EP0782163A2 - Hitzeaktivierbare elektrische Hilfsschalter - Google Patents
Hitzeaktivierbare elektrische Hilfsschalter Download PDFInfo
- Publication number
- EP0782163A2 EP0782163A2 EP96308920A EP96308920A EP0782163A2 EP 0782163 A2 EP0782163 A2 EP 0782163A2 EP 96308920 A EP96308920 A EP 96308920A EP 96308920 A EP96308920 A EP 96308920A EP 0782163 A2 EP0782163 A2 EP 0782163A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- bimetallic element
- switch apparatus
- electrical switch
- base plate
- thermally actuatable
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H61/00—Electrothermal relays
- H01H61/002—Structural combination of a time delay electrothermal relay with an electrothermal protective relay, e.g. a start relay
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B31/00—Compressor arrangements
- F25B31/02—Compressor arrangements of motor-compressor units
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H61/00—Electrothermal relays
- H01H61/002—Structural combination of a time delay electrothermal relay with an electrothermal protective relay, e.g. a start relay
- H01H2061/004—PTC resistor in series with start winding, e.g. adapted for being switched off after starting for limiting power dissipation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H37/00—Thermally-actuated switches
- H01H37/02—Details
- H01H37/32—Thermally-sensitive members
- H01H37/52—Thermally-sensitive members actuated due to deflection of bimetallic element
- H01H37/54—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting
- H01H37/5427—Thermally-sensitive members actuated due to deflection of bimetallic element wherein the bimetallic element is inherently snap acting encapsulated in sealed miniaturised housing
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H61/00—Electrothermal relays
- H01H61/02—Electrothermal relays wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively
Definitions
- This invention relates generally to electric motor starting and more specifically to apparatus for turning off a solid state motor starter after energization of the motor in order to conserve electrical energy.
- Solid state motor starting devices to start split phase electric motors.
- Such devices comprise a positive temperature coefficient of resistivity (PTC) element serially connected to the start winding of the motor.
- the PTC element has a low level of resistance upon energization allowing an inrush of current through the start winding.
- the resistance of the PTC element greatly increases effectively de-energizing the start winding.
- the PTC element remains in the high resistance, energized state maintaining the start winding off until the motor is de-energized. Although this is effective in starting the motor, it results in a continuous expenditure of energy in keeping the PTC element energized. For example, when used with refrigerator compressor motors approximately 2-2.2 watts of energy are consumed whenever the compressor motor is running. This energy consumption is undesirable and considered to be wasted.
- Another object of the invention is the provision of apparatus useful with a solid state motor starter which can minimize or even eliminate the expenditure of energy by the solid state motor starter once the motor is in the running condition.
- an auxiliary electrical switch made in accordance with the invention comprises an electrically conductive, generally U-shaped bimetallic blade having a high expansion layer on the outside and a first end mounted on an electrically conductive base plate.
- a movable contact is mounted on the high expansion layer at the second end aligned with, and at room temperature, in engagement with a stationary contact mounted on an electrically conductive stationary contact support.
- a thermal generator is disposed in heat conductive relationship with the bimetallic blade.
- the movable end stationary contacts are serially connected to the PTC element of the motor starter.
- the thermal generator in the form of a PTC pill, wire-wound resistor, composite resistor or the like, is disposed on the bimetallic blade and is electrically connected across the main winding of the motor.
- the PTC element of the motor starter allows current to flow through the start winding and then switches to a high resistance state effectively shutting off the start winding as the motor reaches normal running speed in approximately 0.5 to 1.0 second.
- Current also passes through the thermal generator of the auxiliary switch causing the bimetallic element to deflect at a time following the resistance increase of the PTC element moving the movable contact away from the stationary contact of the auxiliary switch thereby de-energizing the PTC element of the motor starter.
- the auxiliary switch contacts remain open as long as the main winding is energized consuming a low level of power, on the order of 0.5 watts or less.
- the auxiliary switch is thermally coupled to the discharge tube of a compressor which serves as the thermal generator.
- high pressure refrigerant gas being pumped through the compressor system provides heat energy through the discharge tube to raise the temperature of the bimetallic element to its actuation temperature to switch out the PTC element of the motor starter without the expenditure of further energy.
- a thermally actuatable, auxiliary electrical switch 10 made in accordance with the invention comprises a generally U-shaped bimetallic element 12 having a first end 14 mounted to base plate 16.
- Bimetallic element 12 is electrically conductive and has a high expansion side 12a on the outside and a low expansion side 12b on the inside of the U-shaped configuration.
- End 14 is attached to base plate 16, formed of any suitable electrically conductive material such as a nickel zinc coated steel, as by welding.
- a leg 24 extends upwardly from base plate 16, as seen in Fig. 1, with a platform 26 extending transversely therefrom.
- a movable electrical contact 28 is mounted on the high expansion side 12a at a second end 30 of bimetallic element 12 aligned with a stationary electrical contact 32 on the surface of platform 26 facing base plate 16.
- a thermal generator 34 is mounted in heat transfer relation with bimetallic element 12 as by mounting it directly thereon intermediate its first and second end utilizing a thermally conductive epoxy.
- Thermal generator 34 can be a PTC pill 36 as shown in Fig. 1, a wire-wound resistor 38 shown wrapped around a layer of electrically insulative material 40 disposed on bimetallic element 12, as shown in Fig. la, a composite resistor or any other thermal generating component.
- a first electrical lead 42 is connected to base plate 16 and a second electrical lead 44 is connected to stationary contact support 18 in any suitable manner, as by welding thereto.
- Electrical lead 46 is shown connected to one face surface of PTC pill 36 in a conventional manner with its opposite face surface electrically connected to bimetallic element 12. If desired, PTC pill 36 can be electrically isolated from element 12 and provided with a separate electrical lead for the opposite face surface.
- the auxiliary switch can be calibrated for opening temperature by bending platform 26 of stationary contact support 18 toward and away from base plate 16.
- auxiliary switch 10 is shown used with a split-phase motor comprising a main winding MW and start winding SW.
- a solid state motor starting device 50 comprising a PTC element is connected in series with start winding SW.
- Stationary contact 32 is serially connected to starting device 50 by means of lead 44 and movable contact 28 is connected to line L 2 by means of lead 42.
- Thermal generator 34 is connected across main winding MW, also connected across lines L 1 , L 2 .
- a motor protector 52 is provided in line L 1 .
- the PTC element of solid state starting device 50 At the time the motor is energized the PTC element of solid state starting device 50 is in a low resistance state allowing an inrush of current to flow through the start winding for a brief period of time, e.g., 0.5 to 1 second, to get the motor started and then switches to its high resistance state and effectively stops the flow of current through the start winding.
- starter 50 Without the use of auxiliary switch 10, starter 50 remains energized in the high resistance state dissipating approximately 2-2.2 watts of energy.
- the thermal generator 34 connected across the main winding starts to heat the bimetallic element 12 causing the bimetallic element to deflect at a time following the change in resistance of the starter 50 causing movable contact 28 to move out of engagement with stationary contact 32.
- a second embodiment of the invention is shown in which the entire power normally consumed by the solid state starter is conserved upon switching of the auxiliary switch 10'.
- generally U-shaped bimetallic element 12 which can be the same bimetallic element as that employed in the Fig. 1 embodiment, is mounted on and electrically connected to one leg 54 of a generally U-shaped base plate 16'.
- a stationary contact support 18' is crimped around second leg 56 of U-shaped base plate 16' with a layer 22 of electrically insulative material interposed therebetween.
- Layer 22 can be the same as that of the Fig. 1 embodiment.
- Movable contact 28, mounted on the high expansion side 12a of end 30 of bimetallic element 12 is aligned with and, at ambient temperature conditions, in engagement with stationary contact 32.
- Switch 10' is thermally coupled to the port of the discharge tube 60e of compressor system 60 shown in Fig. 4, electrically isolated from the tube, as by strapping bight portion 58 of base plate 16' thereto.
- refrigerator compressor system 60 comprises an evaporator 60a, compressor 60b, condenser 60c and expansion valve 60d coupled together as indicated by the arrows with auxiliary switch 10' thermally coupled to discharge tube 60e.
- the solid state starter At the time the circuit is closed in the refrigerator compressor system the solid state starter is in its low resistance state and allows current to flow through the start winding for approximately 0.5 to 1.0 second. The PTC element of the starter then switches to a high resistance state thereby decreasing current to a milliamp level, that is, effectively turning off the start winding. In this condition and without auxiliary switch 10', the PTC element of the solid state starter remains in the high resistance state dissipating approximately 2-2.2 watts the entire time that the compressor is running. However, with the auxiliary switch 10' mounted on the discharge tube the switch will disconnect the solid state starter from the circuit shortly after the compressor motor is energized, e.g., on the order of a few seconds for cycles following the initial cycle.
- the high pressure refrigerant gas being pumped through the compressor system causes the discharge tube to heat up so that the discharge tube serves as the thermal generator 34.
- the heat from the discharge tube is transferred to bimetallic element 12 raising its temperature to its actuation temperature to open contacts 28, 32 and switch out the solid state starter thereby saving the entire amount of energy, i.e., 2-2.2 watts, normally dissipated by the PTC element of the motor starter.
- a temperature profile of a refrigerator system employing an auxiliary switch made in accordance with the Fig. 3 embodiment is shown with curve a representing the temperature of the discharge tube, curve b the fusite header through which electrical connection to the system is made and curve c the temperature of the internal air of a housing mounting the motor starter and motor protector mounted on the fusite header. It will be seen that although the temperature excursion of the fusite header and the internal air is quite limited, the temperature level of the discharge tube cycles between approximately 38° C and 62° C as the compressor motor cycles between the unenergized and energized conditions under the control of a thermostat.
- Auxiliary switch 100 comprises a generally U-shaped bimetallic element 12 which again can be the same element as that employed in the embodiments described above.
- Bimetallic element 12 has one end attached to base portion 102, as by welding with its second end mounting movable electrical contact 28.
- Base portion 102 is integrally formed with a terminal 104 which is mounted on a housing member 106 formed of suitable electrically insulative material.
- Terminal 104 has downwardly extending legs 108 which are received in a slot 110 of a sidewall of housing 106.
- Legs 108 are formed with a locking portion 112 bent out of the plane in which the legs 108 lie which interact with a ledge 114 of the sidewall of housing 106 to lock the terminal in place.
- a stationary electrical contact support 116 is integrally formed with a second terminal 118 which is also provided with downwardly extending legs 120 for placement in another slot in a sidewall of housing 106 and is locked thereon using a corresponding locking portion 122.
- Stationary electrical contact 32 is attached to support 116 so that contacts 28, 32 are in alignment with one another.
- Housing 106 is formed with a cut-out 134 in bottom wall 136 so that leg 31 of bimetallic element 12 and heat sink plate 128 of clip 124 can be received therein for intimate thermal coupling with one another.
- Bimetallic element 12 and discharge tube 60e are electrically isolated from one another as by interposing a thin layer of electrically insulating material, such as Kapton, a trademark of DuPont de Nemours & Co. for polyimide (not shown) between heat sink plate 128 and leg 31.
- a cover 140 is received over housing 106 as shown in Fig. 6. Due to the arrangement of the components of switch 100, it can be readily assembled using mechanized techniques utilizing motion limited to vertical direction, i.e., an up-down motion as seen in Fig. 6.
Landscapes
- Thermally Actuated Switches (AREA)
- Motor And Converter Starters (AREA)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US886095P | 1995-12-19 | 1995-12-19 | |
US8860 | 1995-12-19 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0782163A2 true EP0782163A2 (de) | 1997-07-02 |
EP0782163A3 EP0782163A3 (de) | 1998-07-29 |
Family
ID=21734117
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96308920A Withdrawn EP0782163A3 (de) | 1995-12-19 | 1996-12-09 | Hitzeaktivierbare elektrische Hilfsschalter |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0782163A3 (de) |
JP (1) | JPH09180610A (de) |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1526932A (fr) * | 1965-12-02 | 1968-05-31 | Cambridge Instr Co Ltd | Améliorations aux commutateurs à commande électrique |
US3803525A (en) * | 1972-11-02 | 1974-04-09 | Gte Sylvania Inc | Temperature compensated fluid sensor |
GB2136217A (en) * | 1983-03-05 | 1984-09-12 | Danfoss As | Improvements in and relating to electric motor-driven compresser units |
EP0430662A2 (de) * | 1989-11-29 | 1991-06-05 | Texas Instruments Incorporated | PSC-Motor-Startsystem |
-
1996
- 1996-12-09 EP EP96308920A patent/EP0782163A3/de not_active Withdrawn
- 1996-12-18 JP JP33862496A patent/JPH09180610A/ja active Pending
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1526932A (fr) * | 1965-12-02 | 1968-05-31 | Cambridge Instr Co Ltd | Améliorations aux commutateurs à commande électrique |
US3803525A (en) * | 1972-11-02 | 1974-04-09 | Gte Sylvania Inc | Temperature compensated fluid sensor |
GB2136217A (en) * | 1983-03-05 | 1984-09-12 | Danfoss As | Improvements in and relating to electric motor-driven compresser units |
EP0430662A2 (de) * | 1989-11-29 | 1991-06-05 | Texas Instruments Incorporated | PSC-Motor-Startsystem |
Also Published As
Publication number | Publication date |
---|---|
JPH09180610A (ja) | 1997-07-11 |
EP0782163A3 (de) | 1998-07-29 |
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