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November 29, 2011

How to convert electrical energy to infrared energy or to microwave energy?

To convert to IR, use an IR lamp, aka heat lamp. IR is heat energy.

 To convert to microwave, you need a magnetron and a high voltage power supply, as is found in a microwave oven. 
For the reverse, it is more difficult.

November 27, 2011

Describe the Application of Synchronous Motors

Synchronous motors are usually used in large sizes because in small sizes they are costlier as compared with induction machines. The principal advantages of using synchronous machine are as follows:
–Power factor of synchronous machine can be controlled very easily by controlling the field current.

What is Synchronous Motor?

A synchronous motor is the same physical machine as a generator, except that the direction of real power flow is reversed

What are the Advantages of Parallel operation of synchronous generators?

There are several major advantages to operate generators in parallel:

  • Several generators can supply a bigger load than one machine by itself. 
  • Having many generators increases the reliability of the power system. 
  • It allows one or more generators to be removed for shutdown or preventive maintenance.

What is Synchronous Generator?

Synchronous generators or alternators are used to convert mechanical power derived from steam, gas, or hydraulic-turbine to ac electric power.

  • Synchronous generators are the primary source of electrical energy we consume today.

November 25, 2011

What is synchronous Condenser? Where and why it is used?

An overexcited synchronous motor running at no- load and used for power-factor correction is called synchronous condenser. It is also called synchronous capacitor. 

It is used in a large system where the use of static capacitor is inefficient and expensive. It is used for power-factor correction .

November 22, 2011

Why the induction motor never runs at synchronous speed?

  • If rotor & stator have same speed, no relative motion 
  • slip zero, no voltage induce in rotor 
  • current zero, torque zero 

Write down the significance of the name ‘induction’ in case of induction motor.

The supply is connected to the stator and the rotor received power by induction caused by stator rotating flux, hence the motor obtains its name –induction motor.

Why induction motor treated as a rotating transformer?

  • Transformer has two sides: primary & secondary.
  • Transformer transforms energy from primary to secondary by induction. 
  • Similarly, Induction motor has primary (stator) & secondary (rotor).
  • Voltage is induced in secondary by rotating flux of const. magnitude i.e the process of induction.
Thus induction motor treated as a rotating transformer.

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