Utilization of Electrical Energy : Electric Traction

By Vishal Singh|Updated : January 4th, 2022

Complete coverage of syllabus is a very important aspect for any competitive examination but before that important subject and their concept must be covered thoroughly. In this article, we are going to discuss Utilization of Electrical Energy : Electric Traction which is very useful for SSC JE Exams

INDUSTRIAL DRIVES

Every machine consists of Engine or motor (called the prime mover)Transmission system, and Working machine. The prime mover with its control system and the transmission system impart motion and operate the machine. The drive may be simply a hand-powered or animal powered, mechanical or electrical.

An electric drive is defined as a form of machine equipment designed to convert electrical energy into mechanical energy and provide electrical control of this process.

TYPES OF ELECTRIC DRIVES

Group drive:

This is drive, also called the shaft drive, in which a single motor drives a number of machines through belts from a common shaft. The group drive is economical in consideration of the initial cost of the motors and control gear.

Disadvantages:

  • Cumbersome speed control of individual machines
  • High noise level
  • Untidy look
  • Less safe operation
  • Loss of flexibility of layout
  • Stoppage of all operations on breakdown of large single motor
  • Low operation efficiency etc.

Group drive   used, with advantage in those industrial processes, where there is a sequence of Continuity in the operation and where it is desirable to stop these processes simultaneously as in flour mills.

Individual drive:

In these each machine driven by its own separate motor with the help of gears. pulleys etc. Though it costs more than group drive, but each operator has complete control of his machine, which enables him to vary its speed when needed and stop while not in use, thus 0ljminatlng no-load losses. The motor and control unit can be hilt   integral part of the machine which results in a good appearance, cleanliness and safety. For driving heavy machines such as for lifts, cranes, shapers. lathes etc. and for the purposes where constancy of speed and flexibility of control is required. individual drive is essential.

Multi-motor drive:

In these separate motors are provided for actuating different parts of the driven mechanism. Such a drive is essential in complicated metal cutting machine tools, paper making machines, rolling mills, and similar types of machinery. The use of individual and multi-motor drives has enabled introduction of automation in production processes which apart from increasing the productivity of various organizations, has increased the reliability and safety of operation

SELECTION OF ELECTRIC MOTOR

Selection of motor depends on Conditions under which an electric motor must operate

Type of load it must handle

Nature of electric supply, type of drive

Type of drive

(a)    3-phaseac

(b)   single phase ac

(c)    single phase dc

Characteristics

(a)    operating or running characteristics

(b)   starting, character

(c)    speed control

(d)   braking characteristics

Mechanical considerations:

(a)    Type of enclosure

(b)   Type of hearing

(c)    Type of power transmission for drive

(d)   Type of cooling, noise level

Service capacity and rating pall-out torque and over load capacity, requirement for continuous, intermittent or variable load cycle

  1. Appearance
  2. Cost (initial or capital cost and operating cost-pf, losses, maintenance and depreciation).

Nature of Load:

The load may be a

  • constant torque load
  • load requiring torque which may increase in direct proportion to the speed
  • load requiring torque which may increase with the square or cube of the speed, or
  • load requiring torque which may decrease with the increase in speed.

There are various methods of transmitting mechanical power developed by a motor to the machines.

Types of drives

Direct drive: It is nearly 100% efficient and needs minimum space but is used where there in a possibility of arranging the driving member in line with the driven member and where the speed of the driven member is the Same as that of the driving member.

Belt drives: These are least expensive drives and are used where a speed change is desired is the transmission of power and where it is not essential to maintain a fixed rest is between the driving and driven shaft.

Flat belts: These are extensively used for line-shaft drives and can transmit a maximum power of about 250kW. The power transmitted by a flat belt increases in proportion to its width and varies largely with its quality and thickness. There is a slip of 3 – 4% in the belt drive. V—belt drive is essentially a short centre and silent drive with a negligible slip (say about 1%) and is suitable for motors of ratings up to 450 kW.

Rope drive: These drive by means of means of ropes running over pulleys having a number of V-grooves. This is a long centre drive and is used for power ranges beyond the limit of V-belt drive. Rope drive gives negligible slip and can take sudden loads. This drive is indispensable for very high-speed ratio.

Chain drive: These are more expensive, more efficient and can transmit larger amount of power. It is noiseless, slip less and smooth in operation.

gear drive: This is a short centre positive drive and is uses when a high-speed motor is to do drive a low-speed machine.

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