US3583173A

US3583173A - Electric refrigeration and air-conditioning protection circuit

Info

Publication number: US3583173A
Application number: US867320A
Authority: US
Inventors: Roger F Chesebro
Original assignee: FRASER AND JOHNSTON CO
Current assignee: YORK-LUXAIRE Inc A CORP OF DE; FRASER AND JOHNSTON CO
Priority date: 1969-10-17
Filing date: 1969-10-17
Publication date: 1971-06-08
Anticipated expiration: 1988-06-08

Abstract

An electric refrigeration compressor protection circuit to prevent restarting of the compressor motor until after a predetermined minimum time after each stopping of the compressor motor comprising a timer motor and timer switch having its contacts in series with the room thermostat, compressor overload switches and the energizing coil of a compressor contactor switch in a low voltage control circuit and with means responsive to the energization of the compressor motor to stop the timer motor and with the timer contacts arranged to be normally opened but closed only momentarily at spaced time intervals during operation of the timer motor.

Description

United States tet Inventor Roger F. Chesebro Bay Village, Ohio Appl. No. 867,320

Filed Oct. 17, 1969 Patented June 8, 1971 Assignee Fraser & Johnston Company San Lorenzo, Calif.

ELECTRIC REFRIGERATION AND AIR- CONDITIONING PROTECTION CIRCUIT Primary Examiner-Meyer Perlin A!t0meysF. H. Henson and F. E. Blake ABSTRACT: An electric refrigeration compressor protection circuit to prevent restarting of the compressor motor until after a predetermined minimum time after each stopping of the compressor motor comprising a timer motor and timer switch having its contacts in series with the room thermostat, compressor overload switches and the energizing coil of a compressor contactor switch in a low voltage control circuit and with means responsive to the energization of the compressor motor to stop the timer motor and with the timer contacts arranged to be normally opened but closed only momentarily at spaced time intervals during operation of the timer motor.

COM PRESSOR PATENTEDJUH 8197i 3583.173

COMPRESSOR u FIG.2 c g l8 l9 I 2: lo l6 H3] 21 I5 26 [F COMPRESSOR f7 24 23 25 I 22 l 1 l l INVENTOR Roger F Chesebro ATTORNEY ELECTRIC REFRIGERATION AND AIR-CONDITIONING PROTECTION CIRCUIT CROSS-REFERENCES TO RELATED PATENT APPLICATIONS BACKGROUND OF THE INVENTION Protective circuits for electric refrigeration and air-conditioning systems are well known and they often employ a form of timing device to prevent immediate restarting of the compressor until after a predetermined time interval during which the system pressures can equalize. In recent years the timing device has been in the form of a timer motor switch which runs either intermittently or continuously. In any event, the timer switch contacts are subject to considerable usage and it is therefore desirable to provide the most simple and reliable timer switch contact structures as possible. Also, the application of the timer switch contacts in the protection circuit should be such as to minimize their periods of operation and also minimize the possibilities of arcing and welding of the contacts during operation so as to prolong the life of both the timer switch contacts and the timer motor.

DESCRIPTION OF THE PRIOR ART Reference may be made to the following listed U.S. Pats. which disclose prior arrangement of timer switches in the protection circuits for electric refrigeration or air-conditioning compressor motors:

No. 2,276,369 to Buchanan, issued Mar. l7, I942;

No. 2,967,977 to McNicol et al., issued Jan. I0, I961;

No. 3,054,271 to McGrath et al., issued Sept. 18, 1962.

SUMMARY OF THE INVENTION In accordance with the present invention. the timer switch contacts which are normally open but momentarily closed at spaced time intervals while a timer motor connected thereto is running, are connected in the low voltage control circuit in series with the control switch or thermostat, the normally closed overload switches, and the compressor contactor switch coil. The timer motor is connected to be energized and operated only when the compressor motor is not energized and operating and for such purpose a simple relay with normally closed contacts in series with the timer motor and a source of current may be connected with its operating coil in parallel with the compressor motor or in such other circuit arrangements as would be responsive to the energization of the compressor motor to stop the running of the timer motor. Thus the compressor contactor switch can be closed and the compressor motor energized only when all of the thermostat, timer switch and overload switches are enclosed. It will be noted that the timer motor is at the same time stopped while the compressor motor is running. Thereafter, when the compressor motor stops due to the opening of either the thermostat or overload switches, the timer motor restarts to open the timer switch and to prevent the restarting of the compressor motor until after the lapse of at least a predetermined minimum time interval when the timer switch contacts may be again momentarily closed. Since the timer motor runs only when the compressor motor is not running and since the timer switch contacts are simple single-pole make and break contacts connected in the low voltage control circuit, long timer switch life with a minimum chance of switch contact arcing and welding is assured.

Further features and advantages of the invention will be apparent with reference to the following specification and drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. II is a schematic wiring and diagram of the preferred form of the invention with the switch contacts shown in the positions assumed when the compressor motor is not running and the timer motor is running;

FIG. 2 is a schematic wiring diagram similar to FIG. 1 but showing the switch contacts in their positions assumed when the compressor motor is running and the timer motor is not running; and

FIG. 3 is a fragmentary schematic wiring diagram showing a modified form of the invention in which the timer motor is energized from the low voltage source instead of from the high voltage source as shown by FIGS. 1 and 2 of the drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. I and 2 of the drawing, the compressor motor I0 is adapted to be connected and energized to be operated from the high voltage source terminals 11 and [2 whenever the

contactor switch contacts

13 and 14 are closed upon the energization of the contactor coil IS. The contactor coil 15 is connected to be energized from the low voltage control source at

terminals

16 and 17 through a series circuit including normally closed

overload switch contacts

18 and 19 and normally open timer switch contacts 20. The thermostatic control switch 21 is also connected in the series circuit including the timer switch 20 and the

overload switches

18 and 19. The normally opened timer switch contacts 20 are periodically and momentarily closed at spaced time intervals in response to the rotation of the switch actuating cam 22 which causes the cam projection 23 to reciprocate the switch contact operating rod 24 upwards to momentarily close the switch contact 20.

The timer cam 22 is rotated by the operation of the timer motor 25 which may be connected to a suitable source of current through the normally closed relay contacts 26. As shown by FIGS. I and 2 of the drawing the timer motor 25 is connected through the normally closed relay contacts 26 to the high voltage source terminals II and 12 but in the modified form of the invention shown by FIG. 3 of the drawing the timer switch motor 25 is connected through the normally closed contacts 26 to the low voltage source terminals 16 and I7. Either arrangement of connection for energizing the timer motor 25 may be used depending upon the desired operating voltage for the timer motor 25.

The normally closed relay contacts 26 are connected to be opened whenever the relay coil 27 is energized and the relay coil 27 is connected in parallel with the compressor motor 10 so as to be energized simultaneously therewith whenever the contactor coil 15 is energized to close the contact switches 13 and I4 and energize the compressor motor 10. Thus the timer motor 25 is connected to be running only when the compressor motor 10 is not running and vice versa. Although a simple circuit including the relay coil 27 and normally closed relay contacts 26 has been specifically shown for purposes of preventing the operation of the timer motor whenever the compressor motor 10 is running, it should be obvious that various other circuit arrangements known to those skilled in the art could be used to obtain the desired function of the timer motor 25 to be running whenever the compressor motor 10 is not running.

The operation of the protective circuit of the invention will now be described again with reference to FIGS. 1 and 2 of the drawing. When the control switch or thermostatic switch 21 is closed because of a demand for refrigeration or cooling as shown by FIG. 2 of the drawing, the compressor contactor coil 15 can be energized only when the normally closed

overload switches

18 and 19 are also closed and the timer switch contact 21 is momentarily closed. At such time with the compres sor contactor coil 15 thus energized, the contactor switches 13 and 14 will close to energize both the compressor motor 10 and the relay coil 27 to open the normally closed relay contacts 26 and stop the timer motor 25 with the cam 23 holding the timer switch contacts 2] closed. Thereafter the compressor motor 10 may continue to run until such time as either the thermostatic control switch 21 opens or, in the event of trouhle, an overload switch contact l8 or l9 may open. When any of the switches l8 and I) or 2| open to deenergize the compressor contaetor coil 15 and open the contaetor switches 13 and I4 to stop the compressor motor 10, the relay coil 27 will he deenergized to close its normally closed relay contacts 26 and again start the timer motor 25 to run thus opening the timer switch contact 20 as shown by FIG. I of the drawing. Should thereafter either the thermostat control switch 21 or the

overload switches

18 and 19 immediately reclose such as might occur by a chattering of thermostat switch contacts or by unusual operation of the overload switches l8, 19, the compressor motor can nevertheless not immediately restart because the timer switch contacts 20 have opened and remain open while the timer motor 25 is running until the timer contact operating cam 23 again reaches the position shown by FIG. 2 of the drawings to momentarily reclose the timer contact switch 20. l have found that a suitable time interval of about 6 minutes for a single rotation of the timer switch cam 22 will assure equalization of the system pressures before the contaetor coil can again be energized to close the contactor switches l3, l4 and rcoperate the compressor motor 10. However, this invention is not limited to any predetermined minimum time between the momentary closures of the timer switch while the timer motor 25 is operating.

It should now be understood that a simple and reliable protective circuit is obtained in that the timer switch contact 20 is a simple single-pole make and break switch operating in a low voltage circuit where there will be a minimum possibility for contact arcing and welding. In addition the arrangement of the invention wherein the timer motor 25 is operated only when the compressor motor 10 is not operated, minimizes the duty cycle for the timer motor 25 so as to obtain extremely long motor lifetime in application.

Various modifications will occur to those skilled in the art.

l claim as my invention:

1. A control circuit for a refrigeration system having an electric motor driven refrigerant compressor comprising, a first source of relatively high voltage, electric current adapted for energizing said compressor motor, a second source of relatively low voltage electric current adapted for control purposes, a contaetor having normally open contacts and a coil to be energized to close its normally open contacts, means connecting said compressor motor in series with said normally open contacts to said first source, a control switch and a normally open timer switch connected in series with said second source and said contaetor coil to energize said contaetor coil when all of said switches are closed, an electric timer motor,

means responsive to connect and energize to operate said timer motor from one of said sources only when said compressor motor is not energized, and means connecting said timer motor shaft to said timer switch in a manner to momentarily close said normally open timer switch at predetermined spaced time intervals during operation of said timer motor whereby to energize said contaetor coil and said compressor motor when both said timer and control switch are closed, said timer motor being subsequently reenergized to open said timer switch and prevent a subsequent reenergization of said contaetor coil and compressor motor until at least a predetermined time interval after said compressor motor has been deenergized responsive to opening of any of said series connected switches.

2. The invention of claim 1 in which the means responsive to energize and operate said timer motor is a relay having a coil connected to be energized by the energizing circuit for said compressor motor, said relay having normally closed contacts connected in circuit with said timer motor and said first source of electric current to thereby energize said timer motor only when said compressor motor and said relay coil are deenergized.

3. The invention of claim 2 in which at least one compressor overload responsive normally closed switch is connected in the series circuit with said control switch and said timer switch.

4. The invention of claim 1 in which the means responsive to energize and operate said timer motor is a relay having a coil connected to be energized by the energizing circuit for said compressor motor, said relay having normally closed contacts connected in circuit with said timer motor and said second source of electric current to thereby energize said timer motor only when said compressor motor and said relay coil are deenergized.

5. The invention of claim 4 in which at least one compressor overload responsive normally closed switch is connected in the series circuit with said control switch and said timer switch.

6. The invention of claim 1 in which at least one compressor overload responsive normally closed switch is connected in the series circuit with said control switch and said timer switch.

7. The invention of claim 6 in which said control switch is a thermostatic responsive control switch.

8. The invention of claim 1 in which said control switch is a thermostatic responsive control switch.

Claims

1. A control circuit for a refrigeration system having an electric motor driven refrigerant compressor comprising, a first source of relatively high voltage electric current adapted for energizing said compressor motor, a second source of relatively low voltage electric current adapted for control purposes, a contactor having normally open contacts and a coil to be energized to close its normally open contacts, means connecting said compressor motor in series with said normally open contacts to said first source, a control switch and a normally open timer switch connected in series with said second source and said contactor coil to energize said contactor coil when all of said switches are closed, an electric timer motor, means responsive to connect and energize to operate said timer motor from one of said sources only when said compressor motor is not energized, and means connecting said timer motor shaft to said timer switch in a manner to momentarily close said normally open timer switch at predetermined spaced time intervals during operation of said timer motor whereby to energize said contactor coil and said compresSor motor when both said timer and control switch are closed, said timer motor being subsequently reenergized to open said timer switch and prevent a subsequent reenergization of said contactor coil and compressor motor until at least a predetermined time interval after said compressor motor has been deenergized responsive to opening of any of said series connected switches.