78 Questions
What is the primary function of electric drives?
To control the motion of electrical machines
Who introduced the concept of electric drives?
B.S. Iakobi
What is the role of the energy transmitting device in an electric drive?
To deliver power to the driven machine
What is the term for the machine that performs the desired production process?
Working machine
In what year were electric drives industrially adopted?
1870
What is the purpose of the electric motor in an electric drive?
To supply power for the desired motion
What are the three major components of an electric drive?
Electric motor, working machine, and energy transmitting device
What is the term for the system that controls the rotation of the motor shaft?
Controlling system
What is the main benefit of regenerative braking?
Considerable energy saving
What is a major disadvantage of Electric Drives?
The value of the obtained drive output power is low
What is a domestic application of Electric Drives?
Refrigeration
What is the main difference between AC and DC drives?
Type of power supply
What is the function of a rectifier circuit in AC drives?
Converting AC to DC
What is a characteristic of DC drives?
Self-starting
What is Mechatronics defined as?
The synergistic combination of mechanical engineering, electronic engineering, control engineering and systems thinking
What is an example of a Mechatronic system?
Automatic washing machine
What is a characteristic of Mechatronic systems?
Multi-disciplinary approach
What is a benefit of Mechatronic systems?
Improved system performance
What is the primary function of the power source in an electric drive system?
To provide power to the system for desired operation
What is the main function of the power electronic converter in an electric drive system?
To convert supplied input electrical energy into a form that can drive the motor
What is the purpose of the control unit in an electric drive system?
To control the power converter according to the provided input and feedback signal
What type of motors are used in DC drives?
Series, shunt, or compound DC motors
What is the advantage of electric drives in terms of starting or loading?
Easy and instant starting or loading
What is the benefit of using electrical energy in electric drives?
It is easy to transfer, store, and handle
What is the advantage of electric drives in terms of motor efficiency?
High efficiency with low losses
What is the benefit of using microcontrollers in electric drives?
Easy to perform control unit functionality
What type of operation can electric drives perform?
Four-quadrant operation
What is the classification of electric drives based on the type of supply input?
DC drives and AC drives
What is the characteristic of Bipolar Junction Transistors (BJTs) that allows them to handle two polarities?
They have two junctions: Emitter-Base junction and Collector-Base junction
What is the purpose of Metal Oxide Semiconductor Field-Effect Transistors (MOSFETs)?
To control voltage
What is the advantage of Static Induction Transistors (SITs) over Field-Effect Transistors?
Higher voltage breakdown
What is the composition of Insulated Gate Bipolar Transistors (IGBTs)?
P–N–P–N four alternating layers
What is the structure of a Power Bipolar Junction Transistor (BJT)?
Vertically oriented device with alternate P and N-type layers connected
What are the four regions of operation of a Power Transistor?
Cut off, Active, Quasi saturation, and Hard saturation
What happens when an NPN power transistor is connected in reverse bias condition?
It enters Cut off mode
What is the term for the device that controls the current, including the process of amplification and switching?
Bipolar Junction Transistor (BJT)
What is the characteristic of Metal Oxide Semiconductor Field-Effect Transistors (MOSFETs) that allows them to operate with high efficiency?
Wide channel
What is the characteristic of Insulated Gate Bipolar Transistors (IGBTs) that makes them suitable for switching purposes?
High power gain
What is the state of the transistor when the collector-base region is reverse biased and the base-emitter region is forward biased?
Inactive state
What is the advantage of power transistors in terms of voltage gain?
It is high
What is the main characteristic of power transistors that allows them to control high current and voltage ratings?
Their ability to control high current and voltage ratings
What are power transistors used in?
In a variety of applications, including switch-mode power supplies, relays, converters, power amplifiers, and more
What is the type of transistor that features emitter, base, and collector terminals?
BJT
In what region does a transistor operate when the collector-base and base-emitter regions are connected in forward bias?
Hard saturation region
What is the term for the leakage current that flows through the transistor from collector to emitter when it is in the cut off state?
Leakage current
What is the disadvantage of power transistors when it comes to thermal stability?
They have low thermal stability
What type of transistor is particularly designed to control high current – voltage rating?
Power transistor
What is the term for the situation when the collector-base and base-emitter regions are connected in forward bias pattern?
Hard saturation state
What is the mode of operation in which the SCR will be in the ON state and will be conducting?
Forward Conduction Mode
What happens when the applied forward bias voltage between the anode and cathode increases beyond the breakdown voltage?
The junction J2 will be forward biased and the SCR will start conducting
What is the effect of applying a positive voltage to the gate terminal of the SCR?
The SCR will move to the conduction state
What is the characteristic of the VI curve of the SCR in the reverse blocking region?
A small leakage current flows in the reverse direction
What is the effect of increasing the gate current Ig in the VI curve of the SCR?
The SCR moves to the conduction mode faster
What is the purpose of using SCRs in the circuit diagram shown?
To control the speed of a DC motor
What is the mode of operation in which the positive voltage is applied to the Cathode (-) and the Negative voltage is given to the Anode (+)?
Reverse Blocking Mode
What is the characteristic of the junctions J1 and J3 in the reverse blocking mode?
They are reverse biased
What is the term for the current that flows through the SCR in the reverse direction in the VI curve?
Reverse leakage current
What is the purpose of applying a positive voltage to the anode and negative voltage to the cathode in the VI curve?
To move the SCR to the forward blocking mode
What is the main advantage of using concurrent engineering in Mechatronics?
To overcome the drawbacks of traditional design methods
What is the primary advantage of power transistors?
High voltage gain
What is the primary feature of Quaternary level Mechatronics?
Introduction of intelligence and fault detection and isolation capability
What is the main characteristic of a Mechatronic system?
High degree of flexibility and low cost
What is the most common application of SCRs?
Rectification
What is the structure of an SCR?
Four-layered semiconductor device
What is the main application of Mechatronics in robotics?
Welding and nuclear inspection
What is the function of the gate terminal in an SCR?
It acts as a control terminal
What is the main advantage of using Power Transistors?
They can control high current and voltage ratings
What is the term for the machine that uses SCRs to convert AC current to DC current?
Rectifier
What is the main difference between Primary and Secondary level Mechatronics?
Integration of microelectronics into electrically controlled devices
What is the main disadvantage of Mechatronics?
Higher initial cost of the system
What is the characteristic of SCRs that makes them suitable for industrial applications?
They can handle high current and voltage
What is the mode of operation of an SCR when the positive voltage is applied to the anode and the negative voltage applied to the cathode, with no pulse applied to the gate?
Forward Blocking mode
What is the term used to describe the philosophy adopted in the design of electromechanical systems?
Mechatronics
What happens when the voltage applied to the SCR reaches the breakdown voltage of the SCR?
The junction J2 gets depleted due to avalanche breakdown
What is the main feature of Tertiary level Mechatronics?
Incorporation of advanced feedback functions into control strategy
What is the main benefit of using Mechatronics in manufacturing?
Greater extent of machine utilization
What is the primary function of power transistors in switch-mode power supplies (SMPS)?
To switch power
What is the benefit of using power transistors in power amplifiers?
High current density
Study Notes
Electric Drives
- Definition: Electric Drives are electro-mechanical systems designed to control the motion of electrical machines.
- Components: Electric motor, energy transmitting device, and working (or driven) machine.
- Function: Converts electrical energy into mechanical energy to impart motion to machines.
Block Diagram of Electric Drives
- Power Source: Provides power to the system.
- Power Electronic Converter: Converts input electrical energy into a form that can drive the motor.
- Motor: Converts applied energy into mechanical motion.
- Load: Part of the system that requires motion, such as pumps, machines, etc.
- Control Unit and Sensor Unit: Controls the power converter and senses the voltage or current signal as feedback.
Classification of Electric Drives
- DC Drives: Use DC motors and are used in adjustable speed drives and position control.
- AC Drives: Use AC motors and are used in applications such as pumps, machines, etc.
Advantages of Electric Drives
- Flexible motion control
- Easy starting and loading
- High efficiency with low losses and overload capability
- Easy to achieve dynamic load characteristics
- Can perform four-quadrant operation in the Torque/Speed plane
Disadvantages of Electric Drives
- Requires a power supply
- Output power is limited
- Poor dynamic response
- System operation fails in case of power breakouts
- Expensive
Applications of Electric Drives
- Industrial applications: pumps, fans, motors, transportation systems, etc.
- Domestic applications: refrigeration, air conditioning, belt conveyors, etc.
Mechatronics
- Definition: The synergistic combination of mechanical engineering, electronic engineering, control engineering, and systems thinking in the design of products and manufacturing processes.
- Multi-disciplinary approach: combines mechanical, electrical, and software engineering to design and manufacture products.
Evolution of Mechatronics
- Primary Level Mechatronics: Basic control systems with sensors and actuators.
- Secondary Level Mechatronics: Integrates microelectronics into electrically controlled devices.
- Tertiary Level Mechatronics: Incorporates advanced feedback functions and microprocessors.
- Quaternary Level Mechatronics: Includes intelligent control and fault detection capabilities.
Power Transistors
- Definition: Three-terminal devices composed of semiconductor materials, used to control high current-voltage rating.
- Types: Bipolar Junction Transistors (BJTs), Metal Oxide Semiconductor Field-Effect Transistors (MOSFETs), Static Induction Transistors (SITs), and Insulated Gate Bipolar Transistors (IGBTs).
Applications of Power Transistors
- Switch-mode power supplies (SMPS)
- Relays
- Converters
- Power amplifiers
- DC to AC converters
- Power supply
- Power control circuits
- Inverters### Power Transistor Structure
- A bipolar junction transistor (BJT) is a vertically oriented device with a large cross-section area that accommodates alternate P and N-type layers connected together.
- A BJT is composed of PNP or NPN transistors and features three terminals: emitter, base, and collector.
Power Transistor Operation
- Based on forward and reverse bias conditions, a power transistor operates in four regions:
- Cut-off region
- Active region
- Quasi-saturation region
- Hard saturation region
V-I Output Characteristics of a Power Transistor
- The output characteristics show the relationship between VCE and IC.
Advantages and Disadvantages of Power Transistors
- Advantages:
- High voltage gain
- High current density
- Low forward voltage
- Large gain-bandwidth product
- Disadvantages:
- Low thermal stability
- Complex control
- High noise
Applications of Power Transistors
- Power transistors are used in:
- Switch-mode power supplies (SMPS)
- Relays
- Converters
- Power amplifiers
- DC to AC converters
- Power supply
- Power control circuits
- Inverters
SCR (Silicon Controlled Rectifier)
- An SCR is a unidirectional device that allows current to flow in one direction and opposes it in another direction.
- It has three terminals: Anode (A), Cathode (K), and Gate (G).
- SCR Symbol: similar to a diode symbol with an additional gate terminal.
Construction of SCR
- SCR is a four-layered semiconductor device with NPNP or PNPN structure, forming three junctions (J1, J2, and J3).
- The Anode is a P-layer, and the Cathode is an N-layer.
- The Gate acts as a control terminal.
- SCRs are constructed in three types: planar, Mesa, and Press pack.
Working Principle of SCR
- SCR operates in three modes:
- Forward Blocking mode: No current flows due to reverse-biased J2.
- Forward Conduction mode: SCR conducts when voltage exceeds breakdown voltage or a positive voltage is applied to the gate.
- Reverse Blocking mode: No current flows due to reverse-biased J1 and J3.
VI Characteristics of SCR
- Obtained by operating the SCR in three regions: forward blocking, forward conduction, and reverse blocking.
- The graph shows the relationship between voltage and current, including leakage currents and breakdown voltage.
SCR Applications
- SCRs are used in various applications, including:
- Converter circuits
- Control circuits
- Speed control of motors
- Thyristor applications
Learn about electric drives, which are electro-mechanical systems that control the motion of electrical machines, used in various industrial processes and equipment.
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