FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
PROVISIONAL SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
Brushless DC ceiling fan
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTORS
Alakkal Kizhakkethil Sivadas of Crompton Greaves Ltd CG Global R&D Centre, Kanjur (E), Mumbai 400042 Maharashtra, India, an Indian National.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention :

FIELD OF INVENTION
This invention relates to a BLDC motor driven ceiling fan. This invention also relates to a control unit for BLDC motor.
BACKGROUND OF INVENTION
Ceiling fans are generally induction motor, a DC motor or brushless DC motor driven. Induction motor driven fans are used where an alternating current (AC) power supply is available and is very common across the world.
A DC motor driven fan is used where a direct current (DC) power supply, from a battery or from non-conventional energy source such as solar power or any other type of power source is available which is stand alone or other wise. This is very common at remote areas or when normal AC power supply is not available due to any reason. A BLDC motor driven fan can be used on either a DC power supply or normal AC power supply with suitable and minor changes in settings in the associated control circuit. These kinds of fans are preferred as they have advantages like reduced power consumption, higher performance and controllability and increased life. A BLDC motor driven ceiling fan includes a control unit to sense the rotor polarity and energize corresponding set of coils in the stator windings. The control unit comprises a hall sensor based circuit and a switching and protection circuit. These are incorporated in two printed circuit boards (PCB).
PCB with the sensor circuit is of shape and size matching with the stator slot geometry, is inserted and locked in position. PCB with switching and protection circuit is attached to a suitable holder which is turn is fixed to the motor at the lower end of the fan shaft. All the above electronic circuit in two PCBs are disposed within the motor housing. Sensor PCB is connected to the control and switching PCB by


means of a set of five wires and a connector. Motor windings are connected to the control and switching PCB by means of another set of wires and cables. External power supply is connected to the control and switching PCB by a long wire as usual from the main power line.
PCB is attached to the motor shaft using a screw and tightening the same. This screw can get loosened due to vibration when the fan is under operation. Improper installation of fan adds to vibration and in turn loosening of the PCB mounting. As the space available within the fan is limited, loosened PCB and the wires attached to it can get entangled with the rotating member and cause damage and burning of fan. This affects the reliability of the fan.
Interconnection of sensor PCB to the control and switching PCB is made using long wires. This has to be done with additional care and needs to be properly tied during assembly. This causes extra assembly time and need of long cables and adds to cost. Sensor PCB is inserted in the stator slots in the initial stage of assembly. Winding needs to be varnished for protection and better heat transfer which in turn ensures higher insulation life. In this case, stator winding with sensor PCB introduces a limitation in varnish process. As hall sensors can not be subjected to higher temperature during varnishing and subsequent curing process, special air drying at normal ambient temperature is required to be used. This increases the process time substantially and increases the over all cost.
OBJECTS OF INVENTION
An object of the invention is to provide a BLDC motor driven ceiling fan which is simple in construction and which comprises a control unit which is fully located


within the motor housing and which, besides possessing the various advantages of a BLDC motor driven ceiling fan, also has further advantages.
Another object of the invention is to provide a BLDC motor driven ceiling fan which comprises reduced number of components, which reduces assembly and installation time, which is compact, free from fitment errors, reliable and user friendly, which is noise free in operation and which reduces the cost considerably.
Another object of the invention is to provide a control unit which is compact and reduces the cost considerably.
DETAILED DESCRIPTION OF THE INVENTION
According to the invention there is provided a BLDC motor driven ceiling fan comprising a control unit comprising an electronic controller comprising a printed circuit board (PCB), the PCB being disposed within the motor housing and fixed to the stator pack, the control unit further comprising hall sensors which get located in the stator slots, the stator windings and hall sensors being connected to the PCB which in turn is connected to a power supply.
According to the invention there is also provided a control unit for a BLDC motor, the control unit comprising an electronic controller comprising a printed circuit board (PCB) incorporating sensing, switching and protection circuit, the PCB being disposed within the motor housing and fixed directly to the stator, the PCB further comprising hall sensors which gets located in stator slots, the stator windings being connected to the PCB which in turn is connected to a power supply.


According to the invention, ceiling fan is driven by BLDC motor. Motor housing comprises upper and lower end shields rotatably held onto the fan shaft. Top end shield has two bearings held in the bearing- housing with a spacer between them. Fan blades are fixed to top end shield. The upper end of the fan shaft is fixed to the lower end of the down rod of the fan. The upper end of the down rod is fixed to the shackle of the fan. Stator with windings is directly attached to the shaft. Stator is provided with a circular holes suitably spaced and the PCB is attached directly to the stator using a holder. Holder has multiple latches or snaps, protruding down, which will get engaged in the corresponding circular holes on the PCB. Electronic controller PCB is thus well supported and attached directly to the stator. Stator windings are connected to the electronic controller by means of small wires and a connector. The stator comprises a mounting bracket provided with a centre slot corresponding to the lower end of the fan shaft and a plurality of spaced first upright support members and a plurality of spaced second upright support members at the upper surface thereof, each of the upright support members being provided with an upwardly tapered lateral extension at the upper end thereof, the PCB is provided with a plurality of spaced through openings as equally spaced as the upright support members, the PCB being disposed around the lower end of the fan shaft and supported at the upper ends of the upright support members with the upright support members engaged in the openings in the PCB and the tapered lateral extensions abutting against the upper surface of the PCB. The control unit of the ceiling fan comprises 1,2 or 3 hall sensors. Hall sensors are an integral part of the PCB. On assembly hall sensors assume its position directly in the stator slot. The two lead wires for connecting the electronic controller to the AC


mains, are taken up through the hollow fan shaft and hollow down rod. During operation of the fan, depending upon the polarity of the rotor as sensed by the hall sensors, the electronic controller energizers the corresponding set of coils in the stator windings to control the rotation of the ceiling fan.
According to the invention, sensor circuit, control, switching and protection circuit are all integrated into a single PCB and is fully located in the motor housing. Electronic controller does not require any protective casing as it is housed within the motor. Wires for interconnection between hall sensors and PCB are eliminated. Electronic control unit is attached directly and firmly to the stator itself, eliminating the possibility of loosening and wire entangling, on operation. Size of shaft is considerably less. Size of fan is smaller and is compact. Electronic controller and the fan is more reliable. Need of special air drying varnish during process is eliminated as pre-varnished stator can be used directly. This reduces process time and cost. Fan does not require any additional efforts for installation. Number of hardware used in the motor for controller mounting is zero.
Configuration of PCB holder can vary. Hall sensors can be one or multiple. This can be used for any other application other than ceiling fan. Such variations in the configuration and construction of the invention are obvious to those skilled in the art and the scope of the invention is to be construed and understood to be accordingly.