Circuit breaker and undervoltage release of a circuit breaker

Abstract

Undervoltage release (5) of a circuit breaker (1), comprising undervoltage release (5) - a capacitor storage device (7) designed to store a trigger energy (15), - a trip unit (9) which is configured to activate a trip unit (3) to switch off the circuit breaker (1) when the trip energy (15) is supplied to the trip unit (9), and - a monitoring unit (13) configured to monitor an auxiliary voltage (19) and to supply the release energy (15) stored by the capacitor storage (7) to the release unit (9) when the auxiliary voltage (19) falls below a threshold value stored by the monitoring unit (13), with a charging unit (11) configured to charge the capacitor storage (7), wherein the monitoring unit (13) is configured to control the charging unit (11).

Description

[0001] The invention relates to an undervoltage release of a circuit breaker.

[0002] Circuit breakers are used for switching high electrical currents, especially overload and short-circuit currents. For this purpose, a circuit breaker has at least one switching contact that can move between an on position and an off position.

[0003] A circuit breaker requires an auxiliary voltage to operate, which is used, among other things, to trigger switching operations. If this auxiliary voltage fails or falls below a certain threshold, the circuit breaker can no longer be operated correctly. For safety reasons, the circuit breaker is switched off in such cases by an undervoltage release. Standards specify the auxiliary voltages at which the undervoltage release must and must not trip. For example, standards stipulate that the circuit breaker must be switched off if the auxiliary voltage drops below 35% of the rated auxiliary voltage, while the undervoltage release, on the other hand, must not trip at auxiliary voltages above 70% of the rated auxiliary voltage. In this example, the undervoltage release is permitted to switch off the circuit breaker in the range between 70% and 35% of the rated auxiliary voltage.

[0004] For each auxiliary voltage variant, suitable releases must be selected and tested for that auxiliary voltage, including a tolerance. These variants are qualified and approved in type tests. For example, nominal auxiliary voltages of 24 V, 48 V, 60 V, 110 V, 125 V, 220 V, and 250 V are defined for DC voltages and 120 V, 220 V, 230 V, 240 V, 277 V, 347 V, 480 V, and 600 V for AC voltages. Thus, in this example, a maximum of fifteen different nominal auxiliary voltages result. In the worst-case scenario, fifteen variants of undervoltage releases must then be selected for a medium-voltage circuit breaker type. As part of the qualification process, each of these variants is tested at the nominal auxiliary voltage, an undervoltage, and an overvoltage. This results in 45 qualification tests.

[0005] Conventional undervoltage releases store the necessary tripping energy in a spring. A permanently energized release uses an electromagnet, which incorporates a trip coil, to keep the spring tensioned and releases the spring in the event of a power failure or insufficient auxiliary voltage. This releases the spring and trips the circuit breaker. Such an undervoltage release presents several challenges. A balance of forces must be maintained between the permanently energized release and the spring to reliably prevent tripping of the undervoltage release under varying operating conditions, such as across a temperature range and during vibrations. Furthermore, the release requires a constant power supply, which causes it to heat up. Temperature changes alter the resistance of the trip coil.Additionally, continuous current causes self-heating. This directly alters the holding force, further complicating the design. Alternatively, the holding current would have to be regulated electronically to compensate for temperature effects. Furthermore, depending on the duration of current application, the components of the magnetic circuit become more strongly magnetized, leading to greater variations in the holding force after switching off and thus to greater variations in the triggering behavior.

[0006] US patent 2014 / 0218838 A1 discloses an electromagnetic drive with an undervoltage release.

[0007] The invention is based on the objective of providing an improved undervoltage release for a circuit breaker.

[0008] The problem is solved according to the invention by an undervoltage release having the features of claim 1 and a circuit breaker having the features of claim 12.

[0009] Advantageous embodiments of the invention are the subject of the dependent claims.

[0010] An undervoltage release of a circuit breaker according to the invention comprises - a capacitor storage device designed to store trigger energy, - a trip unit which is configured to activate a trip unit to switch off the circuit breaker when trip energy is supplied to the trip unit, and - a monitoring unit which is set up to monitor an auxiliary voltage and supply the energy stored by the capacitor storage to the triggering unit when the auxiliary voltage falls below a threshold value stored by the monitoring unit.

[0011] Furthermore, the undervoltage release includes a charging unit designed to recharge the capacitor storage. This allows the capacitor storage to be recharged after the undervoltage release has been triggered, and its charge level can be maintained at a constant level. The monitoring unit also controls the charging unit. This allows the monitoring unit to track the charge level and capacity of the capacitor storage and, if necessary, issue an error message.

[0012] The undervoltage release according to the invention stores tripping energy for activating a switching unit to disconnect the circuit breaker in a capacitor. Unlike, for example, an undervoltage release with an electromagnet that permanently holds a spring tensioned, an undervoltage release according to the invention does not require a continuous holding current. Only a continuous, but very small, current is required to power the monitoring unit. As a result, very little energy is required for the undervoltage release over time, and there is virtually no self-heating of the undervoltage release, thus eliminating any variation in the tripping behavior due to self-heating. Since the actual release mechanism is not continuously energized, there is no magnetization of the release components, which makes the undervoltage release's behavior more stable.An unavoidable temperature effect caused by external influences within the permissible operating temperature can be countered by appropriately dimensioning the charge of the capacitor storage.

[0013] The undervoltage release is preferably an undervoltage release for medium or high voltages, in particular for voltages between 1 kV and 52 kV.

[0014] In a further embodiment of the undervoltage release according to the invention, the charging unit comprises charging electronics which can be configured, for example by jumpers, for nominal auxiliary voltages in a range of 24 V to 250 V for DC voltages and in a range of 100 V to 240 V for AC voltages. Alternatively, the charging unit comprises two charging electronics, wherein a first charging electronics unit can be configured, for example by jumpers, for nominal auxiliary voltages in a range of 24 V to 60 V for DC voltages, and the second charging electronics unit can be configured, for example by jumpers, for nominal auxiliary voltages in a range of 110 V to 250 V for both DC and AC voltages.This allows the operation of the undervoltage release to be adapted to different rated auxiliary voltages, meaning that only one version of the capacitor unit and only one version of the undervoltage release can be used for a wide range of rated auxiliary voltages. This results in significant volume savings in the production of the undervoltage release and also considerably reduces the effort required for qualification and approval testing.

[0015] In a further embodiment of the undervoltage release according to the invention, the threshold value stored by the monitoring unit is configurable. This allows the threshold value to be adapted to a specific requirement. For example, a threshold value of approximately 50% of the nominal auxiliary voltage is set. However, a different threshold value can also be set if necessary.

[0016] In a further embodiment of the undervoltage release according to the invention, the monitoring unit is configured to supply the release unit with the energy stored in the capacitor storage unit, with a tripping delay after the threshold value has been undershot. This prevents, for example, an unnecessary tripping of the circuit breaker in the event of only a temporary drop in the auxiliary voltage below the threshold value.

[0017] In a further embodiment of the undervoltage release according to the invention, the tripping delay is configurable. This allows the tripping delay to be adapted to a specific requirement. For example, the tripping delay is configurable in a range of 50 ms to 150 ms. If necessary, longer tripping delays in the range of seconds can also be implemented.

[0018] In a further embodiment of the undervoltage release according to the invention, the capacitor storage element comprises an electrolytic capacitor or supercapacitor for storing the tripping energy. Electrolytic capacitors and supercapacitors are particularly suitable for storing the tripping energy due to their high capacitance.

[0019] In a further embodiment of the undervoltage release according to the invention, the release unit has a solenoid with a spring-loaded armature for activating the switching unit. For example, the monitoring unit is configured to supply the release unit with the tripping energy stored in the capacitor by applying an electrical voltage provided by the capacitor to the solenoid of the switching unit. Thus, the release unit has a conventional (not continuously energized) solenoid that is only briefly energized by the capacitor when the auxiliary voltage falls below the threshold value.

[0020] A circuit breaker according to the invention comprises an undervoltage release according to the invention. The advantages of a circuit breaker according to the invention result from the advantages of an undervoltage release according to the invention mentioned above.

[0021] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings. These drawings show: Fig. 1 a block diagram of an exemplary embodiment of a circuit breaker, Fig. 2 a block diagram of an exemplary embodiment of an undervoltage release of a circuit breaker.

[0022] Corresponding parts are marked with the same reference symbols in the figures.

[0023] Fig. 1 ( Fig. Figure 1 shows a block diagram of an embodiment of a circuit breaker 1. The circuit breaker 1 has a tripping unit 3 and an undervoltage release 5. Other components of the circuit breaker 1 are not shown.

[0024] The switching unit 3 is designed to switch off the circuit breaker 1. For example, the switching unit 3 is designed as a spring-loaded actuator.

[0025] The undervoltage release 5 is configured to activate the switching unit 3 when an auxiliary voltage of the circuit breaker 1 falls below a threshold value.

[0026] Fig. 2 ( Fig. Figure 2) shows a block diagram of an embodiment of the undervoltage release 5. The undervoltage release 5 comprises a capacitor storage unit 7, a tripping unit 9, a charging unit 11 and a monitoring unit 13.

[0027] The capacitor storage device 7 is designed to store a trigger energy 15. For example, the capacitor storage device 7 has an electrolytic capacitor or supercapacitor for storing the trigger energy 15.

[0028] The trip unit 9 is configured to activate the switch-off unit 3 to switch off the circuit breaker 1 when the trip energy 15 is supplied to the trip unit 9.

[0029] The charging unit 11 is set up to charge 17 the capacitor storage 7.

[0030] The monitoring unit 13 is configured to monitor the auxiliary voltage 19 of the circuit breaker 1 and to supply the tripping energy 15 stored in the capacitor storage 7 to the trip unit 9 when the auxiliary voltage 19 falls below a threshold value stored by the monitoring unit 13. Furthermore, the monitoring unit 13 is configured to control 21 the charging unit 11. The monitoring unit 13 can be integrated into the trip unit 9 or designed as a separate unit. Designing it as a separate unit allows the monitoring unit 13 to be mounted separately from the trip unit 9 in a location within the circuit breaker 1 where it is less exposed to adverse conditions such as switching shocks, vibrations, or temperature changes than at the installation location of the trip unit 9.

[0031] For example, the switching unit 3 has a spring-loaded actuator for switching off the circuit breaker 1. The spring-loaded actuator has a spring that is tensioned and latched when the circuit breaker 1 is switched on. The tripping unit 9 has, for example, a solenoid with an electromagnet and a spring-loaded armature. When the auxiliary voltage 19 falls below the threshold value, the monitoring unit 13 electrically connects the capacitor storage 7 to the tripping unit 9, applying an electrical voltage supplied by the capacitor storage 7 to the electromagnet of the solenoid of the tripping unit 9. This energizes the electromagnet and moves the armature of the solenoid. The movement of the armature releases the spring of the spring-loaded actuator of the switching unit 3, whereupon the spring-loaded actuator switches off the circuit breaker 1.

[0032] The charging unit 11, for example, has charging electronics that can be configured, for example by jumpers, for nominal auxiliary voltages in a range of 24 V to 250 V for DC voltages and in a range of 100 V to 240 V for AC voltages. Alternatively, the charging unit has two charging electronics, wherein the first charging electronics can be configured, for example by jumpers, for nominal auxiliary voltages in a range of 24 V to 60 V for DC voltages, and the second charging electronics can be configured, for example by jumpers, for nominal auxiliary voltages in a range of 110 V to 250 V for both DC and AC voltages.

[0033] The monitoring unit 13 is configured, for example, to supply the tripping unit 9 with the tripping energy 15 stored in the capacitor storage 7, with a tripping delay after the auxiliary voltage falls below the threshold value. Furthermore, both the threshold value and the tripping delay are configurable.

[0034] Although the invention has been further illustrated and described in detail by means of preferred embodiments, the invention is not limited by the disclosed examples and other variations can be derived from them by a person skilled in the art without leaving the scope of protection of the invention. Reference symbol list 1 circuit breaker 3 Switching unit 5 undervoltage releases 7 Capacitor storage 9 Trigger unit 11 charging unit 13 Monitoring unit 15 Trigger energy 17 charging 19 Auxiliary voltage 21 Control

Claims

[1] Undervoltage release (5) of a circuit breaker (1), comprising undervoltage release (5) - a capacitor storage device (7) designed to store a trigger energy (15), - a trip unit (9) which is configured to activate a trip unit (3) to switch off the circuit breaker (1) when the trip energy (15) is supplied to the trip unit (9), and - a monitoring unit (13) configured to monitor an auxiliary voltage (19) and to supply the release energy (15) stored by the capacitor storage (7) to the release unit (9) when the auxiliary voltage (19) falls below a threshold value stored by the monitoring unit (13), with a charging unit (11) configured to charge the capacitor storage (7), wherein the monitoring unit (13) is configured to control the charging unit (11). [2] Undervoltage release (5) according to claim 1, wherein the charging unit (11) has charging electronics which are configurable for nominal auxiliary voltages in a range of 24 V to 250 V for DC voltages and in a range of 100 V to 240 V for AC voltages. [3] Undervoltage release (5) according to claim 1, wherein the charging unit (11) has two charging electronics, wherein a first charging electronic is configurable for nominal auxiliary voltages in a range of 24 V to 60 V for DC voltages and the second charging electronic is configurable for nominal auxiliary voltages in a range of 110 V to 250 V for DC and AC voltages. [4] Undervoltage release (5) according to one of the preceding claims, wherein the threshold stored by the monitoring unit (13) is configurable. [5] Undervoltage release (5) according to one of the preceding claims, wherein the monitoring unit (13) is configured to supply the release unit (9) with the release energy (15) stored by the capacitor storage (7) with a release delay after the threshold of the auxiliary voltage (19) has been undershot. [6] Undervoltage release (5) according to claim 5, wherein the tripping delay is configurable. [7] Undervoltage release (5) according to one of the preceding claims, wherein the capacitor storage (7) comprises an electrolytic capacitor or supercapacitor for storing the release energy (15). [8] Undervoltage release (5) according to one of the preceding claims, wherein the release unit (9) has a lifting magnet with a spring-loaded armature for activating the switching unit (3). [9] Undervoltage release (5) according to claim 8, wherein the monitoring unit (13) is configured to supply the release energy (15) stored by the capacitor storage (7) to the release unit (9) by applying an electrical voltage provided by the capacitor storage (7) to the solenoid of the switching unit (3) via the monitoring unit (13). [10] Circuit breaker (1) with an undervoltage release (5) according to one of the preceding claims.

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