JP7554127B2 - Alternator - Google Patents

Description

The present invention relates to an AC generator, and more specifically to an improvement to an AC generator equipped with an automatic voltage regulator (AVR).

When an AC generator is operated with a constant field current, if the load current changes due to the start or stop of a load such as a motor connected to the AC generator, the output voltage of the AC generator changes with this change in load current, making it impossible to obtain a stable output voltage.

Therefore, in order to stabilize the output voltage, AC generators are usually equipped with an automatic voltage regulator (hereinafter referred to as "AVR") to stabilize the output voltage (see Patent Document 1).

This AVR compares the output voltage of the generator body with a preset voltage and controls the output voltage of the generator body by changing the magnitude of the field current of the generator body so that the output voltage approaches the preset voltage. When the output voltage of the generator body becomes lower than the preset voltage, the field current applied to the generator field winding (not shown) provided in the excitation circuit 212 is increased, and conversely, when the output voltage of the generator body becomes higher than the set voltage, the applied field current is reduced.

The AVR is usually connected to the output terminal of the generator armature winding 211 of the generator main body 210 to be controlled, and is configured to be driven by the power generated by the generator main body 210. As an example, as shown in FIG. 7, when the generator armature winding 211 of the generator main body 210 controlled by the AVR 220 is a three-phase, four-wire generator armature winding 211 that outputs 200V and is composed of three-phase windings V, W, and U star-connected with a phase difference of 120° in electrical angle, the single-phase AC of 115V obtained between the neutral terminal o at the neutral point O and the output terminal of one of the three-phase windings V, W, and U (between o-v, o-w, or o-u (between o-u in the illustrated example) is used as the power supply voltage for the AVR 220.

However, when the AVR 220 is driven by the output voltage of the generator body 210 in this manner, if the load current of the generator body 210 suddenly increases due to the introduction of a large motor device, for example, the output voltage of the generator body 210 drops significantly and it takes a long time for the output voltage to recover to the set voltage, resulting in a problem that the motor device cannot be started smoothly.

In other words, if the output voltage of the generator body 210 drops significantly due to the application of a large load, the AVR 220 increases the field current by an amount commensurate with the drop, thereby restoring the output voltage of the generator body 210 to the set voltage.

However, as mentioned above, the AVR 220 uses the output voltage of the generator armature winding 211 as its power supply voltage. Therefore, if the output voltage of the generator body 210 drops significantly, the power supply voltage of the AVR 220 will also drop significantly, and the AVR 220 will not be able to increase the field current in proportion to the drop in the output voltage of the generator body 210.

Therefore, as mentioned above, when a large motor device is turned on and the load current increases suddenly, the output voltage of the generator main body 210 drops significantly, and it takes a long time for the output voltage to recover to the set voltage, making it impossible to start the motor device smoothly.

JP 2012-10480 A

As mentioned above, the problem of a large voltage drop and a delay in returning to the set voltage when a large load is applied occurs because the drop in the output voltage of the generator body 210 reduces the power supply voltage of the AVR 220 to a level where the required increase in field current cannot be achieved.

Therefore, one way to solve this problem would be to raise the power supply voltage of AVR220 to 200V by using the voltage between any two output terminals of the three-phase windings V, W, and U (v-w, w-u, or v-u) as the power supply voltage of AVR220.

By configuring it in this way, even if the output voltage of the generator body 210 drops due to the application of a large load and the power supply voltage of the AVR 220 drops, the power supply voltage after the drop is maintained at a relatively high value (e.g., 115 V or higher) compared to when the power supply voltage is 115 V between the output terminals o-v, o-w, or o-u. This ensures the power supply voltage required to increase the field current of the generator body 210 to the required level, making it possible to reduce the voltage drop of the generator body 210 and quickly restore the set voltage.

However, in order to change the power supply voltage of the AVR220 from 115V to 200V in this way, the AVR220 needs to be designed to withstand being powered by a 200V power supply.

Therefore, if this configuration is to be adopted for an AC generator 200 equipped with an AVR that is already designed to be driven by a 115V power source, it is not possible to simply switch the power wiring of the AVR 220 from output terminals o-v, o-w, or o-u to output terminals v-w, w-u, or v-u. It is necessary to either replace the AVR 220 itself with one that is compatible with 200V, or to modify the structure of the AVR 220 so that it can withstand the application of a voltage of 200V by replacing parts of the AVR 220, etc.

Since AVRs capable of withstanding such a voltage of 200V are more expensive than AVRs compatible with a voltage of 115V, the increased costs associated with replacing or modifying the structure of the AVR 220 described above will be reflected in the price of the AC generator 200, reducing the price competitiveness of the AC generator 200 in the market.

In addition, one possible method for suppressing fluctuations in the AC generator's output voltage in response to changes in the load current is to make the AC generator's core larger and make it an iron machine (a machine with a high proportion of iron core). Also, in addition to the three-phase winding mentioned above, an auxiliary winding can be provided in the AC generator's armature winding, and when a large load is applied, the output voltage of the auxiliary winding can also be applied to the AVR, temporarily increasing the AVR's power supply voltage.

However, these methods have the disadvantage of increasing the weight and cost due to the increase in the iron core and number of parts.

Moreover, these methods require a review of the basic design of the AC generator itself, and cannot be adopted as an improvement for stabilizing the output voltage of existing AC generators, such as AC generators that have already been commercialized.

Therefore, there is a demand for the development of an AC generator that can reduce the drop in output voltage even when a large load is applied, and can quickly restore the set voltage, without making major design changes to the generator itself, and without replacing the AVR itself or any AVR parts, by using existing 115V compatible AVRs as is.

In order to solve the above problem, the inventor of the present invention considered that even an AVR compatible with 115V has a certain margin in its voltage resistance, and even if it does not have the voltage resistance to withstand a power supply voltage increased to 200V, if it is operated with a power supply voltage somewhat higher than 115V, it should be possible to operate it without replacing parts, etc., and without causing breakdowns, etc.

Therefore, even if a 115V compatible AVR is used as is without replacing any parts, etc., if it is operated at a voltage higher than 115V within a range that does not cause any malfunctions in the AVR, it is thought that it should be possible to reduce the drop in the output voltage of the generator body even when a large load is applied, and to quickly return to the set voltage, compared to when it is operated at a voltage of 115V.

However, existing three-phase, four-wire, 200V AC generators can only extract 115V and 200V voltages, and it is not possible to arbitrarily extract a voltage greater than 115V but less than 200V as the power supply voltage for the AVR.

The present invention was made based on the above-mentioned viewpoint of the inventor of the present invention, and aims to provide an AC generator that can reduce the voltage drop and quickly return to the set voltage even when a large load is applied, by simply making relatively simple modifications without making major changes to the configuration of existing AC generators, and therefore can improve the starting performance of the motor even when a large motor is connected as a load to the AC generator.

Below, the means for solving the problem are described together with the reference symbols used in the description of the embodiment of the invention. These reference symbols are intended to clarify the correspondence between the description of the claims and the description of the embodiment of the invention, and needless to say, are not used in a restrictive manner in interpreting the technical scope of the present invention.

In order to achieve the above object, the AC generator 1 of the present invention comprises:
An AC generator 1 including a generator armature winding 11 consisting of three-phase windings U, V, and W star-connected with a phase difference of 120° electrical angle centered on a neutral point O, and an excitation circuit 12 including at least a generator field winding 124, and a generator main body 10 capable of outputting three-phase AC of a predetermined voltage from output terminals u, v, and w provided on each of the three-phase windings U, V, and W of the generator armature winding 11, and an automatic voltage regulator (AVR) 20 that uses the generator main body 10 as a power source and controls the output voltage of the generator main body 10 to approach a preset voltage by changing the field current applied to the generator field winding 124 of the excitation circuit 12 of the generator main body 10,
The automatic voltage regulator (AVR) 20 is provided with a pair of power supply input units 21 and 22 for inputting the AC voltage output by the generator main body 10 as a power supply voltage,
One of the power supply input units 21 is connected to the output terminal (output terminal u in the illustrated example) provided on a winding of one of the three-phase windings U, V, and W (U phase in the illustrated example),
The other power supply input section 22 is characterized in that it can be connected to a center tap vm provided on one of the remaining windings W, V (V phase in the illustrated example) of the three-phase windings V, W, and U (claim 1; see FIG. 1).

The excitation circuit 12 may be composed of only the generator field winding 124, or may be configured so that the output current of the automatic voltage regulator (AVR) 20 is directly applied to the generator field winding 124, and the field current applied to the generator field winding 124 is directly controlled by the automatic voltage regulator (AVR) 20.

In addition, the excitation circuit 12 of the generator main body 10 may be provided with an exciter 120, which is an AC generator equipped with an exciter armature winding 121 and an exciter field winding 122 that generate a field current to be applied to the generator field winding 124 in addition to the aforementioned generator field winding 124, and the automatic voltage regulator (AVR) 20 may be configured to change the field current to be applied to the generator field winding 124 of the generator main body 10 by controlling the field current to be applied to the exciter field winding 122 of the exciter 120 (see claim 2 and FIG. 2).

The other power supply input section 22 provided in the automatic voltage regulator (AVR) 20 may be selectively connectable to either the intermediate tap vm or the neutral point O (neutral point terminal o) by operating, for example, a changeover switch 30 (Claim 3; see Figure 3).

Furthermore, each of the three-phase windings U, V, and W is formed by combining a plurality of element coils 14 to 17, and the connection state between the element coils 14 to 17 can be switched between a low-voltage connection that performs a predetermined low-voltage output (for example, a three-phase, four-wire 200V output) and a high-voltage connection that performs a high-voltage output that is twice the voltage of the output in the low-voltage connection (for example, a three-phase, four-wire 400V output),
Each of the three-phase windings U, V, and W is provided with low voltage output terminals u1, v1, and w1 for outputting the low voltage and high voltage output terminals u2, v2, and w2 for outputting the high voltage,
At the time of the low voltage connection, the element coils 14 to 17 are connected between the neutral point O and each of the low voltage output terminals u1, v1, and w1 so that two windings having the same number of turns are connected in parallel,
During the high voltage connection, the neutral point O and each of the high voltage output terminals u2, v2, w2 are connected by the element coils 14 to 17 connected in series, and the element coils 14 to 17 are connected so that each of the low voltage output terminals u1, v1, w1 is disposed at a position where the number of turns of each of the three-phase windings U, V, W is 1/2,
The one power supply input section 21 of the automatic voltage regulator (AVR) 20 is connected to any one of the low voltage output terminals u1, v1, w1 (low voltage output terminal u1 in the illustrated example),
The center tap vm may be provided on the winding between one of the remaining terminals (v1, w1) of the low-voltage output terminals (u1, v1, w1) (v1 in the illustrated example) and the neutral point O (Claim 4; see FIG. 4).

In addition, when each of the three-phase windings U, V, and W of the generator armature winding 11 is formed by connecting a plurality of element coils 14 to 17,
Preferably, the center tap vm is provided at a connection portion between the element coils (between element coils 16 and 17 in the illustrated example) of the winding of one phase (V phase in the illustrated example) in which the center tap vm is provided (Claim 5; see Figures 4 and 5).

By using the configuration of the present invention described above, the AC generator 1 of the present invention can achieve the following remarkable effects:

One of the power supply input units 21 of the AVR20 is connected to an output terminal (output terminal u in the illustrated example) provided on one of the three-phase windings V, W, U (U phase in the illustrated example), and the other of the power supply input units 22 can be connected to an intermediate tap vm provided on one of the remaining windings W and V (V phase in the illustrated example) of the three-phase windings V, W, U. This makes it possible to drive the AVR20 with a u-vm terminal voltage (147 V in the illustrated example) that is higher than the u-o terminal voltage (115 V, for example).

As a result, compared to the conventional configuration in which the voltage between the u-o terminals (115V as an example) is used as the power supply voltage for the AVR20, the power supply voltage of the AVR is boosted, so even if the output voltage of the generator main body 10 drops due to the application of a large load, causing the power supply voltage of the AVR20 to drop, it is possible to maintain the power supply voltage after the drop within a specified range (115V or higher as an example).

As a result, even if the output voltage of the generator main body 10 drops, the AVR 20 can generate a field current of a corresponding magnitude, and even when a large load is applied, the output voltage of the generator main body 10 can be prevented from dropping significantly, and the set voltage can be restored quickly, making it possible to smoothly start the motor equipment.

In addition, as the power generated by the generator body 10 increases, the rotational resistance of the generator body 10 also increases. For example, if the AC generator 1 of the present invention is mounted on an engine-driven generator, if the rotational resistance of the generator body 10 increases suddenly due to a large motor load being applied when the engine is not sufficiently warmed up, the engine may stall (stall).

However, in a configuration in which the other power supply input section 22 provided in the AVR 20 can be selectively connected to either the intermediate tap vm or the neutral point O (neutral point terminal o), for example, when the engine is not sufficiently warmed up, the motor load is applied with the other power supply input section 22 provided in the AVR 20 deliberately connected to the neutral point O (neutral point terminal o), thereby lowering the output voltage of the generator main body 10 and delaying the return to the set voltage, so that the rotational resistance applied to the engine gradually increases over time, thereby preventing engine stall, and making it possible to change the power supply voltage of the AVR 20 according to the operating state of the drive source that drives the generator main body 10.

Furthermore, in a configuration in which the generator body 10 is an output voltage switching type generator body 10 equipped with low voltage output terminals (u1, v1, w1) for performing low voltage output (three-phase 200V output as an example) and high voltage output terminals (u2, v2, w2) for performing high voltage output (three-phase 400V output as an example) at twice the voltage of the low voltage output for each of the three-phase windings U, V, W, by connecting one of the power supply input parts 21 of the AVR 20 to the aforementioned position and providing an intermediate tap vm at the aforementioned position, even when the output voltage of the generator body 10 is switched from low voltage output (three-phase 200V) to high voltage output (three-phase 400V), the power supply voltage of the AVR 20 is maintained at the power supply voltage at the time of low voltage connection (147V as an example), and a voltage exceeding the voltage resistance capacity of the AVR is prevented from being applied.

In addition, in a configuration in which the aforementioned intermediate tap vm is provided at the connection portion between element coils 14 to 17 (the connection portion between element coils 16 and 17 in the illustrated example), for example, the connection portions of element coils 16 and 17 and the conductor provided at the intermediate tap vm can be simultaneously connected using a crimp terminal 32, eliminating the need for a separate work process for attaching the intermediate tap vm, and the attachment of the intermediate tap vm can be performed simultaneously with the connection work of element coils 14 to 17.

1 is a schematic diagram of an alternating current generator according to the present invention; FIG. 2 is an explanatory diagram showing one configuration example of an excitation circuit provided in the generator body. FIG. 6 is a schematic explanatory diagram showing a modified example of an AC generator according to the present invention. 1A and 1B are explanatory diagrams of three-phase windings of an AC generator with variable output voltage, where (A) shows a low voltage connection and (B) shows a high voltage connection. 5A and 5B are explanatory diagrams showing an example of the configuration of the three-phase winding (V-phase winding) shown in FIG. 4, in which (A) shows a low-voltage connection and (B) shows a high-voltage connection. 1A and 1B are waveform diagrams of the output voltage of the generator body during a motor load application test, in which (A) shows the waveform of the present invention (AVR power supply voltage 147V) and (B) shows the waveform of a comparative example (AVR power supply voltage 115V). FIG. 1 is a schematic diagram of a conventional AC generator.

Below, we will explain an example of the configuration of the AC generator 1 of the present invention with reference to the attached drawings.

[Overall configuration of AC generator]
Reference numeral 1 in FIG. 1 denotes an AC generator of the present invention. This AC generator 1 includes a generator main body 10 capable of outputting three-phase, four-wire AC of a predetermined voltage (200 V in this embodiment), and an automatic voltage regulator (AVR) 20 that uses this generator main body 10 as a power source and changes the field current of the generator main body 10 to control the output voltage of the generator main body 10 to approach a preset set voltage (200 V in this embodiment).

[Generator body]
The generator body 10 described above has a generator armature winding 11 consisting of three-phase windings U, V, and W. One end of each of the three-phase windings U, V, and W is connected to a neutral point O and is star-connected with a phase difference of 120° electrical angle around the neutral point O.

This generator body 10 is provided with an excitation circuit 12 for exciting the generator body 10, and the magnitude of the field current applied to the generator field winding 124 provided in this excitation circuit 12 is controlled by the AVR 20 described below, so that the output voltage of the generator body 10 can be controlled to approach a predetermined set voltage (200 V in this embodiment).

This excitation circuit 12 may be configured only with the generator field winding 124, and the output current of the AVR 20 may be directly applied to the generator field winding 124 so that the AVR 20 changes the field current that it applies directly to the generator field winding 124. In this embodiment, however, in addition to the aforementioned generator field winding 124, the excitation circuit 12 also includes an exciter (excitation AC generator) 120 having an exciter armature winding 121 and an exciter field winding 122 as shown in FIG. 2, and an AC output of the exciter armature winding 121 of the exciter 120 is A rectifier 123 is provided to rectify the current to DC, and the DC obtained by rectification with the rectifier 123 can be applied as a field current to the generator field winding 124. The magnitude of the field current applied to the exciter armature winding 121 provided in the exciter 120 described above is controlled by the output of the AVR 20 via the output units 23 and 24, and the magnitude of the current output by the exciter armature winding 121 is changed, thereby changing the magnitude of the field current applied to the generator field winding 124.

[Automatic Voltage Regulator (AVR)]
The AC generator 1 is provided with an automatic voltage regulator (AVR) 20 that controls the output voltage of the generator main body 10 by changing the magnitude of the field current applied to the above-mentioned generator field winding 124 .

The AVR 20 detects the output voltage of the generator body 10, and compares this detected output voltage of the generator body 10 with a preset voltage. If there is a difference between the detected output voltage of the generator body 10 and the preset voltage, it controls the field current applied to the generator field winding 124 provided in the excitation circuit 12 so that the output voltage of the generator body 10 matches the preset voltage.

In the AC generator 1 of this embodiment, which has the excitation circuit 12 configured as described with reference to FIG. 2, the AVR 20 changes the field current applied to the generator field winding 124 by changing the field current applied to the exciter field winding 122 provided in the excitation circuit 12 of the generator main body 10 as described above.

This AVR 20 is driven by the AC generated in the generator armature winding 11 of the generator main body 10 as the power supply voltage. The AVR 20 is provided with a pair of power supply input units 21, 22 that are connected to the generator main body 10, and these power supply input units 21, 22 are connected to the three-phase windings U, V, and W provided in the generator armature winding 11 of the generator main body 10.

As shown in FIG. 1, in the AC generator 1 of the present invention, one power supply input section 21 provided on the AVR 20 is connected to the output terminals u, v, w of one of the three-phase windings U, V, W (in the illustrated example, the output terminal u of the U-phase winding), and the other power supply input section 22 is connected to an intermediate tap vm provided at an arbitrary position on one of the remaining two-phase windings (in the illustrated example, the V-phase), and the voltage between the output terminal u and the intermediate tap vm is the power supply voltage of the AVR 20.

This intermediate tap vm may be located anywhere on the V-phase winding as long as the voltage between the output terminal u and the intermediate tap vm is within the range of the AVR20's withstand voltage capability, but it is preferable to locate it at a position that provides the highest possible voltage within the range of the AVR20's withstand voltage capability.

In this embodiment, the intermediate tap vm is provided at a position where the voltage between the output terminal u and the intermediate tap vm is, for example, 147 V.

[Action, etc.]
In the AC generator 1 of the present invention configured as described above, when a large load such as a motor device connected to the generator main body 10 is applied, the load current of the generator main body 10 increases, and as the load current increases, the output voltage of the generator main body 10 decreases.

When the AVR 20 detects this drop in the output voltage of the generator main body 10, it increases the field current applied to the exciter field winding 122 provided in the excitation circuit 12, thereby increasing the output current of the exciter armature winding 121 and increasing the field current applied to the generator field winding 124 of the generator main body 10, thereby restoring the output voltage of the generator armature winding 11 to the set voltage.

Here, in a conventional structure (see Figure 7) in which the voltage between the neutral point O and the output terminal u (115 V as an example) was used as the power supply voltage for the AVR20, when the output voltage of the generator main body 10 dropped, the power supply voltage for the AVR20 also dropped below 115 V.

As a result, even if the AVR 20 attempts to increase the field current to match the drop in the output voltage of the generator main body 10, the AVR 20's power supply voltage has dropped, so the generator main body 10's field current (the field current applied to the exciter field winding 122 of the exciter 120) cannot be increased by the required amount.

As a result, the drop in the output voltage of the generator body 10 becomes large, and it takes a relatively long time for the output voltage of the generator body 10 to return to the set voltage.

In contrast, in the configuration of the present invention in which the voltage between the output terminal u and the center tap vm (147 V as an example) is used as the power supply voltage for the AVR20, even if the output voltage of the generator main body 10 drops due to the application of a large load, the power supply voltage of the AVR20 after the drop can be maintained at a higher level (for example, maintained at 115 V or higher) compared to when the voltage between the neutral point O and the output terminal u (115 V as an example) is used as the power supply voltage.

As a result, the field current applied to the exciter field winding 122 provided in the excitation circuit 12 can be immediately increased to the required level (thus increasing the field current applied by the exciter 120 to the generator field winding 124 of the generator main body 10 via the rectifier 123 to the required level), which in turn reduces the drop in the output voltage of the generator main body 10 and enables the output voltage of the generator main body 10 to be quickly restored to the set voltage.

[Modification 1]
In the AC generator 1 of the present invention described above with reference to FIG. 1, the other power supply input section 22 provided in the AVR 20 is connected only to the center tap vm.

In contrast, the other power supply input section 22 of the AVR 20 may be configured to be selectively connectable to either the center tap vm or the neutral point O (neutral point terminal o provided at the neutral point O), as shown in FIG. 3.

In the embodiment shown in FIG. 3, in order to enable such selective connection, a changeover switch 30 is provided in the circuit between the other power supply input section 22 of the AVR 20 and the intermediate tap vm and neutral terminal o, so that the other power supply input section 22 of the AVR 20 can be selectively connected to either the intermediate tap vm or the neutral terminal o.

By configuring it in this way, it is possible to select the power supply voltage of the AVR 20 to either 115V or 147V, depending on, for example, the driving state of the driving source (e.g., an engine) that drives the AC generator 1.

For example, if the driving source of the AC generator 1 of the present invention is an engine, when a large load is applied before the engine has been sufficiently warmed up, the motor load is applied in a state where the other power supply input section 22 provided in the automatic voltage regulator (AVR) is connected to the neutral point O (neutral point terminal o) (with the power supply voltage of the AVR 20 set to 115 V).

When the amount of electricity generated by the generator body 10 increases, the rotational resistance increases. However, by intentionally lowering the power supply voltage of the AVR 20 to 115V and applying a load in this manner, the output voltage of the generator body 10 when the load is applied is intentionally lowered and the return to the set voltage is delayed. This allows the rotational resistance applied to the engine to increase gradually over a relatively long period of time after the load is applied, thereby preventing the engine from stalling.

On the other hand, when the engine has been sufficiently warmed up, i.e., when there is no risk of the engine stalling even due to an increase in the rotational resistance of the generator body 10, by connecting the other power supply input section 22 of the AVR 20 to the center tap vm (the power supply voltage of the AVR 20 is set to 147 V) and applying a load, the drop in the output voltage of the generator body 10 is reduced and the voltage is quickly restored to the set voltage, allowing the motor load to be started smoothly.

[Modification 2]
In the above explanation with reference to Figs. 1 and 3, the configuration of the present invention has been described by taking as an example a case where it is applied to a generator main body 10 capable of outputting only AC of a three-phase, four-wire output of a predetermined voltage (for example, 200V).

Instead of this configuration, the configuration of the present invention may also be applied to an output voltage variable AC generator in which each three-phase winding U, V, W is formed by combining multiple element coils 14 to 17, and the connection state of the element coils 14 to 17 can be switched between a low voltage connection that provides a predetermined low voltage output (for example, a three-phase, four-wire 200V output) and a high voltage connection that provides a high voltage output that is twice the voltage of the output in the low voltage connection (for example, a three-phase, four-wire 400V output).

In this case, even if the output voltage of the generator main body 10 doubles due to switching from a low-voltage connection to a high-voltage connection, the power supply voltage of the AVR 20 must be configured to remain the same as the power supply voltage at the time of the low-voltage connection (147 V, for example).

To make it possible to extract such a power supply voltage, in this embodiment, as shown in Figure 4, each of the three-phase windings U, V, and W is formed by combining four element coils 14 to 17.

The element coils 14 to 17 that make up the windings U, V, and W of each phase are composed of two four-stage element coils 14, 16 and two five-stage element coils 15, 17, as shown in FIG. 4. Each of the three-phase windings U, V, and W is provided with a low-voltage output terminal u1, v1, and w1 and a high-voltage output terminal u2, v2, and w2. By switching between the neutral point O and the low-voltage output terminals u1, v1, and w1, or between the neutral point O and the high-voltage output terminals u2, v2, and w2 to one of the connections shown in FIG. 4(A) or FIG. 4(B), the output of the generator body 10 can be switched between a low-voltage connection that outputs 200V three-phase, four-wire output (see FIG. 4(A) and FIG. 5(A)), and a high-voltage connection that outputs 400V three-phase, four-wire output (see FIG. 4(B) and FIG. 5(B)).

When low voltage output is required, as shown in FIG. 4(A), a set of element coils (14-15) in which one 4-stage element coil 14 and one 5-stage element coil 15 are connected in series, and a set of element coils (16-17) in which the other 4-stage element coil 16 and the other 5-stage element coil 17 are connected in series are connected in parallel between the neutral point O and each low voltage output terminal u1, v1, w1, so that a 3-phase 4-wire 200V output can be obtained from the neutral point terminal o connected to the neutral point O and each low voltage output terminal u1, v1, w1.

On the other hand, when performing high voltage output, as shown in FIG. 4(B), a set of element coils (16-17) in which the other four-stage element coil 16 and the other five-stage element coil 17 are connected in series, and a set of element coils (14-15) in which one four-stage element coil 14 and one five-stage element coil 15 are connected in series are connected in series between the neutral point O and each high voltage output terminal u2, v2, w2. It is configured so that a three-phase, four-wire output of 400V can be obtained from v2 and w2, and by configuring each of the low-voltage output terminals u1, v1, and w1 to be positioned between one set of element coils (14-15) and the other set of element coils (16-17), that is, at a position where the number of turns of each of the three-phase windings U, V, and W is 1/2, a voltage of 115V can be obtained between the neutral terminal connected to the neutral point O and each of the low-voltage output terminals (between o-u1, o-v1, and o-w1).

In this way, when the configuration of the present invention is applied to an AC generator 10 with a variable output voltage, the power input section 21 of the AVR 20 is connected to one of the low-voltage output terminals u1, v1, and w1 (low-voltage output terminal u1 in the illustrated example).

Then, an intermediate tap vm is provided between one of the remaining terminals (v1, w1) of the low-voltage output terminals (u1, v1, w1) (v1 in the illustrated example) and the neutral point O, in the illustrated example, at the connection between the other 4-stage element coil 16 and the other 5-stage element coil 17, and the other power supply input unit 22 provided in the AVR 20 can be connected to this intermediate tap vm.

By connecting the power supply inputs 21 and 22 of the AVR 20 to the above positions, the power supply voltage of the AVR 20 can be made common (147 V in both cases in this embodiment) regardless of whether the generator body 10 is in the low voltage connection shown in Figure 4 (A) or the high voltage connection shown in Figure 4 (B). Even if the output voltage of the generator body 10 doubles when switched to the high voltage connection, a voltage exceeding the voltage resistance capacity of the AVR 20 is prevented from being applied.

In addition, in the configuration in which the intermediate tap vm is attached to the connection portion between the element coils 16 and 17 as described above, when the connection portion is connected using a crimp terminal 32 or the like as shown in FIG. 5, not only the connection portion of the element coils 16 and 17 but also the conductor provided on the intermediate tap vm is inserted into the crimp terminal 32 and crimped together, so that the intermediate tap vm can be attached at the same time as the connection between the element coils 16 and 17, and there is no need to provide a separate process for attaching the intermediate tap vm.

Next, the results of a test to verify the effectiveness of the present invention are shown below as examples.

[Purpose of the test]
It has been confirmed that by adopting the configuration of the present invention in an AC generator, it is possible to reduce the drop in the output voltage of the generator body when a large load is applied, and to shorten the time it takes for the voltage to return to the set voltage after a voltage drop.

[Test Method]
The AC generator (rated output 80 kVA) described with reference to Figs. 4 and 5 was operated at a frequency of 50 Hz and a rated voltage of 200 V (low voltage connection in Figs. 4(A) and 5(A)), and the change in output voltage before and after the application of a load was observed.

As an example, an AC generator was used in which the voltage (147 V) between the low-voltage output terminal u1 and the center tap vm in the low-voltage connection shown in Figure 4 (A) was used as the power supply voltage for the AVR.

As a comparative example, an AC generator was used in which the voltage (115 V) between the low-voltage output terminal u1 and the neutral point O (neutral point terminal o) in the low-voltage connection shown in Figure 4 (A) was used as the power supply voltage for the AVR.

As the load, we performed a "rated load application test" to measure the change in output voltage when the rated load was applied, and a "motor load application test" to measure the change in output voltage when a motor load was applied.

The drop in output voltage was evaluated by the "voltage drop rate (%)" calculated by the following formula, with the output voltage at the point when the output voltage of the generator body became the lowest after the load was applied being defined as the "minimum voltage."
Voltage drop rate = (rated voltage - minimum voltage) / rated voltage x 100 (%)

The motor used in the "motor load application test" for both the example and the comparative example was the "TKKH3-FBK21E" (output 37 kW) manufactured by Toshiba Industrial Products Systems Corporation.

[Test Results]
The results of the rated load test are shown in Table 1, and the results of the motor load test are shown in Table 2.

Figure 6(A) shows the change in the output voltage waveform of the AC generator of the embodiment before and after the motor load is applied, and Figure 6(B) shows the change in the output voltage waveform of the AC generator of the comparative example.

[Considerations]
From the above test results, both in the rated load application test and the motor load application test, it was confirmed that the voltage drop rate was smaller in the AC generator of the embodiment, and the drop in output voltage when a load was applied was reduced, and it was confirmed that the adoption of the configuration of the present invention contributes to stabilizing the output voltage of the generator body.

In addition, from the output voltage waveforms shown in Figures 6(A) and (B), it can be seen that the AC generator (embodiment) of the present invention returns to the rated voltage (200V) in a shorter time after the load is applied, and it has been confirmed that the motor can be started smoothly.

Reference Signs List 1 AC generator 10 Generator body 11 Generator armature winding 12 Excitation circuit 120 Exciter 121 Exciter armature winding 122 Exciter field winding 123 Rectifier 124 Generator field winding 14 Element coil (4 stages/one side)
15 element coil (5 stages/one side)
16 Element coil (4 stages/other side)
17 Element coil (5 stages/other side)
20 Automatic Voltage Regulator (AVR)
21 Power supply input section (one side)
22 Power supply input section (other side)
23, 24 Output section 30 Changeover switch 32 Crimp terminal 200 AC generator 210 Generator body 211 Generator armature winding 212 Excitation circuit 220 Automatic voltage regulator (AVR)
U, V, W Three-phase windings u, v, w Output terminals u1, v1, w1 Low-voltage output terminals u2, v2, w2 High-voltage output terminal O Neutral point o Neutral point terminal vm Center tap

Claims (5)

An AC generator including a generator armature winding consisting of a three-phase winding star-connected with a phase difference of 120° electrical angle centered on a neutral point, and an excitation circuit having at least a generator field winding, the generator main body being capable of outputting three-phase AC of a predetermined voltage from output terminals provided on each of the three-phase windings, and an automatic voltage regulator that uses the generator main body as a power source and controls the output voltage of the generator main body to approach a preset voltage by changing the field current applied to the generator field winding of the excitation circuit of the generator main body,
a pair of power supply input units for inputting the AC voltage output by the generator body as a power supply voltage to the automatic voltage regulator;
One of the power supply input units is connected to the output terminal provided on one of the three-phase windings,
The other power supply input section is connectable to a center tap provided on one of the remaining windings among the three-phase windings. the excitation circuit provided in the generator body includes an exciter having an exciter armature winding and an exciter field winding that generate a field current to be applied to the generator field winding;
2. The alternating current generator according to claim 1, wherein the automatic voltage regulator changes the field current applied to the generator field winding of the generator body by controlling the field current applied to the exciter field winding of the exciter. An alternating current generator according to claim 1 or 2, characterized in that the other power supply input section provided in the automatic voltage regulator can be selectively connected to either the center tap or the neutral point. Each of the three-phase windings is formed by a combination of a plurality of element coils, and the connection state between the element coils can be switched between a low voltage connection for performing a predetermined low voltage output and a high voltage connection for performing a high voltage output that is twice the voltage of the output of the low voltage connection,
A low voltage output terminal for performing the low voltage output and a high voltage output terminal for performing the high voltage output are provided for each of the three-phase windings,
At the time of the low voltage connection, the element coil is connected so that two windings having the same number of turns are connected in parallel between the neutral point and each of the low voltage output terminals,
During the high voltage connection, the neutral point and each of the high voltage output terminals are connected by the element coils connected in series, and the element coils are connected so that each of the low voltage output terminals is disposed at a position where the number of turns of each three-phase winding is 1/2;
The one power supply input of the automatic voltage regulator is connected to any one of the low voltage output terminals,
4. The alternating current generator according to claim 1, wherein the center tap is provided on a winding between the neutral point and any one of the remaining low voltage output terminals. Each of the three-phase windings of the generator armature winding is formed by connecting a plurality of element coils,
5. The alternating current generator according to claim 1, wherein the center tap is provided at a connection between the element coils of the one phase winding having the center tap.

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