Book at a Glance

PART I - Electric Motors, Drives and Energy Saving

Chapter 1. Theory, Performance and Constructional features of Induction Motors and Energy Saving


Brief theory of operation of a polyphase motor
Motor output and torque
Motor ratings and frame sizes
Preferred ratings at different voltages
Influence of service conditions on motor performance
No-load performance Effect loading on motorperformance
Effect of steel laminations on core losses
Circle diagram
Types of induction motors
Mounting of motors
Weatherproof (WP) motors
Degree of protection
Cooling systems in large motors
Single phase motors
Theory of operation
Energy conservation , energy auditing and energy efficient motors (EEM)

Energy conservation
The fast changing global ecology, green house effect, global warming, melting of polar ice and glaciers and rising levels of seas are all frightening phenomena and a matter of grave concern for those who care. Human endeavour around the world in the changed scenario is to minimize these effects as far as possible by observing certain niceties and disciplines in our daily lives, for instance by minimizing effluent discharges and toxic gases at the first instance and then treating them at source before discharging them into drains or releasing them into the atmosphere (see Appendix Chapter 13 for effluent treatment). Restrictions on the use of certain hazardous substances (RoHS) in the manufacture of electrical and electronic equipment (EEE) and their waste management (WEEE) is yet another effort to minimizing the hazardous wastes (see Section 14.1.1)
–  Using only energy efficient (EE) motors at all new installations.
–  Retrofitting old installations with EE motors.
–  Replacing failed motors with EE motors rather than getting them rewound.
–  Using only the right size of motor: the normal trend in industries, agriculture and domestic applications has been to choose a higher size motor as a safety measure. But at most times these motors operate at much below their capacities. It is possible that the load itself was much less than was contemplated by adding a number of margins and safety factors rendering the motor unduly oversized, and operating at much below its capacity. Consequently at poor p.f. and efficiency and this is not desirable.
–  Improvising electrical and mechanical designs of machines and reducing their electrical and mechanical losses.
–  Improvising process lines by employing better bearings, hydraulic couplings and energy efficient belt drives etc.
–  Employing static drives for cyclic and varying speed duties and discarding conventional throttle (valve) or vane controls to make flow of liquid, gas or heating more efficient.
–  Employing low loss (higher size) cables (Section A16.9)
–  Using low loss (higher bus-section) bus systems (Section 28.8.5)

Management approach
For the energy conservation programme to be successful, management awareness to energy efficient systems is first and foremost for others in the system to follow energy disciplines. It is similar to adapting to quality systems by one and all in an organization to implement ISO requirements and sustain the same in the long term (Section 11.1).

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