Electrical Adda

Classification of Protective Relays : Based on Technology : Relay Classification Relays are broadly classified into 4 types based on technology used in manufacturing and based upon mode of operation , Sensing the fault  and giving Trip indication to circuit breakers . These Protective Relays are used in HT & LT Applications ,  HT applications in 33 KV side and in LV side 440 Volts . ELECTRO-MAGNETIC RELAY  :  Works on principle of  Electro - Magnetic Attraction . Based on amount of current flowing in the coil , Electromagnetic force is developed that will be exerted on moving armature. There  are 2 types of Electromagnetic Relays Presently used in Industrial & Commercial  applications . Induction Disc Type Relay  . Plunger Type Relay . 1.1 Induction Disc Type Relay : Induction Disc type Relay Relay consists of 2 Electromagnets , Disc , Moving contact and fixed contact , plug setting multiplier . 2 Windings are connected to 2 electromagnets.  The Primary current carries Current

1. Distribution Transformer  Standard Ratings : Distribution Transformer 25  Kva       63 Kva 100 Kva 200 Kva 315 Kva 500 Kva 750 Kva 1000 Kva 1250 Kva 1500 Kva 2000 Kva 2500 Kva 3000 Kva 3500 Kva 2. Transformer Manufacturers : Kirloskar Electric  Vijai Electricals Volt Amp Crompton Greaves ABB Siemens Pete  3. Transformer Protection :  Overload , Overcurrent , Short- circuit .   Earth Fault .  Differential Protection .  Restricted Earth Fault .  Gas Detection .  Over voltage , Under Frequency .  Pressure Relief Device . 4. Transformer Core  : CRGO  Material  Amorphous Material  Mostly  Amorphous core Material is used in T/F  because  Reduces Core Losses , Magnetization losses  Total No load losses reduced By by 3% of full load losses. transformer Noise & Vibration reduced . 5. Transformer Oil  : Mineral oil which is free from fatty acids are used in transformer  Chemical name is Hydrotreated Light Nepthanic Distillate. low viscosity oil flash point at 140 degree centigrade . 6. T

Star delta starter generally find application in Industrial & Commercial loads . Star delta starter reduces starting current by (3 to 5) times than that DOL starter. It is important  to know ratings of starter components for different  HP motors . 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 & Manufacturi

VFD / VSD (Variable Frequency Drive or Speed Drive) Introduction : VFD are used to control motor speed to get the desired output . Motors running at constant speed generate full flow of air , but to reduce the flow we are using dampers , we are using full energy of motor and using low output air flow this causes waste of energy , so we use Vfd for air flow control . VFD are alternate for dampers , valves , etc  Energy Savings by using VFD is (30- 70 % )  . Applications : Pumps, Fans, Compressors, Elevators , Cranes , HVAC systems, conveyors Advantages :  Smooth & Controlled Start Stop . Minimize Inrush Currents . Regulate Speed or Torque  Energy saving ( power Consumption is less). VFD Parts : Rectifier, DC chokes , Snubber Capacitor , IGBT . Working : When a 3 phase Ac supply given to VFD is Rectified by SCR to Pulsating dc , Ripples in dc is reduced using filters ( choke + capacitor ) , Pure dc obtained after filtering Dc supply f