0
A series circuit contains a generator two devices and connecting wires. The resistances of the two devices are 15 ohms and 10 ohms. The voltage supplied by the generator is 75 V. What will be the volt?
Wiki User
∙ 7y agoWant this question answered?
Be notified when an answer is posted
Add your answer:
Earn +20 pts
How to compute the minimum load of 16 MW generator?
A generator, rated at 16 MW, should be able to continuously supply a load of 16 MW. You don't need to compute its 'minimum load', because the minimum load will be zero watts! In other words, you can run the generator with no load whatsoever if you wish to waste fuel.The point is that the power supplied by a generator is determined by the load, NOT by the generator itself -so it is important that the generator is capable of supplying the maximum load applied to it. A generator's 'rated power output' simply tells us the maximum load it is capable of supplying.
Why would a generator produce high kvar output?
A generator would be forced to produce a high output kVAr if it has a lot of non-linear loads connected to it i.e. fluorescent lighting, switchmode power supplied equipment (PCs, old servers etc).
What are the condition for parallel operation of the generators?
Parallel Operation of DC Generators: In a dc power plant, power is usually supplied from several generators of small ratings connected in parallel instead of from one large generator. This is due to the following reasons: (i) Continuity of service: If a single large generator is used in the power plant, then in case of its breakdown, the whole plant will be shut down. However, if power is supplied from a number of small units operating in parallel, then in case of failure of one unit, the continuity of supply can be maintained by other healthy units. (ii) Efficiency: Generators run most efficiently when loaded to their rated capacity. Therefore, when load demand on power plant decreases, one or more generators can be shut down and the remaining units can be efficiently loaded. (iii) Maintenance and repair: Generators generally require routinemaintenance and repair. Therefore, if generators are operated in parallel, the routine or emergency operations can be performed by isolating the affected generator while load is being supplied by other units. This leads to both safety and economy. (iv) Increasing plant capacity: In the modern world of increasing population, the use of electricity is continuously increasing. When added capacity is required, the new unit can be simply paralleled with the old units. (v) Non-availability of single large unit: In many situations, a single unit of desired large capacity may not be available. In that case a number of smaller units can be operated in parallel to meet the load requirement. Generally a single large unit is more expensive. Connecting Shunt Generators in Parallel: The generators in a power plant are connected in parallel through bus-bars. The bus-bars are heavy thick copper bars and they act as +ve and -ve terminals. The positive terminals of the generators are .connected to the +ve side of bus-bars and negative terminals to the negative side of bus-bars. Fig. (1) shows shunt generator 1 connected to the bus-bars and supplying load. When the load on the power plant increases beyond the capacity of this generator, the second shunt generator 2 is connected in parallel with the first to meet the increased load demand. The procedure for paralleling generator 2 with generator 1 is as under: (i) The prime mover of generator 2 is brought up to the rated speed. Now switch S4 in the field circuit of the generator 2 is closed. (ii) Next circuit breaker CB-2 is closed and the excitation of generator 2 is adjusted till it generates voltage equal to the bus-bars voltage. This is indicated by voltmeter V2. (iii) Now the generator 2 is ready to be paralleled with generator 1. The main switch S3 is closed, thus putting generator 2 in parallel with 51 generator 1. Note that generator 2 is not supplying any load because its generated emf is equal to bus-bars voltage. The generator is said to be "floating" (i.e. not supplying any load) on the bus-bars. Figure(1) (iv) If generator 2 is to deliver any current, then its generated voltage E should be greater than the bus-bars voltage V. In that case, current supplied by it is I = (E - V)/Ra where Ra is the resistance of the armature circuit. By increasing the field current (and hence induced emf E), the generator 2 can be made to supply proper amount of load. (v) The load may be shifted from one shunt generator to another merely by adjusting the field excitation. Thus if generator 1 is to be shut down, the whole load can be shifted onto generator 2 provided it has the capacity to supply that load. In that case, reduce the current supplied by generator 1 to zero (This will be indicated by ammeter A1) open C.B.-1 and then open the main switch S1. Load Sharing: The load sharing between shunt generators in parallel can be easily regulated because of their drooping characteristics. The load may be shifted from one generator to another merely by adjusting the field excitation. Let us discuss the load sharing of two generators which have unequal no-load voltages. Let E1, E2 = no-load voltages of the two generators R1, R2 = their armature resistances V = common terminal voltage (Bus-bars voltage). Then 1 1 1 R I E V   and 2 2 2 R I E V   Thus current output of the generators depends upon the values of E1 and E2. These values may be changed by field rheostats. The common terminal voltage (or bus-bars voltage) will depend upon (i) the emfs of individual generators and (ii) the total load current supplied. It is generally desired to keep the busbars voltage constant. This can be 52 achieved by adjusting the field excitations of the generators operating in parallel. Compound Generators in Parallel: Under-compounded generators also operate satisfactorily in parallel but over compounded generators will not operate satisfactorily unless their series fields are paralleled. This is achieved by connecting two negative brushes together as shown in Fig. (2) (i). The conductor used to connect these brushes is generally called equalizer bar. Suppose that an attempt is made to operate the two generators in parallel without an equalizer bar. If, for any reason, the current supplied by generator 1 increases slightly, the current in its series field will increase and raise the generated voltage. This will cause generator 1 to take more load. Since total load supplied to the system is constant, the current in generator 2 must decrease and as a result its series field is weakened. Since this effect is cumulative, the generator 1 will take the entire load and drive generator 2 as a motor. After machine 2 changes from a generator to a motor, the current in the shunt field will remain in the same direction, but the current in the armature and series field will reverse. Thus the magnetizing action, of the series field opposes that of the shunt field. As the current taken by the machine 2 increases, the demagnetizing action of series field becomes greater and the resultant field becomes weaker. The resultant field will finally become zero and at that time machine 2 will be short circuited machine 1, opening the breaker of either or both machines. Figure (2) When the equalizer bar is used, a stabilizing action exists and neither machine tends to take all the load. To consider this, suppose that current delivered by generator 1 increases. The increased current will not only pass through the series field of generator 1 but also through the equalizer bar and series field of generator 2. Therefore, the voltage of both the machines increases and the generator 2 will take a part of the load.
Why is a synchronous machine not self starting?
A synchronous generator generally requires DC power supplied to the rotor winding to make it into an electromagnet. As the rotor spins, a voltage will be induced in the stator windings (the stationary windings). A synchronous generator needs something to supply this initial DC power to the rotor, so it may be deemed to not be "self starting". "Self starting" may have several different interpretations, though. A "black start" generator could be deemed as being self starting, even though this initial power is (usually) supplied by a set of batteries. Many generators pull this power from the power grid, so if the grid is not energized (black start conditions), these generators cannot start until at least part of the power grid is put back in service with another generator.
What is dc separately excited shunt generator?
Either or both can be separately excited. To generate voltage you need a big magnet( the field). Most generators use an electro-magnet. Now the electro-magnet needs a source of power (electricity). We could use the generators own output to excite the field (magnet), this is called self excitation. The problem with self excitation is that we have to wait for the generator to turn and start generating, also to start generating (Building up) there must be some left over magnetism from the last time it was run (called residual magnetism) or not even a little voltage will be generated to start the field current flowing. To solve these problems we could use separately excited. This means we must have a separate source of power to excite the field to produce the magnetism. Sometimes a battery or gasoline driven generator is used to excite the field of a very large generator to get it generating and then we can use some of the generated output to either recharge the battery or switch over to from the battery. In any case we have adjustable control of the generator all the time. This is why most generators are designed to be separately excited. And that is why you car has a voltage regulator. It wakes up the alternator when the engine is started by separately exciting it (the field) with the battery and then regulates the output voltage of the alternator as the engine changes speed with the driver's commands from the gas pedal.
What is the load rejection and load pick-up in the power generation?
Load rejection occurs when load is suddenly removed from the generator. The most obvious example of this is the breaker connecting the generator to the power grid opens. This results in a full load rejection. Load pick up means the generator is supplying power to a given load. When a generator comes on line, it will pick up some load that might have been supplied by another generator.
What is the difference between a seperately excited DC generator and DC shunt generator?
The difference between a separately excited DC generator and a Shunt DC generator is that for a separately excited Dc generator , the excitation field winding is supplied by an external source different from that supplying the armature while for shunt generator, the excitation field windind is connected in series with the armature and supplied by a single source.
What is the source for mechanical motion supplied to a generator called?
friction
What does an electromagnet do in a generator?
in a generator electromagnets are used for producing flux for rotor to cut so it can produce current in small generator they will have residual magnetism and in big generator current is supplied to electromagnet from another small dc generator
What does a conductor do in a dc generator?
It is a conductor, it conducts the electric current generated to the load that is being supplied with power.
What happens if excitation fails in parallel oprating generator?
when excitation fails,Reactive power will be supplied by the system to which the generator is connected and generator will work as induction generator and its speed will rise a little. generator which was in over excitation mode will work in underexcitation.but there is under excitation limit which should not be reached so we should detect loss of excitation and trip generator
What does the voltage regulator do on a generator?
A voltage regulator controls the output voltage of a generator. This ensures only the specified ÊvoltageÊis supplied thus preventing damage to the circuit and other electrical appliances.Ê
Why is necessary to control over speed in a motor?
over speed control is recommended for all prime mover driven generator to prevent over frequency operation of load connected to a system supplied by the generator and also to prevent possible over frequency operation of the generator itself from Ac system.
Give an example of one type of energy conversion?
Mechanical energy is supplied to a generator from an engine, a steam turbine for example, and converted to electrical energy
What are the nutrients in a plant fertiliser?
Plant food contains the 3 most needed substances in fertilizer: nitrogen usually supplied by nitrates, phosphorous usually supplied by phosphates, and potassium usually supplied by salts. Other trace compounds are also present.
How do you connect usb 36.0 mega pixel webcam to desk top?
Use the USB connector and plug it in. If it was supplied with drivers, install those before connecting it.
If 2kw generator is supplied to 10 ampere load how much will be its power factor?
The 10 A in the load includes the real power and the reactive power, if it is a single phase 120 V generator it can supply 16.67 A; that means a 2000 KW load at a power factor of 1.00, of for example a 1600 W load at a power factor of 0.80, in both cases the output current of the generator will be 16.67 Ampers, it is the same with the 10 A load, the power factor is included in the supplied current.Rosa María Valdespino.
