industrial control elec406 · 3.textile mills – double cage induction motor •in textile mills...

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Industrial Control

ELEC406 Dr. Munaf Salim

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Module Three

Actuators

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Industrial Drives (Power Drives)

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Drives used in an automated system are of different types

• Electrical drives

These are direct current (DC) or alternating current (AC) servo motors. They are small in size

and are easy to control.

• Hydraulic drives

These drives have large power to size ratio and provide stepless motion with great accuracy. But

these are difficult to maintain and are bulky. Generally they employ petroleum based hydraulic

oil which may have fire hazards at upper level of working temperatures. Also hydraulic elements

need special treatment to protect them against corrosion.

• Pneumatic drives

This drives use air as working medium which is available in abundant and is fire proof. They are

simple in construction and are cheaper. However these drives generate low power, have less

positioning accuracy and are noisy.


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Feed Drives

Spindle drives

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Drives used in an automated system are of different types

• Electrical drives

These are direct current (DC) or alternating current (AC) servo motors. They are small in size

and are easy to control.

• Hydraulic drives

These drives have large power to size ratio and provide stepless motion with great accuracy. But

these are difficult to maintain and are bulky. Generally they employ petroleum based hydraulic

oil which may have fire hazards at upper level of working temperatures. Also hydraulic elements

need special treatment to protect them against corrosion.

• Pneumatic drives

This drives use air as working medium which is available in abundant and is fire proof. They are

simple in construction and are cheaper. However these drives generate low power, have less

positioning accuracy and are noisy.

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Industrial Drives

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Electrical Drives

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Electrical Drives

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Drives for different industrial application

1.Paper mill- Synchronous motor A paper mill requires a drive which must fulfill the following requirements

•To manufacture different thickness of papers it is required to vary the speed of entire series of rolls.

•Relative speed of rolls should be constant otherwise the paper may be tearing.

•It is required to adjust the speed at any one group of rolls relative to other in order to draw the paper.

2.Rolling mills or steel mills – separately excited DC motor

•Separately excited DC motor is mainly used in rolling mills.

•The motor required for these mills should have high starting torque about 2 to 2.5times the rated torque.

•It should have strong construction.

•The ward leonard speed control of D.C motors or slip ring induction motors are used.

3.Textile mills – Double cage induction motor

•In textile mills group drive is employed.

•The motors employed must have high starting torque with constant speed.

•The motors used must be totally enclosed and moisture proof to prevent entry of dust and moisture enter into

machine.

•Hence totally enclosed, fan cooled, high torque double cage induction motors are used. .

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4.Cement mills

•Various types of loads available in a cement factory and the motor used for them are given below

a)Hammer crusher – Three phase slip ring induction motor

•The lime stones are broken into smaller sizes in the crushing mill.

•For this purpose high starting torque motor is required.

•Hence three phase slip ring induction motor is used because it has high starting torque.

b)Ball mills – Synchronous motor

•In ball mills, the raw materials grind in powder form synchronous motor are used for this process.

c)Rotary driers – Slip ring induction motor

•The cement slurry is dried by blowers and speed of blower is varied depending upon the amount of air required to blow. Hence

slip ring induction motor with pole changing speed control isemployed.

d)Slurring pumps and agitators – Three phase Squirrel cage induction motor

•These are used in the wet process

•Three phase Squirrel cage induction motors used for slurring pumps and agitators

5.Machine tools – D.C shunt motor or 3Ф Squirrel cage induction motor

•The starting torque required is less in most of the machine tools since they start up light.

•Therefore 3 phase squirrel cage induction motor is used for machine tool application.

•Different speed operation is obtained by using two or three speed motor with suitable gear combination.

•D.C shunt motors are used for machine tool application like planners where rapid reversal, and wide speed control are required. In

the case of grinders, totally enclosed motors are used to prevent metallic dust getting into it.

6.Lift and hoists – DC compound motor or 3Ф slip ring induction motor

•The essential requirements for a lift are high overload capacity, high smooth accelerating torque of 2 to 2.5 times the full load

torque at starting and maximum degree of silence.

•D.C compound motor and three phase slip ring induction motor are used for lifts and hoists.

7.Belt conveyor – Double squirrel cage induction motor

•The conveyors are required to transport bulk materials like coal, are sand on either flat belt or bucket system.

•It requires a high starting torque so as to accelerate the load for transport.

•Hence totally enclosed surface cooled motors are used.

•Double squirrel cage induction motors are used in belt conveyors.

8.Ship – Synchronous motors Three phase induction motors and synchronous motors are used for very big ships.

•A three phase alternator gives the supply to the synchronous motor.

•The prime mover used for the alternator is steam turbine by varying the voltage and frequency of alternator the speed of motor is

controlled.

9.Air compressor - 3 Ф Induction motor

•Air compressors are used for pneumatic drill, 3Ф induction motors are used to drive compressors.

•Repulsion motor is used for various industrial machinery air compressors.

•Single phase induction motor is used for small air compressors.

10.Punches and shears

•For punches and shears D.C cumulative compound motors and

•A.C 3 Ф slip ring induction motors provided with fly wheel are used.

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11.Rotary printing

•The rotary printing machinery requires variable speed motor.

•D.C compound motors or A.C 3 Ф induction motors with rotor resistance control are used for printing machineries.

12.Pumps

Centrifugal pump

•The load torque varies as square of the speed in a centrifugal pump.

•At starting the torque required is less.

•Hence 3 Ф squirrel cage induction motor is used for centrifugal pump.

•The liquid handled by the pump does not enter the motor.

•Hence totally enclosed motor is preferred.

Reciprocating pump

•A reciprocating pump requires two times the full load torque at starting.

•A double cage induction motor is suitable for reciprocating pump.

•3 Ф slip ring induction motor is also used for this type of pump.

•D.C shunt motor is used where D.C supply is available.

13.Draught fan

•The single phase split phase induction motors are used for draught fan.

•The single phase split phase induction motor has shunt characteristics and so the operating speed is almost constant.

14.Ceiling fans

•Single phase capacitor start and run motors are used for ceiling fan.

15.Cranes – D.C series motor

•The D.C series motors are used for cranes because they have high starting torque.

•Because they have high starting torque, which helps the motor to reach the speed in a short time and also prevents the motor from

stalling in case of heavy loads.

•A.C 3 Ф slip ring inductions are also used for cranes.

•For starting and special adjustments proper graded rotor resistance is used with slip ring induction motor.

16.Mines- The various loads in a mine are winders, ventilating fans, conveyors, compressors and pumps.

•The winder consists of two cages and a rope for transporting material from bottom of the mine to the surface.• Acceleration and

braking operations are repeated. A 3 Ф slip ring induction motor with ward leonard speed control is used for winder.• Ventilating

fans are used for circulating fresh air. A 3 Ф squirrel cage induction motor is used for ventilating fan if no speed control is not

required.

•Conveyors require a high starting torque, so a double squirrel cage motor is used.

•Compressor is used to provide compressed air for pneumatic drills used for mining operations. It requires shunt characteristics

and so 3 Ф squirrel cage induction motor is used.

•Centrifugal pumps are used to pump out the water falling through the rock layers. It requires high starting torque therefore a 3 Ф

slip ring induction motor is used for pumps.

17.Domestic appliances – Universal motor or Single phase induction motor

•Small universal motor is used for various domestic appliances such as for domestic refrigerators, shavers, vacuum cleaner, mixi,

cloth washing machines etc.

18. Spinning mills – moderate starting torque & smooth acceleration essential. 4 pole to 8 pole Squirrel cage motor

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Electrical Drives

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Dynamics of Motor Load System

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Dynamics of Motor Load System

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Friction Torque

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Friction Torque

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Characteristics of Different types of Loads

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Constant Torque characteristics

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Torque Proportional to speed:

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Torque proportional to square of the speed

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Torque Inversely proportional to speed

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Multi Quadrant Operation

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Problem

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DC Motor Drives

DC Motor Drives

Shunt motors Separately excited motors

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DC Motor Drives

EXAMPLE: A d.c. separately excited motor has the following specification:

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Speed control of shunt or separately excited motors:

Controlling speed by adding resistance Controlling speed by adjusting armature voltage

Controlling speed by adding resistance

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EXAMPLE

EXAMPLE

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EXAMPLE

EXAMPLE

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Example

Example

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Controlling speed by adjusting armature voltage

Controlling speed by adjusting field voltage

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EXAMPLE

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EXAMPLE

Example H.W The speed of the separately-excited dc machine of previous Example is observed to be 2950 r/min with the field current at the same value as in previous Example. For a terminal voltage of 125 V, calculate the terminal current and power and the electromagnetic power for the machine. Is it acting as a motor or a generator?

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Example

Example

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Dynamic model and control of d.c. motors


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Open-loop control of permanent magnet motors

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Closed-loop control of permanent magnet motors

Motor speed control using pulse width modulator (PWM)

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Example

Example

industrial control elec406 · 3.textile mills – double cage induction motor •in textile mills...

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