Brake Test

• It is direct test useful to find efficiency of small DC Motor.

Theory

• The output power of the DC Motor is measured by applying brake to a pulley.
• One rope is wound round the pulley and its two ends are attached to spring balances W₁ and W₂. 

Compare : Static RAM and Dynamic RAM

Static RAM

• It can store data as long as the supply is kept on.
• It consists of flip flop as a memory cells.
• It is available in both bipolar and MOS technology.
• It is used where speed is prime consideration

Reluctance Motor : Construction, Working, Advantages, Disadvantages and Applications

Single Phase unexcited Synchronous Motor

• The characteristic of single phase unexcited synchronous motor in which excitation does not necessary is given below.

        ( 1 ) It operates on single phase supply. 

        ( 2 ) The stator rotating magnetic field rotates at synchronous speed. 

        ( 3 ) It does not require DC Excitation. 

Hysteresis Motor : Construction, Working, Advantages, Disadvantages, Characteristics and Applications

Single Phase unexcited Synchronous Motor

• The characteristic of single phase unexcited synchronous motor in which excitation does not necessary is given below.

       ( 1 ) It operates on single phase supply. 

       ( 2 ) The stator rotating magnetic field rotates at synchronous speed. 

Earthing Transformer : Construction, Working and Application

• It is a special transformer which provides return path for earth fault on Delta connected transformer.

Construction

• It has primary winding but no secondary winding. 
• It is a core type transformer consists of three limbs. 
• Each limb carries two windings which have equal number of turns. 

Tertiary Winding : Construction , Working and Application

• The three winding transformer as its name suggest consists of three winding : Primary winding, secondary winding and third winding is called as tertiary winding.

Construction

• The construction of three winding transformer is similar to that of core type transformer. 

Zig zag Transformer : Advantages, Application

• It is also called as interconnected star connection. The characteristic of zig zag connection is combined characteristics of star and delta connection. 
• There are six windings in the three cores and each core consists of two winding which has equal number of turns. 
• Fig A. shows star connection in which each phase consists of two windings. In order to convert this winding into zig – zag connection.