EP1516423A1

EP1516423A1 - Device for regulating the voltage in generators by means of coil tapping and a control relay

Info

Publication number: EP1516423A1
Application number: EP03738024A
Authority: EP
Inventors: Ernst Hatz; Franz Moser
Original assignee: Motorenfabrik Hatz GmbH and Co KG
Current assignee: Motorenfabrik Hatz GmbH and Co KG
Priority date: 2002-06-25
Filing date: 2003-06-13
Publication date: 2005-03-23
Also published as: WO2004001951A1; KR20050012795A; AU2003245937A1; DE10228226B4; RU2004134334A; CN1663109A; DE10228226A1; JP2005531272A

Abstract

The invention relates to a device for automatically regulating the voltage of a generator according to the load current. Said device comprises a first couple of clamps which can be connected to a couple of generator clamps carrying the load current and taps a first generator voltage from the generator coil, a second couple of clamps which can be connected to the couple of generator clamps and picks up a second generator voltage that is smaller than the first generator voltage from the generator coil, a third couple of clamps that supplies a control voltage to a control circuit which is provided with a control relay (9) having a switch for switching the connection between the couple of generator clamps and the first couple of clamps or the second couple of clamps. The couple of generator clamps, which is connected to the first couple of clamps by means of the switch, is connected to the second couple of clamps if the control voltage is greater than or equal to an upper threshold voltage of the control relay while the couple of generator clamps, which is connected to the second couple of clamps by means of the switch, is connected to the first couple of clamps if the control voltage is less than or equal to a lower threshold voltage of the control relay. The inventive device also comprises a bridging element that bridges the connection established by the switch between the couple of generator clamps and the first couple of clamps and is provided with a varistor, the on-state voltage of which lies above the difference between the two generator voltages but below the first generator voltage.

Description

Device for voltage regulation on electrical power generators by means of winding tapping and control relay

The present invention relates to a device for the automatic, load current-dependent regulation of the voltage of an electrical power generator ("generator"). In particular, it relates to the use of such a device for regulating the voltage of a generator driven by a reciprocating piston internal combustion engine.

Devices for regulating the voltage of generators are known. In the case of electrical power generators with electromagnets for exciting the induction coils, the generator voltage can be adapted to different load conditions, for example by varying the control current for the electromagnets and a concomitant variation in the magnetic flux through the induction coils. However, such a simple voltage regulation is not possible with permanently excited generators. For voltage regulation, technically complex control measures are necessary, which is possible, for example, in the form of sliding contacts along the main coils for setting the number of active coil turns. The disadvantage here is the high susceptibility to wear of the sliding contacts, which is due in particular to abrasion and sparking. Moreover, often do not lead to avoid Windungskurzschlüsse to a non sigenden to vernachläs ^¬ power dissipation. A further disadvantage is that currency ^¬ the switching process can always short power interruptions rend. DE 26 59 600 AI describes a device for automatic, load current-dependent control of an electrical power generator, in which the control of the generator output voltage is carried out by short-circuiting a partial coil of a phase with a triac, which is connected to a winding tap and the star point.

US 2001/002802 AI describes a motor whose speed / torque characteristic is changed by switching the supply voltage to winding taps of the stator phase coils.

DE 100 47 287 AI describes an apparatus and a method for generating different output voltages with an AC generator, the configuration of the connections of the stator windings for generating different output voltages being changeable by means of a configuration circuit.

In contrast, it is the object of the present invention to avoid complex control measures for adapting the generator voltage to different load conditions. In addition, power interruptions should no longer occur during switching operations.

According to a proposal of the invention, this object is achieved by the features of the independent claim. Advantageous embodiments of the invention are given by the features of the dependent claims.

According to the invention, a device for automatic, load current-dependent regulation of the voltage of an electric power generator is specified, in which a first and a two-phase tes pair of terminals for tapping a first or a second generator voltage are provided on the generator winding. Both the first and the second pair of terminals can be connected to a generator pair via which the load current is to be conducted. There are always more winding turns between the first pair of terminals than between the second pair of terminals, so that the voltage tapped at the first pair of terminals is always greater than the voltage tapped at the second pair of terminals. Both the first and the second pair of terminals can be connected at any point in the generator winding, as long as it is ensured that there are more turns between the first pair of terminals than between the second pair of terminals. The first generator voltage is preferably the main generator voltage, ie the voltage tapped from the complete winding of the generator. The second generator voltage is always a tap voltage which is less than the main generator voltage.

Furthermore, the device according to the invention has a third pair of terminals through which the control voltage for a control circuit can be tapped. The control voltage preferably corresponds to the voltage difference between the first generator voltage and the second generator voltage. The control circuit is preferably designed in such a way that it becomes live only from a certain forward voltage. This can be achieved, for example, by a Zener diode whose breakdown voltage corresponds to the forward voltage of the control circuit.

The control circuit has a control relay with a switch for alternately connecting the generator terminal pair with the first or second pair of clamps clamped to the generator winding. By flipping the switch of the control relay, the generator terminal pair connected by the switch to the first pair of terminals is connected to the second pair of terminals if the control voltage tapped at the third pair of terminals assumes a value that is greater than or equal to an upper threshold voltage of the switching relay. If the control circuit is only live from a forward voltage, the upper threshold voltage is the sum of the forward voltage of the control circuit, for example the breakdown voltage of a Zener diode located there, and the pull-in voltage of the switching relay. Conversely, the generator terminal connected by the switch to the second pair of terminals is connected to the first pair of terminals by flipping the switch if the control voltage is less than or equal to a lower threshold voltage of the switching relay. The lower threshold voltage results from the forward voltage of the control circuit, for example the breakdown voltage of the Zener diode, and the release voltage of the switching relay.

The release voltage of the switching relay is always less than the pull-in voltage of the switching relay, where the switching hysteresis of the switching relay is responsible. The switching hysteresis is necessary for stable switching of the switching relay, since the same upper and lower threshold voltage, i.e. H. one for tightening and loosening the same switching voltage, an unstable switching state, with a constant switching back and forth would follow.

The distance between the upper and lower threshold voltage, ie the width of the switching hysteresis, generally depends on the dimensioning of the switching relay. The relative position of the switching hysteresis can be varied by dimensioning a Zener diode arranged in the circuit. A smaller breakdown voltage of the Zener diode leads to a shift in the switching hysteresis to smaller control voltages, and vice versa. The Zener diode also serves to level the potential of the switching hysteresis.

If there are other elements in the control circuit, for example a rectifier diode, by means of which a DC control relay can advantageously be used, forward voltages of these elements may also have to be taken into account for the level of the control voltage required for switching the control relay.

Furthermore, the device according to the invention has a bridge element for bridging the connection of the first terminal pair caused by the switch to the generator terminal pair. The bridge element is provided with a voltage-dependent resistor ("varistor"), which is not used here as overvoltage protection and therefore atypically used, and has a forward voltage that is above the difference between the first and second generator voltage and below the first generator voltage tapped at the first pair of terminals. If the switch of the control relay connects the generator terminal pair to the first or second pair of terminals, practically no voltage drops along the connection of the first pair of terminals to the generator terminal pair. Due to the lack of potential difference and the resulting current impermeability of the varistor, the bridge element acts as a blocking element. However, if the switch of the control relay is switched between the first and second pair of terminals, it is during the switching process the potential of the first terminal pair at the varistor and the bridge element serves as a pass-through element, which is suitable for conducting the load current via the connection between the first terminal pair and the generator terminal pair, which is interrupted by the open switch. In order to avoid a short circuit when the switch connects the second pair of terminals to the pair of generator terminals, the forward voltage of the varistor must be selected so that it lies above the difference between the first and second generator voltage. An interruption in the current during the switching process can advantageously be avoided by the bridge element.

A preferred embodiment of the invention provides that the voltage regulation takes place within a tolerance range of + 5%. This means that the voltage is regulated up or down as soon as the nominal voltage is undercut or exceeded by 5%. It is also preferred if the voltage regulation takes place in the vicinity of approximately 50% -80% of the nominal load current with an ohmic load. If the load is ohm ¹ sch-inductive, the switching points shift in a corresponding manner to higher relative proportions of the nominal load current. In particular, the device according to the invention is designed in conformity with execution class G2 of the DIN 8528 standard, which standardizes the voltage regulation accuracy for power generator sets in accordance with the tolerances in public networks.

The invention will now be explained in more detail on the basis of the description of an exemplary embodiment, reference being made to the accompanying drawings. Show it 1 shows a circuit diagram of a device according to the invention for voltage regulation of a permanently excited synchronous generator,

Fig. 2 shows the course of the phase voltage of a three-phase phase as a function of the load current with ohmic load (dashed lines) and ohmic shear inductive load (solid lines), and the switching processes triggered by the device according to the invention.

1 shows an example of the circuit diagram of a device according to the invention for voltage regulation of a phase of a permanently excited synchronous generator. From the generator, only the generator winding 1 and the generator terminals N, Ll are shown. A first pair of terminals 1U1, 1U2 and a second pair of terminals 1U1, 2U2 tap a first or second generator voltage from the generator winding 1. The first pair of terminals 1U1, 1U2 encompasses the full number of turns of the generator winding, while the second pair of terminals 1U1, 2U2 encompasses a smaller number of turns. Since the induced voltage is proportional to the number of turns, the second generator voltage is always lower than the first generator voltage. Both the first and the second pair of terminals can be connected to the generator terminal L1, N.

A switching relay 8 with a switch 9 is used to connect the generator terminal Ll, N to the first or second pair of terminals. The switching relay 8 is located in a control circuit 2, which is connected to terminals 2U2 and 1U2 of the first and second pair of terminals, and thus the Taps differential voltage between the first and second generator voltage. In the control circuit 2 there are also a Zener diode 6 and a Rectifier diode 7 arranged. The zener diode 6 has a blocking effect, such that the control circuit 2 becomes live only when the zener breakdown voltage is exceeded. The rectifier diode 7 serves to rectify the alternating current, as a result of which a direct current switching relay 8 can advantageously be used.

As soon as the voltage induced between the terminals 1U1 and 2U2 exceeds an upper threshold voltage, which is predetermined by the breakdown voltage of the Zener diode 6, the forward voltage of the rectifier diode 7 and the starting voltage of the control relay 8, a current flows in the control circuit 2 which brings the control relay 8 to tighten the switch 9. As a result, the voltage applied to the generator terminal pair N, Ll is switched from the higher voltage value 1U2 to the lower voltage value 2U2. The load current that triggers this switching process is then conducted via the circuit 4 of the second pair of terminals. The reduction in the load current between the terminals of the control circuit 1U2, 2U2 causes a further increase in the control voltage tapped there, which supports the switching process. The effect of the load current on the voltage in this branch is therefore retained.

If the load current rises again, the tapped control voltage drops, which causes the switching relay 8 to switch again as soon as the control voltage reaches a lower threshold voltage. The lower threshold voltage is predetermined by the breakdown voltage of the Zener diode 6, the forward voltage of the rectifier diode 7 and the release voltage of the control relay 8. Due to the switching hysteresis of the switching relay, the lower threshold voltage is always lower than the upper threshold voltage. The control voltage drops to below the breakdown voltage of the Zener diode 6, no more current flows in the control circuit 2. The increasing internal resistance between the terminals of the control circuit 1U2, 2U2 caused by the load current when switching from the second pair of terminals to the first pair of terminals leads to a further drop in the control voltage, which supports the changeover process.

An interruption of the current flow during the switching is prevented by a varistor 10 arranged in a bridge element 5. The varistor is high-impedance when de-energized and therefore does not allow any electrical current to flow. If, on the other hand, the voltage at its connections rises, it tilts into the low-resistance state at a certain forward voltage and conducts the electrical current via the circuit 3. If the switch 9 connects the first pair of terminals to the generator terminal pair, then practically falls over the connections of the bridge link no voltage off - the varistor has a high resistance and acts as a blocking element. During the switchover of the switch 9 from the first pair of terminals to the second pair of terminals, the potential of the terminal 1U2 is present at the varistor, as a result of which it is brought into the low-resistance state and conducts the load current. If the switch 9 has established the connection of the generator terminal pair to the second pair of terminals, the current is conducted via the circuit 4, as a result of which the varistor again becomes high-resistance and blocks the current flow through the bridge element. The same applies when switching switch 9 from terminal 2U2 to terminal 1U2. A higher forward voltage of the varistor than the difference between the voltage tapped at the terminals 2U2 and 1U2 prevents a short circuit from occurring over the circuit 3 when the switch 9 has the generator terminal pair N, Ll connects the second pair of terminals 1U1, 2U2. In order to keep the varistor internal losses as low as possible, switch 9 should switch as quickly as possible.

2 shows the dependence of the phase voltage U _Str (phase voltage) tapped by the generator terminal L1, N, expressed in% of the nominal voltage U _str t on the load current I _L , expressed in% of the nominal load current I _LN , in the case of a pure one ohm 'see load (dashed lines) at which current and voltage are in phase, ie cos φ = 1, where φ corresponds to the angle between current and voltage, or an ohmic-inductive load (solid lines) at which cos φ = 0.8 applies.

The voltage profile 2 corresponds to the voltage of the first generator voltage tapped from the first pair of terminals 1U1, 1U2, while the voltage profile 1 corresponds to the voltage of the second, smaller generator voltage tapped from the second pair of terminals 1U1, 2U2.

The switching process is based on a tolerance range of + 7%. When idling (ie I _L = 0), the generator terminal voltage is approximately 107% of the nominal voltage and corresponds to the voltage tapped between 1U1 and 2U2.

Consider an ohmic load (dashed lines). If the generator is loaded electrically starting from the zero load (dashed curve 1; I = 0) and the load current is increased continuously, the switching threshold (upper threshold voltage) of the control relay is reached at approx. 77% of the nominal load current the generator terminal Ll is connected to the terminal 1U2 of the first pair of terminals. This has a chip voltage jump from approx. 94% to approx. 101% of the phase voltage. With a further increase in the load current, the phase voltage decreases according to the dashed curve 2.

If the generator is then relieved, i.e. if the load current is continuously reduced, the voltage tapped at the generator terminal increases according to the dashed curve 2 until it reaches the switching threshold (lower threshold voltage) of the switching relay at approx. 55% of the nominal load current, and the generator terminal Ll is connected to the terminal 2U2 of the second pair of terminals. This results in a voltage jump from approx. 105% to approx. 98% of the phase voltage. If the load current is reduced further, the phase voltage increases according to the dashed curve 1. When idling (I _L = 0), it finally reaches 107% of the nominal phase voltage.

The hysteresis of the control relay can be seen between the two switching thresholds. The peaks of the hysteresis are approx. 77% and approx. 55% of the nominal load current. The area framed by the hysteresis depends on the relative distance between the switching thresholds and the slope of the phase voltage.

The device according to the invention is provided for regulating the phase voltage of each three-phase phase, that is to say three times in the case of three three-phase phases. It is particularly advantageous in the case of an unbalanced load, since the voltage drops in a heavily loaded phase and the voltage increases in a weakly loaded phase.

In particular, the devices according to the invention can be cascaded in a row, the distance between the first and second generator voltage being within the Cascade is getting narrower, so that the voltage regulation becomes finer.

A preferred use of the device according to the invention is the automatic, load current-dependent regulation of the voltage of an electric power generator driven by a reciprocating piston internal combustion engine. In particular, this can be a synchronous generator driven by a diesel engine. A permanently excited power generator is preferred according to the invention.

Claims

claims

1. Device for automatic, load current-dependent regulation of the voltage of an electrical power generator ("generator"), which comprises: a first pair of terminals (lUl, 1U2), which can be connected to a generator terminal pair (N, Ll) carrying the load current, for tapping one first generator voltage on the generator winding, a second pair of terminals (lUl, 2U2), which can be connected to the generator terminal pair (N, Ll), for tapping a second generator voltage on the generator winding, which is smaller than the first generator voltage, a third pair of terminals (1U2, 2U2 ) to supply a control circuit (2) with a control voltage, which control circuit (2) is equipped with a control relay (8) with a switch (9) for switching the connection between the generator terminal pair (N, Ll) and the first or second terminal pair, whereby the generator terminal pair (N, Ll) connected to the second terminal pair by the switch (9) with the first pair of terminals (1U1, 1U2) aar (1U1, 2U2) is connected if the control voltage is greater than or equal to an upper threshold voltage of the switching relay, while the generator terminal pair (N, Ll) connected to the second terminal pair (1U1, 2U2) by the switch (9) to the first terminal pair (1U1, 1U2) is connected if the control voltage is less than or equal to a lower threshold voltage of the control relay, a bridge element (5) which bridges the connection between the generator terminal pair (N, Ll) and the first terminal pair (1U1, 1U2) created by the switch (9), with a voltage-dependent resistor ("varistor") (10) whose forward voltage is above the difference between the first and second generator voltage and below the first generator voltage tapped at the first pair of terminals.

Apparatus according to claim 1, characterized in that the control voltage of the control circuit corresponds to the voltage difference between the first generator voltage and the second generator voltage.

Device according to claim 1, characterized in that the control circuit (2) becomes current-permeable when a forward voltage is reached.

Apparatus according to claim 3, characterized in that the control circuit (2) has a Zener diode (6) whose breakdown voltage corresponds to the forward voltage of the control circuit (2).

Device according to claim 1, characterized in that the control circuit (2) has a current-rectifying element, in particular a rectifier diode (7).

6. The device according to claim 1, characterized in that the tapped with the first pair of terminals (1U1, 1U2) corresponds to the first generator voltage of the main generator voltage.

7. The device according to claim 1, characterized in that the voltage regulation takes place within a tolerance range of ± 5%.

8. The device according to claim 1, characterized in that the voltage control takes place at ohmic load at approximately 50% - 80% of the nominal load current.

9. The device according to claim 1, characterized in that it conforms to execution class G2 of the DIN 8528 standard.

10. The apparatus of claim 1, wherein the electrical power generator is permanently excited.

11. Arrangement characterized by devices according to one of the preceding claims for each three-phase phase.

12. Arrangement characterized by cascaded devices according to one of the preceding claims, wherein the voltage difference between the first generation gate voltage and the second generator voltage within the cascade continuously decreases.

13. Use of the device according to one of the preceding claims for automatic, load current-dependent regulation of the voltage of an electric power generator, in particular a synchronous generator, driven by a reciprocating piston internal combustion engine, in particular a diesel engine.