# No Load And Blocked Rotor Test On Three Phase Induction Motor Pdf

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File Name: no load and blocked rotor test on three phase induction motor .zip
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Aim: - To draw the Circle diagram of a 3-Phase Induction motor.

## No Load and Blocked Rotor Test

Phone : ,. Name Type Range Qty No. Ammeter MI Panel type 5 A 1 2. Voltmeter MI Panel type V 1 3. Wattmeter U. THEORY : NO-LOAD TEST : Objectives : To determine for an induction motor on no-load, relationship between a b c d Applied voltage and speed, Applied voltage and stator current Applied voltage and power factor Applied voltage and power input Brief theory : In this experiment it is intended to study the effect of variation of applied voltage on the speed, power input, power factor, stator current of an induction motor running on no-load.

The effect of change of applied voltage on the above mentioned quantities are explained as follows : a Effect on Speed : Speed remains practically constant untill very low voltage are reached. Unless heavily loaded, the speed of an induction motor is affected very little by fluctuations of voltage. The component of the stator current which provides the ampere-turns balancing the rotor ampere-turns will steadily diminish as the rotor current decrease with the increase in rotor speed.

The increase in the magnetising component is however, more than sufficient to balance this decrease. At very low voltages the induction is so low that almost the whole of the stator current is employed in balancing the rotor current. At normal voltage the rotor current requires only a small proportion of the stator currents to balance them.

The higher saturation of the magnetic circuit requires a much stronger magnetising current to maintain the air-gap flux. Thus, there is a continuous increase in the power factor angle and hence a fall in power factor. Frictional losses of the motor are practically constant as the speed does not change with voltage. The loss component of the stator current, I W is due to frictional losses and iron-losses. As voltage is increased, iron-loss component and magnetising component of stator current will increase.

The increase in magnetising current will be more than the increase in iron-loss component of stator current. Thus there will be a fall in power factor as the voltage is increased. As stated earlier, frictional losses are nearly constant at all voltages until the motor speed falls rapidly , while the iron-losses continue to increase with the increase in the applied voltage. In fig, by extrapolating the power input curve to the left until it cuts the ordinate of zero voltage, when there can be no iron-loss, it is possible to make a rough estimate of the power spent in friction and windage.

The effect of change of stator input voltage on the above-mentioned quantities are shown graphically. Let the readings of ammeter, voltmeter and two wattmeters connected in the circuit be, I 0, V 0, W 01 and W 02 respectively during no load test.

No load current, I 0 has been directly measured by the ammeter. To obtain more reliable values range of both the wattmeter should be 2. Connect the circuit as per diagram shown on attached sheet. Ensure Motor is unloaded and the Variac is set at zero position. Switch on the 3 phase A. Record the readings of all the meters connected in the circuit and tabulate observation.

Calculate the power input and power factor for each reading. Plot characteristic of quantities as indicated in figure A. This experiment is performed on a three-phase Squirrel Cage Induction Motor when the rotor is not allowed to rotate performed by tightening the belt.

The effect of variation of stator voltage on input power, and stator current are explained as follows :- a Effect on input Power : When the rotor is blocked, only a small amount of voltage can be applied across stator terminals to allow up to normal full-load current to flow through the windings. The iron losses will be very small as at that low voltage magnetisation will be low.

The 3. With the increase in stator applied voltage, the losses will increase as the square of the current. Figure C shows the effect of change of stator voltage on the quantities.

In this test, rotor is not allowed to move blocked either by tightening the belt, in case provided or by hand and reduced voltage 25 to 30 percent of the rated voltage of rated frequency is applied to the stator winding.

This test is performed with rated current following in the stator winding. Short circuit current, I SC observed during the block rotor test corresponds to reduced applied voltage, V SC, which should be converted to rated voltage of the motor for plotting the circle diagram.

The relation between the short circuit current and the applied voltage is approximately a straight line. Thus, one of the wattmeter connected in the circuit will give negative reading in both the test, which may be recorded by reversing by terminals of the pressure coil or the current coil.

Connect the circuit as per diagram shown in fig B. Adjust the variac at zero position. Change the ranges of all the instruments for block rotor test as suggest in the discussion on circuit diagram. Block the rotor either by tightening the belt firmly or by hand. Switch-on the ac supply and apply reduced voltage, so that the input current drawn by the motor under blocked rotor condition is equal to the full load current of the motor. Record the readings of all the meters, connected in the circuit.

Switch-off the ac supply fed to the motor. Measure the resistance per phase of the stator winding, following ohm s law concept. Tabulate your readings as per table shown. Draw characteristics of the quantities similar to as shown in Fig. C : Effect of exchange of stator applied voltage on power input, rotor and stator current. Form no-load test I 0 is known and f 0 is found out as taking all quantities on per phase values.

D with V 1 as vertical reference axis. D : Circle diagram of an induction motor. From blocked rotor test I 2 is known. Thus OD represents the total current drawn by the stator. The locus of the current I 1 will pass through the two extreme points, namely through C at no load and through D which corresponds to block rotor condition. The centre of semicircle may be found out thus : draw a perpendicular bisector from the line CD.

This will cut the horizontal line CB drawn from C at the point Q. Draw also a horizontal line OO parallel to the line CB. As applied voltage V 1 is shown as vertical line, CL which is equal to I 0 cos 0 is proportional to the no load input. Thus the length CL can be equated to the no load input power W 0 which supplies core-loss, friction and windage loss and a small amount of I 2 R-loss.

The vertical distance DM represents the input power under blocked rotor condition with rated voltage applied across the stator. Distance NM has been assumed to be equal to CL representing core loss and friction and windage losses.

This is an approximation as under blocked rotor condition, there is no friction and windage loss. The remaining part, DN of the input at blocked rotor condition is wasted as I 2 R-loss in the stator and rotor, the output under blocked rotor condition being zero. The line CD represents the output line. The vertical distance above this line up to the periphery of the circle expressed in power scale will represent the output power. The line CR separating the stator and rotor I 2 R-loss is the torque line.

Vertical distance above this line up to the periphery of the circle is the developed torque. Let us redraw the circle diagram of Fig D and let us assume that the motor is taking a current represented by OP in Fig E. The perpendicular line PG represents power input. GH represents fixed losses. JP represents output power and KP represents output torque.

E : Method of construction of circle diagram of an induction motor. To determine the maximum power developed by motor, draw a line parallel to the output line tangent to the circle at point S. Draw a vertical line ST from the point S to the output line. The length ST represents the maximum output. Similarly, to determine maximum torque developed by the motor, draw a line parallel to the torque line. The length XY represents the maximum torque. A V, 40 hp, 50 Hz, 4 pole delta-connected induction motor gave the following test No-load test : V, 20 A, W Blocked-rotor test : V, 45 A, W Draw the circle diagram and determine a the line current and power factor rated output; b the maximum output; c the maximum torque; d the full-load efficiency; e the full-load rotor speed; Assume stator and rotor I 2 R-losses to be equal at standstill.

The test data given are assumed to be of line values. F is constructed through the following steps: Represent voltage V on the vertical axis. Draw a horizontal line OE from O. No-load power factor angle is 85 O.

Thus, represent no-load current by the vector OC whose length is 2 cm and is lagging the vertical voltage axis by 85 O. Similarly, represent the input current of A under blocked rotor condition by a vector CD of 18 cm length and lagging voltage vector by 69 O. Join OD. With Q as centre and QC as redius draw a semicircle. From D on the semicircle draw a vertical line DM on the horizontal axis. Now CD represents the output line and CR represents the torque line.

F : Circle diagram of an induction motor. To locate the position of JP we may raise the vertical line MD and cut 4. DG is 4. Now draw a line from G parallel to the output line CD to cut the circle at P. From P drop a vertical line PJ onto the output line.

OP represents the full load input current.

## 7.noload And Blocked Rotor Test On Singlephase Induction Motor

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. Sehra and K. Sehra , K. Gautam , Vijay Bhuria Published The asynchronous polyphase induction motor has been the motor of choice in industrial settings for about the past half century because power electronics can be used to control its output behavior.

Phone : ,. Name Type Range Qty No. Ammeter MI Panel type 5 A 1 2. Voltmeter MI Panel type V 1 3. Wattmeter U. THEORY : NO-LOAD TEST : Objectives : To determine for an induction motor on no-load, relationship between a b c d Applied voltage and speed, Applied voltage and stator current Applied voltage and power factor Applied voltage and power input Brief theory : In this experiment it is intended to study the effect of variation of applied voltage on the speed, power input, power factor, stator current of an induction motor running on no-load. The effect of change of applied voltage on the above mentioned quantities are explained as follows : a Effect on Speed : Speed remains practically constant untill very low voltage are reached.

The machine is brought to its rated speed by applying rated three phase volt- age at the stator (Vnl). Corresponding no-load current (Inl) and no-load real power.

## Blocked rotor test

The no load test of 3 phase induction motor is performed on induction motor when it is running without load. This test tells us the magnitude of constant losses occurring in the motor. The set up for no load test of induction motor is shown in the figure.

Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity. Use of this web site signifies your agreement to the terms and conditions. Estimation of induction motor parameters based on field test coupled with genetic algorithm Abstract: This paper proposed a technique for estimating the parameters of three-phase induction motor in order to conduct on-site energy audits of existing motors, which are then used to project a cost savings.

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Теперь рука была закинута за голову, следовательно, Хейл лежал на спине. Неужели высвободился. Однако тот не подавал никаких признаков жизни.

Некая антиправительственная организация разработала план под кодовым названием Шервудский лес.

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22.06.2021 at 04:19

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