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(11) | EP 1 113 476 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Electronic trip unit with a rating plug for circuit breakers, which has a switchable motor and line protection function |
| (57) A circuit breaker (10) is rendered more versatile by providing an electronic trip
unit (34) having more than one algorithm embedded in the software thereof to function
as either a line protector or a motor protector. The rating plugs (40) of the invention
may either be switchable between line and motor protection or the rating plugs may
simply include a particular jumper thus enabling the circuit breaker to be converted
from line to motor or motor to line based upon the rating plug selected. Whether the
rating plug is switchable or the non-switchable jumper-type rating plugs of the invention
are being employed the electronic trip unit and current transformer need not be changed
in order to change the function of the circuit breaker between line protection and
motor protection. |
[0001] The invention relates to the field of power distribution systems. More particularly, the invention relates to circuit breakers easily switchable between line protection and motor protection functions.
[0002] Circuit breakers are used to protect equipment for overcurrent situations caused for example by short circuits in or near such equipment. In the event an overcurrent condition occurs the circuit breaker will open resulting in the separation of contacts therein ending current flow. Circuit breakers open in a number of ways including magnetic fields, temperature, and by computerized systems commonly known as electronic tripping units which include software, running a particular algorithm to detect a particular undesirable current condition. When such condition is matched, the electronic tripping unit causes the circuit breaker to open. There are many different types of devices that can be protected by circuit breakers and circuit breakers themselves are unique to the intended function thereof. In one example, one type of circuit breaker would be designed and built to function as a line protection device while another type of circuit breaker would be designed and built to function as a motor protection device. The electronic tripping units employed with each of these circuit breakers are different and each employ distinct software and algorithms. Additionally the current transformers are usually replaced together with a trip unit. In the older prior art distinct circuit breakers would need to be employed for each different type of function and for each different circuit breaker rating. In order to reduce the number of components in stock, it is known to provide a plurality of different rating plugs which are connectable to a single circuit breaker and electronic trip unit in order to change the rating of the circuit breaker without disassembly of the entire circuit breaker. Such rating plugs work well for their intended purpose and enable quick and easy changing of ratings in the circuit breakers with which they are intended to be used. The art still requires however that completely distinct circuit breakers be employed for line protection functions and for motor protection functions. In order to change a particular circuit from line protection to motor protection, the entire circuit breaker would need to be replaced or the electronic trip unit and current transformers would need to be replaced after disassembly of the circuit breaker.
[0003] A circuit breaker of the invention includes a contact arm tripable by an electronic tripping unit operably connected to the contact arm. The electronic tripping unit preferably includes at least two independently selectable trip algorithms and a rating plug having a switch in communication with said electronic tripping unit, or a jumper enables rapid "in-the-field" selection between the at least two algorithms for selective functions.
[0004] An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a circuit breaker of the invention; and
Figure 2 is an exploded view of a portion of the interior components of the circuit breaker of the invention illustrating the relative position of the components providing the benefits of the invention.
[0005] Referring to Figure 1, a perspective view of a circuit breaker 10 of the invention is depicted. The breaker 10 includes a housing base 12 and a housing cover 14 each of which are conventional. A contact arm (not shown) is disposed within circuit breaker 10. Also visible in the drawing is a switch handle 16 recognizable by one of ordinary skill in the art. In an engagement area 18, the circuit breaker 10 provides for the connection electrically and mechanically of an electronic trip unit, a current transformer assembly and a rating plug. These are discussed hereunder in connection with Figure 2. The configuration illustrated in Figure 1 is familiar to those of skill in the art.
[0006] For clarity in understanding the invention, each of several conventional components are identified. Detailed discussion of these components is not necessary as they are well known to those of skill in the art.
[0007] Referring to Figure 2, a conventional current transformer carrier 20 carries current transformers 22 (illustrated as three in the drawing although four is also a preferred arrangement for the invention). Each current transformer 22 provides a load lug 24 for connection of the circuit breaker to a desired electrical connection (not shown). Current transformer carrier 20 and the current transformer 22 are received within engagement area 18 as is known to one of ordinary skill in the art. For completeness, a push-to-trip assembly comprising components 26, 28, 30 and 32 which is conventional is illustrated. In the invention, an electronic trip unit 34 is mounted to carrier 20 on pins 36. The particular physical attributes of electronic trip unit 34 are known to the art since all of the hardware used therein is conventional. The software in electronic trip unit 34 is, however, distinct from the prior art since the completed circuit breaker 10 of the invention is to be easily switchable from a line protection circuit breaker to a motor protection circuit breaker. Electronic trip unit 34 (ETU) therefore includes at least two algorithms, one of which is directed to a motor protection function and one of which is directed to a line protection function. The circuit breaker 10 is thus capable of performing either function and need only be "told" which function to undertake.
[0008] Still referring to Figure 2, a rating plug 40 includes an electronics assembly 42 with preferably two switches 44a and 44b. Each of which preferably includes a knob 46 for ease of turning of switches 44a and 44b. Plug 40 further includes housing 48 and but for the additional switches are similar in structure to the prior art. Rating plugs of the prior art have employed one switch directed to the rating of the breaker (or in some cases two switches where one is a ground fault interruption); the invention provides two switches, one of which is adapted to select between two algorithms in the electronic trip unit 34 to determine the function (line protection or motor protection) of the breaker and the other of which is adapted to set the desired rating of the circuit breaker. The rating switch preferably provides 32 gradations from .4x to 1x of the breaker fixed rating Ict for each of line protection and motor protection. The 32 gradations are made up of 16 gradations at 63% (0.4x to 0.63 x Ict) and 16 gradations at 100% (0.625 to 1x Ict) of the Ict for each of line protection and motor protection. The settings at 63% and 100% are switchable at one switch while the 16 positions are at the other switch. Since 32 gradations are available for each of line protection and motor protection it will be understood that 64 total settings are possible in the rating plug of the invention without disassembly. It will be understood that the nominal current rating In for the breaker as set by the rating plug is dictated by In < Ict. The rating plug is connectable to the electronic tripping unit through an opening 50 in electronic tripping unit housing 52. Rating plug 40 is protected by and accessible rating plug cover 54 which engages with cover 14 of circuit breaker 10 when in the completed condition. Because the rating plug 40 is accessible and is capable of switching the circuit breaker function simply and easily. The invention further reduces necessary components for the manufacturer to stock since a single breaker and trip unit can be readily adapted to function as a line protector or a motor protector.
[0009] In another embodiment of the invention, not specifically shown, the rating plug 40 may dispense with switches in favor of jumpers. In a jumper rating plug application, the rating plug is removed and another installed when function or nominal current rating is desired to be changed. This embodiment of the invention still greatly simplifies function changeover since it avoids time consuming disassembly and replacement of electronic tripping units and current transformers.
1. A function changeable circuit breaker (10) comprising:
an electronic tripping unit (34) having at least two independently selectable trip algorithms therein; and
a rating plug (40) having a switch (44) in communication with said electronic tripping unit (34), said switch (44) selecting between each of said at least two algorithms.
2. A function changeable circuit breaker (10) comprising:
an electronic tripping unit (34) having at least two independently selectable trip algorithms therein; and
a rating plug (40) having a jumper selecting one of said at least two algorithms.
3. A circuit breaker (10) comprising:
a contact arm;
an electronic tripping unit (34) operably connected to said contact arm;
an electronic tripping unit (34) having at least two independently selectable trip algorithms therein; and
a rating plug (40) having a switch (44) in communication with said electronic tripping unit (34), said switch (44) selecting between each of said at least two algorithms.
4. An interchangeable trip and rating system for a circuit breaker (10) comprising:
an electronic tripping unit (34) having at least two independently selectable trip algorithms therein;
a rating plug (40) having a switch (44) in communication with said electronic tripping unit (34), said switch (44) selecting between each of said at least two algorithms.
5. A function changeable circuit breaker (10) as claimed in claim 1 wherein said at least
two algorithms include one algorithm directed to a line protection function and one
algorithm directed to a motor protection function.
6. A function changeable circuit breaker (10) as claimed in claim 1 wherein said rating
plug includes two switches (44a, 44b)).
7. A function changeable circuit breaker (10) as claimed in claim 6 wherein said two
switches (44a, 44b) control a selection between said at least two algorithms and a
rating of said circuit breaker (10).
8. A function changeable circuit breaker (10) as claimed in claim 7 wherein said selection
of rating of said circuit breaker (10) provides 32 rating levels.
9. A function changeable circuit breaker (10) as claimed in claim 2 wherein said rating
plug (40) includes a switch (44) to select among 32 rating levels for said circuit
breaker.
10. A circuit breaker (10) comprising:
a contact arm;
an electronic tripping unit (34) operably connected to said contact arm;
a software program embedded in said electronic tripping unit (34), said software program having at least two individually;
an electronic tripping unit (34) having at least two independently selectable trip algorithms therein; and
a rating plug (40) having a jumper selecting one of said at least two algorithms.