CA1106915A - Field excitation equipment - Google Patents
Field excitation equipmentInfo
- Publication number
- CA1106915A CA1106915A CA306,135A CA306135A CA1106915A CA 1106915 A CA1106915 A CA 1106915A CA 306135 A CA306135 A CA 306135A CA 1106915 A CA1106915 A CA 1106915A
- Authority
- CA
- Canada
- Prior art keywords
- field
- semiconductor element
- electric switch
- excitation equipment
- voltage
- 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
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/08—Control of generator circuit during starting or stopping of driving means, e.g. for initiating excitation
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Eletrric Generators (AREA)
- Nonwoven Fabrics (AREA)
- Treatments For Attaching Organic Compounds To Fibrous Goods (AREA)
- Synchronous Machinery (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE:
This invention relater to a field excitation equipment for an electric machine, comprising an exciter which is connected to the field winding of the machine and an electric swith for breaking the field current. A discharge resistor is arranged to be connected to the field winding when the electric switch is opened. The equipment is characterized in that the discharge resistor is, in series with a controlled semiconductor element, connected in parallel with the field winding, and that a contact member is arranged, when the electric switch is opened, to connect the control electrode of the semiconductor element and one of the main current connections of the element in order to make the semiconductor element conducting.
This invention relater to a field excitation equipment for an electric machine, comprising an exciter which is connected to the field winding of the machine and an electric swith for breaking the field current. A discharge resistor is arranged to be connected to the field winding when the electric switch is opened. The equipment is characterized in that the discharge resistor is, in series with a controlled semiconductor element, connected in parallel with the field winding, and that a contact member is arranged, when the electric switch is opened, to connect the control electrode of the semiconductor element and one of the main current connections of the element in order to make the semiconductor element conducting.
Description
11~6~
Field ex¢itation equipment The present invention relates to a field excitation equipment for an eleetrical maehine comprising an exeiter eonneeted to the field winding of the machine via a normally cloged electric switch, a diseharge resistor being arranged to be eonnected to the field winding when the eleetrie switch is opened.
In equipment for field excitation of eleetrical machines, for example syn-ehronous generators, a field exciter, for example a controlled or uneontrolled reetifier, is conne¢ted to the field winding of the machine and supplies direet eurrent to this. If a fault oeeurs, for example a short-eireuit on the a.e. siae of the generator, it is important that the field eurrent of the machine is broken. For this purpose it iB normal to arrange a single-or two-pole electric switch, a so-called field circuit-breaker, with one pole in one of or one pole in each of the two d.c. lines between the field exciter and the field winding. In the case of faults of this type, the-field circuit-breaker iB released and separates the field winding from the exciter. In order for the field current to be rapidly reduced to zero without harmful overvoltages occurring because of the inductive energy stored in the field winding,it is known to arrange an additional contact on the field circuit-breaker, which eontact is elosed when the field circuit-breaker iB released and then connects a discharge or de-excitation resistor to the field winding. This additional contact-on the circuit-breaker involves a considerable complieation and increases the price of the eircuit-breaker, _1_ ~'' __ _ .:
among other things because it makes it impossible to use stan-dard circuit-breakers, The object of the invention is to provide a device which enables the use of a conventional electric switch of standard type as field circuit-breaker.
It is of the utmost importance, when the field circuit-breaker is released, that a de-excitation circuit under all circumstances is connected to the field winding since this will otherwise be destroyed because of overvoltages occurring. For several types of fault which may frequently occur, for example short-circuiting on the a.c. voltage side in a generator station, the ordinary supply voltages will disappear and thus these cannot be used for the connection of the de-excitation circuit. T~
ensure a safe connection of the de-excitation circuit under all circumstances, the connection of said circuit should furthermore not be dependent on any auxiliary supply sources.
Thus, the invention relates to equipment in which there is used an electric switch of standard type as field circuit-breaker, and in which, upon release of the field circuit-breaker, a safe connection of the de-excitation circuit is performed quite independently of external supply voltages.
The present invention provides more particularly a field excitation equipment for an electric machine, comprising an exciter which is connected to a field winding of the machine and an electric switch for breaking the field current, a discharge resistor being arranged to be connected to the field winding when the electric switch is opened, characterized in that the discharge resistor is, in series with a controlled semiconductor element, connected in parallel with the field winding, and that a contact member is arranged, when the electric switch is opened, to connect the control electrode of the semiconductor element and one of the main current connections of the element in order to make the semiconductor element conducting.
.
In the following the invention will be described in greater detail with reference to the accompanying Figures 1 and 2. Figure 1 shows a field excitation equipment according to the invention and Figure 2 shows an alternative embodiment of the reserve firing circuit for the thyristors in Figure 1.
Figure 1 shows an uncontrolled static convertor consisting of diodes Dl-D6, which operates as a field exciter and supplies excitation current to the field winding F of a three-phase synchronous generator G. The rectifier is supplied through connections R, S, T from a three-phase a.c. voltage source (not shown). As an alternative, the field exciter may consist of a controlled thyristor convertor in a conventional manner, or of a rotating exciter.
The two main contacts Kll and K12 of a two-pole electric switch Kl are connected in the two lines between the field exciter and the field winding. The switch may consist of a circuit-breaker or, in equipment of smaller dimensions, of a contactor. The switch is also provided in thenormal manner with an auxiliary contact K13 for low power. During normal operation, the three contacts of the switch are switched on, but in the case of a fault of the above-mentioned type the switch is switched off by tripping members (not shown) and the contacts are opened.
- 2a -1~6~5 To effect de-excitation of the field winding when the electric switch is disconnected, two discharge resistors R1 and R2 are arranged to be connected across the field winding by means of one thyristor each, T1 and T2, respecti-vely. The resistors preferably have voltage-dependent resistanoe, but they may alternatively be linear. Each thyristor is provided with a safety circuit against transient overvoltages, said circuit consisting of a resistor R11 and R21, respectively, in series with a capacitor C1 and C2, respectively.
Further, each thyristor has a firing circuit consisting of a diode, D11 and D21, respectively, which is connected between the anode of the thyristor and its control electrode in series with a resistor, R12 and R22, respectively, and a contact, K21 and K22, respectively, of a relay K2. When the contacts are energized, the anode voltages provide control currents of a suitable magnitude to the control means of the thyristors by means of the resistors (R12 and R22, respectively), the thyristors are ignited, the field current flows through resistors R1 and R2, and the energy stored in field winding F is consumed in the discharge resistors without causing harmful overvoltages (if the resistors are correctly dimensioned).
Diodes D11 and D21 prevent the flow of a negative control currsnt when the thyristors are subjected to off-state voltage.
Relay K2 is connected to a d.c. voltage source ~ (which may be a separate battery or the auxiliary supply network of the station) in series with auxiliary contact K13 of switch K1. In undisturbed operation , as mentioned, K13 is on and relay K2 is energized, and therefore K21 and K22 are open.
A tripping of field circuit-breaker K1 makes K2 currentless, whereupon K~1 and K22 are energized and the thyristors are ignited and switch in the discharge resistors. If the voltage of source ~ should disappear, the same result would be obtained, and the de-excitation circuit is there-fore quite independent for its connection of the presence of external supply voltages.
An indicating member, consisting of a contactor K3 in the shown case, receives voltage by way of any of diodes D7 and D~ if any of thyristors T1 and T2 becomes defective and loses its blocking capacity. Such a fault means that part of the field current is continuously shunted away through the discharge resistor belonging to the defective thyristor also in the case of undisturbed operation, resulting in unnecessary power losses.
The method described above results in a very safe activation of the de-excitation circuit. Since a failing activation probably results in the _~_ -1~69~
field winding becoming destroyed and thus in considerable economic losses, it may be suitable, at least in case of ma~or plants, to arrange a reserve firing circuit for thyri6tors T1 and T2 to further ensure the connection of the de-excitation circuit when necessary. In Figure 1, this reserve firing circuit consists of a voltage divider R4-R5 connected across thyris-tor T2. ~etween the voltage divider and the control means of the thyristor there is connected a break-down diode D10 in series with a diode D9 (which prevents a negative control current). When the anode-cathode voltage of the thyristor reaches a certain value, breakdown i8 achieved in diode D10 and the control current is supplied to the thyristor. The magnitude of the control current is adapted to a suitable value by means of the resistance of the voltage divider and by resistor R3.
In the shown case only thyristor T2 is pfovided with a reserve firing circuit. Therefore, there is a risk, in those cases when the reserve firing circuit is activated, that the thyristor T2 will become overloaded and destroyed. Since these cases will be very rare, however, this risk can be accepted.
Figure 2 shows an alternative embodiment of the reserve firing circuit.A resistive-capacitive voltage divider C4-C5-R6-R7 iB connected across thyristor T2. At a predetermined level of the off-state voltage across thyristor T2, zener diode D12 delivers a control current to auxiliary thyristor T3, which supplies a suitable control voltage to thyristors T1 and T2 by means of R13, R10 and C3. Resistors R8 and R9 ensure that each thyristor receives a control current of suitable magnitude.
~,. .
The above description refers to a device with two parallel de-excitation circuits, each consisting of a thyristor in series with a resistor. Depend-ing on the size of the eguipment and other factors, only one such circuit, or more than two circuits, may be used.
If considered appropriate, relay K2 may be omitted and contacts K21 and K22 then consist of auxiliary contacts on field circuit-breaker K1.
The controllable semiconductor elements T1 and T2 for connection of thedischarge resistors preferably consist of thyristors, as described above, but alternatively they may consist of switch transistors or other con-trollable semiconductor elements.
/
In the embodiments described the electric switch (K1) arranged between ~?69~5 the exciter (Dl-D6) and the field winding (F) is a two-pole switch. This result in a galvanic separation between the exciter and field winding when the switch is switched off. As an alternative, two single-pole switches may be used. In certain cases it may be sufficient to use one single single-pole switch.
The field exciter shown in Figures 1 and 2 consists of a diode rectifier. Instead of this, a controlled thyristor convertor can be used. The electric switch which is to break the field current in the event of a fault may then be located in the a.c. leads of the exciter and, for example, consist of a three-pole electric switch (a.c. circuit-breaker or contactor).
Field ex¢itation equipment The present invention relates to a field excitation equipment for an eleetrical maehine comprising an exeiter eonneeted to the field winding of the machine via a normally cloged electric switch, a diseharge resistor being arranged to be eonnected to the field winding when the eleetrie switch is opened.
In equipment for field excitation of eleetrical machines, for example syn-ehronous generators, a field exciter, for example a controlled or uneontrolled reetifier, is conne¢ted to the field winding of the machine and supplies direet eurrent to this. If a fault oeeurs, for example a short-eireuit on the a.e. siae of the generator, it is important that the field eurrent of the machine is broken. For this purpose it iB normal to arrange a single-or two-pole electric switch, a so-called field circuit-breaker, with one pole in one of or one pole in each of the two d.c. lines between the field exciter and the field winding. In the case of faults of this type, the-field circuit-breaker iB released and separates the field winding from the exciter. In order for the field current to be rapidly reduced to zero without harmful overvoltages occurring because of the inductive energy stored in the field winding,it is known to arrange an additional contact on the field circuit-breaker, which eontact is elosed when the field circuit-breaker iB released and then connects a discharge or de-excitation resistor to the field winding. This additional contact-on the circuit-breaker involves a considerable complieation and increases the price of the eircuit-breaker, _1_ ~'' __ _ .:
among other things because it makes it impossible to use stan-dard circuit-breakers, The object of the invention is to provide a device which enables the use of a conventional electric switch of standard type as field circuit-breaker.
It is of the utmost importance, when the field circuit-breaker is released, that a de-excitation circuit under all circumstances is connected to the field winding since this will otherwise be destroyed because of overvoltages occurring. For several types of fault which may frequently occur, for example short-circuiting on the a.c. voltage side in a generator station, the ordinary supply voltages will disappear and thus these cannot be used for the connection of the de-excitation circuit. T~
ensure a safe connection of the de-excitation circuit under all circumstances, the connection of said circuit should furthermore not be dependent on any auxiliary supply sources.
Thus, the invention relates to equipment in which there is used an electric switch of standard type as field circuit-breaker, and in which, upon release of the field circuit-breaker, a safe connection of the de-excitation circuit is performed quite independently of external supply voltages.
The present invention provides more particularly a field excitation equipment for an electric machine, comprising an exciter which is connected to a field winding of the machine and an electric switch for breaking the field current, a discharge resistor being arranged to be connected to the field winding when the electric switch is opened, characterized in that the discharge resistor is, in series with a controlled semiconductor element, connected in parallel with the field winding, and that a contact member is arranged, when the electric switch is opened, to connect the control electrode of the semiconductor element and one of the main current connections of the element in order to make the semiconductor element conducting.
.
In the following the invention will be described in greater detail with reference to the accompanying Figures 1 and 2. Figure 1 shows a field excitation equipment according to the invention and Figure 2 shows an alternative embodiment of the reserve firing circuit for the thyristors in Figure 1.
Figure 1 shows an uncontrolled static convertor consisting of diodes Dl-D6, which operates as a field exciter and supplies excitation current to the field winding F of a three-phase synchronous generator G. The rectifier is supplied through connections R, S, T from a three-phase a.c. voltage source (not shown). As an alternative, the field exciter may consist of a controlled thyristor convertor in a conventional manner, or of a rotating exciter.
The two main contacts Kll and K12 of a two-pole electric switch Kl are connected in the two lines between the field exciter and the field winding. The switch may consist of a circuit-breaker or, in equipment of smaller dimensions, of a contactor. The switch is also provided in thenormal manner with an auxiliary contact K13 for low power. During normal operation, the three contacts of the switch are switched on, but in the case of a fault of the above-mentioned type the switch is switched off by tripping members (not shown) and the contacts are opened.
- 2a -1~6~5 To effect de-excitation of the field winding when the electric switch is disconnected, two discharge resistors R1 and R2 are arranged to be connected across the field winding by means of one thyristor each, T1 and T2, respecti-vely. The resistors preferably have voltage-dependent resistanoe, but they may alternatively be linear. Each thyristor is provided with a safety circuit against transient overvoltages, said circuit consisting of a resistor R11 and R21, respectively, in series with a capacitor C1 and C2, respectively.
Further, each thyristor has a firing circuit consisting of a diode, D11 and D21, respectively, which is connected between the anode of the thyristor and its control electrode in series with a resistor, R12 and R22, respectively, and a contact, K21 and K22, respectively, of a relay K2. When the contacts are energized, the anode voltages provide control currents of a suitable magnitude to the control means of the thyristors by means of the resistors (R12 and R22, respectively), the thyristors are ignited, the field current flows through resistors R1 and R2, and the energy stored in field winding F is consumed in the discharge resistors without causing harmful overvoltages (if the resistors are correctly dimensioned).
Diodes D11 and D21 prevent the flow of a negative control currsnt when the thyristors are subjected to off-state voltage.
Relay K2 is connected to a d.c. voltage source ~ (which may be a separate battery or the auxiliary supply network of the station) in series with auxiliary contact K13 of switch K1. In undisturbed operation , as mentioned, K13 is on and relay K2 is energized, and therefore K21 and K22 are open.
A tripping of field circuit-breaker K1 makes K2 currentless, whereupon K~1 and K22 are energized and the thyristors are ignited and switch in the discharge resistors. If the voltage of source ~ should disappear, the same result would be obtained, and the de-excitation circuit is there-fore quite independent for its connection of the presence of external supply voltages.
An indicating member, consisting of a contactor K3 in the shown case, receives voltage by way of any of diodes D7 and D~ if any of thyristors T1 and T2 becomes defective and loses its blocking capacity. Such a fault means that part of the field current is continuously shunted away through the discharge resistor belonging to the defective thyristor also in the case of undisturbed operation, resulting in unnecessary power losses.
The method described above results in a very safe activation of the de-excitation circuit. Since a failing activation probably results in the _~_ -1~69~
field winding becoming destroyed and thus in considerable economic losses, it may be suitable, at least in case of ma~or plants, to arrange a reserve firing circuit for thyri6tors T1 and T2 to further ensure the connection of the de-excitation circuit when necessary. In Figure 1, this reserve firing circuit consists of a voltage divider R4-R5 connected across thyris-tor T2. ~etween the voltage divider and the control means of the thyristor there is connected a break-down diode D10 in series with a diode D9 (which prevents a negative control current). When the anode-cathode voltage of the thyristor reaches a certain value, breakdown i8 achieved in diode D10 and the control current is supplied to the thyristor. The magnitude of the control current is adapted to a suitable value by means of the resistance of the voltage divider and by resistor R3.
In the shown case only thyristor T2 is pfovided with a reserve firing circuit. Therefore, there is a risk, in those cases when the reserve firing circuit is activated, that the thyristor T2 will become overloaded and destroyed. Since these cases will be very rare, however, this risk can be accepted.
Figure 2 shows an alternative embodiment of the reserve firing circuit.A resistive-capacitive voltage divider C4-C5-R6-R7 iB connected across thyristor T2. At a predetermined level of the off-state voltage across thyristor T2, zener diode D12 delivers a control current to auxiliary thyristor T3, which supplies a suitable control voltage to thyristors T1 and T2 by means of R13, R10 and C3. Resistors R8 and R9 ensure that each thyristor receives a control current of suitable magnitude.
~,. .
The above description refers to a device with two parallel de-excitation circuits, each consisting of a thyristor in series with a resistor. Depend-ing on the size of the eguipment and other factors, only one such circuit, or more than two circuits, may be used.
If considered appropriate, relay K2 may be omitted and contacts K21 and K22 then consist of auxiliary contacts on field circuit-breaker K1.
The controllable semiconductor elements T1 and T2 for connection of thedischarge resistors preferably consist of thyristors, as described above, but alternatively they may consist of switch transistors or other con-trollable semiconductor elements.
/
In the embodiments described the electric switch (K1) arranged between ~?69~5 the exciter (Dl-D6) and the field winding (F) is a two-pole switch. This result in a galvanic separation between the exciter and field winding when the switch is switched off. As an alternative, two single-pole switches may be used. In certain cases it may be sufficient to use one single single-pole switch.
The field exciter shown in Figures 1 and 2 consists of a diode rectifier. Instead of this, a controlled thyristor convertor can be used. The electric switch which is to break the field current in the event of a fault may then be located in the a.c. leads of the exciter and, for example, consist of a three-pole electric switch (a.c. circuit-breaker or contactor).
Claims (7)
1. Field excitation equipment for an electric machine, comprising an exciter which is connected to a field winding of the machine and an electric switch for breaking the field current, a discharge resistor being arranged to be connected to the field winding when the electric switch is opened, charac-terized in that the discharge resistor is, in series with a controlled semiconductor element, connected in parallel with the field winding, and that a contact member is arranged, when the electric switch is opened, to connect the control electrode of the semiconductor element and one of the main current connec-tions of the element in order to make the semiconductor element conducting.
2. Field excitation equipment according to claim 1, characterized in that the contact member consists of an auxiliary contact on the electric switch.
3. Filed excitation equipment according to claim 1, characterized in that the contact member consists of a contact of a switching member operated by an auxiliary contact of the electric switch.
4. Field excitation equipment according to claim 3, characterized in that said contact is arranged to be closed when no voltage is applied to the switching member.
5. Field excitation equipment according to claim 1, characterized in that the controlled semiconductor element consists of a thyristor.
6. Field excitation equipment according to claim 1, characterized in that a voltage-sensing circuit is connected to the control connection of the controlled semiconductor element and arranged to sense the voltage across the field winding, and, when said voltage exceeds a predetermined value, to supply a control signal to the semiconductor element to make the element conducting.
7. Field excitation equipment according to claim 1, characterized in that an indicating member is arranged to sense a voltage across the discharge resistor, which occurs during the non-current carrying interval of the semiconductor element, for indication of the loss of blocking capacity of the semi-conductor element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7707362-5 | 1977-06-27 | ||
| SE7707362A SE406397B (en) | 1977-06-27 | 1977-06-27 | FIELD FEEDING EQUIPMENT |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1106915A true CA1106915A (en) | 1981-08-11 |
Family
ID=20331687
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA306,135A Expired CA1106915A (en) | 1977-06-27 | 1978-06-23 | Field excitation equipment |
Country Status (7)
| Country | Link |
|---|---|
| AT (1) | AT362456B (en) |
| BR (1) | BR7804018A (en) |
| CA (1) | CA1106915A (en) |
| DE (1) | DE2826325C2 (en) |
| NO (1) | NO148618C (en) |
| PT (1) | PT68209A (en) |
| SE (1) | SE406397B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8009443B2 (en) | 2009-01-29 | 2011-08-30 | Brusa Elektronik Ag | DC/DC converter and AC/DC converter |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU873370A1 (en) * | 1979-03-11 | 1981-10-15 | Предприятие П/Я М-5113 | Synchronous machine excitation system |
| EP2524423A1 (en) | 2010-01-13 | 2012-11-21 | Brusa Elektronik AG | Control device and method for controlling a separately excited rotor winding of a synchronous machine |
| EP2684288B1 (en) | 2011-03-11 | 2022-04-20 | BRUSA Elektronik AG | Synchronous machine comprising an excitation circuit with a switching element |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB930129A (en) * | 1961-03-13 | 1963-07-03 | Gen Electric Co Ltd | Improvements in or relating to field excitation arrangements for electric alternators |
-
1977
- 1977-06-27 SE SE7707362A patent/SE406397B/en not_active IP Right Cessation
-
1978
- 1978-06-16 DE DE2826325A patent/DE2826325C2/en not_active Expired
- 1978-06-23 CA CA306,135A patent/CA1106915A/en not_active Expired
- 1978-06-23 NO NO782188A patent/NO148618C/en unknown
- 1978-06-23 PT PT68209A patent/PT68209A/en unknown
- 1978-06-23 AT AT459678A patent/AT362456B/en not_active IP Right Cessation
- 1978-06-26 BR BR7804018A patent/BR7804018A/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8009443B2 (en) | 2009-01-29 | 2011-08-30 | Brusa Elektronik Ag | DC/DC converter and AC/DC converter |
Also Published As
| Publication number | Publication date |
|---|---|
| SE406397B (en) | 1979-02-05 |
| DE2826325A1 (en) | 1979-01-11 |
| NO148618C (en) | 1983-11-09 |
| SE7707362L (en) | 1978-12-28 |
| PT68209A (en) | 1978-07-01 |
| NO148618B (en) | 1983-08-01 |
| BR7804018A (en) | 1979-04-17 |
| DE2826325C2 (en) | 1984-09-20 |
| ATA459678A (en) | 1980-10-15 |
| AT362456B (en) | 1981-05-25 |
| NO782188L (en) | 1978-12-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |