Workhorses of our day-to-day life are the electric motors. We always go for a “Give and Take” policy. The input given to the motor is expected to turn into the output, but normally some power is lost and the full input can’t turn into output. Therefore, the term “efficiency” comes. Motors are continuously transforming electrical energy into mechanical motion in everything from fans, elevators, and home appliances to industrial pumps and compressors. More than merely an engineering statistic, motor efficiency is a critical component that influences equipment performance, environmental effect, and operating costs. Significant yearly energy savings can result from even a modest increase in efficiency, particularly in sectors with sizable motor fleets.
What is Motor Efficiency?
An electric motor is a kind of machine that uses the interplay of a magnetic field and current in its winding to create force in order to transform electrical energy into mechanical energy. Generators are responsible for converting mechanical energy into electrical energy if this process is truly reversed. The primary phenomenon that motors use is electromagnetism. The ratio between motor Output and Input is called efficiency which is indicated by the symbol of “η” and represented in the “%”. This is the factor which tells about performance of the motor. It is the ratio between output and input power at shaft it can be written as efficiency (e) = output power / input power i.e.
Motor Efficiency = Motor Output Power / Motor
Input Power
Motor efficiency is denoted by the symbol η.
Efficiency = η = (Output / Input) x 100
It is represented d as a percentage:
Efficiency (%)=Mechanical Output Power (Watts)Electrical Input Power (Watts)×100
For example, if a motor consumes 1000 watts of
electrical power and delivers 700 watts as mechanical output, it has an
efficiency of:
700/1000×100=70%
That means 30% of the power is lost. It can be mainly due to
heat, magnetic losses, or friction.
In fact, Efficiency = η = Input – Losses / Input
So, Efficiency = η = Output / Output + Losses.
No machine remains without losses. The output is always less
than the input, and therefore, the general equation is:
Output = Input – Losses
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| Power Flow Diagram Source:electricalampere.com |
Which Motor Has the Highest Efficiency?
What is the maximum efficiency of an electric motor?
96–98% efficiency can be achieved by the advanced motors. Only
when the motor runs under optimal conditions and at full load can maximum
efficiency be achieved. When Cu losses are equal to the constant
losses of the motor, maximum efficiency will be maximum. Differentiating
with respect to the input current, when copper loss is equal to core loss, the
efficiency is maximum.
What is the average efficiency of an electric motor?
Losses That Reduce Motor Efficiency
Losses That Reduce Motor Efficiency
Losses are responsible for reducing the efficiency. Let’s learn about them. The common losses are depicted below:
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| Losses in electric motor Source:oswos.com |
Copper Loss: Due to resistance heating in stator or rotor windings. There are two: Stator Copper Loss and Rotor Copper Loss. These are dependent on the resistance and the current. This loss is also called ohmic loss and expressed by:
Copper Loss = I2R
Core Loss or Iron Loss: Hysteresis losses, eddy current losses, and extra losses are the
three categories of iron losses. The frequency and maximum flux density
determine the iron losses, which are expressed per unit weight. This implies
that iron losses increase with motor rotation speed.
Hysteresis Loss: Each of the numerous tiny domains
that make up magnetic materials has a unique magnetic orientation. Losses
happen when the domains' magnetic orientation shifts. Because the material
undergoes hysteresis during magnetization, these demagnetization losses are
known as hysteresis losses. The area of hysteresis the material travels through
during demagnetization determines the losses.
Eddy Current Loss: When the stator's magnetic flux varies, eddy currents happen. The
stator is heated and experiences losses as a result of the eddy currents.
Mechanical Loss: Friction losses and ventilation losses are two categories of
mechanical losses. Frictional losses, which happen in the bearings, for
instance, are influenced by speed.
How to improve the Motor Efficiency?
Hysteresis is the source of core magnetic losses, whereas
eddy currents and magnetic core saturation account for 20% of overall losses.
Utilizing high-quality materials and quality control can reduce losses and
increase productivity. Steels with a tiny proportion of silicon are used in
laminations in place of less expensive carbon steels in order to lessen the
effects of hysteresis and saturation. Core losses can be eliminated in this
fashion. It is possible to minimize core losses and flux density by lengthening
the lamination and decreasing its thickness. Making sure there is adequate
insulation between the sheets or laminations utilized can significantly reduce
eddy current losses.
The motor mounting rated speed, bearing size, grease type,
and temperature rise all affect how often a lubrication is necessary.
Therefore, use caution whenever you apply lubricants. Even if two varieties of
grease use the same ingredients, don't mix them.
Conclusion
Motor efficiency is the key to reduce expenses and improving performance. An efficient motor wastes far less heat and transforms more energy into labor. From tiny workshops to enormous factories, every efficiency percentage counts. Longer service life and fewer malfunctions are the results of high-efficiency motors. Greater savings and a reduced carbon impact result from more intelligent energy use. Invest in efficiency now and get the benefits for years to come.
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