Energy Efficiency Made Simple Vol IV 2015

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great a sacrifice of efficiency via core loss, and too great a burden of copper loss through impaired permeability. The possibility of obtaining grain texture and orientation should not be ruled out, bringing additional benefits.

Electro technology – at well over 100 years old – is due for a radical breakthrough. The sky’s no longer the limit!

This excess consumption is not only an unnecessary burden on the energy bill, but it damages the equipment and motor as the excess energy released is through the winding and core of the motor in the form of heat, vibration and noise. Power electronics in induction electric motor efficient operation There are VFD systems that not only vary the frequency, and therefore the speed, but have facilities to monitor the load and adjust the voltage to optimise the power usage. VFD operation of induction motors gives a number of benefits in power saving as they are able to optimise and control the speed of the driven equipment. There are other benefits that can be obtained by controlling the input voltage to the motor because of this unique characteristic of ac induction motors. • Reducing speed eliminates the necessity of throttling and wasting power • Reducing voltage moves the PF curve to the left resulting in reduced current, reduced current due to the improved power factor and reduced voltage reduced I 2 R losses (copper losses) • Reducing voltage reduces flux density in the iron (laminations) reducing iron loss • VFD systems reduce the stresses on the motor as they are effective soft start devices. The low frequency start controls the current and torque produced by the motor which results in low current and not the six to 10 times starting current found in DOL motor starting systems • Mechanically this is beneficial as there is no shock load applied to the mechanical system such as coupling, shafts and load Transmission lines and the distribution system In the early days of commercial electric power, transmission of electric power at the same voltage as used by lighting and mechanical loads restricted the distance between generating plant and consumers. In 1882, generation was dc, which could not easily be increased in voltage for long-distance transmission. Different classes of load (for example, lighting, fixed motors, and traction and railway systems) re- quired different voltages, and so used different generators and circuits. When the ac systemwas introduced, transformers developed that enabled voltages to be increased and decreased as required assisting in facilitating transmission over long distances. Losses in transmission line are related to I 2 R so reducing the current reduces the losses proportionally to the square of the current whereas the power is proportional to the product of voltage and current.

Becker

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ENERGY EFFICIENCY MADE SIMPLE 2015