1.practical for Energy Conservation Technique for Diploma electrical engineering.

AIM: STUDY OF POWER FACTOR IMPROVEMENT.

Objective: after studying this experiment, it will be possible to;

            (1) Identify the disadvantage of low power factor.

            (2) Identify the causes of low power factor

            (3) Mechanism of power factor correction improvement

Significance:-Machines and devices with inductive property forms the considerable part of energy considerable part of energy consumption system. Due to the inherent property of inductor the current always lags behinds voltage with reference to time and thus the total amount of electrical energy produced is divided into two sectionsL1) Real power : the main function desired from the device (2) Reactive Power: the power necessary for the functioning of the device. The ratio of such division is governed by the important parameter named as power factor and is a versatile master key for unlocking the many of our power systems problems.

Theory:

            Technically, the power factor is defined as cosine of angle between voltage vector and current vector of a.c. circuits. It is represented diagrammatically as shown in figure-1. It can also be derived from other relations as shown in figure-2 and figure-3.

Disadvantages of low power factor: As mentioned previously, majority of inductive devices present in the system results into low power factoe which leads to one or more of the following disadvantages:

1.      Large KVA rating of equipment

2.      Greater conductor size in transmission, distribution and consumer systems.

3.      Large copper loss

4.      Poor voltage regulation

5.      Reduction handling capacity of the system.

Thus low power factor is an objectionable feature in the supply system as well as form economical point of view.

Causes of low power factor:  Normally the power factor of the load on the supply system is lower than 0.8 lag. Following are the causes of low power factor.

1.      Induction motor works at a power factor which is extremely small on light load (0.2 to 0.3) and rises to 0.8 to 0.9 at full load.

2.      Arc lamps, electric discharge lamps and industrial heat furnaces operate at low lagging power factor.

3.      The load on the power system is varying: being high during morning and evening and low at other time. During low load periods, supply voltage is increased which increases the magnetization current. This results in the decreased power factor.

Power factor improvement:  So, to eliminate the causes and improve the power factor, we desperately require to consider the property of the elements which is compensative in nature. Capacitor is one of each element in which the current leads the applied voltage and this property can be utilized to improve the power factor. The same thing is illustrated diagrammatically in figure-4.

            As shown in the figure, due to the capacitive effect the charging current flows ahead of voltage vector and resultant current drawn from supply is brought to II and from ф₁ to ф_2. Thus improving the power factor.

Elements utilized in power factor improvement: The following equipment can be utilized for power factor improvement.

1.      Static capacitors

2.      Synchronous condensers

3.      Phase advancers

Calculation of power factor correction: With the of power factor triangle, the power factor improvement can be calculated in terms of leading KVAR supplied by power factor correction improvement.

As shown in figure-5,

KVAR₁=KVAR₂=KVAR_c

Therefore,

KVAR_c = KVAR₁ + KVAR₂  

Where KVAR_c = Leading KVAR supplied by power factor correction improvement. If we divide the main triangle into two subordinate right angle triangles, we can have the following relationship of KVAR from the basic rules:

1.      KVAR₁/KW = tan ф₁ i.e. KVAR₁ = KW tanф₁

2.      KVAR₂/KW = tanф₂ i.e. KVAR₂ = KW tanф₂  

Utilizing these results for equation (a) we get,

KVAR_c  = KW tanф₁ - KW tanф₂

Therefore,

KVAR_c = KW(tanф₁ -  tanф₂ )

This is an important relation to find out the leading KVAR_c supplied by power factor correction improvement.

As power factor improvement is intended for reducing maximum demand and also decreasing the tariff rate on KWH, it also incurs the capital the cost of p.f. improving equipment in terms of rate interest and depreciation. The net saving is also affected by all such factors. Therefore,

The value to which the power factor should be improved so as to have maximum net annual saving is known as the MOST ECONOMICAL POWER FACTOR.

Importance of power factor improvement:

It is desired below for both consumers and generating stations.

(i)    Consumers: A consumer has to pay less electricity charges for his maximum demand in KVA plus the units consumed.

(ii)  Generating Stations: Number of units supplied by it depends upon the power factor. Greater the p.f. of generating stations, higher the KWH it delivers to the system. This is according to the formula, KW = KVAcosф

Suppose if we consider the following parameters for power factor improvement, P- Peak load in KW taken by consumer at p.f. cosф, rate is x Rs. Per KVA maximum demand per annum, cosф₂ is improved p.f. due to p.f. improving equipment, y Rs. Is expenditure incurred on p.f. improving equipment per KVAR per annum then,

Most economical p.f.

 cosф₂ = square root of (1-(y/x)2).

Share

Blogger Widget

2.practical for Energy Conservation Technique for Diploma electrical engineering.

PRACTICAL -2

AIM: STUDY OF ENERGY EFFICIENT MOTORS.

 OBJECTIVES: after studying this experiment, it will be possible to;

(I)   Identify various electrical, mechanical, magnetic & design parameters responsible for energy efficient motors.

(II) Categorization of various losses occurring during the operation of motors.

(III) Identify various measures to improve the efficiency.

(IV) Advantage of energy efficient motors.

SIGNIFICANCE: Statistical data shows that the electrical motors consume more than half (50%) of the total electricity produced and (2) more than 75% of the electrical consumption in industry. Further it is major equipment responsible for low power factor in the system. So if various parameters and design factors are considered in appropriate conditions, the motor performance improves which result into saving of electrical and mechanical energy. This is the concept of energy efficient motors.

THEORY:

Electrical motor is a device which converts the electrical energy into mechanical energy. This conversion when considered in relative aspects defines the efficiency as follows:

Efficiency η = mechanical input/electrical input

                     = output/input

                     = output/(output + losses)

                     = (input – losses)/input

As there are various types of motors

(1)   Operating on a.c./d.c. supply

(2)   Working on 1-phase/3-phase

(3)   Working on the principle of dynamically induced e.m.f., rotating magnetic field

(4)   Magnetic locking, reluctance, hysteresis & some other.

There are various types of motors

(1)   Stator/field system

(2)   Rotor/armature

As a result of interaction of electric and magnetic energy within this part mechanical energy produced which is utilized for various purpose. As the mechanical energy is not directly converted from electrical energy but takes the path through magnetic energy, the various losses occurring between as well as in electrical and mechanical form. The losses are recognized as under:

(1)   Rotor copper losses

(2)   Stator copper losses

(3)   Core losses(i) Hysteresis losses (ii) eddy current losses

(4)   Windage and friction losses

(5)   Stray load losses-which is partly electrical and mechanical

Further, the motor is designed considering one of the following parameters which also affect the motors performance considerably.

(1)   Voltage

(2)   Frequency

(3)   Voltage unbalance

(4)   Load

(5)   Output

(6)   Speed

(7)   Sleep

When we consider the duty of the motor it classifies it into three classes.

(1)   Continuous duty

(2)   Intermittent duty

(3)   Short duty

Thus the performance of motor depends on all such instant mixture of selected parameters set which defines its losses and ultimately the efficiencu of energy conversion. This is the base for developing energy efficient motors. When we develop the energy efficient motors, we also consider the factors such as:

CHARACTERISTICS:

(1)   Starting characteristics

(2)   Running characteristics

(3)   No load characteristics

(4)   Torque/speed characteristics

(5)   Torque/slip characteristics

The following design parameters are also considered.

DESIGN PARAMETERS:

1.      Physical parameters: Size of machine, length & diameter of machine, weight of machine, cross sectional area of conductors, width of slots. Resistivity, conductivity of materials, air gap etc.

2.      Electrical parameters: Voltage rating, frequency, current density, di-electric strength of materials, resistance and inductance of material, various capacitive effects, etc.

3.      Magnetic parameters: Flux density, mmf, magnetic saturation limit, permeability of material, armature reaction etc.

4.      Thermal parameters: Cooling path, thermal insulation, air flow etc.

5.      Mechanical parameters: Speed, torque, slip, etc.

Thus all such conditions are necessary for developing energy efficient motors, when considered appropriately. It thus results into the measures of improving the efficiency of motors.

Share

Blogger Widget

3.practical for Energy Conservation Technique. for diploma in electrical engineering

PRACTICAL -3

AIM: TO STUDY OF ILLUMINATION AND ENERGY CONSERVATION.

OBJECTIVE: 

 Light is an inevitable part of active human life. It effectively or adversely affects the activity by its presence. In the absence of natural light, the light produced through electrical phenomena has really provided its best suitable alternate. But there are various phenomena and factors which accounts for consumption of such electrical energy. And, if they are manipulated properly with the advancement of new technology, it can result into the conservation of energy, a big demand of 21^st century. Because light application is a significant part of total electrical energy produced.

THEORY:

In technical terms, the light is defined as electromagnetic radiation in the form of waves which produces a sensation of vision within the brain through eyes and science dealing with it is termed as illumination engineering. There is certain term, which is noted below for reference.

(1)   Luminous flux

(2)   Luminous intensity

(3)   Lumen

(4)   Lux efficacy

(5)   Glare

(6)   Brightness

There two basic purpose of light:

(1)   To identify the object

(2)   To identity (or render) the colors of the object.

The use of light can be divided into three categories:

(1)   Ambient lighting: It provides security and safety.

(2)   Task lighting: It is used to accomplish the task accurately. It is also not necessary to cover the entire area,

(3)   Accent lighting: It illuminates walls to blend more closely with naturally bright areas like ceilings.

The science of light i.e. illumination is governed by two laws:

(1)   Inverse square laws

(2)   Lambert’s cosine laws.

Ø  The candela power of light is derived using polar curves.

Ø  Depending up on reflecting or diffusing surfaces, there are various types of reflections or shades used for illumination.

Ø  Depending up on the requirement there are three types of lighting schemes which are arranged for illumination.

(1)   Direct lighting

(2)   Indirect lighting

(3)   Semi-direct lighting

For the effective illumination purpose, following guiding factors are considered:

1. Space height ratio: = The horizontal lamps/Total lumens radiated by lamps
2. Utilization factor: = Total lumens utilized on working planes/ Total lumens radiated by lamp
3. Depreciation factor: = Illumination under normal working conditions/ Illumination when everything is clean.
4. Waste light factor: = It takes into the account the overlapping of light waves.

Ø  With proper combination of all such factors, the area of lighting is broadly classified as under. :

1.      Household lighting

2.      Commercial lighting

3.      Factory lighting

4.      Flood lighting

Therefore, if we wish to prepare optimum lighting design, it could be achieved by the following means

1. Choosing the proper light sources suited to the system such as color rendering, higher efficacy etc.
2.  Proper selection of luminaries to use the lamp output efficiently.
3. Proper arrangement of luminaries considering the standards of lighting and structural limitations.
4. Introducing control strategies based on variations in occupancy (location and time) and variation in the available day light.
5. Combining local lighting and general lighting for intricate jobs requiring very high level of illumination.

Ø  Ultimately, it is the lamps which transfer the electrical energy in the form of light, so its statistics in the form of efficacy, color rendering index and life are considered in table-1.

Further, distribution of energy after conversion in light is broadly classified as under as observation table-1

SR NO.	LAMP	LIGHT	HEAT ENERGY	MAGNETIC ENERGY
1	incandescent
2	Fluorescent
3	Vapour lamp			less

Thus, if we carefully observe the table-1 and table-2 then, it is evident that efficacy (lumen/watt) magnetic and heat energy generation are factors on which energy conservation can be implemented. While lamp life and color rendering index are those factor economical aspects.

            Therefore, we need to concentrate on it and analyze it as under:

v  Incandescent lamp: try to reduce the voltage fluctuation. Because as per data in developed country lamps produces 90 lumens/watt while in India it gives 50/0 lumens/watt due to voltage variation. Therefore, we need more Incandescent lamp

v  Improvement in design: this includes the aspect of reduction in heat losses and lamps developed considering the same basis are:

1. New fluorescent lamps
2. Ballasted circular fluorescent lamps.
3. Compact fluorescent lamps.

The typical power rating changes from 60 watt to 16 watt same amount of light produced. Thus about 75% saving over the incandescent lamp.

v  Fluorescent lamps: The major limiting factor in fluorescent lamp is magnetic losses. These are eliminated by the use of electronic ballasts. It is a device which converts the low frequency into high frequency for current limiting application then again converts it to 50 Hz frequency for tube light operation. Typical power consumption is 1 to 3 watts for such operation. Thus results into 85% of saving as compared to magnetic ballast of 16 watt rating.

Share

Blogger Widget