presentation on vfd at igit

8/3/2019 Presentation on VFD at IGIT

1/54


2/54

Orissa Power Generation Corporation is a joint

venture of Govt.of Orissa & AES Corp. USA

It is having 2 x 210 MW Thermal Power Plant,

namely Ib Thermal Power Plant.

It is situated at Banharpalli in the district of

Jharsu uda,Orissa


3/54

VARIABLE FREQUENCY DRIVE

ANENERGY SAVING

SOLUTION


4/54

Motor driven equipment accounts for 65

percent of the electricity consumed in

industry. Industrial systems can account for a

large part of the energy used in manufacturing

processes and there is definitely an

opportunity for increased efficiency and

significant savings through system

improvements. Based on analysis of the motor

systems it is estimated that industrial motor

energy use could be reduced by up to 18

ercent.


5/54

Saving energy by using adjustablespeed drives

An adjustable speed drive often uses lessenergy than an alternative fixed speed mode ofoperation. Fans and pumps are the most

common energy saving applications. When afan is driven by a fixed speed motor, theairflow may sometimes be higher/lower than it

needs to be. Airflow can be regulated by usinga damper which restricts the flow, but it ismore efficient to regulate the airflow byregulating the speed of the motor.


6/54

Saving energy with adjustable speed pumpoperation is similar to saving energy with

adjustable speed fan operation. It is moreefficient to regulate the flow of fluid byregulating the speed of the motor rather thanby restricting the flow using a control valve.

Process control and energy conservation arethe two primary reasons for using anadjustable speed drive. Historically, adjustablespeed drives were developed for processcontrol, but energy conservation has emerged

as an equally important objective.


7/54

Now a days solid state AC & DC Drives

maintain a good efficiency even at reducedspeed. The development in electronics &

simplicity of squirrel cage Motors are likely

to ensure that the invertor& squirrel cageMotors combination is mostly preferable

ones.


8/54

The following are process control benefits thatmight be provided by an adjustable speed

drive: Smoother operation

Acceleration control

Different operating speed for each processrecipe

Compensate for changing process variables

Allow slow operation for setup purposes Adjust the rate of production

Allow accurate positioning


9/54

VARIABLE SPEED DRIVE

Many electric motor-driven devices operate at

full speed even when the loads they are servingare less than their capacity. To match the output

of the device to the load, some sort of part load

control is in use for the majority of their life.Examples include pumps, fans, conveyors,

injection molding machines, air compressors

.Many part load control strategies wasteenergy. The most efficient method of part load

control, resulting in minimal wasted energy, is

the variable speed drive (VSD).


10/54

What is a variable speed drive?

The basic function of a variable speed drive(VSD) is to control the flow of energy from the

mains to the process. Energy is supplied to the

process through the motor shaft.Two physical quantities describe the state of the

shaft: torque and speed. To control the flow of

energy we must therefore,ultimately, control thesequantities.


11/54

Initially, DC motors were used as VSDs

because they could easily achieve the required

speed and torque without the need for

sophisticated electronics.

However, the evolution ofAC variable speeddrive technology has been driven partly by the

desire to emulate the excellent performance of

the DC motor, such as fast torque response andspeed accuracy, while using rugged,

inexpensive and maintenance free AC motors.


12/54

The four milestones of variable speed drives:

DC MotorDrives

ACDrives, frequency control, PWMACDrives, flux vector control, PWM

ACDrives, Direct Torque Control


13/54

DC Motor Drives

Field orientation via mechanical commutator

Controlling variables are Armature Current and

Field Current, measured directly from the motor

Torque control is direct


14/54

In a DC motor, the magnetic field is created by the

current through the field winding in the stator. Thisfield is always at right angles to the field created by

the armature winding. This condition, known as

field orientation, is needed to generate maximumtorque. The commutator-brush assembly ensures

this condition is maintained regardless of the rotor

position.Once field orientation is achieved, the DC

motors torque is easily controlled by varying thearmature current and by keeping the magnetising

current constant.


15/54

ADVANTAGE

Accurate and fast torque control

High dynamic speed response

Simple to controlDRAWBACK

Reduced motor reliability

Regular maintenance

Motor costly to purchase

Needs encoder for feedback


16/54

AC Drive with frequency control

Controlling variables are Voltage and Frequency

Simulation of variable AC sine wave using

modulator Flux provided with constant V/f ratio

Open-loop drive


17/54

Both voltage and frequency reference are fed into a

modulator which simulates an AC sine wave and

feeds this to the motors stator windings. This

technique is called Pulse Width Modulation (PWM)

and utilises the fact that there is a diode rectifier

towards the mains and the intermediate DC voltageis kept constant. The inverter controls the motor in

the form of a PWM pulse train dictating both the

voltage and frequency.Significantly, this method does not use a feedback

device which takes speed or position measurements

from the motors shaft and feeds these back into the

control loop.


18/54

Advantages

Low cost

No feedback device required simpleDrawbacks

Field orientation not used

Motor status ignored Torque is not controlled

Delaying modulator used

Torque cannot be controlled with any degree ofaccuracy. Furthermore, the technique uses amodulator which basically slows downcommunication between the incoming voltage and

frequency signals and the need for the motor to


19/54

AC Drives -flux vector control using PWM

Features

Field-oriented control - simulates DC drive

Motor electrical characteristics are simulated

- Motor Model

Closed-loop drive

Torque controlled indirectly


20/54

With flux vectorPWM drives, field orientation is

achieved by electronic means rather than the

mechanical commutator/ brush assembly of the DCmotor. Firstly, information about the rotor status is

obtained by feeding back rotor speed and angular

position relative to the stator field by means of a

pulse encoder. A drive that uses speed encoders isreferred to as a closed-loop drive. The electronic

controller of a flux-vector drive creates electrical

quantities such as voltage, current and frequency,which are the controlling variables, and feeds these

through a modulator to the AC induction motor.

Torque, therefore, is controlled indirectly.


21/54

Advantages

Good torque response

Accurate speed control

Full torque at zero speed

Drawbacks

Feedback is needed

Costly Modulator needed


22/54

AC Drives -Direct Torque Control

In DTC technology field orientation is achieved

without feedback using advanced motor theory tocalculate the motor torque directly and without using

modulation. The controlling variables are motor

magnetising flux and motor torque.


23/54

Advantage

Torque & Flux are being directly controlled no need

for a modulator.Improve speed accuracy & faster Torque control.

.


24/54

Variable frequency drives are making their

way into systems and equipment for energy

savings and as a means of part load control. Inthe future, expect more centrifugal chillers to

be installed with variable frequency drives as

opposed to inlet vane control, as well as anincreased use of variable frequency drives for

screw air compressors.


25/54

Asprices continue to fall, variable frequency

drives will be used more frequently for soft

start capabilities and even for balancing fluid

systems as opposed to using balancing

(throttling) valves.

The convenience of adding a drive to precisely

and easily control equipment speed rather than

complex, expensive, and maintenance intensive

mechanical drives, or using guesswork to

control processes, will continue to increase

demand for this technology.


26/54

Fluid flow control

The majority of variable frequency drive applications

are for centrifugal pumps and fans.The savings potential for these devices is the largest

since the theoretical input power varies with the cube

of fan/pump speed and volume.

For example, a fan operating at half speed will requireonly about 13 percent of full speed power. Losses in

the variable frequency drive will reduce savings

somewhat, but the savings are still very impressive.Air and water flow control is accomplished by either

of several methods, including recirculating a portion

of the flow, throttling, variable inlet vanes, and

variable frequency drives.


27/54

Recirculating part of the flow results in the fan or

pump operating at full volume all the time. Only a

portion of the flow is used for the system or processand the rest is recirculated back to the inlet of the fan

or pump. This is the least efficient means of

controlling flow.

Throttling essentially chokes the outlet of the pump orfan to decrease flow much like holding your thumb

over the end of a garden hose. The pressure increases

and the flow decreases. This results in some energysavings over a constant volume recirculating system

but is still wasteful. So VFD provides most efficient

method to save energy.


28/54

WORKING PRINCIPLE OFVFD

In a Motor the stator and rotor contain pole pairs

wound with copper wire. When a current isapplied, a magnetic field is generated and the

north/south field rotates through the stationary

stator as the rotor spins to catch up to therotating field. The spinning of the rotor provides

the torque necessary to drive a load.

An electric motor turns at a given speeddepending on the number of poles in the motor

and the frequency of the alternating current

applied.


29/54

Motor speed can be changed by changing

the alternating current frequency.

Nearly all variable frequency drivesmanufactured today are referred to as

pulse width modulation drives. These

drives contain electronic circuitry that

converts the 50 Hertz line power to direct

current, then pulses the output voltage forvarying lengths of time to mimic an

alternating current at the frequency

desired.


30/54

Variable frequency drives can be installed

with manual or automatic bypasses. In the

early days of the variable frequency drives,bypasses were more common since variable

frequency drives were not as reliable as they

are at the present time. The bypasses wereinstalled in the event of a drive failure to

ensure the system or process would remain on

line.


31/54

Bypasses are still available but not always

installed. The criticality of the application must

be considered in each case to determinewhether the added cost and security of a bypass

is warranted.Harmonic filtering may be

necessary in some applications. Variablefrequency drives can produce harmonics that

can make their way back to the rest of the

building and interfere with sensitive electronicequipment and machines. Line reactors can be

used on smaller drives of 20 hp and less to

dampen and mitigate harmonics.


32/54

For larger applications, an isolation

transformer may be warranted. The isolation

transformer can be installed either on the drive

or on the piece of equipment to be protected

from the harmonics.Because the equipment being protected may

be much lower in power, it may be most

economical to isolate the piece of equipment

from the building supply.


33/54

Energy

Saving


34/54


35/54

In Ib Thermal PowerStation Ball Tube Mill isused for pulverization of the Coal .Primary air

is used inside the Mill for the transportation of

the Coal to the Furnace.So the Mill ispressurised to primary air pressure of

600mmwc.As the inside of the Mill is

presssuried so there is chance of leakage ofCoal dust from Mil trunnions.Seal Air Fan is

used for the sealing of the trunnions so that the

coal dust will not escape outside.


36/54

The Seal Air header is always maintained at

pressure 1200mmWC.But Seal Air Fan isdesigned to develop a pressure of

1660mmWC & flow of 13344Mcube

/hr.The Fan is inlet damper control with

damper is on suction side of the Fan.The

Fan sucks clean air from atomsphere

through auto viscous filter.The Fan is

driven by 120KW,2990RPM,415V ,205

amp induction motor.


37/54

Single stage,Centrifugal typeOrientation: Horizontal suction Top Horizontal

delivery.

Medium: Air.Capacity: 3.9 m3 /sec

SP wet of medium: 1.0535 kg / m3

Total Head leveloped: 1662 mmwc

Speeed: 2880 RPM

Drive Motor

Rating: 120 kw


38/54

The required flow & pressure was achieved

by throttling ofSuction damper with a 30 %

opening. Since the Motor was running at full

speed so there is a loss of energy & also

during starting the motor was taking 5 to 6

times full load current stressing the insulation

consequently failure of motor.


39/54


40/54

A considerable energy saving is achieved by

running the motor at lower speed with 100%

damper opening. Conventional dampercontrol & inverter control with 100% damper

opening, at different air flow quantities is

shown in the graph.At 100% air flow quantity the amount of

power consumption is same for both damper

control & frequency control. The amount ofpower consumption is quite considerable

when the air flow quantity requirement is less.


41/54


42/54


43/54


44/54


45/54


46/54

ENERGY CALCULATION BEFORE

COMMISSINING OFVFD

Average Energy advance for 1 day = 2489 KWH

Average KW during operation = 104 KW

Average Power Factor during operation = .945

Average Current during operation = 144 Amps.


47/54


48/54


49/54

ENERGY CALCULATION AFTER

COMMISSINING OFVFD

Average Energy advance for 1 day = 1806 KWH

Average KW during operation = 74 KW

Average Power Factor during operation = .990

Average Current during operation = 97.2 Amps.


50/54

CALCULATION OF SAVINGS

Avg. Energy Adv. before comm. ofVFD for 1 day = 2489 KWHAvg. Energy Adv. after comm. ofVFD for 1 day = 1806 KWH

Energy saving for 1 day = 2489 1806 = 683 KWH

% Energy Saved = 27.5 %

1. Energy saving of 27.5% achieved after commissioning ofVFD in1 Sear Air Fan.

2. Energy saved for 1 day = 683 KWH.

3. Payback period for 1 drive is 1.4 years.

4. Improvement of power factor from .945 to .990 is achieved due tocommissioning ofVFD.

5. Reduction of average KW from 104 to 74 is achieved due to

commissioning ofVFD.

6. Reduction of Motor current from 144 Amps to 97.2 Amps

is achieved due to commissioning of VFD.

C i


51/54

Conclusion:

1.Variable speed drive saves energy by reducing

throttle loss & improving fan/pump efficiencyat low flow.

2.Variable speed drive provide elegant options

to vary flow so that advantage can be taken ofproduction variation ambient temp. variation.

3.Variable speed drive can be provided by belt,

pulley, gear hydraulic & compressor to saveenergy.

4.Increased life of rotating components due to

lower operating speed.


52/54

5. Reduced noise & vibration level.6. Smooth starting without any jerk& without

any transient overloading of supply.

7. System harmonies with use of electronicsvariable speed drives can be mitigated by the

use of filter.

8. Improve system power factor.


53/54

PLEASE.PLEASE.


54/54

THANKS

presentation on vfd at igit

Documents