US2468693A - Thermal relay - Google Patents

Thermal relay Download PDF

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Publication number
US2468693A
US2468693A US551405A US55140544A US2468693A US 2468693 A US2468693 A US 2468693A US 551405 A US551405 A US 551405A US 55140544 A US55140544 A US 55140544A US 2468693 A US2468693 A US 2468693A
Authority
US
United States
Prior art keywords
thermal
heat
relay
tripping
thermal relay
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.)
Expired - Lifetime
Application number
US551405A
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English (en)
Inventor
Stoecklin Josef
Kach Alfred
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BBC Brown Boveri AG Germany
Original Assignee
Bbc Brown Boveri & Cie
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Bbc Brown Boveri & Cie filed Critical Bbc Brown Boveri & Cie
Application granted granted Critical
Publication of US2468693A publication Critical patent/US2468693A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H37/00—Thermally-actuated switches
    • H01H37/004—Thermally-actuated switches with thermal image

Definitions

  • thermal image designates a device which has the same time-temperature characteristics as the electrical equipment to be protected when the device is heated by the current supplied to, or proportional to the current supplied to, the electrical equipment.
  • This image is generally of the samekind as the protected object itself but reproduced to a smaller scale and in a simplified form.
  • time-temperature' curve of electrical machines, apparatus and the like is not a uniform exponential curve, but during the heating resulting from increasing current, the slope of the time-temperature curve of the equipment passes from a higher to a lower value. This condition must also be satisfied by the thermal relay if it is to afford the intended protection in dependence upon the magnitude and previous mode of variation of the power current.
  • both the thermal tripping member and the heat-storing masses of the thermal image are heated in common by a resistance which is fed by a current proportional to the power current of the equipment to be protected, and the trippin member is combined into a block with the heat-storing masses and the heating resistance; heat insulation of the same or different heat transmission, as may be required, being arranged between the heating resistance and respectively, the tripping member and the heat-storage masses to obtain a displacement of the tripping member in accordance with the temperature of the electrical apparatus to be protected.
  • Fig. 1 is a somewhat schematic view ⁇ of a thermal relay embodying the invention
  • Fig. 2 is a transverse section through the thermal relay as taken on line 2-2 of Fig. 1.
  • a current proportional to the power current of an electrical apparatus which is to be protected, for instance an electrical machine, is developed by a current transformer a and flows through a fiat strip or ribbon-shaped heating resistance b.
  • the resistance strip b is a single inverted U-shaped loop in an open-ended duct 0, and this loop extends around the tripping member d which comprises a series of reversely bowed bimetallic plates which absorb a part of the heat developed by the heating resistance. The remainder of the developed heat is absorbed by the metal plate e; and the end wall of an open-ended metal frame 9 which form the boundary walls of the duct 0, the heating resistance I) being spaced from the duct walls by sheets of insulation f1.
  • Sheets of insulation f2 are located between the heating resistance b and the tripping member d.
  • Interchangeable heat storage plates ez of different mass are held in contact with the heated wall of the frame g by a spacer or filler plate u, and the block assembly of the heating resistance b and heat-absorbing members is encased within the metallic housing h which limits the escape of heat to the surrounding atmosphere.
  • the block assembly is supported by bars 7' of low heat conductivity which are secured to a frame or base plate, not shown.
  • the total mass and the composition of the heat-storage plates 62 are selected in accordance with the time-temperature characteristic of the protected apparatus under various loadings.
  • the inner metallic frame g is a fixed part of the thermal relay which, with the metal plate e1, has a constant heat-absorbing and heat-radiating characteristic that may be modified, as desired, by the introduction of heat-absorbing plates es of difierent mass.
  • the thermal tripping member 11 actuates over the axle i and the gear sector It a differential gearing l, m, 12 whose differential wheels I, m are provided with pointers.
  • the pointer on the free wheel 1 indicates continuously on a scale the temperature of the protected object, whilst the wheel m and its pointer can be adjusted by hand to the desired tripping temperature.
  • the thermometer pointer on the wheel I can be provided with a maximum indicator pointer not shown in the drawing for the purpose of indicatin the maximum temperature reached.
  • the planet wheel 12 causes the tilting-lever o of switch p to turn and when the tripping temperature is reached this lever passes its dead centre and closes the release contact p. If the protected object becomes warm during no-load, for instance a transformer, then this no-load heating can be taken into account on the scale of the thermometer by malting the scale of the latter commence only at noload heating.
  • the lower support of the tripping member is connected with the bearing of the axle i by means of a rigid arm q, so that any displacement of the tripping member d within the conduit 0 has no effect on the temperature indication and tripping temperature.
  • the heating current in the resistance b can be adjusted by means of the variable shunt r to the desired value. It is also expedient to provide the usual compensation for the variable ambient temperature; this has not been shown in the drawing in order not to complicate the figure unnecessarily.
  • an electro-magnetic tripping relay s is connected in series with the resistance b, this relay having two pairs of contacts one of which lies parallel to the tripping contact p of the thermal relay, whilst the other pair short-circuits the heating resistance b when the electro-magnet s is attracted.
  • This limit-current release can of course also occur with a delayed action.
  • the entire relay together with all the accessories is as usual enclosed in a casing t. Thermal and limit-release can be indicated by a common signal or by separate signals of the acoustical or optical kind either through a window in the casing t or at a remotely located spot.
  • the thermal image with the thermal relay according to the invention is not at the same time a mechanical reproduction of the protected object.
  • This possesses the advantage that the same relay can be used for different types of protected objects.
  • a thermal relay for the protection of electrical apparatus of dififerent types and having a preselected time-temperature characteristic, when energized by a current proportional to the current supplied to a particular electrical apparatus, which is substantially identical with the time-temperature characteristic of said particular electrical apparatus; said thermal relay comprising thermal tripping means, heat storage means, heating resistance means in heat-transfer relation to both said thermal tripping means and said heat storage means, layers of heat insulation ping means and heat storage means to limit the radiation of heat therefrom; said heat storage means including a metal body constituting a minimum heat storage mass, and interchangeable metal plates in thermal contact with said metal body to increase the total heat storage mass to a magnitude which develops said predetermined time-temperature characteristic.
  • heating resistance means includes parallel fiat strip resistors extending along opposite sides of and separated from said thermal tripping means by certain of said layers of heat insulation material.

Landscapes

  • Breakers (AREA)
  • Thermally Actuated Switches (AREA)
US551405A 1942-12-31 1944-08-26 Thermal relay Expired - Lifetime US2468693A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH574077X 1942-12-31

Publications (1)

Publication Number Publication Date
US2468693A true US2468693A (en) 1949-04-26

Family

ID=4521093

Family Applications (1)

Application Number Title Priority Date Filing Date
US551405A Expired - Lifetime US2468693A (en) 1942-12-31 1944-08-26 Thermal relay

Country Status (6)

Country Link
US (1) US2468693A (enrdf_load_stackoverflow)
BE (1) BE455388A (enrdf_load_stackoverflow)
CH (1) CH238409A (enrdf_load_stackoverflow)
FR (1) FR901804A (enrdf_load_stackoverflow)
GB (1) GB574077A (enrdf_load_stackoverflow)
NL (1) NL118498C (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2497684A (en) * 1947-09-18 1950-02-14 Gen Electric Protective system for dynamoelectric machines
US2881289A (en) * 1956-06-18 1959-04-07 Gen Motors Corp Circuit control
US3077776A (en) * 1959-02-13 1963-02-19 Westinghouse Electric Corp Thermal indicator for electrical apparatus
US3460397A (en) * 1967-10-02 1969-08-12 Nasa Mechanical actuator

Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1281482A (en) * 1914-06-15 1918-10-15 Baruch Electric Controller Corp Electric-circuit protector.
US1308048A (en) * 1919-07-01 Assioncb
US1429660A (en) * 1918-02-01 1922-09-19 Motor Protector Mfg Company Thermal relay
US1477455A (en) * 1917-04-18 1923-12-11 Westinghouse Electric & Mfg Co Electrical system
US1699752A (en) * 1925-03-26 1929-01-22 Westinghouse Electric & Mfg Co Thermal relay
US1728038A (en) * 1922-08-14 1929-09-10 Gen Electric Automatic circuit controller
US1834375A (en) * 1930-12-19 1931-12-01 Westinghouse Electric & Mfg Co Close control thermostat
US1917163A (en) * 1931-04-30 1933-07-04 Gen Electric Temperature indicator
GB412082A (en) * 1932-10-13 1934-06-21 Walter Stahel Bimetallic element
US2056040A (en) * 1934-02-15 1936-09-29 Gen Electric Control system
US2372498A (en) * 1942-05-06 1945-03-27 Gen Electric Control system

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1308048A (en) * 1919-07-01 Assioncb
US1281482A (en) * 1914-06-15 1918-10-15 Baruch Electric Controller Corp Electric-circuit protector.
US1477455A (en) * 1917-04-18 1923-12-11 Westinghouse Electric & Mfg Co Electrical system
US1429660A (en) * 1918-02-01 1922-09-19 Motor Protector Mfg Company Thermal relay
US1728038A (en) * 1922-08-14 1929-09-10 Gen Electric Automatic circuit controller
US1699752A (en) * 1925-03-26 1929-01-22 Westinghouse Electric & Mfg Co Thermal relay
US1834375A (en) * 1930-12-19 1931-12-01 Westinghouse Electric & Mfg Co Close control thermostat
US1917163A (en) * 1931-04-30 1933-07-04 Gen Electric Temperature indicator
GB412082A (en) * 1932-10-13 1934-06-21 Walter Stahel Bimetallic element
US2056040A (en) * 1934-02-15 1936-09-29 Gen Electric Control system
US2372498A (en) * 1942-05-06 1945-03-27 Gen Electric Control system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2497684A (en) * 1947-09-18 1950-02-14 Gen Electric Protective system for dynamoelectric machines
US2881289A (en) * 1956-06-18 1959-04-07 Gen Motors Corp Circuit control
US3077776A (en) * 1959-02-13 1963-02-19 Westinghouse Electric Corp Thermal indicator for electrical apparatus
US3460397A (en) * 1967-10-02 1969-08-12 Nasa Mechanical actuator

Also Published As

Publication number Publication date
BE455388A (enrdf_load_stackoverflow)
GB574077A (en) 1945-12-19
CH238409A (de) 1945-07-15
FR901804A (fr) 1945-08-07
NL118498C (enrdf_load_stackoverflow)

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