What is an Electric drive and how to select an electric drive

Major topics

What is an electric drive

An electric motor along with its controller is called as electric drive, an electric drive can be defined as a form of machine equipment which is designed to convert the electrical energy to mechanical energy and it will also provide electrical control of this process

What are the advantages of electrical drives

  • Flexible control characteristics
  • It has low noise and high efficiency and no-load losses
  • It has a cleaner operation and low maintenance required
  • Electric energy can be transported easily
  • It is adaptable to most operating conditions
  • It is provided with automatic fault detection systems
  • It could be started instantly and it can be fully loaded immediately
  • Control gear requirements for speed control starting and braking is usually simple and it can be operated easily

Electric drives have flexible control characteristics, load requirements can be satisfied by shaping the steady-state and dynamic characteristics of electric drives. It is available in a wide range of speed, torque, and power. Another advantage of an electric drive is that it can be used in almost all operating conditions such as explosive and radioactive environments. They are provided with the automatic fault detection system, PLC’s and computers can be used to control it automatically in the desired sequence. Electric braking will give smooth deceleration and it will increase the life of the equipment while compared to other breaking methods.

Disadvantages of Electric drive

  • The electric drive system is only tied up to the electrified area
  • Conditions which will arise due to the short circuit such as leakage from conductors and breakdown of over-head conductors could lead to fatal accidents
  • Failure in supply for a few minutes could paralyze the whole system

Electric drive system

How to select electric drives

  • Steady-state operation requirements

Speed range, speed regulation, efficiency, quadrants of operation and converter ratings

  • Transient operation requirements

Acceleration and deceleration values, starting, braking, and reversing performance

  • Power source requirements

Capacity, voltage magnitude, voltage fluctuations, power factor, harmonics and its effect on loads, ability to accept regenerated power

  • Environment and location
  • Space and weight restriction
  • Efficiency and reliability

Components of Electric drives

  • Power source
  • Motor
  • Power processing unit
  • Control unit
  • Mechanical load

Power source

It provides energy to electric motors regulated and unregulated energy and the unregulated will be regulated for high efficiency

  • DC sources are batteries, fuel cell, photovoltaic
  • AC source is single/three-phase utility

Motor

It receives power from an electrical source it would convert electrical energy to mechanical energy

DC motors – permanent magnet or wound field

AC motors – induction, synchronous (wound-rotor, IPMSM)

Power processing unit

It provides a regulated power supply to motor it could enable motor operation in reverse, braking, and variable speeds

power electronic converter combinations such as controlled rectifiers, inverters

Highly efficient there won’t be any losses and it is flexible voltage and current can be easily shaped through switching control and several conversions will be possible like AC – DC, DC-DC, DC-AC, DC-DC

Control unit

It supervises all the operation and improves the stability and performance

Analog control – noisy, inflexible, infinite bandwidth

Digital control – configurable, smaller bandwidth

DSP/microprocessor – flexible, lower bandwidth, real-time

Classification of electrical drives

  • Group drive
  • Individual drive
  • Multi-motor drive

Group drive

If several machines are organized on a single shaft and if it is driven by one motor then it is called a group drive

Individual drive

If a single motor is used to drive a single mechanism and it does all the work related to the load then it is called as individual drives examples are lathe machines and single spindle drilling machines

Multi-motor drive

In this type, each operation is done by a separate drive motor and the system contains several individual drives each of it will operate their own mechanism examples are rolling mills and traveling cranes

Applications of electric drives

  • Line shaft drives
  • Single load drives- electric saws, drills, fans
  • Multi-motor drives

Several motors single mechanical load complex drive functions such as assembly lines robotics…It is mostly used for motion control such as transportation, fans, motors, it is easy to control by varying voltage and current, it has a wide range of speed high efficiency, switch-mode converters, and electrical motors are very clean. Easy to store and to transport energy. It provides a regulated power supply to the motor and it can enable the operation of the motor in reverse braking and variable speed. Electrical energy can be generated and transported to the desired point efficiently

News Reporter
post-graduate in Electronics & communication