Contents
What are the questions for three phase circuits?
1. None of the options are correct 2. Removal of one of the phases 3. Reverse the polarity of any two phases 4. Reverse the polarity of all the three phases 11. Question 1. Two phase supply system 2. All the options are correct 3. Single phase supply system 4. Three phase supply system 12. Question 1. True 2. False 13. Question 1. Zero 2. Unity 3.
What is an un-balanced three phase load?
Any three phase loads in which the impedences in one or more phases differ from the impedances of the other phases is called an un-balanced three phase load. In case when one of the supply phases of three phase system supplying power to three phase load is out or nor available, then such a condition is called single phasing.
When is a three phase circuit considered unbalanced?
A 3-phase system is considered unbalanced when the following conditions: 1 When the phase voltages of three phase system are unequal in magnitude 2 When the phase angle between the phases is not equal to 120 o More
What is the output of a three phase machine?
The output of a three phase machine 1.5 times of that of single pole machine of same size. In case of single phase system, the power delivered is pulsating in nature which causes excessive vibrations in the large motors. In three phase system, the power deliver to the loads are constant if the loads are balanced
How is the frequency of a polyphase circuit determined?
A polyphase system is essentially a combination of several single phase voltages having same magnitude and frequency but each phase is displaced from another phases by equal angle (electrical degrees) which depends on the number of phases and can be determined from the following relation
When to use a three phase power system?
Single phase system supplying power to loads has its own limitations and has been replaced by polyphase system. For general supply of power three phase system is universally used. For generation, transmission and distribution of the electrical power 3-phase system has been universally adopted.
Which is the most common three phase motor?
1. In a Y-connected circuit, the magnitude of each line current is 2. In a balanced three-phase load, each phase has 3. The most common type of ac motor is the 4. The term ‘squirrel-cage’ applies to a type of three-phase ac generator. 5. Polyphase is characterized by two or more sinusoidal voltages, each having a different phase angle.