NSCET E-LEARNING PRESENTATION 1/III EEE_ EE8601_SSD_UNIT 1.pdf · •Control unit: It controls the power modulator which operates at small voltage and power levels. It also operates

NSCET

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Electrical and Electronics Engineering

IIIYEAR/6th Semester

EE8601-Solid State Drives

K.Malar M.Tech.,MBA.,M.Phil.,BA(Hindi) Assistant Professor

Nadar Saraswathi College of Engineering & Technology, Vadapudupatti, Annanji (po), Theni – 625531.

TOPIC NAME

UNIT 01 –Drive Characteristics

―Abigail Adams

“Learning is not attained by chance, it must be sought

for with ardor and attended to with diligence.”

Department of EEE, NSCET, Theni Page-00


DRIVE CHARACTERISTICS • Introduction

• Electric Drives

• Block Diagram of a drive

• Classification of Electric Drives

• Advantages and Disadvantages of Electric Drives

• Factors to be considered in selecting a drive

• Selection of motor

• Four quadrant operation of a drive

• Load Torque

• Equations governing motor load dynamics

• Steady State Stability

• Mathematical condition for the stability of the equilibrium point

Introduction


• Electrical energy is utilized in many forms. Driving load by electric motor is one such application.

• Electric drives are quick to start, have high efficiency and the speed can be easily controlled.

• Different motors have different characteristics and depending upon load characteristics, the motor with suitable characteristics can be chosen for a particular applications.

• Hence electric drives are widely preferred over other types of mechanical drives.

• But while selecting a motor for a particular drive many factors are required to be considered.

• All the desired properties are never available in one type of motor. But the motor which fulfills majority requirements should be selected.

Electric Drives


• Systems employed for motion control are called as Electric drives

• It may employ prime movers such as petrol engine, diesel engine ,gas or steam turbines for supplying mechanical energy for motion control

• Drives employing electric motors are called as Electric drives

Block Diagram of a drive


Parts of Electric Drives

Various parts of Electric Drives

Source

Power modulator

Control unit

Sensing unit


• Source:

Source may be either AC or DC supply

• Power Modulator:

Regulates the output power of the source

It controls the power from the source of the motor in such a manner that motor transmits the speed torque characteristics required by the load

• Control unit:

It controls the power modulator which operates at small voltage and power levels.

It also operates the power modulator as required.

It also generates the command for the protection of power modulator and motor.

Sensing unit:

It senses the certain drive parameter such as motor current and speed

It mainly required either for protection of closed loop operation


Classification of Electric Drives

• Electric Drives are classified into 3 types

Individual drive

Multimotor drive

Group drive



Group Drive:

• If several group of motors are organised on one shaft and driven by one motor,then the system is called as group drive

• Advantage of Group Drives:

Most economical

Disadvantage of Group drives:

Any fault that occurs in the driving motor renders all the driving equipment idle

Low efficiency

Not safe to operate

Individual Drive

• If single motor is used to drive a given mechanism and it does all the jobs connected with this load ,then the system is called as group drive

• Advantage of Group Drives:

If anyone motor fails,it doesnot affect other operation


Power loss occurs

More cost


Multimotor drive


• Each operation of the mechanism is taken care of by separate drive motor

• The system contains several individual drives each of which is used to operate its own mechanism

Advantage of Group Drives:

Each machine driven by a separated motor it can be run and stopped as desired

Flexible


Initial High cost


Advantages of Electric Drives

• They are available in wide range of torque ,speed and power

• Don’t pollute the environment

• It can operate in all four quadrants of speed –torque plane

• They can be started instantly and stopped immediately

• It has flexible control characteristics

• They are adaptable to any operating conditions such as explosive,radio active environment etc

• Work area is clean

Disadvantages of Electric Drives

• It can cause noise pollution

• Initial cost is high

• Power failure completely disables the system


Factors to be considered while selecting a drive

• These factors can be divided into three types:

1. Electrical aspects

2. Mechanical aspects

3. Economical aspects


Electrical aspects:


1. Nature of supply: Supply available cab be dc or ac. Again in ac supply, it can be single phase or three phase supply.

2. Speed control: It must be possible to raise the speed below and above rated value.

3. Power factor: The motor must be able to operate at high power factor closer to unity value.

4. Efficiency: efficiency of motor should be high

Mechanical aspects


1. Type of enclosure: Whether enclosure of machine should partially closed to cover the rotating parts only or completely covered.

2. Types of bearing: The types of bearing depends upon speed.

3. Noise level: The noise produced due to rotation of motor should be minimum.

Economical aspects: 1. Capital cost: The price to be paid for purchasing motor and

interest and depreciation on its price over its life is main deciding factor.

2. Running charges: These will vary according to demand for power.

3. Maintenance charges: Frequent maintenance may increase total expenditure.


Selection Of Motors For Different Drives 1. The selection of driving motor mainly depends on the following

factors:

2. Electrical characteristics

3. Mechanical characteristics

4. Size and ratings of motors

5. Cost



Electrical characteristics Following electrical characteristics of motor to be considered.

1. Starting characteristics of a motor

2. Running characteristics of a motor

3. Techniques for speed control

4. Techniques for braking


Mechanical characteristics:

Following mechanical characteristics of motor to be considered.

1. Types of enclosure

2. Types of bearings

3. How transmission of power would take place.

4. Cooling types

5. Acceptable level of noise.

Size and rating of motors: This depend on following parameters:

1. Types of load cycle

2. Overload capacity of a motor for an applications



Cost and other Factors

• Cost:

There are two types of costs involved:

1. Capital costs

2. Running costs

• Other factors:

1. Types of available supply: AC or DC.

2. Matching the mechanical output of the motor with the load requirement.

Different Enclosures

• The type of enclosure for a motor is to be decided based on the applications, type of work the motor is supposed to perform and place where it is installed.

• Various types of commonly used enclosures are as follows:

1. Open type

2. Protected type

3. Drip proof type

4. Splash proof type

5. Totally enclosed

6. Pipe ventilated

7. Frame proof



• Open type enclosure:

In this type of enclosure, the machine is open from both ends. This allows free ventilation.

• Protected type enclosure:

In this type, the machine is not completely open from both ends, instead some openings are provided for ventilation with enhanced protection.

The advantage of this type of enclosure is that without degrading the ventilation, the protection is enhanced.

• Drip proof enclosure:

this type of enclosure does not allow the liquids or moisture to reach the motors.

• Splash proof type:

These enclosures are designed in such a away that liquid or dust particles at an angle between vertical and 1000 will not able to enter the machine.

• Totally enclosed type:

This type of enclosure does not allow any foreign particles to enter into the motor and block the passage of ventilation.

• Pipe ventilated type:

In this type the pipes are used for providing ventilation.

• Flame proof enclosure:

This is a special type of enclosure which is used when the motor is to be used in the explosive atmosphere.


• When actual faults occur in electrical power system, such as phase to earth fault, phase to phase fault and double phase to earth fault, the system becomes unbalanced means, the conditions of voltages and currents in all phases are no longer symmetrical.

• Such faults are solved by symmetrical component analysis.

• That means these vectors sets are described as negative, positive and zero sequence, respectively.


https://www.electrical4u.com/power-system/







• The methods commonly used for grounding the system neutral are

• Solid grounding (or effective grounding)

• Resistance Grounding

• Reactance Grounding

• Peterson-coil grounding (or resonant groundings)


https://circuitglobe.com/solid-grounding.html

https://circuitglobe.com/resistance-and-reactance-grounding.html

https://circuitglobe.com/resistance-and-reactance-grounding.html

https://circuitglobe.com/peterson-coil-grounding.html










• For cases where there is no neutral point available for Neutral Earthing (e.g. for a delta winding), an earthing transformer may be used to provide a return path for single phase fault currents.

• In such cases the impedance of the earthing transformer may be sufficient to act as effective earthing impedance.

• Additional impedance can be added in series if required.

• A special ‘zig-zag’ transformer is sometimes used for earthing delta windings to provide a low zero-sequence impedance





















Documents

NSCET E-LEARNING PRESENTATION 1/III EEE_ EE8601_SSD_UNIT 1.pdf · •Control unit: It controls the power modulator which operates at small voltage and power levels. It also operates