Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
1999-10-14
2001-04-03
Masih, Karen (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S803000, C318S801000, C318S798000, C318S800000, C318S802000, C318S811000
Reexamination Certificate
active
06211635
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a brushless motor driving system for driving an outdoor fan of an air conditioner.
BACKGROUND OF THE INVENTION
Recently, many brushless motors have been used to drive outdoor fans to be installed in the outdoor unit of air conditioners. Even if not driven by motor, the outdoor fan may be rotating by wind, at different rotational directions and speeds. When an outdoor fan happens to be rotating, first, the fan should be applied with brake, stopped and set to home position to start the motor, before the operation of the air conditioner is started.
Normally, the brushless motor necessitates a sensor to detect the present rotor position, that is, the position of the magnetic pole. When braking to stop and setting the outdoor fans to home position, actual rotational direction and speed of the fan are identified based on the output of the sensor, and current is supplied into the stator coil according to the detection data. With the driving systems according to the prior art, however, they used one unit of Hall probe for each phase, that is, three in total, as position sensor, thus causing a complicated control, resulting in high cost.
On the other hand, with the driving systems according to the prior art, when braking to stop and setting to home position, DC current is supplied into stator coil, thus resulting in a possibility of demagnetizing the permanent magnet forming the rotor, or of an excessive current being supplied to destroy the driving circuit for energizing stator coil.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a brushless motor driving system for driving an outdoor fan of an air conditioner, which can make an easier control for braking, stopping and setting to home position of the outdoor fan driven by brushless motor, even if being rotated by external causes such as wind.
It is another object of the invention to provide a brushless motor driving system for driving an outdoor fan of an air conditioner, which can be started without applying excessive load to the driving circuit and the motor, and with minimized demagnetization of the permanent magnet.
To achieve the above-mentioned objects, the first aspect of the present invention provides a brushless motor driving system for driving an outdoor fan of an air conditioner comprising;
a single Hall probe for detecting the position of a rotor of a brushless motor for driving the outdoor fan of the air conditioner.
The driving system also includes an inverter circuit consisting of six switching elements connected in three-phase bridge connection, DC terminals of the inverter circuit being connected to a main DC power source, AC terminals of the inverter circuit being connected to star-connected stator coils of the brushless motor.
The driving system also includes control means for controlling the switching elements in the inverter circuit in synchronization with the output signal from the Hall probe. The control means includes DC excitation means.
Before starting the brushless motor, the DC excitation means controls one switching element of one phase of a positive or negative side of the inverter circuit and switching elements of the other two phases of the other side to supply a PWM-controlled DC current to the stator coils of the motor, thereby bringing the rotor to brake and stop at the home position.
The above DC excitation means can switch current conduction phases to others every time when the Hall probe detects the predetermined magnetic pole position of the rotor, thus resulting in a minimized demagnetization of the permanent magnet.
The above DC excitation means switches current conduction phases to others every time when the Hall probe detects the predetermined magnetic pole position of the rotor, thus resulting in a minimized demagnetization on the permanent magnet.
The DC excitation means controlls the duty of the PWM-current according to the rotational speed of the motor based on the magnetic pole position detection signal of the Hall probe. This configuration can speedily bring the rotor to stop while suppressing a possible demagnetization of the permanent magnet.
The inverter circuit comprises a plurality of driving circuits for driving the switching elements individually, an auxiliary DC power supply for directly supplying operating electric power to the negative side of the driving circuits, and a plurality of capacitors each of which is parallel connected to a corresponding one of the positive side driving circuits and is charged up by the auxiliary DC power supply through the negative side switching element of the same phase, the DC excitation means applies PWM-control to the positive side switching elements. The DC excitation means may be better to make PWM-control of the positive side of the switching elements. This configuration can suppress a possible voltage drop of the capacitors to be charged up.
The second aspect of the invention provides a brushless motor driving system for driving an outdoor fan of an air conditioner comprising;
a single Hall probe for detecting the position of a rotor of a brushless motor for driving the outdoor fan of the air conditioner.
The driving system also includes an inverter circuit consisting of six switching elements connected in three-phase bridge connection, DC terminals of the inverter circuit being connected to a main DC power source, AC terminals of the inverter circuit being connected to star-connected stator coils of the brushless motor.
The driving system also includes control means for controlling the switching elements in the inverter circuit in synchronization with the output signal from the Hall probe, where the control means includes zero vector conduction means.
Before starting the brushless motor, the zero vector conduction means turns either one of all of the positive side switching elements and all of the negative side switching elements to on-state and the other to off-state, thereby bringing the rotor to brake and stop at -the home position. This configuration can obtain not only an easier control of braking, stopping and setting to home-position to be made before starting, even if the fan is rotating by external causes, but also an improvement to reduce power consumption.
The third aspect of the invention provides a brushless motor driving system for driving an outdoor fan of an air conditioner comprising;
a single Hall probe for detecting a position of a rotor of a brushless motor for driving the outdoor fan of an air conditioner.
The driving system also includes an inverter circuit consisting of six switching elements connected in three-phase bridge connection, DC terminals of the inverter circuit being connected to a main DC power source, AC terminals of the inverter circuit being connected to star-connected stator coils of the brushless motor.
The driving system also includes control means for controlling the switching elements in the inverter circuit in synchronization with the output signal from the Hall probe, where the control means including DC excitation means.
Before starting the brushless motor, the DC excitation means controls the switching elements in combination of first and second control modes to brake the rotor to stop. The first control mode makes either one of all of the positive side switching elements and all of the negative side switching elements to on-state and the other to off-state, for an either one switching element of one phase of a positive or negative side of the inverter circuit and the other side of the other two-phase. The second control mode applies a PWM-control to either one of the one-phase and two-phase switching elements, and a continuous conduction control to the other. This configuration can have not only an easier stop control for braking, stopping and setting to home position, even if the fan is rotating by external causes, but also a starting operation without applying excessive load to the driving circuit and the motor, and with suppressed demagnetization of permanent magnet.
The control means detects the rotational
Kambe Takayuki
Miyazaki Hiroshi
Takuma Junichi
Toshi Tomoaki
Foley & Lardner
Masih Karen
Toshiba Carrier Corporation
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