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What happens when unequal voltage ratios of transformers used in parallel operation of transformers?
Wiki User
∙ 12y ago
You cannot connect Transformers of different voltage in parallel. This is because circulating currents will be set up between the two transformers that may exceed their rated currents.
Wiki User
∙ 12y ago
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What is an unequal sided triangle called?
scalene
Will the voltage dropped across each resistor be same if two unequal resistors are connected in parallel?
yes ,they can be connected ,then they both will drive the current through that resistance ,the current through that resistance will be the sum of currents due to each individual source taking only one at a time (use superpositon theorem)
What is the formula for section modulus of unequal angle iron?
(Assumes the angle iron isn't constrained on either side.)Where:w = width (parallel to axis)h = height (perpendicular to axis)t = thicknessx = Distance to farthest fiber = h-(t*(2*(h-t)+w) + (h-t)^2 / (2*(w+h-t)))Section Modulus = Moment of Inertia / xSection Modulus = (t*x^3 + w*(h-x)^3 - (w-t)*(h-x-t)^3)/ 3/ xHope that helps
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.
What is near-far effect?
Adjacent channel interference nearby frequency leak into passband. The problem can be worse if an adjacent channel user is transmitting in very close range to a subscriber receiver. This problem is referred as near far affect. By Kazi Ashique Ahmed Rafi it usaully occurs in CDMA when users are transmitting unequal powers. by salman ahmed
What shape has 4 unequal sides not parallel?
quadrilateral
What shape has a pair of unequal parallel sides?
trapezium :)
Does trapezium have parallel sides?
A trapezium has two parallel sides (of unequal length) and two non-parallel sides.
What quadrilateral has opposite sides that are not parallel?
A trapezium (US) has no sides parallel, while a trapezoid has one set of unequal parallel sides.
What is the name of a polygon with 4 unequal sides and no sides that are parallel?
quadrilateral
Can unequal groups only be added in math?
No, any operation can be done to them.
What is the name of a quadrilateral with sides of unequal length and two parallel sides?
it is a trapezium
What quadrilateral has one pair of opposite sides that are parallel?
The trapezoid (UK trapezium) has only 1 pair of unequal parallel sides.
When can a trapezoid be a parallelogram?
It cannot. A trapezium is a quadrilateral that has one pair of parallel but unequal sides and another pair of non-parallel sides. A parallelogram has two pairs of parallel and equal sides.
What shape has one pair of parallel sides of different lengths and two right angles?
A trapezium (has only one pair of unequal parallel lines).
What is a way you can compare and contrast a trapezoid and a parallelogram?
A trapezoid has 1 pair of unequal parallel sides whereas a parallelogram has 2 pairs of parallel sides
What is the name of a four sided shape with sides of unequal length and no two sides are parallel?
rhombus
