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Transcript of EMF METHOD - files.teceee-in.webnode.infiles.teceee-in.webnode.in/200000001-752dd76282/Circuit...
1
REGULATION OF 3 PHASE ALTERNATOR BY EMF AND MMF METHOD
EMF METHOD
MMF METHOD
2
FORMULA:
Synchronous Impedance: ๐ง๐ =๐ธ1
๐ผ๐ ๐ ohms
Where E1 = Open circuit voltage for a certain field current
Isc = Short circuit current for the same field current.
Synchronous Impedance: ๐๐ = โ๐๐ 2 โ ๐ ๐
2 Ohms
Lagging power factor: ๐ธ0 = โ(๐ cos โ + ๐ผ๐ ๐)2 + (๐ sin โ + ๐ผ๐๐ )2
Leading Power factor: ๐ธ0 = โ(๐ cos โ + ๐ผ๐ ๐)2 + (๐ sin โ โ ๐ผ๐๐ )2
Unity power factor: ๐ธ0 = โ(๐ + ๐ผ๐ ๐)2 + (๐ผ๐๐ )2
Where V= terminal voltage; I-Full load current
Regulation: %๐ =๐ธ0โ๐
๐ร 100
GRAPH:
The regulation curve is drawn between regulation and power factor
VIVA QUESTIONS:
l. What is an alternator?
2. What are the types of alternatorโ?
3. Define voltage regulation of an alternator.
4. Mention the methods by which voltage regulation can be determined.
5. Which method gives the result nearer to the actual value?
3
V AND INVERTED V CURVES OF SYNCHRONOUS MOTOR
GRAPH:
The curve is drawn between
o Armature current VS excitation current
o Power factor VS Excitation current
FORMULA:
tan โ = โ3[๐2โ๐1
๐2+๐1]
โ = tanโ1[โ3 [๐2โ๐1
๐2+๐1]]
Power factor: ๐๐จ๐ฌ โ
VIVA QUESTIONS:
1. With what condition synchronous motor can be used as a synchronous condenser.
2. What are the special applications of an over excited synchronous motor.
3. Explain the effect of change of excitation of a synchronous motor on its armature current.
4. Explain the effect of change of excitation of a synchronous motor on its power factor.
5. With the given excitation a synchronous motor draws a unity PF current. If the mechanical
Load is increased what will be the power factor and current for the same excitation.
6. Why V curve shift upwards and inverted V curve shift right as the load increases.
7. Explain the effect of change of excitation of a synchronous generator on its armature current.
8. Explain the effect of change of excitation of a synchronous generator on its power factor.
4
LOAD TEST ON 3 PHASE INDUCTION MOTOR
MODEL GRAPH
FORMULA:
๐บ = ๐บ๐ โ ๐บ๐ Kg ; ๐ป๐๐๐๐๐ = ๐ โ ๐. ๐๐ โ ๐น Nm [R-radius of drum; S1, S2- Spring balance]
Input = ๐๐ + ๐๐ ;
Output power = ๐๐ ๐ต๐ป
๐๐ watts; [T- Torque in Nm; N- Speed in rpm]
Power Factor = ๐พ
โ๐๐ฝ๐ณ๐ฐ๐ณ
Efficiency =
๐
๐ ๐๐๐๐๐
๐
๐ ๐๐๐๐๐
ร ๐๐๐
5
GRAPH:
The performance characteristic curves are drawn as
1) Output Power vs. current
2) Output Power vs. Torque
3) Output Power vs. Speed
4) Output Power vs. Efficiency,
Taking Output Power along X-axis and current, torque, speed and efficiency
Along Y-axis.
VIVA QUESTIONS:
1. What are the two types of induction motors?
2. What are the methods of starting of an induction motor?
3. How can the direction of rotation of the motor be reversed?
4. In which induction motor, can you arid external resistance to the rotor?
5. Whether a single phase induction motor is self-starting?
LOAD TEST ON 1 PHASE INDUCTION MOTOR
FORMULA:
๐บ = ๐บ๐ โ ๐บ๐ Kg ; ๐ป๐๐๐๐๐ = ๐ โ ๐. ๐๐ โ ๐น Nm [R-radius of drum; S1, S2- Spring balance]
Input = ๐๐ + ๐๐ ;
Output power = ๐๐ ๐ต๐ป
๐๐ watts; [T- Torque in Nm; N- Speed in rpm]
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Power Factor = ๐พ
โ๐๐ฝ๐ณ๐ฐ๐ณ
Efficiency =
๐
๐ ๐๐๐๐๐
๐
๐ ๐๐๐๐๐
ร ๐๐๐
Percentage of slip = ๐ต๐โ๐ต
๐ต๐ ร ๐๐๐
Power factor = Input power/V1I1
GRAPH:
The performance characteristic curves are drawn as
1) Output Power vs. current
2) Output Power vs. Torque
3) Output Power vs. Speed
4) Output Power vs. Efficiency,
Taking Output Power along X-axis and current, torque, speed and efficiency Along Y-axis.
VIVA QUESTIONS:
l. What are the two types of induction motors?
2. What are the methods of starting of an induction motor?
3. How can the direction of rotation of the motor be reversed?
4. Whether a single phase induction motor is self-starting?
REGULATION OF 3 PHASE ALTERNATOR BY SALIENT POLE ALTERNATOR BY
SLIP TEST
7
FORMULA:
Direct Axis Synchronous Reactance: Xd = ๐ผ๐๐ ๐
๐ผ0 ๐๐๐ ๐ข๐๐๐ก
Quadrature axis Synchronous Reactance Xq = ๐๐
๐๐๐ ๐๐ ๐๐๐ ๐ข๐๐๐ก
MODEL CALCULATION:
๐ฟ๐ =๐ฌ๐๐๐
๐ฐ๐๐๐ ; ๐ฟ๐ =
๐ฌ๐๐๐
๐ฐ๐๐๐
Where , Emax, Emin ,Imax ,Imin where taken in the Reading
Now calculate for Power factor
cos โ = 0.8 , So find the value of ใโ ใ
Therefore, tan ๐ = ๐ sin ๐+๐ผ๐๐
๐ cos ๐+๐ผ๐ ๐ from this equation find ๐
Where, ๐ = ๐ โ โ calculate the value of โ
Now to find the regulation:
We know that, ๐ธ0 = ๐ cos ๐ + ๐ผ๐๐ ๐ + ๐ผ๐๐๐
Where ๐ผ๐ = ๐ผ๐ sin ๐ ๐ผ๐ = ๐ผ๐ cos ๐
Now find the Regulation with above equations by subtitling proper values in below equation we
get,
%๐ ๐๐๐ข๐๐๐ก๐๐๐ =๐ธ0 โ ๐ฃ
๐ฃ ร 100
Calculate for other power factor values with the help of above equations
GRAPH:
The graph is drawn between % regulations vs. Power factor
VIVA QUESTIONS:
1. What is the purpose of slip test on 3 phase alternator?
2. What is meant by direct axis reactance?
8
3. What is meant by quadrature axis reactance?
4. How is the regulation of alternator predetermined by slip test?
5. What is the difference between salient pole alternator and cylindrical rotor type alternator?
REGULATION OF 3 PHASE ALTERNATOR BY ZPF AND ASA METHOD
GRAPH:
1) A graph is drawn b/w If and V which is known as OC curve, by taking If on X-axis and V on
Y-axis.
2) A graph is drawn b/w If and ISC which is known as SC curve, by Taking If on X-axis and
ISCV on Y-axis.
DRAWING ZPF CURVE
1. OCC is drawn.
2. Point A is located such that OA gives If corresponding to Irated. Under short circuit test.
3. Point B is located such that it gives If to voltage from ZPF test.
4. Points A and B joined by curve parallel to OC called ZPF curve.
5. From the curve, ZPF curve is extended.
6. From H, HD is drawn parallel to OCC line.
7. From B, BH is drawn parallel and equal to OA.
8. Point D is point to B and BHD is tangent is obtained.
9. From D, perpendicular to BH at E is drawn.
10. DE gives Ia XL. BE gives If necessary to overcome demagnetizing effect of armature
resistance. EH gives If necessary for balancing armature leakage reactance drop DE.
11. Internal emf, E1 is calculated as
E1 = โ((Vph cosะค + Ia Ra)2 + (Vph sinะค + IaXL)2)
โ+โ โ for lagging pf and
โ-โ โ for leading pf.
12. Find If1 corresponding E1 from OCC.
13. If2 is field current, required to overcome armature reaction (BE)
14. If = โ(If12+If2
2-2If1If2 cos(90ยฑะค)) โ+โ โ for lagging pf and
โ-โ โ for leading pf.
15. From internal emf E1, a horizontal line is drawn cutting the OCC.
16. The regulation is calculated as
% regulation = ((Eo โ Vph)/ Vph)x100.
9
NO LOAD AND BLOCKED ROTOR TEST ON SINGLE PHASE INDUCTION MOTOR
FORMULA:
For NO load test:
cos ๐0 =๐0
๐0๐ผ0
๐ผ๐ = ๐ผ0 cos ๐0 ๐ด
๐ผ๐ = ๐ผ0 sin ๐0 ๐ด
๐ 0 =๐
๐ผ๐ ๐โ๐
๐0 =๐
๐ผ๐ ๐โ๐
For blocked rotor test:
.
cos โ ๐ ๐ =๐๐ ๐
๐๐ ๐๐ผ๐ ๐
๐ผ๐ = ๐ผ0 cos ๐0 ๐ด
๐ผ๐ = ๐ผ0 sin ๐0 ๐ด
๐ 01 =๐๐ ๐
๐ผ๐ ๐2 ๐โ๐
๐01 =๐๐ ๐
๐ผ๐ ๐ ๐โ๐
๐01 = โ๐012 โ ๐ 01
2 ๐โ๐
.
๐๐ = โ๐๐ 2 โ ๐ ๐
2 ๐โ๐
๐ ๐ฟ = ๐ 2 [1
๐ โ 1] ๐โ๐
๐ 2 = [๐ 01 โ๐ ๐
๐ ๐ ] ๐โ๐
๐2 = [๐01 โ๐๐
๐๐ ] ๐โ๐
10
Equivalent circuit diagram:
Calculate and determine of RM and RS
Calculate the determine of ZM and ZC and ZS
VIVA QUESTION:
1. What is a 1-phase induction motor?
2. Write the classification of 1-phase induction motor?
3. Why do we draw the equivalent circuit of 1-phase induction motor?
4. What is double-field revolving theory?
5. Why 1-phase induction, motor is not self-starting?
NO LOAD AND BLOCKED ROTOR TEST ON THREE PHASE INDUCTION MOTOR
FORMULA:
For NO load test:
cos ๐0 =๐0
โ3๐0๐ผ0
๐ผ๐ = ๐ผ0 cos ๐0 ๐ด
๐ผ๐ = ๐ผ0 sin ๐0 ๐ด
๐ 0 =๐
๐ผ๐ ๐โ๐
๐0 =๐
๐ผ๐ ๐โ๐
For blocked rotor test:
.
cos โ ๐ ๐ =๐๐ ๐
โ3๐๐ ๐๐ผ๐ ๐
๐ผ๐ = ๐ผ0 cos ๐0 ๐ด
๐ผ๐ = ๐ผ0 sin ๐0 ๐ด
๐ 01 =๐๐ ๐
๐ผ๐ ๐2 ๐โ๐
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๐01 =๐๐ ๐
๐ผ๐ ๐ ๐โ๐
๐01 = โ๐012 โ ๐ 01
2 ๐โ๐
.
๐๐ = โ๐๐ 2 โ ๐ ๐
2 ๐โ๐
๐ ๐ฟ = ๐ 2 [1
๐ โ 1] ๐โ๐
๐ 2 = [๐ 01 โ ๐ ๐๐]๐โ๐
๐ ๐๐ = [๐ ๐๐ โ 1.6]๐โ๐
Equivalent circuit diagram:
Draw the equivalent circuit with the help of above parameters
SEPARATION OF NO LOAD LOSSES IN 3 PHASE INDUCTION MOTOR
MODEL GRAPH:
FORMULA:
For no load test
cos ๐0 =๐0
โ3๐0๐ผ0
๐ผ๐ = ๐ผ0 cos ๐0 ๐ด
๐ผ๐ = ๐ผ0 sin ๐0 ๐ด
๐ 0 =๐
๐ผ๐ ๐โ๐
12
๐0 =๐
๐ผ๐ ๐โ๐
Loss calculation:
Stator Copper Loss: 3๐ผ02๐
Constant loss =Input power โStator copper loss
Constant loss/phase =Constant loss / 3
GRAPH:
The graph drawn between constant losses (watts) and input voltage (volts)
MEASURMENTS OF NEGATIVE SEQUENCE AND ZERO SEQUENCE IMPEDANCE
OF ALTERNATORS
FORMULA:
For negative sequence:
๐ =๐ฃ
โ3๐ผ
๐2 =๐
โ3๐ผ2
๐ 2 = โ(๐๐2 โ ๐๐
2
For Zero sequence:
๐0 =๐ฃ0
โ3๐ผ0
๐0 =๐
โ3๐ผ02
๐ 2 = โ(๐02 โ ๐0
2