Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
1999-05-21
2001-04-10
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S375000, C318S434000, C388S907500, C388S928100
Reexamination Certificate
active
06215261
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to electronically controlled motors and to systems, such as heating, ventilating and/or air conditioning systems having motors therein operating according to predetermined parameters which are field selected by an OEM or installer before installation in order to correspond to the system in which the motor is to be installed.
DESCRIPTION OF THE PRIOR ART
While conventional brush-commutated DC motors may have advantageous characteristics, including convenience of changing operation speeds, there may be disadvantages such as brush wear, electrical loss, noise and radio frequency interference caused by sparking between the brushes and the segmented commutator, and overall material cost of the motor.
These disadvantages may limit the applicability of such brush-commutated DC motors in many fields, including the refrigeration, heating, ventilating and/or air conditioning (HVAC) fields. Electronically commutated motors, such as brushless DC motors and permanent magnet motors with electronic commutation, have now been developed and generally are believed to have the advantageous characteristics of brush-commutated DC motors without many of the disadvantages thereof while also having other important advantages. Such electronically commutated motors are disclosed in the David M. Erdman U.S. Pat Nos. 4,015,182 and 4,459,519, for instance. Such electronically commutated motors may be advantageously employed, for instance, in HVAC systems which employ variable speed motors.
Present motors have a variety of features and operational and system parameters which must be adjusted to optimize performance by providing a proper speed-torque characteristic for a particular application. Further, in many system applications, the starting torque and/or speed-torque characteristics of the motors must be predictable and repeatable. In addition, it is desirable that motors be operable at optimum efficiency consistent with mass production techniques. Known present variable speed motors cannot easily achieve this advantage because it has traditionally been impractical or too costly to minimize the variable effect on motor characteristics caused by manufacturing tolerances of the internal components of the motor. Present concepts and arrangements for adjusting a motor for different applications require circuit changes such as multiple variable resistors in the electronic control for the motor or permanent software changes in an electronic control microprocessor. Both of the aforementioned arrangements are disadvantageous because they require a unique model to be built for calibrating a system which cannot be easily changed and can be quite expensive.
U.S. Pat. No. 5,592,058 issued Jan. 7, 1997 is entitled “Control System and Methods for a Multiparameter Electronically Commutated Motor” by W. Archer , R. Becerra, B. Beifus, and M. Brattoli. The disclosure of this patent is incorporated by reference herein in its entirety. This patent is an example of an ASIC controlled motor which is programmable. There is a need for such a motor which uses insulated gate bipolar transistors. In addition, there is a need for such a motor which extends the motor safe operating area without the loss of synchronism at high speed and high torque. There is also the need for such a motor which provides better performance at start up and during asymmetric back emf waveforms.
SUMMARY OF THE INVENTION
The invention meets the above needs and overcomes the deficiencies of the prior art by providing: a system which permits interfacing defined parameters or characteristics of a motor with a memory associated with a control for an electronically commutated motor; a system which permits interfacing a system control signal with a motor control for the motor; a system which permits calibrating a motor control to actual characteristics or operating parameters of a motor while driving a known load; a system which permits calibrating the motor to a known load; a system which permits calibrating a motor control to motor characteristics under a no load condition; a motor controlled by a microcontroller via an application specific integrated circuit which controls insulated gate bipolar transistors for selectively energizing the motor windings; a system which permits sensing the position of a rotor of the motor for controlling torque and speed of the motor; a system which permits sensing asymmetric back electromotive force in a winding of the motor for sensing the position of the rotor and for controlling the motor in response thereto; a system which permits selecting varied frequencies of pulse width modulation for controlling the motor; a system which permits limiting current in the windings of the motor to a reference level; a system in a manner which is economically feasible and commercially practical; a system with an overcurrent circuit which provides a fast protection response and a tighter control of the overcurrent activation level and which provides a substitute for the costly and less accurate implementations of overcurrent protection circuits in the prior art; and a dynamic braking feature that reduces audible noise of a rotor driven blower/fan at coast down.
In one form, the invention comprises a motor for use with a power supply comprising a stator, a rotor in magnetic coupling relation to the stator, a plurality of inverter powers switches (IVPs), a user interface for providing user signals indicative of one or more desired operating parameters of the motor, a microcontroller and a high voltage silicon ASIC. Each switch has a control input port and is connected between the stator and the power supply for selectively applying power to the stator in response to a control signal applied to the control input port. The microcontroller has control inputs receiving the user signals and having low voltage output ports for providing low voltage output signals for commutating the stator as a function of the user signals. The high voltage silicon application specific integrated circuit (ASIC) has low voltage input ports connected to the low voltage output ports of the microcontroller and has high voltage output ports connected to the control input ports of the IVPs. The ASIC provides high voltage control signals via its high voltage output ports which high voltage control signals in response to the low voltage output signals provided by the microcontroller.
In another form, the invention comprises a motor for use with a power supply. A rotor is in magnetic coupling relation to a stator. A plurality of switches each have a control input port. The switches are connected between the stator and the power supply for selectively applying power to the stator D in response to a control signal applied to the control input port. A user interface provides user signals indicative of one or more desired operating parameters of the motor. A microcontroller has control inputs receiving the user signals and has low voltage output ports for providing low voltage output signals for commutating the stator as a function of the user signals. An application specific integrated circuit (ASIC) commutates the stator as a function of the low voltage output signals. The ASIC comprises a back emf sensing circuit connected to the stator providing a position signal indicative of the position of the rotor relative to the stator, wherein the back emf sensing circuit provides a zero crossing signal indicative of zero crossings of the back emf signal and wherein the ASIC includes an estimating circuit for commutating the windings as a function of the previous commutation interval between two consecutive zero crossings.
In another form, the invention comprises a motor for use with a power supply such as a voltage source inverter. A stator has a winding having three phases. A rotor is in magnetic coupling relation to the stator. A plurality of switches each has a control input port, the switches being connected between the stator and the power supply for selectively applying power to the stator in response to a control sig
General Electric Company
Ro Bentsu
Senniger Powers Leavitt & Roedel
Wasserbauer Damian
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