pulse - 80% V Rated </li></ul><ul><li>Adjustable pulse length- 0-2s </li></ul>DOL Kick Start 400%
  14. 14. Soft stopping feature <ul><li>Often used with high inertia loads where a </li></ul><ul><li>sudden stop may cause system or product </li></ul><ul><li>damage. </li></ul><ul><li>Adjustable stopping time- 1-30s </li></ul><ul><li>Avoid hammering and cavitations </li></ul><ul><li> on pumps </li></ul><ul><li>Avoid goods tilting on conveyors </li></ul>Working: During ramp-down the controller will gradually reduce the voltage to the motor thus reducing the torque and current. As a consequence the motor speed will fade off. Soft Stopping Ramp
  15. 15. Current limiting feature Current Limiting This mode of soft starting is used when it becomes necessary to limit the maximum starting current due to long start times or to protect the motor. <ul><li>Maximum current of 200- 400% of FLC </li></ul><ul><li>rotor current. </li></ul><ul><li>Adjustable ramp time =1-30 seconds (can be extended With requirement). </li></ul>Current Limiting Curve
  16. 16. Comparison of soft starter with DOL and Y/ Δ starter <ul><li>Staring voltage- </li></ul><ul><li>10 -50% V Rated Ramp voltage of the V rated </li></ul><ul><li>Up to 85% V Rated for kick start </li></ul>Voltage/Time Characteristic Soft
  17. 17. Comparison of soft starter with DOL and Y/ Δ starter 6-700% 100% Soft Starter Soft start Current/Time Characteristic Torque/Speed Characteristic
  18. 18. Low voltage soft starter (208-575V,9-900A) <ul><li>208V –(3-200 HP) </li></ul><ul><li>230V –(5-200 HP) </li></ul><ul><li>460V –(5-700HP) </li></ul><ul><li>575V –(7.5-700 HP) </li></ul><ul><ul><ul><li>2.3kv –(160 -2400 kw) </li></ul></ul></ul><ul><ul><ul><li>3.3 kv –(250-3450 kw) </li></ul></ul></ul><ul><ul><ul><li>4.16kv –(340-5000kw) </li></ul></ul></ul>Classification of soft starter Medium voltage starter(1.0-13.8 kv) <ul><ul><ul><li>6.0kv –(590-4500kw) </li></ul></ul></ul><ul><ul><ul><li>6.6k –(650-4000 kw) </li></ul></ul></ul><ul><ul><ul><li>11kv –(1110-4780 kw) </li></ul></ul></ul><ul><ul><ul><li>13.8kv –(1400-6000 kw) </li></ul></ul></ul>
  19. 19. <ul><li>Standard Duty Soft Starter </li></ul><ul><ul><ul><ul><li>400% Motor FLA@6sec </li></ul></ul></ul></ul><ul><ul><ul><ul><li>300% Motor FLA@30sec </li></ul></ul></ul></ul><ul><li>Medium Duty Soft Starter </li></ul><ul><ul><ul><ul><li>400% Motor FLA@12sec </li></ul></ul></ul></ul><ul><ul><ul><ul><li>300% Motor FLA@40sec </li></ul></ul></ul></ul><ul><li>High Duty Soft Starter </li></ul><ul><ul><ul><ul><li>400% Motor FLA@20sec </li></ul></ul></ul></ul><ul><ul><ul><ul><li>300% Motor FLA@60sec </li></ul></ul></ul></ul>
  20. 20. Advantages <ul><ul><li>Eliminates high inrush current and high mechanical torque on startup. </li></ul></ul><ul><ul><li>Reduction in cable and switch-gear rating in the power supply network. </li></ul></ul><ul><ul><li>Limits line voltage dip. </li></ul></ul><ul><ul><li>Soft, stepless acceleration & deceleration. </li></ul></ul><ul><ul><li>Kick-start function for heavy duty and functional loads with high starting torque. </li></ul></ul><ul><ul><li>Current limiting characteristic. </li></ul></ul><ul><ul><li>By-pass contactor increases energy savings. </li></ul></ul><ul><ul><li>Avoid current and torque peaks, Put less electrical stress on the power supply network and mechanical stress on entire drive. </li></ul></ul><ul><ul><li>Reduce stress on couplings and other transmission devices (gear boxes, shafts, belts, etc). </li></ul></ul>
  21. 21. Advantages(cont…..) <ul><ul><li>Extend lifetime of motor and mechanical components/parts due to reduced mechanical shocks. </li></ul></ul><ul><li>Less space required in the switchgear cabinet(Devices are much narrower than other electromechanical motor starters). </li></ul><ul><li>Reduction in cost. </li></ul><ul><li>Unique starting & stopping characteristics. </li></ul><ul><li>Pump control characteristic. </li></ul><ul><li>Operation above ambient up to 65°C . </li></ul><ul><li>Simple electrical wiring. </li></ul><ul><li>Easy operation, programming and maintenance. </li></ul>
  22. 22. Disadvantages <ul><li>Produces harmonics(less than inverter) </li></ul><ul><li>Operating speed of motor fixed(unlike VFD, frequency is fixed) </li></ul><ul><li>Speed regulation is not possible(used for only starting & stopping and protection) </li></ul><ul><li>Acceleration & deceleration time more depend on load </li></ul>
  23. 23. Some applications <ul><li>Vacuum Pumps; </li></ul><ul><li>Centrifugal Pumps; </li></ul><ul><li>Compressors </li></ul><ul><li>Fans / Exhaustors / Blowers </li></ul><ul><li>Mixers </li></ul><ul><li>Conveyors </li></ul><ul><li>Axial Blowers </li></ul><ul><li>Propeller Fans </li></ul><ul><li>Axial Fans (low inertia – low load) </li></ul><ul><li>Pulverisers </li></ul><ul><li>Mixer </li></ul><ul><li>Ball Mill </li></ul><ul><li>Large Pumps </li></ul><ul><li>Crushers/Grinders </li></ul><ul><li>Ball mills/ Hammer Mills </li></ul><ul><li>Escalators </li></ul><ul><li>Bottling Lines </li></ul>All these and many other applications have been obtained by soft starter.
  24. 24. Thank You….