JPH0379960B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply device for an AC generator that converts AC power into DC power and supplies it to a load, and in particular controls the DC power according to a set current range. This invention relates to a DC power supply device for an AC generator.

In general, a DC power supply for an alternating current generator (hereinafter simply referred to as a DC power supply) uses a transformer to step down the AC voltage supplied through the power line to the required voltage, then rectify and smooth it. It is designed to supply DC voltage to the load.

By the way, in such a DC power supply device,
When the load current increases, there is an inconvenience that the load voltage decreases due to a voltage drop in the line (load current supply line) caused by this increase in load current, and if the load side becomes overloaded, the overload There is a disadvantage that the load is damaged by the current. Conventionally, quick-acting fuses, circuit breakers, etc. are used to prevent overcurrent from being supplied to the load, but it takes a certain period of time for these rapid-acting fuses and circuit breakers to operate after an overload condition occurs. Even though these quick-acting fuses and circuit breakers operate, the load may be damaged.

In view of the above points, the present invention can switch the upper limit value of the output current according to the load, so that a current exceeding this upper limit value is not supplied to the load, and even when the load current fluctuates, the load voltage The present invention provides a DC power supply device that can prevent fluctuations in the power supply line. In the DC power supply device for an AC generator, the output voltage of the AC generator is rectified and smoothed by an AC/DC conversion circuit including a transformer, a diode, and a smoothing capacitor, and is supplied to the load through the power supply line. a first input current detector and a second input current detector that detect a current value, and convert the output of the first input current detector into a value within a predetermined range according to the selected current range, Furthermore, a current range switching circuit that rectifies and outputs the voltage drop that generates and outputs a voltage drop compensation voltage for compensating the line voltage drop due to the load current based on the output of the second input current detector. A compensation circuit inputs the output voltage of the output voltage detection section of the alternator, and also inputs the voltage drop compensation voltage output from the voltage drop compensation circuit, and calculates the voltage drop from the output voltage of the output voltage detection section. A compensation voltage is drawn and the result is supplied to the field circuit to increase the output voltage of the alternator by an amount to compensate for the line voltage drop due to the load current, and the output of the current range switching circuit is changed to the output voltage. and a control circuit that adds the output voltage of the detection section and supplies this result to the field circuit to limit the output of the alternator at an output current according to a set current range. There is.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an example of the configuration of a DC power supply device according to the present invention. In this diagram,
1a to 1c are AC power lines, one end of each of these AC power lines 1a to 1c is connected to an output terminal of an AC generator (not shown), and the other end of each of the AC power lines 1a to 1c is connected to each power input. Terminals 2a-2
c, are connected to one end of each of the primary windings 4a 1 to 4c 1 of the transformer 4 via contact circuits 3a _{to 3c} of the circuit breaker 3, respectively. One end of each of the secondary windings 4a ₂ to 4c ₂ of the transformer 4 is commonly connected to one end of the interphase reactor 5, and the other end of the secondary winding 4a ₂ is connected to a fuse (for example, a quick-blow fuse) 6a ₂ . It is connected to the anode of the diode 7a2 via the diode _7a2 . And the cathode of diode 7a ₂ is resistor 9a ₂ and capacitor 8
a ₂ to the anode of the diode, one end of a resistor 10 and one end of a varistor 11 , and further connected to one end of a capacitor 13 via a switch 12 . The one end of this capacitor 13 is connected to one end of a load 15 via a power output terminal 14. Further, the intermediate tap 16 of the interphase reactor 5 is connected to the resistor 1.
0, the varistor 11, and the capacitor 13, and the load 15 via the ground terminal 17.
connected to the other end. Further, one end of each of the other secondary windings 4a ₃ to 4a ₃ of the transformer 4 is commonly connected to the other end of the interphase reactor 5, and the other end of the secondary winding 4c ₃ is connected to the fuse 6a _3. The cathode of the diode 7a ₃ is connected to the anode of the diode 7a ₃ via the resistor 9a ₃ and the capacitor _{8a 3 ,} and is also connected to the cathode of the diode 7a ₂ . There is. Although not shown, other secondary windings 4b ₂ , 4c ₂ , 4b ₃ , and 4c ₃ are also connected in the same way.

On the other hand, a first current transformer 1 is connected to the power supply line 1a.
8 is provided, and each output terminal of this current transformer 18 is connected to an input terminal of a voltage drop compensation circuit 19. The voltage drop compensation circuit 19 calculates a compensation value for compensating the line voltage drop due to the load current based on the output of the current transformer 18, and calculates the voltage (voltage drop compensation voltage) obtained by this compensation calculation. is supplied to both ends of the resistor 20 via terminals 38a and 38b.

On the other hand, a second current transformer 2 is connected to the power supply line 1b.
1 is provided, and each output terminal of this current transformer 21 is connected to one end of a resistor 22 and one end of a resistor 24, respectively. The resistors 22 to 24 are sequentially connected in series to constitute a current limit value setting circuit 25, and the one end of the resistor 22, the connection point between the resistor 22 and the resistor 23, and the connection point between the resistor 23 and the resistor 24 are Terminal 26a
~26c, respectively. Terminals 26a-2
6c, open terminal 26d and common terminal 26e
constitutes a current range switch 26 for selecting the upper limit value of the current (load current) supplied to the load 15, and this current range switch 26
A common terminal 26e of the resistor 24 is connected to the one end of the resistor 24, and the terminals 26a and 26e are respectively connected to respective input terminals of the diode bridge 27. The diode bridge 27 rectifies the output of the current limit value setting circuit 25, and the positive output terminal of the diode bridge 27 is connected to one end of a capacitor 29 and a varistor 30 via a resistor 28, and a diode 31 connected to the anode of the The signal applied to the anode of this diode 31 is supplied to the positive input terminal of the zener bridge 32 constituting the control circuit 38 via the diode 31 and the terminal 38d. Further, the negative output terminal of the diode bridge 27 is connected to the other end of the capacitor 29 and the varistor 30, and the output obtained at this negative output terminal is the terminal 38c.
to the negative input terminal of the zener bridge 32. The Zener bridge 32 has a cathode of a Zener diode 33, an anode of the Zener diode 33, and an anode of the Zener diode 33 between its positive output terminal and negative output terminal.
Resistors 34 are connected in series, and resistors 3
5. The cathode of the Zener diode 36 and the anode of the Zener diode 36 are connected in series, and a capacitor 37 is connected between the anode and cathode of the Zener diode 36. The positive input terminal is connected to the positive output terminal of the output voltage detection section (not shown) of the alternator through the resistor 20, and the negative input terminal of the zener diode 32 is connected to the negative output terminal of the output voltage detection section (not shown). It is connected. Further, one output terminal of this Zener bridge 32 is connected to the input terminal of an amplifier 40a via a resistor 39a. The amplifier 40a amplifies the output of the Zener bridge 32, and the output terminal of the amplifier 40a is connected to one control input terminal of the field circuit of the alternator via a terminal 38e. Similarly, the other output terminal of the zener bridge 32 is a resistor 39b,
It is connected to the other control input terminal of the field circuit via an amplifier 40b.

Next, the operation of this embodiment with the above configuration will be explained in the second section.
This will be explained with reference to the output voltage/current characteristic diagram shown in the figure. First, the common terminal 26e of the current range switch 26
A state where the terminal 26a and the terminal 26a are connected, that is, a case where the load current is not limited will be described. In this case, when the load current is small, the output voltage of the diode bridge 27 and the voltage drop compensation circuit 19 is almost zero, so the voltage between both input terminals of the zener bridge 32 is the output voltage value of the output voltage detection section of the alternator. is almost equal to Therefore, in this case, the amplifiers 40a, 40b keep their outputs constant to keep the output of the alternator constant. Further, in this case, when the size of the load 15 changes and the load current increases, the power supply lines 1a to 1c
The current flowing through the current transformer 18 increases, and the output current of the current transformer 18 increases. Therefore, the voltage drop compensation circuit 19 generates a voltage corresponding to this current increase and applies the voltage to the resistor 20.
is applied across both terminals of the zener bridge 32 to reduce the voltage between both input terminals of the Zener bridge 32. That is, when the current supplied to the load 15 increases, the voltage between both input terminals of the zener bridge 32 decreases in the same way as when the output voltage of the alternator decreases. Therefore, the amplifiers 40a and 40b change the output voltage in a direction that increases the field current of the alternator, thereby increasing the output voltage of the alternator and increasing the output voltage of the AC/DC conversion circuit 43. As a result, the output voltage of the AC/DC converter circuit 43 is compensated for the line voltage drop caused by the increase in load current, as shown by the solid line A in FIG. decreases to

Next, the common terminal 26e of the current range switch 26
When connected to the terminal 26b and the current range is set to 600 A, a voltage is generated across the resistor 20 constituting the current limit value setting circuit 25 and is supplied to the diode bridge 27. As a result, a voltage signal obtained by rectifying the output of the current transformer 21 is output from the diode bridge 27. When the value of this voltage signal becomes larger than the rising voltage of the diode 31,
The diode 31 becomes conductive, and the voltage smoothed by the resistor 28 and capacitor 29 is applied to the zener bridge 32.
Since the voltage is applied between both input terminals of the zener bridge 32, the voltage between both input terminals of the zener bridge 32 increases in the same way as when the output voltage of the alternator increases. As a result, the amplifiers 40a and 40b change their output in the direction of decreasing the output of the alternator, so the output voltage of the AC/DC converter circuit 43 is reduced to an output current of 600 A, as shown by the solid line B in FIG. It will be limited. Similarly, if the common terminal 26e of the current range switch 26 is connected to the terminals 26c and 26d in sequence, the output voltage of the current limit value setting circuit 25 will increase in sequence according to the switch position, and the output voltage of the diode bridge 27 will increase. rises. As a result, the output voltage of the AC/DC conversion circuit 43 is limited to 400A and 200A, respectively, as shown by solid lines C and D in FIG.

As explained above, the DC power supply device for an alternating current generator according to the present invention is applied to an alternating current generator having an output voltage detection section that detects an output voltage and a field circuit that controls a field current, and In a DC power supply device for an AC generator, the output voltage of the AC generator is rectified and smoothed by an AC/DC conversion circuit comprising a transformer, a diode, and a smoothing capacitor, and then supplied to the load. a first input current detector and a second input current detector that detect the current, and convert the output of the first input current detector into a value within a predetermined range according to the selected current range,
Furthermore, a current range switching circuit that rectifies and outputs the current,
A voltage drop compensation circuit that generates and outputs a voltage drop compensation voltage for compensating for line voltage drop due to load current based on the output of the second input current detector; Input the output voltage and input the voltage drop compensation voltage output from the voltage drop compensation circuit, subtract the voltage drop compensation voltage from the output voltage of the output voltage detection section, and supply this result to the field circuit to adjust the load current. The output voltage of the alternator is increased to compensate for the line voltage drop due to A control circuit is provided to limit the output of the generator to an output current according to the set current range, so the upper limit value of the output current is changed according to the load, and the output voltage is significantly reduced near this upper limit value. A current exceeding the upper limit value can be prevented from being supplied to the load, thereby preventing damage to the load at the time of load short circuit or overload, and also preventing damage to the power supply device. Furthermore, even if the load current fluctuates and the line voltage drop changes, this can be compensated for and the load voltage can be held approximately constant.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a configuration example of a DC power supply device for an alternating current generator according to the present invention, and FIG. 2 is an output voltage/current characteristic diagram for explaining FIG. 1. 1a to 1c...AC power line (power line),
18...Current transformer (second input current detector), 21...
... Current transformer (first input current detector), 19 ... Voltage drop compensation circuit, 26 ... Current range switch (current range switching circuit), 38 ... Control circuit, 43 ...
AC/DC conversion circuit.

Claims (1)

[Claims] 1 Applicable to an alternator having an output voltage detection unit that detects an output voltage and a field circuit that controls a field current, the output voltage of the alternator is transformed via a power supply line. In the DC power supply device for an AC generator, which is rectified and smoothed by an AC/DC conversion circuit having an AC/DC converter, a diode, and a smoothing capacitor and supplies it to a load, a first input current detection unit detects a current value of the power supply line. converting the output of the first input current detector into a value within a predetermined range according to the selected current range;
A current range switching circuit that further rectifies and outputs the voltage drop; and a voltage drop that generates and outputs a voltage drop compensation voltage for compensating for a line voltage drop due to load current based on the output of the second input current detector. a compensation circuit, which inputs the output voltage of the output voltage detection section of the alternator and inputs the voltage drop compensation voltage output from the voltage drop compensation circuit, and calculates the voltage drop from the output voltage of the output voltage detection section; A compensation voltage is drawn and the result is supplied to the field circuit to increase the output voltage of the alternator by an amount to compensate for the line voltage drop due to the load current, and the output of the current range switching circuit is changed to the output voltage. an alternating current generator comprising: a control circuit that adds the output voltage of the detection section and supplies this result to the field circuit to limit the output of the alternator at an output current according to a set current range; DC power supply for machines.