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# Basics of Motor Drives - PowerPoint PPT Presentation

Basics of Motor Drives. Prepared By:- Muhammad Atta- ul - Ghaffar ( Sr.Electrical Engineer) CENTURY PAPER & BOARD MILLS LTD.

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### Basics of Motor Drives

Prepared By:-

(Sr.Electrical Engineer)

CENTURY PAPER & BOARD MILLS LTD.

What is Drive?

• A variable-frequency drive (VFD) is a system for controlling the rotational speed of an AC motor by controlling the frequency of the electrical power supplied to the motor. Variable-frequency drives are also known as adjustable-frequency drives (AFD), variable-speed drives (VSD), AC drives, adjustable-speed drives (ASD), micro-drives or inverter drives. They operate by varying the frequency of the AC voltage supplied to the motor using solid state electronic devices.

Variable Frequency Drive

Principle of Operation

VFD devices that change the operating speed of a motor.

Principle…

Principle….

• Motor speed can be changed by altering the frequency of the electrical supply:

4 pole motor operating on 50 hertz = 1500 rpm.

4 pole motor operating on 40 hertz = 1200 rpm

• By varying frequency, we can adjust the speed over a wide range or vary the speed precisely using precise changes in the electrical frequency input to the motor.

Principle…

• ASD's actually control both frequency and voltage simultaneously to maintain a constant volts/hertz ratio which keeps current flow similar to full speed conditions

• This allows the motor to draw full current at any speed and produce full torque as motor speed changes.

Power & Torque

Power & Torque

Reduced Horsepower = Reduced Energy Use = Energy Savings!!!!!!!!!!!

• Energy Savings.

• Improved Process Control.

• Reduced Starting Voltage.

• Lower System Maintenance.

• Bypass Capability.

• Multi-motor Control.

• Initial Cost. torque using frequency?

• Motor Heating at Low Speed.

• Maintenance.

• Output Harmonics.

• Induced Power Lines Harmonics.

• A typical adjustable speed drive using a silicon controller rectifier (SCR) power conversion' section. The SCR, (also termed a thyristor) converts the fixed voltage alternating current (AC) of the power source to an adjustable voltage, controlled direct current (DC) output which is applied to the armature of a DC motor.

DC Drives…Principle of Operation.

• SCR's provide a controllable power output by "phase angle control", so called because the firing angle (a point in time where the SCR is triggered into conduction) is synchronized with the phase rotation of AC power source. If the device is triggered early in half cycle, maximum power is delivered to the motor; late triggering in the half cycle provides minimum power .

DC Drive

• Nonregenerative DC Drives control", so called because the firing angle (a point in time where the SCR is triggered into conduction) is synchronized with the phase rotation of AC power source. If the device is triggered early in half cycle, maximum power is delivered to the motor; late triggering in the half cycle provides minimum power .:-

• Nonregenerative DC drives are the most conventional type in common usage. In their most basic form they are able to control motor speed and torque in one direction only.

• Regenerative DC Drives:-

• Regenerative adjustable speed drives, also known as four-quadrant drives, are capable of controlling not only the speed and direction of motor rotation, but also the direction of motor torque.

Types of DC Drives

Types of DC Drives control", so called because the firing angle (a point in time where the SCR is triggered into conduction) is synchronized with the phase rotation of AC power source. If the device is triggered early in half cycle, maximum power is delivered to the motor; late triggering in the half cycle provides minimum power .

• Converter Types control", so called because the firing angle (a point in time where the SCR is triggered into conduction) is synchronized with the phase rotation of AC power source. If the device is triggered early in half cycle, maximum power is delivered to the motor; late triggering in the half cycle provides minimum power . :-

• The power conversion or rectified power section of a DC drive is commonly called the converter.

Types of DC Drives

Types of ASD’s

• The VVI is the oldest AC drive technology and was the first AC drive to gain acceptance in the industrial market.

• The VVI is sometimes called a “six-step drive” due to the shape of the voltage waveform it sends to the motor.

• VVI drives are fairly economical between 25 and 150 horsepower for ranges of speed reduction from 15 to 100% (about 10 to 60 Hertz).

• These drives are also used widely on specialty high speed applications (400 to 3000 Hertz).

Variable Voltage Input (VVI)

Advantages: AC drive to gain acceptance in the industrial market.

• Good Speed Range.

• Multiple motor control from one unit.

• Simple Control Regulator.

• Power Factor decreases with decreasing speed.

• Low Speed Motor Cogging (shaft pulsing/jerky motion)

VVI…

Muhammad Atta ul Ghaffar Sr.Elect.Engr. AC drive to gain acceptance in the industrial market.

Current Source Input (CSI)

Advantages:- sensitive to current as opposed to a VVI drive which is more sensitive to voltage.

• High Efficiency

• Inherent Short Circuit Protection

• Power Factor decreases with decreasing speed.

• Low Speed Motor Cogging (shaftpulsing/jerky motion)

• Cannot test drive without motor connected.

• Requires Isolation Transformer on Input Side.

• Large physical size of Drive due to internal power components

CSI…

CSI Circuit and Waveforms sensitive to current as opposed to a VVI drive which is more sensitive to voltage.

• These drives are the newest technology and use sophisticated power electronics to accomplish the same frequency and voltage control.

• They provide good efficiency with very little motor heating associated with the other types of drives.

• Pulse Width Modulated or PWM drives provide the best output current to operate the motor and are becoming very popular for adjustable speed applications.

Pulse Width Modulated

• High Efficiency. power electronics to accomplish the same frequency and voltage control.

• Wide controllable speed range.

• Constant Power Factor regardless of speed.

• Multi motor operation from one drive.

• No cogging problems.

• Competitive Price.

PWM Circuit & Waveforms power electronics to accomplish the same frequency and voltage control.

• There are minimal differences between AC Drives power electronics to accomplish the same frequency and voltage control.and DC Drives regarding their controllability, AC Drives do in fact present more advantages and cost savings in the long run.  Other differences between AC Drives and DC Drives are set out below.

• AC Drives are used for AC Motor speed control, whereas DC Drives are used for DC Motor speed control.

Difference Between AC & DC Drive

• AC Drives power electronics to accomplish the same frequency and voltage control. are used to control AC output, while DC Drives are used to control DC output.

• AC Drives have both a converter and an inverter, whereas DC Drives have a converter.

• In AC Drives, speed control is done by changing the frequency, while in DC Drives speed control is done by armature control (below base speed) and field control (above base speed).

• AC Drives are more expensive than DC Drives.

Difference

Difference power electronics to accomplish the same frequency and voltage control.

Block diagram of DC Drive

Block diagram of AC Drive

• Parameter:- power electronics to accomplish the same frequency and voltage control.

A variable which has a constant value for a specific application is called Parameter.

• Parameter Types:-

• Function Parameter (can be read & write)

• Visualization Parameter (can only be read)

• BICO parameters (can be read and write)

Parameterization

• Function Parameter. power electronics to accomplish the same frequency and voltage control.

The response of a function block is determined by function parameters. Typical examples of function parameters are:

• Normalization of an input signal.

• Acceleration or deceleration times in the ramp-function generator.

• Proportional gain (Kp) and integral time (Tn) in the speed controller.

(combination of parameters is called function block)

Parameterization

• BICO Parameters. power electronics to accomplish the same frequency and voltage control.

With BICO parameters, you can determine the sources of the input signals of a function block.

• Visualization Parameters.

Visualization parameters are used for visualizing internal quantities (e.g. applicable output current). These parameters are only displayed

and cannot be changed by you.

(BICO---BInector COnnector---These connect one function to another)

Parameterization

Faults and alarms messages show on the drives display when any abnormality in the system occurred. These can be reset or diagnose by consulting the product manual provided by the drive manufacturer.

Faults & Alarms in Drives

• Current:- display when any abnormality in the system occurred. These can be reset or diagnose by consulting the product manual provided by the drive manufacturer.

Electricity is the flow of free electrons in a conductor from one atom to the next atom in the same general direction. This flow of electrons is referred to as current. Electrons move through a conductor at

different rates and electric current has different values.

Basics of Electricity

Current display when any abnormality in the system occurred. These can be reset or diagnose by consulting the product manual provided by the drive manufacturer.

Electricity can be compared with water flowing through a pipe. A force is required to get water to flow through a pipe. This force comes from either a water pump or gravity. Voltage is the force that is applied to a conductor that causes electric current to flow.

(Voltage is the Cause, Current is the Effect)

Voltage

Voltage pipe. A force is required to get water to flow through a pipe. This force comes from either a water pump or gravity. Voltage is the force that is applied to a conductor that causes electric current to flow.