Title of Invention

A CSI FED INDUCTION MOTOR DRIVE

Abstract The present invention relates to the field of Induction motor drive more particularly to a Novel High Performance current source inverter Fed Induction Motor Drive with Sinusoidal Motor Voltages and Currents.
Full Text

Field of Invention
The present invention relates to the field of Induction motor drive more particularly to a Novel High Performance current source inverter Fed Induction Motor Drive with Sinusoidal Motor Voltages and Currents. Background of the invention
Synchronous drives and Induction motor drives are used for high power applications such as drives for steel mills, paper mills, textile mills, blower fan drives in refineries, large industries etc. Induction motor drives are used where variable speed, frequent changes in speed are required and synchronous motor drives are employed for constant speed applications.
Induction motor drives are either current source inverter (CSI) fed or voltage source inverter (VSI) fed. Current Source Inverter (CSI) fed induction motor drives have advantages such as inherent regeneration capability and built in short circuit protection. Figure 1 shows the block diagram of CSI fed induction motor drives presently used in the industry. In one of the US patent application 6,166,929, Darning Ma et al had tried to reduce the resonance between one or more output filter capacitor of a current source inverter and induction motor. They have achieved it through active damping control, using a physical damping resistor connected in parallel with each output capacitor. This is accomplished by determining amount of current flowing through the resistor, which is equal to the voltage across the capacitor divided by the value of the resistor. The major drawback of this method is efficiency of the system. There is loss of energy in the resistors and its proportional to square of the amount of current flowing through it. So there is a formidable loss of energy hence efficiency of the system is less.
Limitations of the Prior Art
At high power levels, the devices are switched at low frequency in order to limit the
switching losses. So the CSI fed drives will have high harmonic currents, which give rise to high torque pulsation and harmonic losses. In the existing CSI fed drives, passive filters are used across motor terminals to attenuate the voltage spikes caused during CSI switching. The limitations are,

(i) Poor harmonic elimination: In the existing system, the capacitors are designed to attenuate certain harmonics, so a large amount of harmonics still present in the motor currents, which will result in harmonic torque pulsation and harmonic losses. So the drive performance is poor.
(ii) Bulky capacitor: In traditional drives AC capacitors of the order 0.6 to 1.2 p.u., depending on the switching frequency are used. These capacitors are bulky.
(iii) Resonance between capacitor and magnetizing inductance: In the existing drive, capacitor filters are used across motor terminals. There will be resonance between the filter capacitor, C and the magnetizing inductance L0 of the motor.
The resonance frequency is given byflres = . . The maximum value of C
2^VL0C
is limited by the condition that fires should be above the operating frequency of the motor to avoid resonance. Smaller value of C will not filter out the low order harmonics completely and the performance of the drive will deteriorate as the operating frequency of the motor reduces, (iv) Resonance between capacitor and motor leakage inductance: At higher frequencies the leakage inductance of the machine is more effective. Hence there will be resonance between C and the effective leakage inductance Lh of the motor. Lh is given by Lh = Lls + Llr || L0 and the resonance frequency is given
by f|ires = i • For an operating frequency of the motor, there will be
2wVLhC
resonance between C and L/h if the harmonics at f|ires are present. For an operating frequency of the drive, the harmonic frequency corresponding to this resonance frequency should be eliminated. So the CSI should be switched at higher frequency or selective harmonic elimination PWM technique should be used. This will result in higher switching losses in the CSI. Also the implementation of switching algorithm is complicated, (v) Complicated pulse width modulation (PWM) algorithm: For 7v>20 Hz , selective harmonic elimination PWM technique is employed. For Fs
complicated and normally requires look up tables to store PWM pattern. Also it is difficult to completely avoid harmonics corresponding to resonance with trapezoidal PWM. So the conventional drives are accelerated rapidly at low speeds, (vi) Deterioration of performance with the reduction in operating frequency: In the conventionally known drives the harmonic suppression will deteriorate as Fs reduce. So the drive performance will deteriorate as the fundamental frequency reduces, (vii) Increased current rating of the capacitors: Even though in the existing drive, the capacitors are designed to eliminate certain harmonics, the capacitor draws current at fundamental frequency. This current is proportional to the square of the motor speed. So the current rating of the capacitor increases with the speed. Recent publications show two works in which VSI inverter is used directly across the motor terminals in CSI fed drives [Ref. 11 and 12]. In ref 11, the VSI is directly connected to motor terminals without the use of inductance. In this case the VSI works as voltage clamp and the motor voltage is still PWM with pulsating voltage waveforms. So this system will have all the drawbacks associated with the drives operating from non-sinusoidal voltage waveforms such as common mode voltage, high voltage stress, harmonics etc. In ref.12, the VSI is used to supply the leading VARs to achieve commutation in SCR based CSI not as active filter. Since leading VAR has to be supplied is large, the VSI will have low switching frequency and its bandwidth will be low. So with low bandwidth it cannot filter out harmonics effectively. So large capacitor C is used to suppress the voltage surges and to filter out the harmonics. Even though the authors of ref. 12 have claimed that the C requirements is reduced it is with respect to the SCR based CSI where large C is used to supply leading VARs. But compared to gate turned on (GTO) based CSI where leading VARs not required the C used is still very large and the VSI serve no purpose. The drive will still have problems such as unstable operation at low speeds, resonance between C and motor inductance similar to conventional CSI fed drives. So even though the drive schematic given in ref 11 and 12 appear similar to the present work, the present work differs completely from these two publications.

Objects of the invention
The main object of the present invention is to provide CSI fed induction motor with
sinusoidal motor voltage and current waveform through out the operating region, which
overcomes at least one of the drawbacks of the above mentioned prior art.
Another object of the invention is to provide a CSI drive with an active filter for reducing
the harmonic currents at the motor terminal.
Yet another object of the invention is to provide CSI drive adaptable to the existing drive.
Still another object of the invention is to provide a high bandwidth active filter using
insulated gate bipolar transistor (IGBT).
Still another object of the invention is to provide a CSI drive which uses the CSI switching
frequency as the fundamental frequency, same as the operating frequency of the motor.
Still another object of the invention is to provide a CSI drive with less switching loss at the
inverter and small filter capacitor.
Still another invention is to provide a sensorless vector control scheme, where CSI
switching, motor voltage ¤ts and active filter switching are synchronized.
Statement of the present Invention
The present invention relates to a CSI Fed Induction motor drive comprises:
(i) at least one motor 201
(ii) a three phase Current source Inverter 204 connected with a six-pulse or
twelve-pulse SCR based fully controlled rectifier 206 at the input (iii)an active filter 202 connected between the Current Source Inverter 204 and
the induction motor 201 across motor terminals for eliminating the
harmonic current (iv)a controller for controlling the speed of the motor and synchronizing the
active filter and CSI switching with motor (v) a capacitor 203 connected to the output terminal of CSI to suppress the
voltage spikes due to switching of the currents of the active filter
Summary of the invention
The general utility of the inventions described herein relate to improved CSI fed induction
motor drives. However those skilled in the art will understand that the various aspect of the invention may be employed more generally in the field of power electronics. The invention

provides a CSI fed induction motor drive, which overcomes the following limitations of the existing drive.
• Unlike existing drive, the proposed drive do not have resonance problem.
• Unlike existing drive, the proposed drive has near sinusoidal motor current and voltage waveforms throughout the operating region of the drive. Hence there is no problem of over voltage surge on motor due to the reflected waveform in long cables. Also the common mode voltage problem is reduced. This will overcome the problems of shaft /bearing failure which is common in existing drives.
• Unlike the existing drive, the filtering action is uniform through out the operating region of the drive. The proposed drive has improved motor voltage and current waveforms and smooth ripple. Results in fig 7, fig.8 and fig. 10 illustrate this point.
• Unlike existing drive, the proposed drive has stable low speed operation. In the existing conventional drive the filtering action by the capacitor is poor at low speeds. This leads to large torque ripple at low speeds (Fundamental frequency • In the proposed drive, the DC current controller stabilization is easier, as any
variation in dc current is absorbed by the active filter.
• The active filter can be designed to supply leading currents and SCR based CSI drives with auto-sequential turn off can be used.
• Unlike existing drive, the proposed drive uses fundamental switching with 120 degree mode of conduction. So the PWM circuit is simple. Switching losses in the CSI are reduced. Design of CSI power circuit is simple and power section will be more reliable.
• Since the low speed operation is stable, unlike existing drive, in the proposed drive, the motor need not be accelerated fast.

• A vector control with proper synchronization of active filter action with the flux vectors is used in the present work. To take care of the low frequency conditions.
• A small capacitor is still necessary at the motor terminals to suppress the voltage spikes dues to the switching currents of the active filter. Presence of this capacitor complicates the active filter operation as the uncompensated energy if any may give rise to one type of resonance between the Lf and C and another type of resonance between motor inductance and C. Proper design is a must to overcome this problem. In the present work this problem is overcome by
(i) Positioning the capacitor directly across CSI terminals (ii) Selecting the bandwidth of the active filter such that the resonance frequency between the C and Z/will remain above the bandwidth of the active filter. With this arrangement if there is any resonance between C and motor inductance, the active filter will attenuate it. Brief description of the drawings
The present invention shall now be described with reference to the accompanying drawings
in which,
Figure 1 illustrates the Block diagram of existing CSI drive
Figure 2 illustrates a block diagram showing the proposed CSI Drive.
Figure 3 illustrates the Functional block diagram of the controllers for the proposed CSI
drive
Figure 4 illustrates the Power circuit of the proposed drive
Figure 5 illustrates the simulation results of the existing drive at 10Hz operation.
Figure 6 illustrates the simulation results of the existing drive at 40Hz operation.
Figure 7 illustrates the simulation results of the proposed drive at 10Hz operation.
Figure 8 illustrates the simulation results of the proposed drive at 40Hz operation.
Figure 9 illustrates a comparison of estimated torque (Existing and proposed drive).
Figure 10 illustrates the experimental results of the proposed drive.
Figure 11 illustrates the experimental results of the speed reversal of the proposed drive.

Figure 12 illustrates the Photograph of the experimental setup.
Detailed description of the invention
According to one aspect of the present invention a CSI Fed Induction motor drive
comprises:
(i) an Induction motor;
(ii) a three phase CSI connected with a six-pulse or twelve-pulse SCR based fully controlled rectifier at the input;
(iii) an active filter connected between the CSI and the induction motor across motor terminals for eliminating the harmonic current;
(iv) a controller for controlling the speed of the motor and synchronizing the active filter and CSI switching with motor; and
(v) a capacitor connected to the output terminal of CSI to suppress the voltage spikes due to switching of the currents of the active filter. According to one embodiment of the present invention the active filter has a multilevel inverter configuration.
According to another embodiment of the present invention the controller comprises a DC current controller, active filter current controllers. According to yet another embodiment of the present invention the CSI comprises IGBT or IGBT or GTO based inverters. According to still another embodiment of the present invention the inverter comprise IGBT based inverter operable in a bandwidth of half the switching frequency. According to still another embodiment of the present invention CSI is switched at the fundamental frequency with 120 degree mode of conduction.
According to still another embodiment of the present invention the maximum value of the active filter bandwidth is half of the switching frequency of the inverter. According to still another embodiment of the present invention the controller used is sensor less vector control algorithm or vector control algorithm or constant v/f control. (In the prototype, a sensorless vector control algorithm is used).
According to still another embodiment of the present invention the capacitor is connected directly across the CSI terminals.
According to still another embodiment of the present invention the resonance frequency of between the capacitor and motor remains above the filter bandwidth.

According to still another embodiment of the present invention the value of the capacitor is less than 0.1 per unit.
According to still another embodiment of the present invention the motor voltage and current waveforms are sinusoidal through out the operating region of the drive. According to still another embodiment of the present invention synchronization between the CSI switching, Active filter switching and motor terminals is achieved using the unit vectors along the direct axis and quadrature axis components of the rotor flux. According to still another embodiment of the present invention the fundamental component of the CSI output current is estimated using the unit vectors which are derived from and synchronized with the direct axis and quadrature axis components of the rotor flux.
The present application is here below described in more elaborate way with reference to the drawings. Figure 2 and figure 3 shows the functional block diagram of the existing drive and proposed drive respectively. The proposed drive constitutes of a fully controlled SCR rectifier 206, which rectifies the three-phase 50Hz AC power supply from the mains. Fully controlled SCR rectifier 206 is connected to the three-phase current source inverter 204 through an inductor 205. Three-phase current source inverter 204 supplies the electricity to the induction motor 201. Between current source inverter 204 and induction motor 201 a small capacitor 203 as well as an active filter 202 are provided. The input end rectifiers 206 are six-pulse or twelve-pulse SCR based fully controlled rectifier. L(\c is the dc link reactance (inductance 205). The three-phase CSI 204 are generally GTO based inverters even though isolated gate bipolar transistors (IGBTs) or IGCTs are also used. In figurel, in the existing drive either selective harmonic elimination or trapezoidal PWM is used to switch the CSI devices. So the capacitor value will be high and will be typically in the range 0.6 per unit to 1.2 per unit.
In fig 2, in the proposed drive CSI is switched at fundamental frequency and no PWM techniques are used. The value of small capacitor 203 C is very small 0.05 per unit to 0.1 per unit. Active filter 202 are generally a three phase, IGBT based multilevel Voltage Source Inverter (VSC). Even though conventional two-level inverters are used for medium voltages, they require an interface transformer to match the voltage levels.

Figure 3 shows the functional block diagram of the controller of the proposed drive. DC current controller is used to control the DC link current i(/c- The effect of the voltage at the CSI input terminals vdcj is compensated using feed forward technique. The system with the
compensation is first order in nature and is stabilized using Proportional-Integral (PI) controller. Proportional-Integral (PI) controllers are used to achieve desired bandwidth and zero steady state error. The active filter current controller consists of two PI controllers. The active filter current controller is implemented in stationary axis model and two controllers are sufficient. The effect of motor terminal voltages is compensated using feed forward technique. The stator flux is estimated from the terminal voltages as given in equation A.l.

Where y/ss , v/ and iss are the stator flux space vector, motor voltage space vector and motor current space vector respectively. Rs is stator winding resistance of the motor.
The rotor flux space vector \j/*r is estimated from the stator flux space vector as in equation
A.2.
where Ls, Lr and a are the stator self inductance, rotor self inductance and leakage factor respectively.
The rotor flux position vectors cos(p) and sm(p) are computed using the equation A.3.


Synchronization between the CSI, Active filter and Motor:
The rotor flux position vectors computed using equation A.3 are along d-q axis. The three phase unit vectors ua, ub and uc are computed by d-q to a-b-c transformation. These three
unit vectors are used to switch the CSI and 120 degree mode of fundamental frequency switching is employed. The frequency is decided by these unit vectors and is the frequency of the rotor flux which is nothing but the synchronous frequency of the motor. Thus the synchronization between CSI and motor quantities is achieved. These three phase unit vector multiplied with the i(lc will give actual fundamental current
demanded by the induction motor. The command values of the harmonic current to the
active filter current controller are obtained by subtracting the fundament current from the
CSI out put current.
Computation of all these quantities is done using the rotor unit vectors, so the perfect
synchronization between motor quantities, active filter and the CSI is achieved. This
perfect synchronization is a must for the operation of the drive.
The flux is maintained at the desired value using flux controllers. The flux controllers are
realized using PI controllers. Similarly closed loop control of speed is achieved using
speed controller, which consists of the PI controller. The output of the speed controller is
the actual value of the q-axis current {i ) demanded by the motor and the output of the
flux controller is the actual values of the d-axis current Csd to be supplied by the CSI. Since the capacitor current (ic) is along d-axis and in phase opposition to iSft, the d- axis current
to be supplied to the motor (zv) is obtained by subtracting the magnitude of ic from /*,.
Since these currents should be supplied by the dc link current, the magnitude of the current
command for the dc link current controller is given by C(lc = Ji2x + Q .
Simulation Results:
A. Simulation Results: Conventional CSI Drive:
The vector controlled conventional CSI drive, is simulated using MATLAB-SIMULINK toolbox. Figure 5 and 6 show the CSI current of phase a (//;fl), motor current of phase a

(isn)9 capacitor current of phase a (ica), motor phase voltage of phase a (vifl), harmonic
spectra of ipa and isa as obtained from the simulation for Fs =\0Hz and Fs = 40Hz
respectively. Capacitor of C=0.6p.u. (i.e.66uF) is used for simulation. During simulation, P=18 is used for Fs>20Hz, so 5th, 7th, 11th and 13th are eliminated. From the results it can be seen that at low Fs, the motor current and voltage have significant harmonics (figure 5). The filtering action of the capacitor is good at higher values ofFs. But as Fs increases, the
fundamental component of the capacitor current also increases (figure 6); that means VA rating of the capacitor will rise with Fs.
B. Simulation Results: Proposed CSI drive
The vector control scheme is applied to the proposed CSI drive and the system is simulated using MATLAB SIMULINK toolbox. Figure 7 and figure 8 give the simulation results of ipa , isa, their harmonic spectra, active filter current (iha ) and vsa for Fs =\0Hz and
Fs ~40Hz respectively. Small capacitors of O.lp.u. (C=lluF) are used to filter out the
voltage due to active filter switching ripple. A high band-width of 31416 rad/sec is used for the active filter.
Experimental verification and results:
In order to experimentally verify the proposed drive and validate the simulation results and
the design of the drive, the proposed drive is implemented on an experimental prototype. The power circuit diagram of the experimental set up is given in figure 4 and the photograph of the prototype is given in figure 12. A six pulse three phase fully controlled SCR ac to dc converter is used on the line side. An IGBT based three phase three level diode clamp inverter is designed and fabricated in the laboratory and used as active filter inverter. An IGBT based CSI is designed and fabricated in the laboratory. Diodes are connected in series with the IGBT modules as shown in figure 4 to block the reverse current flow through IGBT body diodes. The loading arrangement in the experimental prototype consists of a separately excited shunt dc generator, coupled to the induction motor. In this type of loading, torque is proportional to speed, whereas the actual load encountered by CSI drives is of the fan type load in which the torque is proportional to square of the speed.

The rating of the experimental prototype is as follows. The same rating is used for
simulation also.
Induction motor: 400V, 8A, 3.78 KW, 1425rpm Three Phase, 50Hz.
DC machine: 230V, 13A, 3KW, 1475rpm, excitation: 230V, 1.1 A.
Input rectifier: Three phase, six pulse SCR rectifier.
Input voltage: 415V, 50Hz, three phase ac supply.
CSI: Three phase IGBT with series blocking diodes.
DC input voltage: 700V Maximum.
DC link current: 50A Maximum.
Active filter: Three phase three level IGBT based diode clamp inverter.
DC bus voltage: 600V (nominal)
DC bus current: 50A Maximum. Fig 10 shows the steady state experimental wave forms of / , isa , iha and vah for
Fs ~\0Hz and FS ~40Hz . These experimental results are in agreement with the
simulation results given in figure 7 and figure 8. These experimental results verify the theory that is explained in the above paragraphs and illustrate the practical feasibility of the proposed drive. Figure 11 shows the current waveform during speed reversal. This results shows that filtering action of the active filter is uniform even during zero speed and transients also.
Even though there are certain patents, given in the reference, which uses a capacitor filter at the motor terminal, none of them refers to the use of an active filter at the motor terminal. The major reasons for the same are as follows:
• Active filter concept is new (gained importance only in mid 1990s) and applied
to the distribution systems at the load end at the point of common coupling. So
the technology is still not well established and requires further work.
• Using active filter across motor terminals is not as straight forward as using at
the point of common coupling. The voltage at the motor terminals need not be
constant and varies with the frequency of operation of the motor. So at low

frequency conditions, the voltage will be very weak and proper design is necessary. A closed loop operation is a must.
• A small capacitor is still necessary at the motor terminals to suppress the voltage
spikes dues to the switching currents of the active filter. Presence of this
capacitor complicates the active filter operation as the uncompensated energy if
any may give rise to one type of resonance between the L/ and C and another
type of resonance between motor inductance and C. Proper design is a must to
overcome this problem.
Advantages of the proposed system
• The CSI is switched at fundamental frequency. So the switching frequency of CSI is same as the operating frequency of the motor. Hence the switching loss in the CSI is reduced which not only improves the system efficiency but also improves the reliability of the CSI-
• The operating voltage of the high power drives is very high. So the multilevel configuration is used for the active filter. Multilevel inverters can synthesize higher voltages, using the semiconductor devices of low voltage rating. This has eliminated the need of an interface transformer between the active filter and motor terminals. So the system cost is reduced.
• For a given switching frequency, the multilevel configuration results in output waveforms with effective switching frequency (N-l) times that of two-level inverter, where N is the number of levels in the multilevel configuration. This results in small filter inductance and also higher bandwidth of the filters.
• Major advantage of the proposed drive is that the proposed drive can be retrofitted with existing CSI drives. Since the active filter is independent, the existing CSI drive can be changed to the proposed configuration by replacing the passive filter by the active filter and making necessary changes in the controller. This will result in improved voltage and current waveforms of the existing drive, resulting in smooth torque.

• Since motor voltage and current waveforms are sinusoidal as proved by the simulation results (figure 7 and figure 8) and experimental results (figure 10). So there will not be high voltage stress due to reflected waveforms in long cables. Also common mode voltage problem is reduced.
• Since the active filters carry only the harmonic current these switches can be operated at very high frequency. So a high bandwidth active filter can be designed using IGBT based inverters. The maximum value of the active filter bandwidth will be half of the switching frequency of the inverter. In the experimental prototype the bandwidth is set at 1 KHz or 6283rad/sec.
• Shunt active filters can be designed to supply the VAR requirements of the induction motor and the CSI can be made to operate in leading power factor conditions. SCR based CSI with auto-sequential turn off can be used. This will bring down the cost of the CSI.
• Any control algorithm like constant v/f or vector control can be used for this drive configuration.
• Like any CSI drive, regeneration is possible. Under regeneration, the polarity of the dc link voltage is reversed and the input SCR rectifier goes into inversion mode.
References
[1] J.Ma, Bin Wu, Navid Zargari and Steven Rizzo, "CSI based drive having active
damping control," US Patent \# 6,166,929, Dec. 26, 2000. [2] J.Ma, Bin Wu, Navid Zargari and Steven Rizzo, "CSI based drive having feed
forward control of inverter input voltages," US Patent \#6,269,010, July 31, 2001. [3] Kubota Hisao and Matsuse Koki, "Reactive power processing circuit for a current
source GTO inverter," US patent \#4,721,897 [4] Fekete G, Niessen E, "Energy Control of induction machines." Hungarian patent,
reg no H 02 P17/00, P 9401116, 2000. [5] Abbondanti Alberto, "Load commutated inverter (LCI) induction motor drive," US
patent \# 4,870,338 Sept. 26, 1988.

[6] Lipo; Thomas A., "Current source inverter fed induction motor drive", US Patent \#
4, 455,522, Aug.2 1982. [7] Zargari, N.; Yuan Xiao; Bin Wu, "A PWM CSI-based vector controlled medium
voltage AC drive with sinusoidal input and output waveforms" Proceedings of
Thirty-Second IEEE- IAS Annual Meeting, IAS *97,vol 1, pp 768-774, Oct. 1997. [8] Bin Wu, Dewan,S.B. and Slemon,G.R., "PWM-CSI inverter for induction motor
drives," IEEE transaction on Industry applications, vol.28, No.l, pp64-71,
Jan/Feb.1992. [9] Espelage, P.M.; Nowak, J.M.; Walker, L.H.;" Symmetrical GTO current source
inverter for wide speed range control of 2300 to 4160 volt, 350 to 7000 HP,
induction motors", Conference Proceedings of IEEE Industry Applications Society
Annual Meeting", vol 1, pp 302-307, Oct. 1988 . [10] Mendalek, N.; Al-Haddad, K.; "Modeling and nonlinear control of shunt active
power filter in the synchronous reference frame", Proceedings of the Ninth
International Conference on Harmonics and Quality of Power. Vol.1, pp 30-35,
Oct. 2000 [11] M. Imecs, A. M. Trzynadlowski, I. I. Incze, and C. Szabo, "Vector control
schemes for tandem-converter fed induction motor drives," IEEE Transactions of
Power Electronics, vol. 20, no. 2, pp. 493-501, March 2005. [12] Sangshi Kwak and Hamid A.Toliyat, " A Hybrid solution for Load Commuted
Inverter Fed Induction Motor Drive," IEEE Transaction on Industry Applications,
Vol.41, No. 1, pp83-90, Jan/Feb. 2005. [13] Bimal K. Bose, "Modern Power Electronics and AC Drives," Third Indian reprint,
Pearson Education (Singapore) Pvt. Ltd., Delhi, India, 2003, Chapter 6 and 8.




We Claim
1. A CSI Fed Induction motor drive comprises:
(i) at least one motor 201
(ii) a three phase Current source Inverter 204 connected with a six-pulse
or twelve-pulse SCR based fully controlled rectifier 206 at the input (iii) an active filter 202 connected between the Current Source Inverter
204 and the induction motor 201 across motor terminals for
eliminating the harmonic current (iv) a controller for controlling the speed of the motor and
synchronizing the active filter and CSI switching with motor (v) a capacitor 203 connected to the output terminal of CSI to suppress
the voltage spikes due to switching of the currents of the active filter
2. The motor drive as claimed in claim 1, wherein the active filter 202 has a multilevel inverter configuration.
3. The motor drive as claimed in claim 1, wherein the controller comprises a DC current controller, active filter current controllers.
4. The motor drive as claimed in claim 1, wherein the current source inverter 204 comprises IGBT and/or GTO based inverters.
5. The motor drive as claimed in claim 1, wherein the current source 204 inverter comprise IGBT based inverter operable in a bandwidth of half the switching frequency.
6. The motor drive as claimed in claim 1, wherein the Current Source Inverter 204 is switched at the fundamental frequency with 120 degrees mode of conduction.
7. The motor drive as claimed in claim 1, wherein the maximum value of the active filter 202 bandwidth is half of the switching frequency of the inverter.
8. The motor drive as claimed in claim 1, wherein the controller used is sensor less vector control algorithm or vector control algorithm or constant v/f control.
9. The motor drive as claimed in claim 1, wherein the small capacitor 203 is connected directly across the current source inverter 204 terminals.

10. The motor drive as claimed in claim 1, wherein the resonance frequency of between
the capacitor 203 and motor 201 remains above the filter bandwidth.
11. The motor drive as claimed in claim 1, wherein the value of the capacitor 203 is
less than 0.1 per unit.
12. The motor drive as claimed in claim 1, wherein the motor voltage and current
waveforms are sinusoidal throughout the operating region of the drive.
13. The motor drive as claimed in claim 1, wherein synchronization between the
current source inverter switching, Active filter switching and motor terminals is
achieved using the unit vectors along the direct axis and quadrature axis
components of the rotor flux.
14. The motor drive as claimed in claim 1, wherein the fundamental component of the
Current Source Inverter output current is estimated using the unit vectors which are
derived from and synchronized with the direct axis and quadrature axis components
of the rotor flux.
15. The motor drive as claimed in claim 1, wherein shunt active filters are designed to
supply the VAR requirements of the induction motor.
16. The motor drive as claimed in claim 1, wherein Current Source Inverter 204
operates in leading power factor conditions.
17. The motor drive as claimed in claim 1, wherein SCR based Current Source Inverter
204 with auto-sequential turn off is employed.
18. A CSI Fed Induction motor drive substantially as here in described with reference
to accompanying drawings.


Documents:

1926-CHE-2005 AMENDED CLAIMS 08-07-2010.pdf

1926-CHE-2005 AMENDED PAGES OF SPECIFICATION 08-07-2010.pdf

1926-CHE-2005 CORRESPONDENCE OTHERS 08-07-2010.pdf

1926-CHE-2005 OTHER DOCUMENT 30-10-2009.pdf

1926-CHE-2005 AMANDED PAGES OF SPECIFICATION 30-10-2009.pdf

1926-CHE-2005 EXAMINATION REPORT REPLY RECEIVED 30-10-2009.pdf

1926-che-2005-abstract.pdf

1926-che-2005-claims.pdf

1926-che-2005-correspondnece-others.pdf

1926-che-2005-correspondnece-po.pdf

1926-che-2005-description(complete).pdf

1926-che-2005-drawings.pdf

1926-che-2005-form 1.pdf

1926-che-2005-form 3.pdf

1926-che-2005-form 5.pdf

1926-che-2005-form 9.pdf


Patent Number 242637
Indian Patent Application Number 1926/CHE/2005
PG Journal Number 37/2010
Publication Date 10-Sep-2010
Grant Date 02-Sep-2010
Date of Filing 26-Dec-2005
Name of Patentee INDIAN INSTITUTE OF SCIENCE
Applicant Address DEPARTMENT OF ELECTRICAL ENGINERING, BANGLORE 560 012, KARNATAKA, INDIA
Inventors:
# Inventor's Name Inventor's Address
1 V.T. RANGANATHAN DEPARTMENT OF ELECTRICAL ENGINERING, BANGLORE 560 012, KARNATAKA, INDIA
2 A.R. BEIG DEPARTMENT OF ELECTRICAL ENGINERING, BANGLORE 560 012, KARNATAKA, INDIA
PCT International Classification Number H 02 P
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA