What is an Electric Drive? Structure, Applications

An Electric drive is a electromechanical system (mechatronic system) intended to set into motion technological equipment. It consists of an electric motor (motors), a transfer mechanism, an electrical energy converter, and a control system. The control system consists of a microcontroller with data connection interfaces, data channels (data network), sensors and actuators.

 History

The first electric drive was invented in 1838 by B.S.Iakobi in Russia. He tested a DC motor which is supplied from a battery to push a boat. Although, the application of electric drive in industrial can happen after so many years like in 1870. At present, this can be observed almost everywhere. We know that the speed of an electrical machine(motor or generator) can be controlled by the source current’s frequency as well as the applied voltage. Although, the revolution speed of a machine can also be controlled accurately by applying the electric drive concept. The main benefit of this concept is too controlling the motion can be optimized simply using the drive.

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Structure of Electric Drive

A generalized structure of the electric drive In general, the main task of the electric drive is the motion control of mechanisms. An electric drive is an automatic control system with a number of feedbacks where different automatic control principles, such as error driven feedback control, model based control, logical binary control, or fuzzy logic control methods, are used.

Microprocessor technique

enables us to apply different control methods in today’s control systems, including control of electric drives. In the drive controller, the signal processors with inbuilt analogue-digital converters, timers, pulse-width modulators and other devices, which simplify drive control, are commonly used.

Integration of devices and functions

Microprocessor techniques make it possible to solve all control tasks, like energy conversion between the drive and the converter, protection and tasks connected with the sequence logic of a technological process. Because of this, a microcontroller is a complex control device, which is realized by the computer control, programmable controller functions and supervision of the process. A drive controller is programmed and controlled by help of commands and subprograms of special functions. Software of a drive is complemented with supplement functions. Since modern industrial systems are based on data communication networks, recent controllers are intended for action with field buses. A controller guarantees a flexible speed regulation and motor protection.

Software solutions

Today’ s theories published will be realized as software of devices. You can tell already today that drive controllers are able to solve all problems and tasks described in course-books of electric drives. Controller software includes a number of contemporary control methods, like adaptive control, model based control etc. Vector control of AC-drives was a technical novelty ten years ago, but today this method is largely used in frequency converters.

Economic considerations

A situation may arise when functional qualities of a drive controller and completeness of the interface are not harmonized. To reduce the price market, compelled producers often simplify the interface of converters. Therefore the number of control buttons and decimal places of sign-number display must be reduced to 3. To display the large variety of drive controller states (different faults, signals etc.), every segment of the 7-segment digit indicator could be used to display coded information. It will be very inconvenient for the operator of the drive equipment to acquire this very special coding. Naturally it is a different question if the user needs programming or reprogramming the converter or not or if the programming and service must be done by specialized firms. Power converters with the most intelligent user interface can communicate in common national languages understandable for everyone. Maximum convenience will be achieved by special human-machine interface (HMI) PC software. In this case, all the useful information about the drive and technological machines can be displayed on the PC screen. Different functional diagrams about energy consumption, technological cycles, amount of production etc. can be used. But, unfortunately this software may be more expensive than the converter hardware.

New sensors and optical data connection

Today the numeric control of electric drives is widely used and the traditional analogue sensors will be replaced with the new digital sensors for measuring of speed and position. To measure the position, the sensors may be the pulse sensors as well as the code sensors. Another problem is measuring of voltages and currents with high harmonic components particularly when the control information is required very quickly, but the filtration of the signals is very complicated and slow. Current transformers deface the signals and they are not acting so fast. Bypasses in the current circuits give the accurate current signal but galvanic connected sensor signals with power circuit are not usable in microcontrollers. For this reason, Hall sensors are used. Hall sensors with magnetelectric current converters guarantee galvanic separation between control and power circuits of electric drives. To forward the output signals of the controller to the converter fibre-optic data channels are used

Block Diagram of Electric Drive

The block diagram of an electric drive is shown below, and the load in the diagram signifies different kinds of equipment which can be built with an electric motor such as washing machine, pumps, fans, etc. The electric drive can be built with source, power modulator, motor, load, sensing unit, control unit, an input command.

Power Source

The power source in the above block diagram offers the necessary energy for the system. And both the converter and the motor interfaces by the power source to provide changeable voltage, frequency and current to the motor.

Power Modulator

This modulator can be used to control the o/p power of the supply. The power controlling of the motor can be done in such a way that the electrical motor sends out the speed-torque feature which is necessary with the load. During the temporary operations, the extreme current will be drawn from the power source.

The drawn current from the power source may excess it otherwise can cause a voltage drop. Therefore the power modulator limits the motor current as well as the source.

The power modulator can change the energy based on the motor requirement. For instance, if the basis is direct current & an induction motor can be used after that power modulator changes the direct current into alternating current. And it also chooses the motor’s mode of operation like braking otherwise motoring.

Motor

The electric motor intended for the specific application can be chosen by believing various features such as price, reaching the level of power & performance necessary by the load throughout the stable state as well as active operations.

Load

The mechanical load can be decided by the environment of the industrial process & the power source can be decided by an available source at the place. However, we can choose the other electric components namely electric motor, controller, & converter.

Control Unit

The control unit is mainly used to control the power modulator, and this modulator can operate at power levels as well as small voltage. And it also works the power modulator as preferred. This unit produces the rules for the safety of the motor as well as power modulator. The i/p control signal regulates the drive’s working point from i/p toward the control unit.

Sensing Unit

The sensing unit in the block diagram is used to sense the particular drive factor such as speed, motor current. This unit is mainly used for the operation of closed loop otherwise protection.

Classification

Usually, these are classified into three types such as group drive, individual drive, and multi-motor drive. Additionally, these drives are further categorized based on the different parameters which are discussed below.

• Electrical Drives are classified into two types based on supply namely AC drives & DC drives.
• Electrical Drives are classified into two types based on running speed namely Constant speed drives & changeable speed drives.
• Electrical Drives are classified into two types based on a number of motors namely Single motor drives & multi-motor drives.
• Electrical Drives are classified into two types based on control parameter namely stable torque drives & stable power drives.

Advantages

The advantages of electrical drives include the following.

• These dries are obtainable with an extensive range of speed, power & torque.
• Not like other main movers, the requirement of refuel otherwise heat up the motor is not necessary.
• They do not contaminate the atmosphere.
• Previously, the motors like synchronous as well as induction were used within stable speed drives. Changeable speed drives utilize a dc motor.
• They have flexible manage characteristics due to the utilization of electric braking.
• At present, the AC motor is used within variable speed drives because of semiconductor converters development.

Disadvantages

The disadvantages of electrical drives include the following.

• This drive cannot be used where the power supply is not accessible.
• The power breakdown totally stops the entire system.
• The primary price of the system is expensive.
• The dynamic response of this drive is poor.
• The drive output power which is obtained is low.
• By using this drive noise pollution can occur.

Applications

The applications of electrical drives include the following.

• The main application of this drive is electric traction which means transportation of materials from one location to another location. The different types of electric tractions mainly include electric trains, buses, trolleys, trams, and solar-powered vehicles inbuilt with battery.
• Electrical drives are extensively used in the huge number of domestic as well as industrial applications which includes motors, transportation systems, factories, textile mills, pumps, fans, robots, etc.
• These are used as main movers for petrol or diesel engines, turbines like gas otherwise steam, motors like hydraulic & electric.

Thus, this is all about the fundamentals of electrical drives. From the above information, finally, we can conclude that a drive is one kind of electrical device used to control the energy which is sent to the electrical motor

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