Motor starter
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Motor starter

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starter are used to start motors generally

starter are used to start motors generally

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Motor starter Motor starter Presentation Transcript

  • starter -B. Prasad Chartered Engineer
  • Necessity of starter  At starting ,the speed of motor is zero so that the back e.m.f. In the armature is zero.  Armature resistance is so low, if it is connected to power supply directly ; huge current will pass thru armature.  The huge current may damage the machine, major heat, very high speed in case of DC series motor.  Ia = V/Ra
  • Function of starter  Start and stop the motor.  Limit inrush current where necessary.  Permit automatic control when required  Protect motor and other connected equipments from over voltage, no voltage, under voltage, single phasing etc.
  • Motor Starter Features.  Rated by current (amperes) or power (horsepower)  Remote ON/OFF control  Motor overload protection  Starting and stopping (electrical life)  Plugging and jogging (rapid making and breaking current)
  • Type of starter forDC Motor  Two point starter for DC series motor  Three point starter for shunt motor  Four point starter for compound motor ForAC Motor  DOL Starter  Star-Delta  Auto-transformer  Variable Frequency drive
  • Wiring Diagram of DOL Starter:
  •  MotorStarting Characteristics on DOL Starter:  Available starting current:    100%.  Peak starting current:           6 to 8 Full Load Current.  Peak starting torque:            100%
  • Advantages of DOL Starter:  Most Economical and Cheapest Starter  Simple to establish, operate and maintain  Simple Control Circuitry  Easy to understand and trouble‐shoot.  It provides 100% torque at the time of starting.  Only one set of cable is required from starter to motor.  Motor is connected in delta at motor terminals.
  • Disadvantages of DOL Starter:  It does not reduce the starting current of the motor.  High Starting Current: Very High Starting Current (Typically 6 to 8 times the FLC of the motor).  Mechanically Harsh: Thermal Stress on the motor, thereby reducing its life.  Voltage Dip: There is a big voltage dip in the electrical installation  High starting Torque: Unnecessary high starting torque, even when not required by the
  • Suitability DOL is Suitable for:  Small water pumps, compressors, fans and conveyor belts.  Motor rating up to 5.5KW DOL is not suitable for:  The peak starting current would result in a serious voltage drop on the supply system  Motor rating above 5.5KW
  • Star delta starter  Most induction motors are started directly on line, but when very large motors are started that way, they cause a disturbance of voltage on the supply lines due to large starting current surges.  To limit the starting current surge, large induction motors are started at reduced voltage and then have full supply voltage reconnected when they run up to near rotated speed.
  • Star-Delta Connection in transformer
  • Star-Delta Connection in motor
  • Star delta power circuit
  • Star delta control circuit
  • MotorStarting Characteristics of Star- Delta Starter:  Available starting current: 33% Full Load Current.  Peak starting current: 1.3 to 2.6 Full Load Current.  Peak starting torque: 33% Full Load Torque.
  • Advantages of Star-Delta starter:  The operation of the star-delta method is simple and rugged  It is relatively cheap compared to other reduced voltage methods.  Good Torque/Current Performance.  It draws 2 times starting current of the full load ampere of the motor connected
  • Disadvantages of Star-Delta starter:  Low Starting Torque, only 33% starting torque  Break In Supply – Possible Transients  Six Terminal Motor Required (Delta Connected).  It requires 2 set of cables from starter to motor.  The delta of motor is formed in starter and not on motor terminals.  Applications with a load torque higher than 50 % of the motor rated torque will not be able to start using the start-delta starter.  Low Starting Torque: reduction of the line voltage by a factor of 1/√3 (57.7%) to the motor and the current is reduced to 1/3 of the current at full voltage, but the starting torque is also reduced 1/3 to 1/5 of the DOL starting torque .
  • Reversing of Direction
  • Variablefrequencydrive(VFD)  A variable -fre q ue ncy drive (VFD), also termed adjustable-frequency drive, variable speed drive, AC drive, micro drive or inverter drive is a type of adjustable-speed drive used in electro-mechanical drive systems.  It co ntro ls AC m o to r spe e d and to rq ue by varying m o to r input fre q ue ncy and vo ltag e .
  • Principle of VFD  Variable frequency Drive, principle of the same is by regulating the frequency, we can regulate the speed of drive Example - n=120f/p  Where,  n - speed  f - frequency  p – nos. of poles
  • VFD flow diagram
  • VFD 3-phase power conversion
  • Application  Cane Carrier Drive,  Feeder Table Drive,  Milling Plant Drive,  Raw juice Pumps,  Sulphited Juice Pumps,  Molasses Pumps,  Injection Pumps,  Cooling Tower Pumps and  Centrifugals for a Sugar Curing and Chemical Dosing pump.
  • Auto transformer
  • Circuit and function  An auto-transformer starter makes it possible to start squirrel-cage induction motors with reduced starting current, as the voltage across the motor is reduced during starting.  In contrast to the star-delta connection, only three motor leads and terminals are required. On starting, the motor is connected to the tappings of the auto-transformer.
  • Starting Characteristics:  Motor terminal voltage less than line voltage (by transformer ratio).  Motor current exceeds line current (by inverse of transformer ratio).  Starting torque is reduced by the square of the terminal voltage. Applications:  Where complete acceleration at reduced amperes is needed.  Where line ampere reduction requirements are severe, and load torque is not minimal.
  • Difference between DOL/Star delta /Autotransformer Sr . DOL Starter Stardelta starter Auto transformer starter 1 Used up to 5 HP Used 5 HP to 20HP Used above 20 HP 2 Does not decrease the starting current Decreases the starting current by 1/3 times Decreases the starting current as required 3 It is cheap It is costly It is more costly 4 It connects directly the motor with supply for starting as well as for running It connects the motor first in star at the time of starting in delta for running It connects the motor according to the taping taken out from the auto transformer
  • Current in Star Delta (380to 415V) MotorKW Rated phase current-A MCB-A Fuse -A MCCB-A 1.1 1.4-1.75 6 6 6 2.2 2.6-3 10 10 6 3.7 4.3-5.2 16 20 16 5.5 5.8-7 20 25 16 7.5 7.5-9.3 25 32 25 11 11-13.2 32 40 32 15 14.5-18 40 50 50 18.5 17.3-21.3 40 63 50 22 21.3-26.6 63 80 80 30 30-36.5 80 100 80 37 36-42 80 125 100
  • Current in DOL (380-415V motor) MotorKW Rated line current-A MCB-A Fuse -A MCCB-A 1.1 2.5-3 16 10 6 2.2 4.5-5 16 20 6 3.7 7.5-9 25 25 16 5.5 10-12 32 32 16 7.5 13-16 40 40 25 11 19-23 50 50 32 15 25-31 63 63 50 18.5 30-37 80 80 50 22 37-46 100 100 80 30 52-63 Not used 125 80
  • WIRE/Cable SIZE International standard wire sizes (IEC 60228)  0.5 mm² 0.75 mm² 1 mm² 1.5 mm² 2.5 mm² 4 mm²  6 mm² 10 mm² 16 mm² 25 mm² 35 mm² 50 mm²  70 mm² 95 mm² 120 mm² 150 mm² 185 mm² 240 mm²  300 mm² 400 mm² 500 mm² 630 mm² 800 mm² 1000 mm
  • ACT FAST AND INITIATE FIRST  बड़ा    सोचो         तेजी से सोचो व     सबसे पहले सोचो  िवचारो     पर िकसी का       एकािधकार नही होता.   ----  धीरभाई अमबानी
  • THANK YOU