GB2564127A - Voltage transformer with overload protection - Google Patents
Voltage transformer with overload protection Download PDFInfo
- Publication number
- GB2564127A GB2564127A GB1710718.6A GB201710718A GB2564127A GB 2564127 A GB2564127 A GB 2564127A GB 201710718 A GB201710718 A GB 201710718A GB 2564127 A GB2564127 A GB 2564127A
- Authority
- GB
- United Kingdom
- Prior art keywords
- voltage transformer
- fuse
- activated switch
- secondary windings
- thermal activated
- 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- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
- H02H5/047—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature using a temperature responsive switch
Abstract
A voltage transformer 1 is protected from overcurrents and overheating by an overload protection system which has low impedance and ensures accuracy of the measuring device. The voltage transformer 1 has a body 2 with primary windings 4 and secondary windings 4 coupled to each other by electromagnetic induction, a measuring device 8 electrically connected to the secondary windings 4 via a low impedance (implying relatively high nominal current rating) fuse 7, and a thermal activated switch 9 electrically arranged between ground and the secondary windings 4 via the fuse 7 in order to short circuit the fuse 7 to ground when the thermal activated switch 9 reaches a threshold temperature. The thermal activated switch 9 may include a bimetallic element 11. The measuring device 8 typically measures the voltage.
Description
Voltage transformer with overload protection
The invention relates to a voltage transformer comprising:
- a body with primary windings and secondary windings coupled to each other by electromagnetic induction;
- a measuring device electrically connected to the secondary windings via a fuse.
Voltage transformers are typically used to decrease or step-down high voltages, which are used in the transport of electricity, to low voltages, e.g. 230 V or 400 V, which is suitable for electrical appliances used in homes and factories, or are used as measuring voltage transformer, with a secondary output voltage of e.g. 110 or 100V (based on the rated primary voltage), suitable for the measuring device to handle.
In order to ensure that the voltage transformer supplies the correct voltage, a measuring device is provided connected to the secondary windings. Preferably, the impedance of the secondary circuit, including the windings is kept as low as possible to allow the measuring to be as accurate as possible, without being dependent on the load of the measuring device itself.
Typically, a low impedance fuse is also provided to the secondary winding for high overcurrents, wherein the secondary windings would fail However, even if the current does not increase too much, the temperature of the voltage transformer could increase too much also causing the voltage transformer to fail This low impedance of the fuse implies a rather high interrupting value, so often there will be a region of too high overcurrents that can damage the voltage Transformer, but cannot be interrupted by the fuse.
US 2011316351 describes a voltage transformer, wherein a temperature sensor is provided at the body of the voltage transformer. When the measured temperature reaches a threshold temperature, a control system actuates a switch arranged in the secondary circuit to disconnect the load, such that the temperature in the voltage transformer cannot rise further.
The disadvantage of this prior art system is that the switch arranged in the secondary circuit in a closed position, provides some additional impedance and the additional temperature sensor and control system increase the costs of the voltage transformer.
GB 2518291 discloses a circuit with a voltage transformer, wherein in the secondary circuit a fuse and a temperature cut out [TCO] are arranged in series. When the temperature of the TCO reaches a temperature threshold, the TCO will interrupt the secondary circuit and disconnect the load from the secondary circuit.
The disadvantage of this known embodiment is that the positioning of the TCO in the secondary circuit increases the impedance, which influences the accuracy of the measurement device. Furthermore, currently available TCO’s have a limited current they can withstand.
It is an object of the invention to reduce or even remove the above mentioned disadvantages.
This object is achieved with a voltage transformer according to the preamble, which is characterized by a thermal activated switch electrically arranged between the secondary windings via the fuse in order to short circuit the secondary winding when the thermal activated switch reaches a threshold temperature.
With the voltage transformer according to the invention, the thermal activated switch is normally in open position, such that the switch does not influence the impedance of the measuring circuit at all and accordingly the accuracy of the measured voltage.
Only when the switch reaches a threshold temperature, the thermal activated switch will close and cause a short circuit over the fuse, causing the fuse to blow and disconnect any loads from the secondary circuit. This will ensure that the voltage transformer is not damaged due to excessive heat.
In a preferred embodiment of the voltage transformer according to the invention the thermal activated switch is in direct heat conducting contact with the body. Having a direct contact with the body on which the primary and secondary windings are arranged, it is ensured that the thermal activated switch will respond directly to a dangerous temperature of the voltage transformer.
In a further preferred embodiment of the voltage transformer according to the invention the thermal activated switch is positioned adjacent to the secondary windings.
This positioning ensures that the electrical field disturbances of the primary windings will have an influence as small as possible on the secondary windings and the thermal activated switch.
In yet a further preferred embodiment of the voltage transformer according to the invention the thermal activated switch comprises a bimetal lever and an electrical contact, wherein the bimetal lever is movable under increasing heat towards the electrical contact to a position, wherein the bimetal lever contacts the electrical contact and an electrical path is provided in order to short circuit the secondary winding over the fuse.
These and other features of the invention will be elucidated in conjunction with the accompanying drawing.
The figure shows a schematic view of an embodiment of a voltage transformer 1. The voltage transformer 1 has a body 2 with primary windings 3 and secondary windings 4. The primary windings 3 are electrically coupled to a power source
5. Due to the coupling by magnetic induction, the secondary windings 4 will generate a voltage to power a load 6.
The load 6 is connected to the secondary windings 4 via a fuse 7, which will ensure that the current in the secondary circuit will not get too high for longer times and damage the voltage transformer (windings 3, 4).
Furthermore, a measuring device 8 is coupled to the secondary windings 4 via the fuse 7. This measuring device 8 can typically measure the voltage in the secondary circuit.
To protect the body 2 with primary windings 3 and secondary windings 4 a thermal activated switch 9 is arranged in direct contact with the body 2 adjacent to the secondary windings 4, The thermal activated switch 9 has an electrical contact 10 connected behind the fuse 7 and a bimetal lever 11 connected to the other terminal of winding 4.
The bimetal lever 11 is during normal operation open, such that the measurements of the measuring device 8 are not influenced. Only if the temperature of the body 2 gets too high, e.g. by a too high load for the voltage transformer, the bimetal lever will move towards the electrical contact 10 and provide a short circuit to earth for the fuse 7, such that the fuse 7 will blow and the load 6 and the measuring device will be 5 disconnected from the secondary windings.
Claims (4)
1. Voltage transformer comprising:
- a body with primary windings and secondary windings coupled to each other by electromagnetic induction;
- a measuring device electrically connected to the secondary windings via a fuse;
characterized by
- a thermal activated switch electrically arranged between the secondary windings via the fuse in order to short circuit the fuse when the thermal activated switch reaches a threshold temperature.
2. Voltage transformer according to claim 1, wherein the thermal activated switch is in direct heat conducting contact with the body.
3. Voltage transformer according to claim 2, wherein the thermal activated switch is positioned adjacent to the secondary windings.
4. Voltage transformer according to any of the preceding claims, wherein the thermal activated switch comprises a bimetal lever and an electrical contact, wherein the bimetal lever is movable under increasing heat towards the electrical contact to a position, wherein the bimetal lever contacts the electrical contact and an electrical path is provided in order to short circuit the fuse.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1710718.6A GB2564127A (en) | 2017-07-04 | 2017-07-04 | Voltage transformer with overload protection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB1710718.6A GB2564127A (en) | 2017-07-04 | 2017-07-04 | Voltage transformer with overload protection |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB201710718D0 GB201710718D0 (en) | 2017-08-16 |
| GB2564127A true GB2564127A (en) | 2019-01-09 |
Family
ID=59592551
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB1710718.6A Withdrawn GB2564127A (en) | 2017-07-04 | 2017-07-04 | Voltage transformer with overload protection |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2564127A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10223032A1 (en) * | 2002-05-22 | 2003-12-11 | Leo Roeckert | Electric heating device e.g. for immersing bath, has short-circuit switch connected across heating element and excess current trip in front of short-circuit switch |
| EP2657951A2 (en) * | 2012-04-26 | 2013-10-30 | Calsonic Kansei Corporation | Vehicle safety device |
-
2017
- 2017-07-04 GB GB1710718.6A patent/GB2564127A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10223032A1 (en) * | 2002-05-22 | 2003-12-11 | Leo Roeckert | Electric heating device e.g. for immersing bath, has short-circuit switch connected across heating element and excess current trip in front of short-circuit switch |
| EP2657951A2 (en) * | 2012-04-26 | 2013-10-30 | Calsonic Kansei Corporation | Vehicle safety device |
Also Published As
| Publication number | Publication date |
|---|---|
| GB201710718D0 (en) | 2017-08-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| COOA | Change in applicant's name or ownership of the application |
Owner name: EATON INTELLIGENT POWER LIMITED Free format text: FORMER OWNER: EATON INDUSTRIES (NETHERLANDS) B.V. |
|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |