International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
Evaluation of Influence of Electrical Steel on
Efficiency and EER of Hermetic Motors in
Compressor Application
Ms. Pooja A. Patwardhan
Mrs. Pragati N. Korde.
Dept. Of Electrical Engineering
University of Pune,India
Email Id-poojapatwardhan22@gmail.com
Dept. Of Electrical Engineering
G.H.R.I.E.T,Pune, India
Email Id-pragati.korde@raisoni.net
Abstract— As per the emerging energy efficiency standards in
various parts of the world, it is becoming imperative for all the
manufacturers of HVAC systems to enhance their system
efficiencies. Compressor is a major contributor to system’s
efficiency. Any improvement in compressor efficiency reflects
positively & veritably in the system.
Electrical induction motor being foremost part of compressor
by means of watts consumed & heat produced, strong interest is
shown to reduce the core losses at the design stage. Therefore, a
rigorous analysis of the electromagnetic behavior is needed to
fulfill such purpose. Considering competitive market and price of
electrical steel, analysis has to be done while choosing correct
grade of steel for motor.
The paper discusses the fundamental factors that are involved
in selection of electrical steel, parameters affecting the
performance of induction motors and hermetic compressor. The
objective of this study is to compare the effect of electrical steel
on dynamometer efficiency and EER of hermetic compressor.
For this various grades of electrical steels are tested for their
magnetic properties by Epstein testing. Performance of the same
is checked for motor efficiency and compressor EER. The
comparative analysis is performed and it is intended to show the
importance of data analysis for manufacturers guiding price
negotiations, parameters for future projects and quality control
data of electrical steel.
Keywords—Core loss, Induction motor, Compressor, electrical
steel, magnetic properties
I.
INTRODUCTION
pressure difference in the system to create a flow of refrigerant
from one part of the system to the other.Compressor energy
efficiency ratio is inversely proportional to wattage consumed
by motor, compressor performance has great impact due to
motor performance. The use of steel with high permeability
has increased considerably in the last few years due to its
competitive price and better magnetic properties [2]. With
lower losses and/or higher permeability motor steel allows a
considerable improvement of efficiency. This work presents
the results of tests obtained from single phase induction
motors driving compressors. This paper elaborates the effect
of magnetic properties on EER of a reciprocating compressor.
It essentially analyses properties of various types of steel &
their impacts on physical properties such as core loss,
electrical design aspects such as dynamometer efficiency &
ultimately the compressor efficiency.
In order to improve efficiency of induction motor, it is
necessary to reduce both core losses and copper losses.
However Improvement in iron losses will contribute to so
called energy efficient motors. In the present study effect of
magnetic properties of electrical steel on motor efficiency and
compressor energy efficiency ratio is investigated by
constructing motors with different grades of electrical steel.
As steel is important parameter considering cost and quality,
study of various grades of steel is important for manufacturers
from procurement point of view. Steel material property is a
complex phenomenon and more research has to be done. This
allows us to identify directions for further research.
Refrigeration systems are present in all world. Compressor
is heart of the system. Large numbers of these compressors are
driven by Single phase or three phase induction motor. Among
the electrical machine users and designers, at the design stage
core loss reduction has to be considered. Therefore, a rigorous
analysis of the electromagnetic behavior is needed to fulfill
such a purpose. Demand of high efficiency motors is the great
challenge facing motor manufacturers.
For evaluating the properties of electrical steel and for
choosing correct grade of electrical steel, we conducted a trial
with two grades of steel. These two steel grades were having
watt loss 6.04 W/kg and 4.58 W/kg respectively. According to
theory, steel with low watt loss must show good efficiency and
greater EER.
A compressor is a pumping device used in a mechanical
refrigeration system to receive and compress low pressure
refrigerant vapour into a smaller volume at higher pressure.
Thus a primary function of a compressor is to establish a
Stators from above steel are build and checked for motor
dynamometer efficiency and EER of compressor. Table1
Shows results of 3 compressors, having above stated steel for
stators. These results raise the question of whether it is
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
II.
INCENTIVE
required to use low watt loss steel for small rated motors or
not.
TABLE 1
EER
Steel 1
Steel 2
10.10
10.03
10.23
10.02
10.01
10.12
The objective of further study is1) To evaluate if fully processed steel can improve the
motor efficiency without changing the established stack height
and winding design.
2) To compare the effect electrical steel on dynamometer
efficiency and EER of hermetic compressor.
3) To evaluate which properties of steel affect the
performance.
4) Data collection for company guiding price negotiation
and quality.
The electric current required is supplied by a power amplifier
.The current is measured by means of temperature stable, low
inductivity precision resistor or via field coil.
Determination of polarization is by sampling the induced
voltage, conversion and integration. Standard measurement is
performed under sinusoidal polarization, by using controlled
algorithm the secondary voltage is checked and constantly
regulated by nominal value. Optionally excitation on the
primary side is possible with free curves and PWM signals.
Two steel grades have been tested for their magnetic
properties. Figure 1 shows core loss values for semi processed
(SP) and Fully processed (FP) steel.
III. SEMI AND FULLY PROCESSED STEEL
Annealed semi-processed (SP) steel has been used for a
long time due to its low price when compared to the fully
processed one [2]. Semi processed steels are finished to final
thickness and physical form (sheets or coils) by the producer
but are not fully annealed to develop final magnetic quality.
With these materials, the achievement of magnetic properties
by the annealing treatment becomes the responsibility of the
user. In fully processed electrical steels the magnetic
properties are completely developed by the steel producer. The
name is derived from the fact that the materials are completely
processed, ready for use without any additional processing
required to achieve the desired magnetic quality. Even though
annealed at the mill, fully processed material may require
further stress relief anneal after stamping. The stresses
introduced during punching degrade the material properties
around the edges of the lamination, and must be removed to
obtain maximum performance. This is particularly true for
parts with narrow sections, or where very high flux density is
required [2].
FIGURE 1: Core Loss
B. Motor and compressor PerformanceStator of same specification and rating has been build
using these two steel and tested for efficiency using
dynamometer testing. There is no significant difference in core
loss values of both the steels. Now according to theory, for the
same core loss, fully processed steel should perform better
than semi processed steel stators. However results of
efficiency for both the steels don’t differ much. Figure 2
shows efficiency comparison for 5 stators
IV. PERFORMANCE ANALYSIS
A. Epstein TestingIn order to evaluate the performance of different steels,
various grades of steel has been tested for their magnetic
properties.Choosing the right lamination material for a
particular electromagnetic application is an important motor
design step, since lamination properties have a direct link to
the efficiency of the motor. Currently, important lamination
properties (core loss and permeability) to be used for
assessment are presented at 50/60 Hz, 1.0/1.5 T sinusoidal [1].
In a measuring coil a material sample is exposed to defined
magnetic field and magnetic flux is created in the steel sheet.
FIGURE 2: Efficiency SP v/s FP
Compressor performance is analysed using Energy
efficiency ratio i.e EER. Energy efficiency ratio is defined in
terms of cooling effect in Btu per hour divided by power used
in watts. Test results of 5 compressor build from above stators
are shown in figure 3.
of compressor lifetime. As line voltage drops during motor
starting, motor with high permiability and polarization can
start at lower voltage also.
V. CONCLUSION
The experiment showed that in case of cost issues
with fully processed steel, semi process steel can be used. But
we need to focus on correct processing of SP steel. Inter
lamina resistance and incorrect grain growth can affect the
performance of Semi-Processed steel. Analysis of fully
processed steel showed that along with core loss there are
other magnetic properties like permeability and polarization
that affect the overall performance of compressor. Compressor
built with steel having high permeability value and
polarization can start at lower voltage and improves overall
performance.
Acknowledgment
The authors would like to thank Emerson Climate
Technologies (India) Pvt Ltd for their support during
experimental work
FIGURE 3: EER SP v/s FP
References
As Semi processed and fully processed steel showing
nearly same perfoemance, use of Semi processed steel is
adoptable in case of cost issues with the fully processed.
C. Aanalysis for two grades of fully processed steel
Experiment further analysed for two grades of fully
processed steel. Table 2 shows deatiled results of magnetic
properties
Steel
(W/Kg)
2500 A/m
5000 A/m
Tsakani Lotten Mthombeni, Member, IEEE, Pragasen Pillay, Fellow,
Loss Measurements Under High Frequencies and High Flux Densities” IEEE
TRANSACTIONS ON ENERGY CONVERSION, VOL. 22, NO. 3,
SEPTEMBER 2007
[2] C. A. da Silva, G. B. Gibelli, H. D. Queiros, R. Carlson, F. J. G. Landgraf,
“Design of Single-Phase Induction Motors with Fully Processed Steel”, XIX
TABLE 2
Magnetic Polarization
Watt loss
[1]
IEEE, and Reinhold M. W. Strnat “New Epstein Frame for Lamination Core
10000 A/m
Permiability
A
6.3053
1.6
1.7
1.8
1814
B
6.3476
1.3
1.3
1.3
1483
Stator of same specification, stack heigh and winding
design has been build using these two grades of fully
processed steel, results showed that for both the steels, motor
efficiency and compressor performance are almost equal.
Table 3 shows performance details.
Steel
TABLE 3
Efficiency %
EER
A
86.52
11.12
B
86.16
11.13
However for steel A having higher polarization and
permiablity, motor and eventually compressor started at lower
voltage than for steel B. Failure of starting the compressor,
which usually occurs at low line voltage, causes the reduction
International Conference on Electrical Machines - ICEM 2010, Rome.