Pumps – Condition responsive control of pump drive motor – Having timer or delay means
Reexamination Certificate
2000-03-30
2001-11-20
Freay, Charles G. (Department: 3746)
Pumps
Condition responsive control of pump drive motor
Having timer or delay means
C417S015000, C417S417000, C417S053000
Reexamination Certificate
active
06318966
ABSTRACT:
BACKGROUND OF THE INVENTION
I. Field of Invention
The present invention is directed to a heating, ventilation, and air-conditioning system and more particularly relates to a method and system for controlling the stage of a compressor motor and/or fan motor of a heating, ventilation, and air-conditioning system. Preferably, the motor for at least one of the components is a reversible motor that reverses when the power connections to the run winding and start winding are switched.
II. Description of the Related Art
Conventional single phase alternating current induction motors for driving compressors are connected to a source of power by a line contactor. Electric motors typically include a stator which is wound with a start winding and run winding connected to the source of power. The stator winding surrounds the motor which rotates a shaft to produce the motor output. In circuit with the run winding and the start winding are a run capacitor and a start capacitor, respectively. In capacitor start motors, start circuits are connected in parallel with a run winding of each speed of the multi-speed motor. The start circuits include a start winding which is connected in series with start capacitors. During a motor start, both the run winding and the start winding are connected across the motor's power source to magnetically excite the rotor and cause rotation. The start winding and start capacitor combination is used to provide the high torque required during typical start conditions. However, the capacitance necessary to start the motor is typically too large for optimum motor efficiency during normal operation. Therefore, a switch or start relay is usually connected in series with a start capacitor and is used to disengage the start circuit when the motor has reached a predetermined speed or after a predetermined time has elapsed.
When the normally closed start relay deenergizes, the start relay contacts close. If the start relay contacts should happen to open when the run capacitor is fully charged, there is a large amount of energy stored in the run capacitor that can be discharged into the start capacitor when the start relay contactor is closed. There is sufficient power to weld the start relay contacts and thus disable the relay for the next operation.
In view of the foregoing, traditional compression motors are connected to a source of power by a line contactor. Furthermore, traditional compressor motors include a start winding, a run winding, a start capacitor, and a run capacitor. Moreover, certain heating, ventilation, and air conditioning systems include a conventional compressor motor, as described above, and a fan motor and a capacitor for the fan motor. Consequently, compressor motors and the associated components for heating, ventilation, and air conditioning systems may operate in higher power environments and may require higher cost.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method and system for controlling a compressor, preferably a two stage compressor that operates in a first stage when the motor rotates in one direction and operates in a second stage when the motor rotates in the reverse direction.
An object of advantage of the present invention is to provide an improved system and method of motor control that overcomes or minimizes one or more of the limitations and disadvantages of the presently available control systems and methods for such compressors and heating, ventilation, and air conditioning (hereinbelow HVAC) systems.
Among other things, the invention reduces the number and cost associated with controlling a two stage compressor by, for example, requiring only one contactor for the application of line power to the condenser fan and compressor motor; implementing a single dual run capacitor for the condenser fan and compressor motor; utilizing a minimum of industry standard components; eliminating the need for a separate condenser fan relay; and using simple control logic. Under the present invention, the power connections to the start winding and run winding of the motor for the compressor are reversed, to thereby change the power characteristics and reverse the motor rotation, by standard, inexpensive relays that are switched when the contactor is open, thereby removing power from the relays and motor windings during this switching. The contactor is preferably open for a sufficient period of time to allow the motor to stop rotating and to ensure that no high currents are applied to the relays during the switching. Preferably, most, if not all, of the components can be placed into a standard sized control box of the HVAC system.
Additional features and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and advantages of the invention may be realized and attained by the system and method particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a method for controlling a two stage, reversible compressor, such as the Bristol Twin Single compressor. Compressors of this type and their use and application are explained in detail in U.S. patent application Ser. No. 09/133,841, filed on Aug. 13, 1998 and entitled “Two Stage Reciprocating Compressors and Associated HVAC Systems and Methods,” and in U.S. patent application Ser. No. 09/235,288, having a filing date of Jan. 22, 1999, and entitled Variable Capacity Compressor Having Adjustable Crankpin Throw Structure, both of which applications are hereby incorporated by reference. Such compressors operate at a first stage when the motor rotates in one direction and at a second stage when the motor rotates in a reverse direction. By means of example, such a compressor with two cylinders may reciprocate the pistons in both cylinders at one stage and will reciprocate only one piston at the other stage. Such a compressor having a single cylinder will reciprocate the piston at full stroke when the motor rotates in one direction and at a lesser stroke (e.g. half stroke) when the motor rotates in the other direction.
The method for controlling the motor of a compressor, such as the Bristol Twin Single compressor, with a system of the present invention includes switching at least one contactor connected to a source of line power to remove the source of line power to a set of relays and to a compressor motor containing a run winding, a start winding, and a common lead; and controlling the set of relays by switching the set of relays to provide the source of line power to permit switching the source of line power to either the run winding or the start winding, wherein prior to the controlling, the at least one contactor removes the source of line power from the set of relays; and waiting a predetermined period of time before performing the controlling.
Also in accordance with the present invention, there is provided a system for controlling an HVAC system with a compressor, such as the Bristol Twin Single compressor. The system includes, preferably, a compressor motor; a fan motor; an electronic controller; a contactor controlled by the electronic controller, wherein the electronic controller determines whether to apply a source of line power to the contactor and the system; and a dual-run capacitor for operating the two-stage reversible compressor and the fan motor.
In yet another embodiment of the present invention, there is provided a computer readable medium containing computer software, which, when run on a computer causes the computer to provide apparatus for controlling the motor of a compressor. The apparatus includes means for switching of at least one contactor connected to a source of line power to remove the source of line power to a set of relays and to a compressor motor containing a run winding, a start winding, and a commo
Madara Steven M.
Rayburn Ronald R.
Tran Johnthinh N.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Freay Charles G.
Gray Michael K.
York International Corporation
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