136 140

136. Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor? 

DC Series motor has high starting torque. 

We cannot start the Induction motor and Synchronous motors on load, but cannot start the DC series motor without load. 

137. What is vacuum circuit breaker? Define with cause and where we use it. 

A breaker is normally used to break a circuit. While breaking the circuit, the contact  terminals will be separated. 

At the time of separation an air gap is formed in between the  terminals. 

Due to existing current flow the air in the gap is ionized and results in the arc. 

Various  mediums are used to quench this arc in respective CB’s. 

But in VCB the medium is vacuum gas. 

Since the air in the CB is having vacuum pressure the arc formation is interrupted. VCB’s can be  used up to 11kv. 

138. What is ACSR cable and where we use it? 

ACSR means Aluminum conductor steel reinforced, this conductor is used in 

transmission & distribution. 

139. What’s is MARX CIRCUIT? 

It is used with generators for charging a number of capacitor in parallel and 

discharging them in series. It is used when voltage required for testing is higher than the  available. 

140. What is the principle of motor? 

Whenever a current carrying conductor is placed in a magnetic field it produce 

turning or twisting movement is called as torque.