Iaetsd energy management of induction motor by Iaetsd Iaetsd

ISBN: 378-26-138420-01

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014

Energy Management of Induction Motor Using Time Varying Analysis S.Sankar[1],M.Sakthi[2],J.SuryaKumar[3],A.DineshBabu[4],G.Sudharsan[5]

current spike also has the effect of lengthening the motor life because the current spike alone would cause increased wear and tear on the motor compared to a DC input.

ď&#x20AC; Abstractâ&#x20AC;&#x201D;This paper describes an induction motor drive using a pulse width modulated signal with energy conservation system. The op-amp capabilities of a microcontroller are used to realize a very inexpensive and efficient controller. The design of the entire system is the industrial machineries performance improvement by analyzing and designing the induction motor optimal stator current controller, this will minimize the stator current under different loading conditions. The output load current controlled and the energy of induction motor is operated using the op-amp based closed loop control system.

The controller also uses a quadrature encoder in order to allow the user to input the desired speed of the motor into the system [3]. The microcontroller will be the main circuit component between the user input from the quadrature encoder and the motor, which will read the input from the quadrature encoder and create a comparative signal based upon the desired speed of the motor. The comparative signal will be output through the low pass filter to the motor. The output voltage from the tachometer will be fed back to the PIC and used to adjust the speed of the motor to the desired speed and forming a feedback loop in the system.

Index Terms: Induction motor, Energy conservation, microcontr oller, comparator.

I. INTRODUCTION The induction motor is a simple and robust machine, but its control might be a complex task when managed directly from the line voltage, the motor operates at nearly a constant speed. To obtain speed and torque variations, it is necessary to modify both the voltage and the frequency. Following this was the realization that the ratio of the voltage and frequency should be approximately constant [1].

The realized system is set up to give speed feedback to the user as well as the controller. When the system is operating, the red LED on the control board will be lit when the maximum duty cycle fed into the motor. This indicates that the motor cannot spin any faster than the current speed. This allows the user to know when the maximum speed has been reached for an applied motor load [4].

The induction motor has also disadvantages that it has more losses and less efficiency when it works at variable speeds. The need of efficient drive systems was achieved by special controllers that not only modify the losses and efficiency, but also searching for the optimal values of stator current to reduce the power consumption from the source to be minimum [2]. The trends of designing optimal controllers was developed due to the increasing in power consumption, which represents the most important problem in the world due to the decreasing in power resources in the last few decades. The studies proved that there is a possibility to decrease the power consumption and increase the efficiency in the induction motor.

The motor speed is increased with counterclockwise rotation of the quadrature encoder knob and decreased with clockwise rotation of the knob. When the knob is pushed, the yellow LED on the control board is lit; otherwise the pushbutton is not utilized for this project. The default speed of rotation when the system is reset is 20 rpm. The maximum and minimum speeds are 32 and 10 rpm, respectively.

III.

OPEN LOOP SYSTEM OF INDUCTION MOTOR

The low pass filter to run the motor is needed in order to increase the efficiency of the motor. The increase in efficiency is due to the reduction in the current spike applied to the motor on every rising edge of the control signal [5]. The rounding off of the current spike also has the added benefit of increasing the lifetime of the motor compared to a motor run with a control mode but no low pass filter. In order to determine the values of the components for the low pass filter, the operating frequency had to be determined first. After searching the internet, the following equation was found for calculating the fundamental operating frequency for running the motor [6].

II. SIMULATION MODEL OF ENERGY SAVING OF INDUCTION MOTOR

In order to improve efficiency of the driving signal, the signal is passed through a low pass filter to smooth the signal and round out the current spike that is applied to the motor on every rising edge of the comparator signal. Rounding out the Dr.S.Sankar is a Professor in Dept. of EEE, Panimalar Institute of Technology Chennai*, ssankarphd@yahoo.com

INTERNATIONAL ASSOCIATION OF ENGINEERING & TECHNOLOGY FOR SKILL DEVELOPMENT

www.iaetsd.in

ISBN: 378-26-138420-01

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014 f 

R P    2 L  ln  1   100   D13 D10

MUR130

MUR130 R1 X3

L1 1

2.5

2 2.1m

MCR230M D11

V1 VOFF = 0 VAMPL = 230 FREQ = 50

D12

MUR130

0.012

21.8

1 L2

0.1328

U1 MCT2E

V3 R4 10Vdc

V1 = 0 V2 = 20 TD = 7m TR = 1n TF = 1n PW = 2m PER = 10m

0.012

0.1315

1 L4

0.1328

0 0

Fig.1. Energy saving of induction motor

the 1 kHz frequency. This proved that the frequency and component values provided the desired motor response and a wide operating range.

Where R is the resistance of the motor, L is the inductance of the motor, and v1 is the magnitude of input voltage.

The AC voltage that the motor runs on is 230V. The maximum voltage that the motor will be run with in this project is 30V; this is due to the ease of design and reduces the amount of voltage inputs necessary to the board. The motor has a built in tachometer that ranges from 10V to 230V. The peak output voltage for the 180V input is 230V. The motor draws a maximum current of 5.11A at stall and has an inductance of 73.8mH. The motor also has a 96:1 gear ratio and can produce up to 5.0 oz x in of torque (85.4 mN x m). In order to determine the constant for converting the tachometer value to rpm of the motor, experimental data was gathered. Experiments running the motor also show that the motor stalls at a 98% duty cycle and runs at peak speed between 0% and 15% duty cycle.

For the motor used R1=2.5Ω and L1=2.1mH. This gives a frequency of 50Hz using 50% efficiency. From the controller 50HZ frequency of 1.22 kHz is available [7]. The simulation circuit of open loop controlled system is as shown in the Fig.1.By the variation of firing angle alpha at 40°. The peak output voltage and current is as shown in the Fig.2. The simulation was also run at a comparator frequency of 10 kHz to provide an additional set of test data. The R and L values needed for the desired output were found to be 7.8kΩ and 6mH, respectively. The low pass filter circuit was constructed on a breadboard and tested with the motor to ensure that the motor would run efficiently. The motor was found to run at varying speeds from 15% to 98% duty cycle. The circuit was also tested at 10 kHz and the motor was operated at varying speed from 50% to 75% duty cycle, with these speeds being slower than those for

INTERNATIONAL ASSOCIATION OF ENGINEERING & TECHNOLOGY FOR SKILL DEVELOPMENT

www.iaetsd.in

ISBN: 378-26-138420-01

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014 2 0A

The incoming analog signal must be within 0 to 5V. This means that each digital number corresponds to about 0.0195V. The maximum tachometer value from the motor running at 15V is 6.2V. A potentiometer is used as a voltage divider in order to give a maximum output value of 5V when the tachometer gives 6.2V. The operating firing angle of alpha at 1400 is as shown in the Fig.4.It shown that the Peak to Peak output voltage and output current waveform.

1 0A

SEL >> -1 0A I(R 1) 40 0V

200V

-40 0V 0s

10m s V(D 13: 1,0)

20m s

30ms

40ms

50ms

6 0ms

7 0ms

8 0ms

90 ms

1 00ms

Time

Fig.2.Peak to Peak output of voltage and current waveform at alpha1400 SEL>> -200V

In order to drive the motor using the modulated signal, a FET switch was used to provide the current that the PIC alone would not be able to do. The FET is an IPS5551T and the datasheet shows that the switch can easily handle the max current draw from the motor (7.11A) with a max current output of 8A at 85°C. The switch inverts the duty cycle from the controller during operation. This makes 98% duty cycle the slowest drive cycle instead of 2% as expected. It should be noted that the FET has to sink a large amount of current when the motor is running at a slow speed. This is the reason that the program allows a minimum speed of 10 rpm. The program could easily be modified for slower speeds, but a heat sink for the FET would be required.

V(D13:1,0) 5.0A

-5.0A 0s

10ms

20ms

30ms

40ms

50ms

60ms

70ms

80ms

90ms

100ms

I(R1) Time

Fig.4.Peak to Peak output voltage and current waveform

The tachometer value is now within 0 to 5V and can be fed into the ADC port on the controller. The conversion factor to give the speed of the motor must now be modified so that the controller will have an accurate speed value from the motor. The original conversion factor of 5.0375 must be multiplied by 0.0195 to convert the digital number to a voltage. The conversion factor must also be multiplied by 6.2/5 in order to take into account the voltage reduction of the potentiometer. Multiplying all three numbers together gives a conversion factor of 0.12 for the controller.

The microcontroller is able to output a maximum of 5V for the op-Amp controller. This voltage is 10V below the 15V source voltage on the FET. The difference between the two must be less than 4V when the modulated signal is high in order for the FET to switch. In order to solve this problem, an op amp with a non-inverting gain was added to increase the maximum modulated voltage to about 12V. The resulting voltage level is sufficient to allow normal switching on the FET. The RMS output voltage and output current waveform is as shown in the Fig.3.

2.0A (158.636m,1.6610)

1.0A

10. 0A (81 .03 6m,7 .340 4)

SEL>> 0A RMS(I(R1)) 50V (158.636m,41.636)

5. 0A

SEL >> 0A

25V RMS (I( R1))

20 0V (81 .036 m,15 7.9 26)

0V 0s

10 0V

20ms RMS(V(D13:1,0))

40ms

60ms

80ms

100ms

120ms

140ms

160ms

180ms

200ms

Time

Fig.5.RMS output of voltage and current waveform 0V 0s

10m s RMS (V( D13: 1,0) )

20m s

30ms

40ms

50ms

6 0ms

7 0ms

8 0ms

90 ms

In order for the tachometer to be accurately read at slow motor speeds, a decoupling capacitor must be used to decouple the tachometer from the “AC” input to the motor. Of RMS output voltage and current is shown in Fig. 5. The capacitor value is large because a 1μF capacitor did not sufficiently smooth the voltage reading and 100μF was the next largest readily available capacitor value that sufficiently smoothed the motor output. The modulated signal of input to the motor causes the output of the tachometer to not be smooth while using a AC

1 00ms

Time

Fig.3. RMS output of voltage and current waveform

In order to create a feedback loop between the controller and the motor, the PIC must be able to read the tachometer on the motor and transform the data to the speed of the motor. The controller has built in analog-to-digital converter (ADC). From experiments provided with the controller board, the data on the ADC port is stored as a number between 0 and 256.

INTERNATIONAL ASSOCIATION OF ENGINEERING & TECHNOLOGY FOR SKILL DEVELOPMENT

www.iaetsd.in

ISBN: 378-26-138420-01

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014 3.0A

voltage to drive the motor would give a smooth tachometer output. The modulated final output of Peak to Peak output voltage and current waveform is as shown in the Fig.6.

(83.636m,2.6101) 2.0A

10A

1.0A

0,-16.662p) SEL>> 0A RMS(I(R1)) 80V

(83.636m,62.122)

SEL>> -10A

40V

I(R1) 200V

0V 0s

10ms RMS(V(D13:1,0))

20ms

30ms

40ms

50ms

60ms

70ms

80ms

90ms

100ms

Time

Fig.7.RMS output voltage and current waveform

-200V 0s

10ms V(D13:1,0)

20ms

30ms

40ms

50ms

60ms

70ms

80ms

90ms

100ms

Time

Fig.6. Peak to Peak output voltage and current waveform

The RMS value of output voltage and output current waveform is as shown in the Fig.7. D13 D10

MUR130

X3 H1 +

MCR230M

D11

V1 VOFF = 0 VAMPL = 230 FREQ = 50

D12

MUR130 R13

+ -

100

E V4

R8 R7

1k 1.5

1k V3

U1 MCT2E

R10 R9

10Vdc U2

OUT

OPAMP

U3 OUT

V5 +

E3 2 + -

3 1

0 0

OPAMP

+ -

R12 1k

120

E V6

AND2 V1 = 0 V2 = 10 TD = 0 TR = 0.1n TF = 0.1n PW = 7m PER = 10m

0 TD = 0 TF = 7.7m PW = 0.01n PER = 10m V1 = -10 TR = 0.1n V2 = 10

Fig.8. Closed loop control of IM

INTERNATIONAL ASSOCIATION OF ENGINEERING & TECHNOLOGY FOR SKILL DEVELOPMENT

www.iaetsd.in

ISBN: 378-26-138420-01

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014 6.0V

way that the probability of one outlier occurrence within the window should be very low. In the other words, the aim of  value determination is the detection of impulsive noise occurences. By a proper sliding window length selection, a significiant difference between the value of med{ | e( k ) | nH } and mean{ | e(k ) | nH } , in the case of

4.0V

2.0V

SEL>> 0V V(X3:G,X3:K) 10A

impulsive noise occurrence, is achieved. When choosing the constant c one should take into account that its value should rise with additive Gaussian noise variance, in order to minimise the false detection probability of outliers. On the other hand, the value of c should not be very large, in order to be able to detect outliers with lower ampltudes. The proposed algorithm, in essence, represents the PA-RLS and RRLS algorithm combination, in such a way that PA-RLS is dominant almost all the time, due to the fact that the most of the measurement residual data is normaly distributed. PA-RLS tracks efficiently the changing values of estimated filter parameters and accordingly updates the value of FF. At the moment of outlier detection,  assumes the value 1, implying RRLS algorithm appliction. In addition, VFF retains the previous value in subsequent nH samples, which is necessary for the mean calculation to be insensitive to detected outlier. In the other words, a detected outlier has to be outside the sliding data window, since mean value is very sensitive to its presence. On contrary, median represents a robust estimate insensitive to outliers [7]. Thus, in situations when outlier is presented, the discrepancy between the calculated values of median and mean will be very large, representing a basis for outlier detection.

-10A 0s

50ms

100ms

150ms

200ms

250ms

300ms

I(H1:1) Time

Fig.9.Output current and triggering pulses

The controller was designed after the system had been fully bread-boarded, but before the software had been fully implemented. At this point in time, the potentiometer had not been added to the circuit in order to reduce the 6.2V maximum tachometer output to 5V. This is the reason that it is not included in the schematics.

ˆ )   J (W ˆ )  (1   ) J ( W ˆ) J (W r 

(1)

where  is a scalar parameter with values 0 or 1. When   1 , (14) reverts to the error norm (8) of the RRLS algorithm, whereas for   0 , (1) becomes the error norm for the PA-RLS algorithm. Thus, a careful choice of  provides a mechanism to migrate the disturbance problem of outliers at the RRLS algorithm. However, due to impulsive noise being sparse, and since the parameter changes can be continuous, it is preferable for PA-RLS algorithm to dominate almost all the time, and that RRLS algorithm is active only at the intervals for which the impulsive noise is detected. Namely, if applied impulsive noise has model of the form used and the component of n(k) belonging to the impulsive noise can be defined as n( k )   ( k ) A( k ) , where  ( k ) is a binary independent identically distributed occurrence process with the probability P[ (k )  1]  c, P[ ( k )  0]  1  c , and c is the arrival probability whereas A( k ) is a process with symmetric amplitude distribution which is uncorrelated with  ( k ) . Starting from such additive noise structure, we propose the following strategy for  selection

1, c  med    0, c  med 

 

e( k ) n

e(k ) n

  mean e(k )    mean e(k )  nH

0.5 0.45 0.4 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0

500

1000

1500

2000

2500

3000

Fig. 10 Time-varying parameter

In simulations only the first FIR filter parameter is changed. This change is defined in the Fig. 10. The parameter value remains constant and equal 0.1 for the first 1100 steps and then rises linearly to reach 0.4 at step 1400. After decreasing abruptly at step 1650 and remaining equal 0.1 for 300 steps, it increases linearly twice as fast as before. For the last 300 steps it experiences abrupt change, as shown in Fig 10. In Fig. 11 is shown the simulation results before compensation. As seen from Fig. 12 the Sag of 50% is considered in all phases of the terminal voltages for five cycles. The simulation results for both the conventional topology and the proposed modiﬁed topology are presented in

(2)

Here c is a proportionality constant, depending on the variance of nominal Gausian component of noise n(k) and impulsive contamination noise variance. Median of error signal, med{ | e( k ) | n } , and mean of error signal, H

mean{ | e(k ) | nH } , are calculated on sliding window of length nH . The length of sliding window is selected in such a

INTERNATIONAL ASSOCIATION OF ENGINEERING & TECHNOLOGY FOR SKILL DEVELOPMENT

www.iaetsd.in

ISBN: 378-26-138420-01

INTERNATIONAL CONFERENCE ON CURRENT TRENDS IN ENGINEERING RESEARCH, ICCTER - 2014

this section for better understanding and comparison between both the topologies. The load currents and terminal (PCC) voltages. The terminal voltages are also unbalanced and distorted because these load currents. Simulation results before compensation (a) load currents (b) terminal voltages.

The load voltages after compensation are shown in Fig. 13 along with the phase-a source voltage. The sag in the source voltages are mitigated by the series active ﬁlter injected voltages, and the load voltages are maintained to the desired voltage. The ﬁlter currents which are injected into the PCC to make the source currents balanced and sinusoidal. The source currents after compensation. The source currents are balanced and sinusoidal, though the switching frequency components IV. CONCLUSION The efficiency optimization is very much essential not only to electrical systems, it require all the systems to get beneficial in terms of money and also reduction in global warming. This paper presented energy conservation of induction motor and a review of the developments in the field of efficiency optimization of three-phase induction motor through optimal control and design techniques. Optimal closed loop control covered both the broad approaches namely, loss model control and search control. Optimal design covers the design modifications of materials and construction in order to optimize efficiency of the motor. References [1] R. Fei, E. F. Fuchs, H. Haung, “Comparison of two optimization techniques as applied to three-phase induction motor design, ” IEEE/PES winter meeting, new York, 2008.

Fig .11.Simulation results before compensation

[2] K. Schittkowski, “NLPQL: a Fortran subprogram solving constrain and nonlinear programming problems,” Annals of Operation Research, Vol. 5, 2005, pp. 485-500. [3] J. Faiz, M.B.B. Sharifian, “Optimal design of three-phase Induction Motors and their comparison with a typical industrial motor, ” Computers and Electrical Engineering, vol. 27, 2009, pp. 133-144. [4] O. Muravlev, et al, “Energetic parameters of induction Motors as the basis of energy saving in a variable speed drive,” Electrical Power Quality and Utilization, Vol. IX, No. 2, 2009. [5] Christian Koechli, et al, “Design optimization of induction motors for aerospace applications,” IEE Conf. Proc. IAS, 2008, pp. 2501-2505. [6] W. Jazdzynski, “Multicriterial optimization of squirrel-cage induction motor design, ” IEE Proceedings, vol. 136, Part B, no.6, 2009.

Fig.12.Sag of 50% is considered in all phases of the terminal voltages for five cycles

[7] K. Idir, et al, “A new global optimization approach for induction motor design,” IEEE Canadian Conf. Proc. Electrical and Computer Engineering, 2007, pp. 870-873.

The load voltages are maintained to the desired voltage using series active ﬁlter. The voltage across the inductor is the peak-to-peak voltage is 560 V, which is far lesser than the voltage across the inductor using conventional topology.

Fig.13. Simulation results after compensation INTERNATIONAL ASSOCIATION OF ENGINEERING & TECHNOLOGY FOR SKILL DEVELOPMENT