Star Delta Starter Sizing & Selection

-
  1. Star delta starter generally find application in Industrial & Commercial loads .
  2. Star delta starter reduces starting current by (3 to 5) times than that DOL starter.
  3. It is important  to know ratings of starter components for different  HP motors .
  4. Improper selection & Sizing of components  in starter may lead to damage to motor  windings , or motor may be in standstill .

Operation of star Delta starter :

At starting / standstill condition motor draws high current ,to reduce the high starting current drawn by motor,  motor is connected in star mode ,where phase voltage is applied across motor causes motor to draw only low starting current untill it reaches (75 to 80 %) of rated speed.  After attaining rated speed motor gets connected in delta connection with full line voltage gets applied on motor winding . Motor continous to run in delta connection because Torque obtained in delta connection is more than in star connection .
Note:- Generally in all industries & Manufacturing units Induction motors run in delta connection only to get Maximum Torque Output .


The Sizing & Selection of star delta starter components are given in below Table .

The above table depicts for different ratings of motor what should the rating of 
  • star/delta contactor .
  • Thermal overload relay setting 
  • Fuse rating 
  • Cable size .


Comments

Post a Comment

Popular posts from this blog

ACB Tripping settings

-
Image
ACB tripping settings   Acb has 6 adjustable tripping settings 1 Long time delay (Tr ) 2 Short time delay( Tsd ) 3 Earth fault delay (Tg) 4 Long time (Ir) 5 Short time (Isd) 6 Earth Fault (Ig) Long time is for maximum overload capacity . Short time is for short circuit current Earth fault is for earth fault current . As per thumb Rule : 1. Long time set at 0.8 means 80% of full load current .Until this level of current  breaker carry without tripping  . Above 0.8 Acb trips. Long time delay causes the breaker to wait for certain time to allow heavy temporary inrush currents to pass away. Generally long time delay is set at  4 Sec. 2. Short time set at 0.6 means  60% of full load current . It determines the Amount of Current the Breaker will carry for short time period.  Generally short time delay set at 0.2 sec. 3. Earth Fault set at 0.3 or 30% of  fault current . It controls the amount of Ground Fault current that will cause the breaker to interrupt the cir
Read more

HIGHER EFFICIENCY MOTORS (HEM)

-
Image
Super premium Efficiency (IE4) motors  IE4 MOTOR The higher price of the IE4 motors is due to :  1. the use of high-quality materials and optimization of assembly and design of these motors to achieve higher efficiencies upto 97% . 2.  Large-diameter copper wires and more quantity of aluminum are used in rotors of these motors to reduce the resistance losses.  3. An optimized cooling fan is also used to reduce the winding losses. 4. use of advanced technologies like diecast copper rotors enables achieving higher efficiencies in the same frame size. The use of the high-quality, expensive materials increases the overall cost of this type of motors. adoption of energy efficient technologies to reduce their energy consumption and carbon emission. 5. Stator and Rotor I2R losses: Stator and Rotor I²R losses appear when heat is generated by resistance from current flowing in the stator windings, rotor conductor bars. These are major losses, typically account for 55% to 60% of tota
Read more

Transformer Magnetic Oil Gauge Indicator

-
Image
conservator tank oil level (Mog) The MOG  (Magnetic Oil Gauge)  is a device by which we can supervise the level of oil inside the tank or conservator of power transformer and also gives us an alert low oil level indication .  A decrease in level of Transformer oil in Conservator is an indication of leak and therefore MOG level is an important parameter to be monitored. Practically under running condition oil level remains at 3/4 th level.
Read more