separation of losses in a 3 phase induction motor

Topics: Electric motor, Test method, Electrical engineering Pages: 21 (2022 words) Published: October 21, 2013
How the efficiency of induction motor is measured?
S. Corino E. Romero L.F. Mantilla
Department of Electrical Engineering and Energy
E.T.S.I.I. y T. Universidad de Cantabria
Avda de Los Castros, 39005 Santander (Spain)
phone:+34 942 201381, fax:+34 942 201381, e-mail: mantillf@unican.es

Abstract
The efficiency is of paramount importance nowadays due
to increasing electrical energy demand, increasing awareness of environmental problems as greenhouse effects and increasing
fossil fuel prices.
This paper tries to show the different results between the
standards for efficiency evaluation and the necessity of
harmonization worldwide. Then, it is going to be explained the different standards for measurement of efficiency, and the main differences between the standards (IEEE 112, IEC 60034-2 and JEC-37).

To complete this study, it is going to be described the steps in order to estimate efficiency on the jobsite and expressed the different efficiency labels motors.

Keywords: energy efficiency, induction motor, standard.
Code: 352-mantilla

There are different efficiency definitions that
describe the relationship between a motor’s rating and
efficiency test results:
Tested. This refers to the efficiency measured
by testing that specific motor.
Nominal or Average Expected.
Nominal
values are the average values obtained after
testing a sample population of the motor
model.
Nameplate. This refers to the efficiency
measured by a specific standard.
Minimum. These values are intended to
represent the lowest point in the bell curve of
motor efficiency distribution.
Apparent Efficiency. This is the product of a
motor’s efficiency and power factor.

1. Introduction
The efficiency is of paramount importance nowadays
because electrical motors are major consumers of
electricity in the modern industrial society; they consume
approximately 69% of electricity in the industrial and
approximately 36% in the tertiary sectors of the European
Union [1]. Three-phase, low voltage squirrel cage
induction motors are the most commonly used electric
motors in industry.
Efficiency data by manufacturers are measured or
calculated according to certain standards. The main
differences between these standards are discussed in this
paper.
There are a lot of examples of agreements, incentives
and initiatives worldwide in order to promote increasing
the efficiency. In Europe, there is an initiative called
SEEEM (Standards for Energy Efficiency of Electric
Motors Systems). SEEEM aims to stimulate and
accelerate the process of harmonization in order to save
energy and reduce greenhouse gas emissions.

2. Losses and Efficiency
A. Definition of energy efficiency
Efficiency is the ratio of mechanical energy output
divided by the electrical energy input.

Pout

Pin

40%

Pstator

25%

Protor

20%

PFe

5%

Pfr,w

10%

Paddit

Figure 2.1 – Typical energy flow of standard motors [2].

B. Motor Losses
Energy losses are the determining factor in motor
efficiency. These losses can be divided in five classes:

Name

Core
Losses

Windage

Percent
of
Total
Losses

Description

Fixed or
Variable

15-15%

Energy
required to
magnetize
core.

Fixed

5-15%

Losses due

Fixed

How to
reduce
Improved
permeability
steel,
lengthening
core, using
thinner
laminations in
the core.
Lower friction

and
Friction

Stator
Losses

Rotor
Losses

to bearing
friction and
air
resistance,
which is
primarily
caused by
the cooling
fan.

25-40%

Heating due
to current
flow
through the
resistance
of the stator
winding.

15-25%

Heating due
to I2R
losses in the
rotor
conductive
bars.

bearings,
improve fan
design and air
flow.

Variable

Variable

Leakage
fluxes
induced by
Additional
load
Load
10-20%
Variable
currents and
Losses
various
other minor
losses.
Table 2.1 – Classes of Motor Energy Losses [2]....
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