DESC:FIELD
The present disclosure relates to the field of electrical machines. More particularly, the present disclosure relates to a single-phase brushless DC motor.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Brushless DC (BLDC) motors are becoming increasingly popular because they do away with wear-prone brushes used in traditional DC motors. However, due to the absence of brushes, there is no mechanical or electrical contact between the stator and rotor of the BLDC motor. Therefore, alternative arrangements are required to indicate the relative positions of the stator and rotor in order to facilitate motor control. Traditionally, BLDC motors are commutated in a six-step pattern with commutation controlled by position sensors such as a hall sensor. However, if the position sensor becomes faulty, entire motor needs to be opened to remove and replace the position sensor as the position sensor is mounted within the motor on the stator armature teeth. This makes the assembly and servicing of the driving circuit and the motor difficult. Thus, to reduce cost and complexity of the drive system, a sensorless drive is always preferred over sensored drives.
However, the existing sensorless control schemes with the conventional back EMF sensing for BLDC motors has certain drawbacks, which limit its applications. More specifically, the conventional single phase BLDC motors have a single copper winding that is wound on the stator armature. The winding is connected to a driving circuitry which includes 4 switches in an H-Bridge configuration. The commutation of motor is achieved by exciting the copper winding using the 4 switches (MOSFETs).
When such motor is designed for operating on high voltage DC, a sophisticated circuitry is required to run the high side switches. This increases the complexity as well as the cost of electronics. Further, a sophisticated microcontroller is required for generating Pulse Width Modulated (PWM) signals for firing the 4 MOSFETs present in the H-bridge driving circuit.
Therefore, there is felt, a need for a brushless DC motor that eliminates the above-mentioned drawbacks.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a single phase brushless DC motor.
Another object of the present disclosure is to provide a single phase brushless DC motor that works on a simple commutation logic.
Still another object of the present disclosure is to provide a single phase brushless DC motor that does not require a sophisticated driving circuitry for controlling the operation of high side switches.
Yet another object of the present disclosure is to provide a single phase brushless DC motor that does not require a sophisticated microcontroller for generating Pulse Width Modulated (PWM) signals for firing the switches present in the driving circuit.
Still another object of the present disclosure is to provide a single phase brushless DC motor with a driving circuit that includes only two switches.
Yet another object of the present disclosure is to provide a single phase brushless DC motor that is sensorless.
Still another object of the present disclosure is to provide a single phase brushless DC motor that eliminates the need of a hall sensor for sensing rotor position, thereby reducing wiring and installation cost and simplifying the motor assembly process.
Yet another object of the present disclosure is to provide a single phase brushless DC motor with improved reliability.
Still another object of the present disclosure is to provide a single phase brushless DC motor that is cost effective.
Yet another object of the present disclosure is to provide a method for driving a single phase brushless DC motor.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
In accordance with one aspect of the disclosure, there is provided a single phase Brushless DC (BLDC) Motor. The motor is adapted to be energized by a DC source. The motor comprises a rotor, a stator armature, a dual winding, and a driving circuit. The rotor includes permanent magnets which produce a permanent magnetic field. The dual winding is connected to the DC source and comprises a first coil and a second coil wound around the teeth of the stator armature in a bifilar manner. The driving circuit is configured to receive a real-time feedback of rotor position, and is further configured to generate, based on the received feedback, excitation signals to alternatively excite the first and second coils for establishing a first stator magnetic field of a first polarity and a second stator magnetic field of a second polarity alternatively. The first and second stator magnetic fields are configured to interact with the permanent magnetic field to generate a mechanical torque for rotor’s rotation.
In an embodiment, the driving circuit comprises a first switch, a second switch, and a control unit. The first switch is connected to the first coil. The second switch is connected to the second coil. The control unit is configured to receive the real-time feedback of back Electro-Motive Force (EMF) generated in one of the first and second coils that is unexcited for detecting the rotor position, and is further configured to generate the excitation signal for exciting the other coil of the first and second coils based on the received feedback. The first and second coils are wound in opposite directions to each other to facilitate generation of the first and second stator magnetic fields of opposite polarities. Each of the first and second switches is selected from the group consisting of a silicon controlled rectifier (SCR), an insulated gate bipolar junction transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), a field effect transistor (FET), a junction field effect transistor (JFET), a triode for alternating current (TRIAC), and an insulated gate field effect transistor (IGFET).
In an embodiment, the motor is a High Voltage (HV) BLDC motor. Alternatively, the motor can be a Low Voltage (LV) BLDC motor.
The present disclosure also envisages a method for driving a single phase Brush Less DC (BLDC) motor. The motor includes a permanent magnet rotor, a stator armature, and a first coil and a second coil wound around the teeth of the stator armature in a bifilar manner. The method comprises the following steps:
• determining, by a control unit, initial position of the rotor;
• exciting, by the control unit, the first and second coils alternatively based on the determined initial position, to run the motor in an open loop configuration, until the motor attains a pre-determined speed;
• receiving, by the control unit, a real-time feedback of the rotor position, subsequent to the attainment of the pre-determined speed; and
• alternatively exciting, by the control unit, the first coil and the second coil to run the motor in a closed loop configuration based on the received rotor position feedback.
In an embodiment, the step of receiving the real-time feedback of rotor position comprises sensing the back Electro-Motive Force (EMF) induced in one of the first and second coils that is non-excited.
In an embodiment, the step of determining initial position of the rotor comprises the following sub-steps:
• generating, by the control unit, momentary current pulses;
• alternatively applying, by the control unit, the momentary current pulses to the first and second coils to excite the first and second coils respectively; and
• measuring, by the control unit, rate of rise of current in each of the first and second coils after application of the current pulses to determine the initial positon of rotor.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
A single phase brushless DC motor of the present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a schematic view of a conventional single phase brushless DC motor;
Figure 2 a schematic view of a single phase brushless DC motor of the present disclosure; and
Figure 3 illustrates a flow diagram depicting steps involved in a method for driving a single phase Brush Less DC (BLDC) motor.
LIST OF REFERENCE NUMERALS
100, 200 – Single phase Brushless DC motor
102, 202 – Power source
104, 204 – Control unit
106, 206 – Permanent magnets
108, 208 – Rotor
110, 210 – Stator armature
112, 212 – Driving circuit
114 – Hall effect sensor
S1, S2, S3, S4, SW1, SW2 – Switches
Cl, Cl-1, Cl-2 – Stator Armature windings/coils
R – Resistor
DETAILED DESCRIPTION
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
When an element is referred to as being "mounted on," "connected to," or "coupled to" another element, it may be directly on, connected or coupled to the other element. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, or section from another element, component, or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Figure 1 illustrates a schematic view of a conventional brushless DC (BLDC) motor 100. The motor 100 includes a rotor 108 having permanent magnets 106, a stator armature 110, and a single copper winding Cl wound around the stator armature 110. The winding Cl is connected to the DC power source 102, which is generally a low voltage (LV) DC power source. To drive the motor 100, the polarity of the current through the winding Cl is changed at regular intervals. To change the polarity of current through the winding Cl, an H-bridge driving circuit 112 including 4 switches (S1, S2, S3, S4) is used. A hall effect sensor 114 is mounted on the stator armature teeth. A control unit 104 of the driving circuit 112 receives feedback of rotor position from the hall effect sensor 114. Based on the received rotor position feedback, the control unit 104 decides the instant of triggering the switches (S1, S2, S3, S4) to facilitate smooth operation of the motor 100. However, the switches (S1, S2, S3, S4) need to be excited using Pulse Width Modulated (PWM) signals. Further, a complicated driving circuitry 112 and a sophisticated control unit 104 (i.e. microcontroller) are required to operate the motor 100.
To overcome these problems, a single phase Brushless DC (BLDC) motor (hereinafter referred as “motor 200”), in accordance with one aspect of the present disclosure, is disclosed with reference to Figure 2. The motor 200 comprises a dual winding including two parallel coils wound around the stator armature 210 in opposite directions. Therefore, for changing the polarity of current through the stator 210, each of the windings are alternatively excited i.e. only one winding is excited at a time. Thus, the requirement of an H-bridge driving circuit 112 having 4 switches (S1, S2, S3, S4) is eliminated and only 2 switches (SW1, SW2) are required for exciting the two windings.
Referring to Figure 2, the BLDC motor 200 is adapted to be energized by a DC source 202. In an embodiment, the motor 200 is a High Voltage (HV) motor. Alternatively, the motor 200 is a Low Voltage (LV) motor. Accordingly, the DC source 202 can be a High Voltage or a Low Voltage source of power. The motor 200 comprises a rotor 208, the stator armature 210, the dual winding, and a driving circuit 212. The rotor 208 includes permanent magnets 206 to produce a permanent magnetic field. The dual winding is connected to the DC source 202 and comprises a first coil Cl-1 and a second coil Cl-2 wound around the teeth of the stator armature 210 in a bifilar manner. The dual winding is connected to the driving circuit 212 in such a way that current through each of the coils (Cl-1, Cl-2) of the dual winding flows in opposite direction and each coil (Cl-1, Cl-2) is controlled by the switch which is connected to it. Thus, only two switches (SW1, SW2) are required in the driving circuit 212 for driving the motor 200. In an embodiment, the dual winding may include 2 copper coils/wires (Cl-1, Cl-2) wound in parallel on the stator armature 210. The driving circuit 212 is configured to receive a real-time feedback of rotor position, and is further configured to generate, based on the received feedback, excitation signals to alternatively excite the first and second coils (Cl-1, Cl-2) for establishing a first stator magnetic field of a first polarity and a second stator magnetic field of a second polarity alternatively. The first and second stator magnetic fields are configured to interact with the permanent magnetic field to generate a mechanical torque for rotor’s rotation. The first and second coils (Cl-1, Cl-2) are wound in opposite directions to each other to facilitate generation of the first and second stator magnetic fields of opposite polarities. For example, in one configuration, the first coil Cl-1 is wound in a clockwise manner and the second coil Cl-2 is wound in an anti-clockwise manner.
In an embodiment, the driving circuit 212 comprises a first switch SW1, a second switch SW2 and a control unit 204. The first switch SW1 is connected to the first coil Cl-1 and the second switch SW2 is connected to the second coil Cl-2. Each of the first and second switches (SW1, SW2) is selected from the group consisting of a silicon controlled rectifier (SCR), an insulated gate bipolar junction transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), a field effect transistor (FET), a junction field effect transistor (JFET), a triode for alternating current (TRIAC), and an insulated gate field effect transistor (IGFET). The control unit 204 is configured to receive the real-time feedback of back Electro-Motive Force (EMF) generated in one of the first and second coils (Cl-1, Cl-2) that is unexcited for detecting the rotor position, and is further configured to generate the excitation signal for exciting the other coil of the first and second coils (Cl-1, Cl-2) based on the received feedback. Thus, only one coil (Cl-1, Cl-2) is excited at a point of time and the other coil is used to sense the rotor position. In an embodiment, the rotor position feedback is obtained by sensing the current through resistor R associated with either of the first and second coils (Cl-1, Cl-2) that is unexcited. The conventional BLDC motors require a hall effect sensor 114 to give rotor position feedback (information of magnet pole position) to the control unit 204. In contrast, in the present motor design only 2 switches (SW1, SW2) are sufficient to drive the motor 200. Since the stator windings are themselves used to sense the rotor position, the need of a hall sensor is eliminated. This reduces wiring and installation cost and also simplifies the motor assembly process.
Further, the dual winding provided on the stator armature 210 is designed in such a way that current in the first and second coils (Cl-1, Cl-2) is limited by the respective coil resistance. Therefore, the control unit 204 is only required to generate ON and OFF signals for triggering or firing the switches (SW1, SW2). This simplifies the design of the control unit 204, thereby eliminating the need for a sophisticated control unit/controller. In an embodiment, the control unit 204 is implemented using one or more processor(s). The processor may be a general-purpose processor, a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), and/or the like. The processor may be configured to retrieve data from and/or write data to a memory. The memory can be for example, a random access memory (RAM), a memory buffer, a hard drive, a database, an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), a read only memory (ROM), a flash memory, a hard disk, a floppy disk, cloud storage, and/or so forth.
In accordance another aspect of the present disclosure, referring to Figure 3, a method 300 for driving a single phase Brushless DC (BLDC) motor 200 is described. The motor 200 includes a permanent magnet rotor 208, a stator armature 210, and a first coil Cl-1 and a second coil Cl-2 wound around the teeth of the stator armature 210 in a bifilar manner. The initial rotor position i.e. the positon of rotor 208 when the motor 200 is at halt is not known. Therefore, the method 300 for driving the motor 200 comprises the following steps:
At Step 302, determining, by a control unit 204, the initial position of the rotor 208;
At Step 304, exciting, by the control unit 204, the first and second coils (Cl-1, Cl-2) alternatively based on the determined initial position, to run the motor 200 in an open loop configuration, until the motor 200 attains a pre-determined speed; and
At Step 308, receiving 308, by the control unit 204, a real-time feedback of the rotor position subsequent to the attainment of the pre-determined speed (Step 306); and
At Step 310, alternatively exciting, by the control unit 204, the first coil Cl-1 and the second coil Cl-2 to run the motor 200 in a closed loop configuration based on the received rotor position feedback.
In an embodiment, the step of receiving the real-time feedback of rotor position comprises sensing the back Electro-Motive Force (EMF) induced in one of the first and second coils (Cl-1, Cl-2) that is non-excited. Thus, in the closed loop configuration, the voltage induced from flux coupling in a non-excited coil is sensed to detect the rotor position.
In an embodiment, the step of determining the initial position of the rotor 208 comprises the following sub-steps:
• generating, by the control unit 204, momentary current pulses;
• alternatively applying, by the control unit 204, the momentary current pulses to the first and second coils (Cl-1, Cl-2) to excite the first and second coils (Cl-1, Cl-2) respectively; and
• measuring, by the control unit 204, rate of rise of current in each of the first and second coils (Cl-1, Cl-2) after application of the current pulses to determine the initial position of rotor 208.
In an embodiment, the step of measuring rate of rise of current in each of the coils (Cl-1, Cl-2) to determine the initial rotor position comprises the following sub-steps:
o receiving, by a crawler and extractor unit of the control unit 204, the measured current rise rates for each of the first and second coils (Cl-1, Cl-2);
o crawling, by the crawler and extractor unit, through a lookup table having pre-determined current rise rates associated with the coils (CL-1, Cl-2) and rotor position associated with each of the current rise rates; and
o extracting, by the crawler and extractor unit, rotor position associated with the received current rise rates from the lookup table.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a single-phase brushless DC motor that:
• works on a simple commutation logic;
• does not require a sophisticated driving circuitry for controlling the operation of switches;
• does not require a sophisticated microcontroller for generating Pulse Width Modulated (PWM) signals for firing the switches present in the driving circuit;
• whose driver circuit that includes only two switches;
• is sensorless;
• eliminates the need of a hall sensor for sensing rotor position, thereby reducing wiring and installation cost and simplifying the motor assembly process;
• has improved reliability; and
• is cost-effective.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments 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.
The foregoing description of the specific embodiments 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 embodiments as described herein.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.
,CLAIMS:WE CLAIM:
1. A single phase Brushless DC (BLDC) Motor (200) adapted to be energized by a DC source (202), said motor (200) comprising:
i. a rotor (208) including permanent magnets (206) to produce a permanent magnetic field;
ii. a stator armature (210);
iii. a dual winding connected to said DC source (202) and comprising a first coil (Cl-1) and a second coil (Cl-2) wound around the teeth of said stator armature (210) in a bifilar manner; and
iv. a driving circuit (212) configured to receive a real-time feedback of rotor position, and further configured to generate, based on said received feedback, excitation signals to alternatively excite said first and second coils (Cl-1, Cl-2) for establishing a first stator magnetic field of a first polarity and a second stator magnetic field of a second polarity alternatively, said first and second stator magnetic fields configured to interact with said permanent magnetic field to generate a mechanical torque for rotor’s rotation.
2. The BLDC motor (200) as claimed in claim 1, wherein said driving circuit (212) comprises:
i. a first switch (SW1) connected to said first coil (Cl-1);
ii. a second switch (SW2) connected to said second coil (Cl-2); and
iii. a control unit (204) configured to receive the real-time feedback of back Electro-Motive Force (EMF) generated in one of said first and second coils (Cl-1, Cl-2) that is unexcited for detecting said rotor position, and further configured to generate said excitation signal for alternatively exciting the other coil of said first and second coils (Cl-1, Cl-2) based on said received feedback.
3. The BLDC motor (200) as claimed in claim 1, wherein each of said first and second switches (SW1, SW2) is selected from the group consisting of a silicon controlled rectifier (SCR), an insulated gate bipolar junction transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), a field effect transistor (FET), a junction field effect transistor (JFET), a triode for alternating current (TRIAC), and an insulated gate field effect transistor (IGFET).
4. The BLDC motor (200) as claimed in claim 1, which is a Low Voltage (LV) BLDC motor.
5. The BLDC motor (200) as claimed in claim 1, which is a High Voltage (HV) BLDC motor.
6. The BLDC motor (200) as claimed in claim 1, wherein said first and second coils (Cl-1, Cl-2) are wound in opposite directions to each other to facilitate generation of said first and second stator magnetic fields of opposite polarities.
7. A method (300) for driving a single phase Brush Less DC (BLDC) motor (200), said motor (200) having a permanent magnet rotor (208), a stator armature (210), and a first coil (Cl-1) and a second coil (Cl-2) wound around the teeth of said stator armature (210) in a bifilar manner, said method (200) comprising:
i. determining (302), by a control unit (204), the initial position of said rotor (208);
ii. exciting (304), by said control unit (204), said first and second coils (Cl-1, Cl-2) alternatively based on said determined initial position, to run said motor (200) in an open loop configuration, until said motor (200) attains a pre-determined speed;
iii. receiving (308), by said control unit (204), a real-time feedback of the rotor position, subsequent to the attainment of said pre-determined speed; and
iv. alternatively exciting (310), by said control unit (204), said first coil (Cl-1) and said second coil (Cl-2) to run said motor (200) in a closed loop configuration based on said received rotor position feedback.
8. The method (300) as claimed in claim 7, wherein the step of receiving said real-time feedback of rotor position comprises sensing the back Electro-Motive Force (EMF) induced in a non-excited coil of said first and second coils (Cl-1, Cl-2).
9. The method (300) as claimed in claim 7, wherein the step of determining the initial position of said rotor (208) comprises the following sub-steps:
i. generating, by said control unit (204), momentary current pulses;
ii. alternatively applying, by said control unit (204), said momentary current pulses to said first and second coils (Cl-1, Cl-2) to excite said first and second coils (Cl-1, Cl-2) respectively; and
iii. measuring, by said control unit (204), rate of rise of current in each of said first and second coils (Cl-, Cl-2) after application of said current pulses to determine the initial positon of rotor (208).