WO2013121442A2

WO2013121442A2 - A method and system for controlling a motor / multi-motor system

Info

Publication number: WO2013121442A2
Application number: PCT/IN2013/000095
Authority: WO
Inventors: Sundar Doraiswamy; Jitendra Veer SINGH; Sreejakumar NAIR
Original assignee: Tribi Systems Private Limited, Company
Priority date: 2012-02-15
Filing date: 2013-02-15
Publication date: 2013-08-22
Also published as: WO2013121442A3

Abstract

A method and system for controlling a motor. The embodiments herein relate to motors and, more particularly, to enabling a motor to run efficiently on available power supplies. Embodiments herein enable a motor to operate using multiple input power sources and intelligently utilize the best possible source at a given point of time. Embodiments herein enable a motor to be started from a compatible and/or incompatible source by eliminating motor inrush currents and thereby ensuring there are no stresses on the power source or the power conditioning equipment. Embodiments herein provide improved algorithms to improve efficiency levels when the equipment is operated from multiple input power sources. Embodiments herein provide for the power source equipment to be optimally sized without catering to motor inrush currents and higher energy consumption if the motor/multi-motor system were to be run without any information on change of input power source.

Description

A METHOD AND SYSTEM FOR CONTROLLING A MOTOR / MULTI- MOTOR SYSTEM

TECHNICAL FIELD

[001] The embodiments herein relate to motors and, more particularly, to enabling a motor / multi-motor system to run efficiently on available power supplies (which may be AC and/or DC).

BACKGROUND

[002] Motor driven solutions need power supplies compatible to their design to be available for functioning. At a lot of locations the availability of power is either at a different level, different type or not consistent or not available (and hence needs localized generation). Currently, motor driven solutions require power supplies compatible to their design which are either AC (which may be 230V, 110V or any other suitable voltage and frequency levels) or DC (of any suitable level) to be available for functioning. Currently, motors can run only on one type of supply and cannot switch between the power supplies. When power conversion is provided, it cannot be without a loss in efficiency and performance. Also when power conversion is done, each time the motor starts the power source and power conversion equipment undergo huge stresses due to the motor inrush currents.

[003] Use of a different type of input power supply necessitates power conditioning, which is normally done via a fixed conversion methodology. For example, an inverter is used to convert a DC power source to the required AC voltage and supply. While in case of AC power source, the AC supply is converted to DC and then back to AC in a plain inverter topology which provides for a fixed voltage and frequency as desired by the type of motor. For cases where only AC voltage correction is needed, it is done using a step-up / step down transformer with the variation in voltage catered to via a servo stabilizer or by switching windings of the transformer depending on the input voltage. A plain conditioning of power source to suit a motor does not add to control performance and at the same time causes stress to the power source and power conditioning components each time the motor starts.

[004] Inconsistent power quality also needs power conditioning to enable a motor application to function. However plain conditioning does not support a weak network where the supply line regulation is poor.

[005] Lack of power results in the need for localized power generation which is normally generator based on fossil fuels and has a large carbon footprint. Also the motor starting currents cause the source to be oversized resulting in the source operating at an inefficient point.

[006] In addition to localized generator based power generation, intermediate storage is also an option used often. In this case, the storage medium is normally batteries. Here again plain power source conditioning done in the former approaches leads to stresses on the source and the power conditioning devices each time the motor starts.

[007] One more option in case of lack of power availability is the use of a renewable source (solar, wind, fuel cell, etc). Here again plain power conditioning results in the source being overdesigned and being subjected to stresses each time the motor starts.

[008] Apart from power conditioning, the equipment continues to function as in the same manner as earlier without any recognition of change of state of input power source and consumes the same amount of energy as earlier. In addition to lack of change of state, in case the power conditioning equipment fails, the end application stops functioning as the bypass is not done in a fail safe manner.

[009] A proposed solution discloses about using multiple input power sources i.e.; AC or DC for starting motor. This solution discloses about the power conditioning circuit for automatically utilizing incompatible source for motor and discloses that the motor can run on one or more type of power and switch between the power supplies. However, this solution does not disclose about eliminating inrush currents and does not disclose any thing about the soft start.

[0010] Another proposed solution discloses a method and system for soft starting a three phase motor and also discloses about the elimination of inrush current occurs during the startup of the motor. This solution also discloses about using multiple input power supplies. However, this solution does not explicitly disclose that the multiple powers may be AC or DC and also does not disclose any thing about checking the compatibility of power source to the motors. Further, this solution also does not disclose about the power conditioning module or about improving efficiency.

SUMMARY

[001 1 ] Embodiments herein provide for enabling motor / multi motor driven application system to operate using multiple input power sources and intelligently utilize the best possible source at any given point of time.

[0012] Embodiments herein provide improved algorithms to improve efficiency levels when the equipment is operated from multiple input power sources.

[0013] In view of the foregoing, the embodiments herein disclose a method and system for eliminating inrush currents occurring during the startup of a motor using a suitable soft start technology like Variable Frequency Drive Technology for AC motors and Variable Voltage for DC motors, thereby ensuring that the input power source can be optimally sized for genuine running load levels.

[0014] Also, disclosed herein is use of power conditioning in co-ordination with a soft-start which ensures that a single motor / multi-motor operation is catered to without any stresses on the power source or the conditioning equipment.

[0015] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[0016] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:

[0017] FIG. 1 depicts a system using multiple motors, according to embodiments as disclosed herein;

[0018] FIG. 2 depicts a motor controller with fail-safe operation, according to embodiments as disclosed herein;

[0019] FIG. 3 depicts the process, according to embodiments as disclosed herein;

[0020] FIG. 4 depicts a graph of the soft-start curve, according to embodiments as disclosed herein;

[0021] FIG. 5 depicts a graph of set point optimization, according to embodiments as disclosed herein;

[0022] FIG. 6 depicts a graph of speed, capacity and demand varying with time, according to embodiments as disclosed herein; and

[0023] FIG. 7 illustrates use of the motor controller in a telecom shelter, according to embodiments as disclosed herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0024] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0025] The embodiments herein disclose a method and system for enabling operation of a motor / multi-motor system using multiple input power sources and intelligently utilize the best possible source at a given point of time. Referring now to the drawings, and more ^: particularly to FIGS. 1 through 7, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.

[0026] FIG. 1 depicts a system using multiple motors according to embodiments as disclosed herein. FIG. 1 depicts a plurality of motors 102 connected to a plurality of power supplies (an AC supply 105 and a DC supply 104) via a motor controller 101 and a power conditioning module 103. The motor controller does selection of a motor / motor group. The motors may be AC or DC supplied.

[0027] For example if the motor is an AC motor and if the motor controller 101 is using an DC source 104 for running the motor 102, the power conditioning module 103 performs power conditioning on the DC source 104 (for example, a battery) and the motor controller 101 performs soft start. The power conditioning module 103 may also perform power conditioning on the AC source 105 (for example, the mains supply), which may be followed by a soft start means, if the motor If 102 is an AC motor, the power conditioning module 103 may also perform power conditioning on the AC source, which may not be followed by a soft start means. The motor controller 101 decides to soft start or not with the AC source, depending on the motor compatibility with the AC source being provided. In another embodiment, the motor controller 101 may pass the AC source power through a bypass mechanism which is provided in a failsafe manner s shown in figure 2. The motor controller 101 senses the sources of supply and determines the type of control and the point of operation of the motor 102, which may be depending on the application and various parameters related to the application as shown in figure 5.

[0028] The motor controller 101 further comprises a means for determining the application parameters. Consider the case where the motor 102 runs an air conditioning unit, the application parameters will include (but not be limited to) temperature, humidity, etc. Consider the case where the motor 102 runs a water pump, the application parameters will include (but not be limited to) pressure and flow rate.

[0029] The motor controller 101 may keep the sources in isolation through a plurality of relays and/or switches which are interlocked to ensure that the sources are not mixed. After the supply source isolation, a further isolation is provided by the motor controller 101 using relays of the bypass mechanism to determine which supply finally gets routed to the motor 102. The method of isolation is as depicted in FIG. 2.

[0030] The method of connection is done by using relays and the motor connections via the bypass mechanism in a failsafe manner to ensure that in case of a unit fault, the end equipment functionality continues un-impeded if the source is compatible to the motor 102. In case of AC motors the AC source may be bypassed directly to the motors, while in case of DC motors the DC source may be bypassed directly to the motors.

[0031] The motor controller 101 increases the voltage and frequency in steps over a preconfigured period of time. For example, the voltage and frequency levels may be increased from a level of 10-30V, 0.1 Hz to 230V, 50 HZ over the preconfigured time. The time may be preconfigured based on the motor characteristics and applications. For example, for a motor used in air conditioning, the time may be configured between 0.5 seconds to 15 seconds. In case of a DC motor system the buildup will only be of voltage. Embodiments discussed further herein are with respect to AC induction motors as an example. It may be obvious of ordinary skill in the art to handle similar applications for DC motors or any other type of motor via the respective motor control algorithms.

[0032] A stepped increase in the voltage and frequency for an AC motor (and voltage for a DC motor) ensures that the motor starts smoothly with a soft start, where the starting currents taken from the power source are less than the running current taken from the power source. As very little voltage is applied and the voltage and frequency are built up in coordination, the motor torque is taken care of, and the gradual build-up of voltage ensures that the motor back emf builds up as the voltage applied to the motor terminals is increased. In case of compressors, the motor starting current is less than the motor running current. The ramp up is over the preconfigured time period and the total energy consumed by the motor 102 during starting (I²T), is also lower as compared to a direct online start.

[0033] In an embodiment herein, the motor controller 101 uses motor speed modulation during regular operation based on the compatibility of the electro-mechanical system.

[0034] Depending on need, the motor controller 101 may also regulate the operation parameters to ensure reduction of energy consumption. For example, consider a case where the motor 102 runs an air conditioning unit, the motor controller 101 may set the temperature set points at levels where the energy consumption will be lower as shown in figure 5.

[0035] As the motor controller ensures elimination of motor inrush currents and also ensures that the energy consumption is reduced, the power equipment can be sized optimally. For example, a solar panel size or a generator size can be reduced to match the exact needs without building in excess capacity to cater to momentary conditions during the starting of the motor.

[0036] In another embodiment herein, the motor controller 101 may provide for motor speed change algorithms which will help improve efficiency of the solution by matching the end equipment output to the demand as shown in figure 6.

[0037] In an embodiment herein, the power conditioning and source determination may be performed by distinct modules.

[0038] In another embodiment herein, power conditioning may be performed based on the source and the requirements of the motor system.

[0039] FIG. 3 depicts the process, according to embodiments as disclosed herein. The motor controller 101 first checks (301) the source of supply. After determining the source of supply, the motor controller 101 then checks (302) on the control status. The motor controller lOlchecks (303) whether controls to be done for that source is compatible. In case the source is compatible (that is the controls were already installed with the end equipment); the motor controller 101 continues (304) to supply the power. Here the existing controls continue to function as the case where a normal power supply would have been provided to it. In case the source is incompatible (vis-a-vis source type, i.e. DC or AC; or at different levels though of the same type, i.e. different voltage / frequency as compared to the equipment design) with the power type, then the motor controller 101 checks (305) the state of the application and depending on the state of the application, the power conditioning module 103 performs (306) power conditioning of the source and the motor controller lOlthe solution starts (307) the motor 102 in a soft start manner. In an embodiment herein, the motor controller 101 may also stop the motor 102. The various actions in method 300 may be performed in the order presented, in a different order or simultaneously. Further, in some embodiments, some actions listed in FIG. 3 may be omitted.

[0040] FIG. 4 depicts a graph of the soft-start curve, according to embodiments as disclosed herein. The graph depicts the steep increase in the current (due to inrush currents) and the steep increase in speed as in prior art solutions. The gradual increase in the speed and the current over time, according to embodiments disclosed herein, is also depicted. The speed and current attain a constant value after a period of time.

[0041] FIG. 5 depicts a graph of set point optimization, according to embodiments as disclosed herein. The graph herein depicts the changes in the optimal set point with time and temperature.

[0042] FIG. 6 depicts a graph of speed, capacity and demand varying with time, according to embodiments as disclosed herein. The graph herein depicts the motor speed being modulated to enable the equipment capacity to meet demand.

[0043] FIG. 7 illustrates use of the motor controller in a telecom shelter, according to embodiments as disclosed herein. The telecom shelter, as depicted, comprises of a motor controller 101 connected to a grid source 701 and a DG set 702 and controlling an AC unit 703 present within the shelter. The motor controller 101 selects a suitable power source to power the AC unit 703. The motor controller 101 further supplies a selected power source to power the SMPS 704, which is connected to the battery 705.

[0044] The motor controller 101 is also connected to a SMPS 704, further connected to a battery 705. The battery 705 may be charged by the grid source 701; the DG set 702 or any other alternate energy source (such as solar power, wind energy and so on) via the SMPS 704. The battery 705 may be used to power one or more BTS / other equipments 706 present within the telecom shelter.

[0045] Embodiments disclosed herein enable co-ordination of soft-start with the power conditioning circuitry, hereby ensuring stress free motor start-up for the input power source.

[0046] Embodiments also disclose efficiency controls in existing equipment without any change to the installed equipment or needing change for standard equipments used.

[0047] Embodiments herein enable connection to the motors which optimizes the hardware used and thereby reduces the CAPEX needed.

[0048] Embodiments herein ensure that the multiple input supplies are not mixed and the required level of electrical isolation is provided.

[0049] Embodiments herein provide for complete functionality, and where-in controls are already existing it provides for alternate set of controls & sensors. This ensures operation when powered through localized generation (renewable or non-renewable) and / or from a storage medium without any change to existing equipment.

[0050] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the claims as described herein.

Claims

CLAIMS We claim:

1. A method for enabling operation of a motor system, wherein said motor system comprises of at least one motor, said method comprising of

deciding on a suitable power source for said motor system;

performing power conditioning on said selected source;

performing analysis for type of control and point of operation of said motor system based on said selected power source; and

supplying power from said selected power source to said motor system based on said analysis.

2. The method, as claimed in claim 1, wherein said suitable power source may be at least one of an AC power source or a DC power source.

3. The method, as claimed in claim 1, wherein said method further comprises of checking compatibility between said selected power source and said motor system.

4. The method, as claimed in claim 1, wherein said type of control depends on at least one of application of said motor system; operational parameters relevant to operation of said motor system; efficiency of said motor system for performing said at least one application and environmental factors relevant to operation of said motor system.

5. The method, as claimed in claim 1, wherein supplying power from said selected power source to said motor system comprises of incrementing at least one of voltage and frequency in an stepped manner to reach said point of operation over a predefined period of time.

6. The method, as claimed in claim 5, wherein said predefined period of time depends on at least one of characteristics of said motor system; or application of said motor system.

7. The method, as claimed in claim 1, wherein said method further comprises of performing modulation of speed of said motor system.

8. The method, as claimed in claim 1, wherein said method further comprises of regulating parameters related to said motor system to reduce energy consumption of said motor.

9. The method, as in claim 1, wherein said method comprises of eliminating inrush currents to said motor system.

10. The method, as claimed in claim 1, wherein said method further comprises of said motor system using at least one of a relay; or a switch to ensure that available power sources are not mixed.

11. A system for enabling operation of a motor system, wherein said motor system comprises of at least one motor, said system configured for

deciding on a suitable power source for said motor system;

performing power conditioning on said selected source;

12. The system, as claimed in claim 1 1, wherein said suitable power source may be at least one of an AC power source or a DC power source.

13. The system, as claimed in claim 11, wherein said system is further configured for checking compatibility between said selected power source and said motor system.

14. The system, as claimed in claim 11, wherein said type of control depends on at least one of application of said motor system; operational parameters relevant to operation of said motor system; efficiency of said motor system for performing said at least one application and environmental factors relevant to operation of said motor system.

15. The system, as claimed in claim 11, wherein the system is further configured for supplying power from said selected power source to said motor system by incrementing at least one of voltage and frequency in an stepped manner to reach said point of operation over a predefined period of time.

16. The system, as claimed in claim 15, wherein said system is configured for considering said predefined period of time depending on at least one of characteristics of said motor system; or application of said motor system.

17. The system, as claimed in claim 11, wherein said system is further configured for performing modulation of speed of said motor system.

18. The system, as claimed in claim 11, wherein said system is further configured for regulating parameters related to said motor system to reduce energy consumption of said motor.

19. The system, as claimed in claim 1 1, wherein said system is further configured for eliminating inrush currents to said motor system.

20. The system, as claimed in claim 1 1, wherein said system is further configured for using at least one of a relay; or a switch to ensure that available power sources are not mixed.