Electric Drives

MEU 07677
 Electric Drives

Electric drives are systems that convert electrical energy into

mechanical energy to control the motion or operation of various types
of machinery or equipment. They play a crucial role in a wide range
of applications, including industrial machinery, transportation
systems, robotics, renewable energy systems, and more. Electric
drives provide efficient, controllable, and flexible means of powering
and controlling mechanical systems
Basic components of an electric drive system typically
include
➢Power Supply: The power supply provides the electrical energy required for the drive system. It may
be connected to an electrical grid, a battery system, or a renewable energy source such as solar panels
or wind turbines.

➢Electric Motor: The electric motor is the primary actuator in the drive system that converts electrical
energy into mechanical energy. Various types of electric motors are used in different applications,
including induction motors, synchronous motors, permanent magnet motors, and DC motors. The
motor selection depends on factors such as power requirements, speed control, efficiency, and torque
characteristics.

➢Motor Controller: The motor controller is responsible for controlling the operation of the electric
motor. It regulates variables such as motor speed, torque, and direction of rotation. The controller may
include power electronics components such as inverters, converters, and amplifiers to modulate the
electrical signals supplied to the motor.
 Basic components of an electric drive system typically
include
➢Sensors: Sensors are used to measure and provide feedback on various
parameters related to the drive system, such as motor speed, position,
temperature, and current. This feedback information is used by the motor
controller to adjust and optimize the motor operation.
➢Control System: The control system comprises algorithms and software that
govern the operation of the motor controller. It receives input signals from the
sensors and generates appropriate control signals to maintain desired motor
performance and respond to external commands or system requirements.
 Applications of Electric drives
➢Industrial Machinery: Electric drives are extensively used in industrial machinery such as conveyors, pumps,
compressors, fans, mixers, CNC machines, printing machines, and packaging equipment. They provide precise
control over speed and torque, allowing for efficient and flexible operation of these machines.
➢Electric Vehicles: Electric drives are a fundamental component of electric vehicles (EVs), including electric
cars, buses, and bikes. They power the wheels, providing the necessary torque and controlling the vehicle's speed
and acceleration. Electric drives in EVs contribute to reduced emissions, improved energy efficiency, and quieter
operation compared to internal combustion engine vehicles.
➢Robotics: Electric drives play a crucial role in robotic systems, enabling precise and coordinated movements.
They are used in robotic arms, grippers, linear actuators, and other motion control mechanisms, allowing robots to
perform tasks with accuracy, repeatability, and versatility.
➢HVAC Systems: Heating, ventilation, and air conditioning (HVAC) systems utilize electric drives in fans,
pumps, and compressors for efficient temperature and humidity control in residential, commercial, and industrial
buildings.
 Contents

➢Construction and operation of power electric drives

i. Describe construction of power semiconductor devices (diode,

thyristor or silicon-controlled rectifier (SCR), triac, gate turn-off
thyristor (GTO), bipolar junction transistor (BJT or BPT), power
MOSFET, static induction transistor (SIT), insulated gate bipolar
transistor (IGBT), MOS-controlled thyristor (MCT), integrated
gate-commutated thyristor (IGCT).
ii. Operating principle of power semiconductor devices.
 Contents

iii. Applications of power semiconductor devices.

iv. Drivers for semiconductor power devices (switches).
 Diode

A diode is the simplest power semiconductor device, consisting

of a P-N junction. It is typically formed by doping one region
of a semiconductor material (e.g., silicon) with a P-type
impurity and the other region with an N-type impurity. This
construction creates a unidirectional flow of current, allowing
it to conduct in one direction (forward bias) and block in the
opposite direction (reverse bias).
 Thyristor or Silicon-Controlled Rectifier
(SCR)

A thyristor or SCR is a four-layer semiconductor device with three P-N junctions. It

consists of a P-N-P-N structure, where the middle P-layer is the control terminal (gate).
The device can be turned on by applying a positive voltage to the gate terminal, allowing
current to flow through it. Once triggered, it remains conducting until the current drops
below a certain threshold.
➢ Holding current refers to the minimum anode current required to maintain the
thyristor in the conducting state after it has been triggered into conduction.
➢Latching current refers to the minimum current required to keep a thyristor (such as an
SCR or silicon-controlled rectifier) in the ON state after it has been triggered into
conduction.
 Triac

A triac is a bidirectional semiconductor device that can conduct current in both

directions. It consists of two thyristors connected in parallel, but in opposite
directions. This construction allows the triac to control AC power by
conducting in both the positive and negative half-cycles.
 Gate Turn-Off Thyristor (GTO)
A GTO is a high-power thyristor with an additional gate terminal that allows it
to be turned off by applying a negative voltage to the gate. It has a similar
structure to a thyristor but includes an N-type region near the cathode, which
enables the device to be turned off quickly by reversing the anode-cathode
voltage.
 Bipolar Junction Transistor (BJT or BPT)
A BJT is a three-layer semiconductor device with two P-N junctions. It consists
of a thin middle layer (base) sandwiched between two heavily doped layers
(emitter and collector). By applying a small current to the base-emitter junction,
a larger current can flow between the collector and emitter terminals. BJTs are
used for amplification and switching applications.
 Power MOSFET
A power MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a
voltage-controlled device. It consists of a P-N junction with a metal gate
separated from the channel by an insulating layer (usually silicon dioxide). By
applying a voltage to the gate, an electric field is created, controlling the
conductivity of the channel between the drain and source terminals.
 Insulated Gate Bipolar Transistor (IGBT)
The IGBT is a combination of a power MOSFET and a BJT. It has a three-layer
structure (N-P-N or P-N-P), with a MOSFET-like gate controlling the
conductivity of the BJT-like channel. IGBTs combine the advantages of low on-
resistance and high voltage capability, making them suitable for high-power
applications.
 Applications of power semiconductor devices

Power semiconductor devices find applications across various industries and electronic systems
due to their ability to efficiently control and manipulate electrical power. Some common
applications include:
Power Supplies: Power semiconductor devices such as diodes, thyristors, and MOSFETs are
used in power supplies for rectification, voltage regulation, and power conversion. They play a
crucial role in converting AC (alternating current) to DC (direct current) for powering electronic
devices.
Motor Control: In industrial and automotive applications, power semiconductor devices like
MOSFETs and IGBTs are used for motor control. They regulate the speed and direction of
electric motors in machines, vehicles, and appliances.
 Applications of power semiconductor devices

Uninterruptible Power Supplies (UPS): UPS systems utilize power semiconductor devices for
battery charging, voltage regulation, and inverter operation. These devices ensure a continuous
and stable power supply to critical loads during mains power failures.
Renewable Energy Systems: Power semiconductor devices are essential components in
renewable energy systems such as solar inverters and wind turbine converters. They convert the
DC power generated by solar panels or wind turbines into usable AC power for grid integration
or local consumption.
Electric Vehicles (EVs): EV propulsion systems rely on power semiconductor devices for motor
control and battery management. These devices enable efficient power conversion and control to
drive electric motors and manage battery charging and discharging.
 Applications of power semiconductor devices

Induction Heating: Power semiconductor devices are used in induction heating systems for
applications such as metal melting, welding, and heat treatment. Thyristors and IGBTs control
the power delivered to induction coils, generating intense heat in conductive materials.
HVAC Systems: Heating, ventilation, and air conditioning (HVAC) systems utilize power
semiconductor devices for motor control, compressor control, and power factor correction.
These devices help optimize energy efficiency and maintain precise temperature and humidity
control.
High-Voltage Transmission: Thyristors and other power semiconductor devices are
employed in high-voltage direct current (HVDC) transmission systems for efficient long-
distance power transmission. They facilitate the conversion and control of high-voltage
electrical energy between AC and DC forms.
 Applications of power semiconductor devices

Railway Traction Systems: Power semiconductor devices are used in traction inverters for
electric trains and trams. They control the power delivered to traction motors, enabling efficient
acceleration, deceleration, and regenerative braking.
Switched-Mode Power Supplies (SMPS): SMPSs utilize power semiconductor devices for
high-frequency switching and voltage regulation. These devices enable compact and
lightweight power supplies used in electronic devices, computers, and telecommunications
equipment.
Drivers for semiconductor power devices (switches)

Drivers for semiconductor power devices, also known as switch drivers, are essential
components used to control the switching operation of power semiconductor devices such as
MOSFETs, IGBTs, and thyristors. These drivers ensure reliable and efficient operation of the
switches by providing the necessary gate or base drive signals. Here are some key drivers for
semiconductor power devices:
Gate Drivers: Gate drivers are specifically designed to control the gate of MOSFETs and
IGBTs. They provide the gate voltage necessary to turn the device on and off quickly and
efficiently. Gate drivers typically have features such as high output current capability, fast
switching speeds, and protection mechanisms to prevent shoot-through currents and
overvoltage spikes.
Drivers for semiconductor power devices (switches)

Base Drivers: Base drivers are used to control the base current of bipolar junction transistors
(BJTs), including power bipolar transistors and thyristors (such as SCRs and triacs). Base
drivers ensure precise turn-on and turn-off of these devices, enabling accurate switching and
current regulation. They also provide isolation between the control circuitry and the high-power
semiconductor devices.
Optocoupler Drivers: Optocoupler drivers, also known as optoisolators, use an optical
coupling mechanism to transmit signals between the input and output sides. They provide
electrical isolation between the control circuitry and the power semiconductor devices,
enhancing safety and reliability in high-voltage applications. Optocoupler drivers are commonly
used in conjunction with gate and base drivers to provide isolation in power electronics systems.
Drivers for semiconductor power devices (switches)

Integrated Gate Driver ICs: Integrated gate driver ICs combine gate driver circuitry with
additional features such as protection, isolation, and temperature monitoring into a single package.
These ICs simplify the design of power electronics systems and improve overall system
performance and reliability. Integrated gate driver ICs are available in various configurations and
voltage ratings to meet the requirements of different applications.
Transformer-Coupled Gate Drivers: Transformer-coupled gate drivers utilize transformers to
provide isolation between the control and power sides of the circuit. They offer high-speed
switching and robust isolation, making them suitable for applications where electrical noise and
high voltage differentials are a concern.
Gate Driver Boards: Gate driver boards are circuit boards that incorporate gate driver
components and interface with control circuitry and power semiconductor devices. These boards
may include features such as overcurrent protection, temperature monitoring, and fault detection
to ensure safe and reliable operation of the power electronics system.