TRANSFORMER 

Basic Working Principle Of An Induction Motor

In a DC motor, supply is needed to be given for the stator winding as well  as the rotor winding. But in an induction motor only the stator winding is fed with an AC supply.

• Alternating flux is produced around the stator winding due to AC supply. This alternating flux revolves with synchronous speed. The revolving flux is called as "Rotating Magnetic Field" (RMF).
• The relative speed between stator RMF and rotor conductors causes an induced emf in the rotor conductors, according to the Faraday's law of electromagnetic induction. The rotor conductors are short circuited, and hence rotor current is produced due to induced emf. That is why such motors are called as induction motors. 
  (This action is same as that occurs in transformers, hence induction motors can be called as rotating transformers.) 
• Now, induced current in rotor will also produce alternating flux around it. This rotor flux lags behind the stator flux. The direction of induced rotor current, according to Lenz's law, is such that it will tend to oppose the cause of its production. 
• As the cause of production of rotor current is the relative velocity between rotating stator flux and the rotor, the rotor will try to catch up with the stator RMF. Thus the rotor rotates in the same direction as that of stator flux to minimize the relative velocity. However, the rotor never succeeds in catching up the synchronous speed. This is the basic working principle of induction motor of either type, single phase of 3 phase. 

Synchronous Speed:

 The rotational speed of the rotating magnetic field is called as synchronous speed.

where, f = frequency of the spply

            P = number of poles

Slip:

Rotor tries to catch up the synchronous speed of the stator field, and hence it rotates. But in practice, rotor never succeeds in catching up. If rotor catches up the stator speed, there wont be any relative speed between the stator flux and the rotor, hence no induced rotor current and no torque production to maintain the rotation. However, this won't stop the motor, the rotor will slow down due to lost of torque, the torque will again be exerted due to relative speed. That is why the rotor rotates at speed which is always less the synchronous speed.

The difference between the synchronous speed (N_s) and actual speed  (N) of the rotor is called as slip.

buchholz relay

Transformer -  8: Captive Power Plant

Sr.No. Description Unit Details

1 Name of manufacturer Areva

2 Service and cooling Indoor/ONAN

3 Rated KVA 10000

4 Rated voltage/Current of primary (on noload) Volt/Amp 24000/240.6

5 Rated voltage/Current of secondary (on noload) Volt/amp 11000/524.8

6 Temperature rise by resistance of winding Deg C 50 (Restricted to class F)

7 Maximum Ambient Temperature Deg C 50

8 Rated Frequency Hz 50

9 Connections

High Voltage Star

Low Voltage Delta

10 Vector Group Reference YNd11

11 Tapping Double Wound

12 Type ON Load Tap Changer

13 Tap Range (+10% to -10% in step of 1.25%)

14 No load loss at rated voltage and frequency 9250(Max)

15 Load loss at rated current and 75 Deg C at particular tap 58500(Max)

16 Impedance voltage at rated current at 75 Deg C 8.11% Tolerance

17 Reactance at rated current and frequency % 8.09

18 Resistance at rated current and frequency % 0.557

19 Efficiency at 75 Deg C at UPF at full load % 99.38

20 Regulation at full load at 75 Deg. C

At Unity Power factor % 0.884

At 0.8 power factor (Lag) % 5.488

21 Class of insulation Class F

22 Material of winding Copper

23 Total Weight Kg 16150

24 Approximate overall Dimension

Length mm

Width mm

Height mm

25 Terimal Arrangement

High Voltage(Primary) Bus Duct

Low Voltage(Secondary) Bus Duct

26 Protection Class IP 32

27 Noise Level As per NEMA TR-1

28 Maximum Flux Density Tesla 1.72(max)

29 Referance Standards IS11171,IS 2026

30 Year of Manufacturer 2011

31 Sr.No. 622000198

OLTC details

Sr.No. Description Unit Details

1 Make: Ctr Manufacturer India Limited

2 Type EN 16

3 Serial No 2921447

4 Year of manufacture 2011

5 Rated current

OLTC Amp 300A Max, 149A Normal

TR Amp 240.6A / 524.8A

6 Rated step voltage Volt 313V

7 Transition resistance Ohm 2.2 Ohm

8 Rated insulation level Kv 70Kv RMS/Min,170 KVP1.2/50

9 Motor voltage / frequency 415V,50 Hz

10 Control voltage / frequency 110V,50Hz

11 No. of service taping position 16

12 Direction of power flow

13 Transformer rating MVA 10 MVA

14 Connection diagram: