Why a synchronous motor does not develop torque on starting?
The stator carries windings connected to an AC supply to produce a rotating magnetic field.At synchronous speedthe rotor poles lock to the rotating magnetic field, beacause of the constant magnetic field in the rotor these cannot use induction windings for starting. Synchronous motors are inherently not self starting.
Why do we have to provide a DC excitation voltage to the synchronous generators rotor?
To keep it short we can conclude that to get steady state torque and to synchronize the rotor we use dc excitation. For dynamically induced emf, you need a constant flux (provided by DC excitation) and a rotating coil. This is the basic principle of DC/AC generator. The voltage induced is AC in both generators.
Why is it desirable to turn the rotor electromagnet of a synchronous motor off during start up?
It is desirable to turn the rotor electromagnet of a synchronous motor off during motor start-up in orderto increase the motor speed improve the power factor of the system to which the motor is connected reduce the vibrations produced in the motor increase the motor pull-out torque a. b. c. d.
What happens when excitation of synchronous generator fails?
If the excitation of the generator fails, suddenly there will be no more magnetically locking between rotor and rotating magnetic field of stator. But still the governor will supply same mechanical power to the rotor due to this sudden magnetic unlocking; the rotor will be accelerated beyond the synchronous speed.
What causes loss of excitation in generator?
The failure of auxiliary supply or failure of driving motor can also cause the loss of excitation in a generator. Failure of excitation that is failure of field system in the generator makes the generator run at a speed above the synchronous speed.
What happens if excitation is changed?
A change in the excitation, thus, affects only the power factor of its output. This reduces the terminal voltage slightly, so let the excitation of the first alternator be increased so as to bring the terminal voltage back to its original value.
What will happen if excitation of DC shunt motor is changed?
What will happen if excitation of DC shunt motor is changed? Explanation: Speed of the DC motor obtained from speed equation is inversely proportional to flux produced by the field. So, reducing the field current flux produced by armature will decrease, and speed will increase.
Does change in excitation affect the synchronous motor speed?
One of the most important features of a synchronous motor is that by changing the field excitation, it can be made to operate from lagging to leading power factor. Since the mechanical load as well as the speed is constant, the power input to the motor (=3 V*Ia *cos ф) is also constant.
When two alternators are operating in parallel the cause for circulating current is?
The effect of differences in wave form between two machines operating in parallel is to cause a circulating current. in the voltage of the machines. rise to inequalities in frequency.
What happens when alternators are connected in parallel?
Alternators are always connected in parallel to increase the power delivered. Alternators connected in series will only increase output voltage but the current delivering capacity of alternators connected in series should to be the same hence will not be able to cater to large loads.
Why alternators are operated in parallel?
Alternators are operated in parallel for the following reasons: Several alternators can supply a bigger load than a single alternator. Parallel operation of the alternator, reduces the operating cost and the cost of energy generation. It ensures the greater security of supply and enables overall economic generation.
What is meant by synchronising current?
If two alternators generating exactly the same emf are perfectly synchronized, there is no resultant emf acting on the local circuit consisting of their two armatures connected in parallel. No current circulates between the two and no power is transferred from one to the other.
Why is synchronization needed?
The need for synchronization originates when processes need to execute concurrently. The main purpose of synchronization is the sharing of resources without interference using mutual exclusion. The other purpose is the coordination of the process interactions in an operating system.
What is synchronous speed?
: a definite speed for an alternating-current machine that is dependent on the frequency of the supply circuit because the rotating member passes one pair of poles for each alternation of the alternating current.
What are two methods of synchronization?
There are two types of thread synchronization mutual exclusive and inter-thread communication.
- Mutual Exclusive. Synchronized method. Synchronized block. static synchronization.
- Cooperation (Inter-thread communication in java)
What are the synchronization techniques?
Synchronization techniques among threads
- Compare and swap.
- Mutual exclusion (mutexes) and threads.
- Semaphores and threads.
- Condition variables and threads.
- Threads as synchronization primitives.
- Space location locks.
- Object locks.
What are the methods of synchronization?
The common methods used for synchronizing the alternators are given below.
- Three Dark Lamps Method.
- Two Bright, One Dark Method.
- Synchroscope Method.
What is synchronization with example?
To synchronize is to coordinate or time events so they happen all at the same time. An example of synchronize is when dancers coordinate their movements. An example of synchronize is when you and a friend both set your watch to 12:15. To cause objects or events to move together or occur at the same time.
What is synchronization and why is it important?
Synchronization control the access the multiple threads to a shared resources. Without synchronization of threads, one thread can modify a shared variable while another thread can update the same shared variable, which leads to significant errors.
What is called synchronization?
Synchronization is the coordination of events to operate a system in unison. For example, the conductor of an orchestra keeps the orchestra synchronized or in time. Systems that operate with all parts in synchrony are said to be synchronous or in sync—and those that are not are asynchronous.
What synchronization means?
the fact of happening at the same time, or the act of making things happen at the same time: the act of making sure that watches or clocks show exactly the same time: The first step is synchronization of watches..
What is the use of synchronization?
To avoid such issues, Java provides us with the synchronized keyword, which acts like a lock to a particular resource. This helps achieve communication between threads such that only one thread accesses the synchronized resource and other threads wait for the resource to become free.
Should I turn sync on or off?
Turning off auto syncing for Google’s services will save some battery life. In the background, Google’s services talk and sync up to the cloud. You can go into the settings menu and enter Google accounts to disable auto syncing. This will also save some battery life.
What does Chronize mean?
: to happen at the same time. transitive verb. 1 : to represent or arrange (events) to indicate coincidence or coexistence. 2 : to make synchronous in operation. 3 : to make (motion-picture sound) exactly simultaneous with the action.
What does neutralizing mean?
verb (used with object), neu·tral·ized, neu·tral·iz·ing. to make neutral; cause to undergo neutralization. to make (something) ineffective; counteract; nullify: carelessness that neutralized our efforts. Military. to put out of action or make incapable of action: to neutralize an enemy position.
What does intercede mean?
intransitive verb. : to intervene between parties with a view to reconciling differences : mediate.
Is there a difference between prayer and intercession?
Prayer, as we have seen in so many of the other series so far is chiefly about speaking with God, having a one2one with Him, talking and listening; in essence knowing God through communicating with Him. Intercession involves a standing in the gap, an intervention, a stepping in on somebody else’s behalf through prayer.
What is another word for intercede?
Frequently Asked Questions About intercede Some common synonyms of intercede are interfere, interpose, intervene, and mediate.
What is the importance of intercession?
Paul believed intercession to be one of the most important aspects of faith and praying life, as praying for others is a recurring theme in his works. Prayer acts as a way for St. Paul to acknowledge God’s power. Intercessory prayer also acts as a way for the Apostle to “share in the Father’s redemptive love”.