JPH1023740A - Power converter - Google Patents

Abstract

(57) [Problem] To provide an alarm when connected to a DC power supply in a polarity opposite to a normal state without using a separate power supply. SOLUTION: Between one power supply terminal P and a smoothing capacitor 16 for supplying an output current of a DC power supply 12 to an inverter main circuit 17, a current suppressing resistor 13 for suppressing an inrush current; A series circuit with a reverse connection protection diode 14 that is in a reverse bias state when the connection state with the diode 12 has a polarity opposite to the normal state is interposed. The short-circuit relay 20 turns on the normally-open contact 20a when a rush current is reduced to a predetermined level or less in a steady state to short-circuit both ends of a series circuit of the current suppressing resistor 13 and the reverse connection protection diode 14. . The light emitting diode 2 connected to both ends of the reverse connection protection diode 14 in a reverse polarity state to this.
Reference numeral 1 denotes a state in which the reverse connection protection diode 14 is reverse-biased, the flywheel diode 17b in the inverter main circuit 17 and the current suppression resistor 13
It is energized and lit through such as.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power converter used by connecting to a DC power supply.

[0002]

2. Description of the Related Art FIG. 4 shows an example of this type of power converter. In FIG. 4, an inverter device 1 as a power converter is supplied with power from a DC power supply 2, and has a configuration in which a three-phase induction motor 3 is driven at a variable speed by a variable voltage and a variable frequency output.

Specifically, in the inverter device 1,
The smoothing capacitor 4 is charged from the DC power supply 2 through the current suppressing resistor 5 and the reverse connection protection diode 6, and power is supplied to the inverter main circuit 7 from both ends of the smoothing capacitor 4. Smoothing capacitor 4
The main circuit voltage detecting circuit 8 provided to detect the voltage between both ends of the current limiting resistor 5 operates the short-circuit relay 9 when the smoothing capacitor 4 is charged to a predetermined level or more. And both ends of the series circuit of the reverse connection protection diode 6 are short-circuited. This prevents power loss in the current suppressing resistor 5 and the reverse connection protection diode 6 in the steady state.

[0004]

According to the above-mentioned conventional configuration, even if the inverter device 1 is erroneously connected to the DC power supply 2 in reverse, the inverter device 1 is protected by the action of the reverse connection protection diode 6. Will be done. However, in the conventional configuration, there is no function of issuing an alarm for the reverse connection state, and there is a problem that this is inconvenient in use. Such a problem can be dealt with by adding a function of detecting a reverse connection state and issuing an alarm.

[0005] When the above functions are added, it is conceivable to use the output of the control power supply provided in the inverter device 1 for generating an alarm. Since it is generally obtained from a power supply (DC power supply 2 in the example of FIG. 4), an alarm output cannot be obtained in a reverse connection state, which is difficult to realize. For this reason, it is actually necessary to separately provide a power supply, which has caused a rise in cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to easily generate an alarm when a DC power supply is connected in a polarity opposite to a normal state without using a separate power supply. It is an object of the present invention to provide a power conversion device that can perform the power conversion.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention is used by connecting to a DC power supply. In a power converter including a smoothing capacitor, a current suppressing resistor for suppressing an inrush current flowing into the smoothing capacitor, and a resistor connected in series with the current suppressing resistor, and a connection state with the DC power supply is a regular A reverse connection protection diode that blocks an output current from the DC power supply when the polarity is opposite to the state, and the current suppressing resistor and the reverse connection that are turned on during a steady state in which the rush current drops below a predetermined level. A switch for short-circuiting both ends of a series circuit of protection diodes, and a switch connected in parallel with the reverse connection protection diode, and a reverse voltage applied to the reverse connection protection diode; In it is obtained by a structure in which a light emitting element to be turned (claim 1).

According to this configuration, when the power converter is connected to the DC power supply with a normal polarity, the inrush current flowing into the smoothing capacitor is suppressed by the current suppressing resistor. At this time, since the forward voltage is applied to the reverse connection protection diode, the light emitting element is not turned on. Thereafter, when the inrush current falls to a predetermined level or less and becomes a steady state, the switch is turned on and both ends of the series circuit of the current suppressing resistor and the reverse connection protection diode are short-circuited. , The occurrence of power loss in the current suppressing resistor and the reverse connection protection diode is prevented, and the light emitting element is kept in the unlit state.

On the other hand, when the power converter is connected to the DC power supply in a polarity opposite to the normal state, the reverse voltage is applied to the reverse connection protection diode. Therefore, charging of the smoothing capacitor is prevented, and the light emitting element is turned on by the output from the DC power supply. Therefore, by turning on the light emitting element, an alarm is issued for a state in which the power converter is connected to the DC power supply with a polarity opposite to a normal state.

In this case, the light emitting device may include a light receiving element constituting a photocoupler, and a contact signal output circuit for outputting a contact signal according to the light receiving state of the light receiving element may be provided. .

According to this configuration, when the light emitting element is turned on, that is, when the power converter is connected to the DC power supply with the polarity opposite to the normal state, the contact signal is output from the contact signal output circuit. Therefore, the contact signal can be used, for example, for shutting down a DC power supply, so that the application range can be expanded.

Further, in a power conversion device which is used by being connected to a DC power supply and which is provided with a smoothing capacitor for smoothing an output current of the DC power supply and providing the smoothed output current to a power conversion section, A current suppressing resistor for suppressing an inrush current flowing in, an output from the DC power supply connected in series with the current suppressing resistor, and when the connection state with the DC power supply has a polarity opposite to a normal state. A reverse connection protection diode that blocks current, a switch that is turned on during a steady state in which the rush current drops below a predetermined level and short-circuits both ends of a series circuit of the current suppression resistor and the reverse connection protection diode, A failure output circuit that is operated by an output from a protection circuit for performing an overload protection operation and shuts off the DC power supply and displays a failure; Ord and are connected in parallel, may be configured to include a switching means for switching said fault output circuit while a reverse voltage is applied to the diode for protection against reverse connection to the operating state (claim 3).

According to this configuration, similarly to the first aspect of the present invention, when the power converter is connected to the DC power supply with a proper polarity, the light emitting element is kept in the off state and the stationary state is maintained. , The occurrence of power loss in the current suppressing resistor and the reverse connection protection diode is prevented.

On the other hand, when the power converter is connected to the DC power supply with a polarity opposite to that of the normal state, the state is such that a reverse voltage is applied to the reverse connection protection diode. The switching means switches the failure output circuit to the operating state. For this reason, the DC output is cut off by the fault output circuit, and a fault is displayed. Therefore, according to the failure display state as described above, an alarm is issued for a state in which the power converter is connected to the DC power supply with a polarity opposite to the normal state.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In FIG. 1, an inverter device 11 as a power converter has a positive input terminal P
And a negative input terminal N, and these input terminals P and N
Are connected to the positive output terminal 12a and the negative output terminal 12b of the DC power supply 12, respectively, so that power is supplied from the DC power supply 12.

In the inverter device 11, the positive side input terminal P is connected to the positive side main circuit bus 15a via a current suppressing resistor 13 and a reverse connection protection diode 14 in series, and the negative side input terminal N is negative. Side is directly connected to the main circuit bus 15b. A smoothing capacitor 16 for current smoothing and an inverter main circuit 17 as a power conversion unit are connected between the main circuit buses 15a and 15b, respectively, and a variable voltage / variable frequency output from the inverter main circuit 17 provides The three-phase induction motor 18 as a load is driven at a variable speed. Although not specifically shown, the inverter main circuit 17 is, for example, six IGBTs 17a (only one is shown) connected in a three-phase bridge.
And a flywheel diode 17b connected to each IGBT 17a.

The main circuit voltage detecting circuit 19 is provided so as to detect the voltage between both ends of the smoothing capacitor 16, and when the detected voltage becomes higher than a predetermined level (when the smoothing capacitor 16 is charged to a predetermined level or higher). ), The short-circuit relay 20 as a switch is operated. The normally open contact 20a of the short-circuit relay 20 is connected in parallel with the series circuit of the current suppressing resistor 13 and the reverse connection protection diode 14.

Therefore, after the smoothing capacitor 16 has been charged to a predetermined level or more, in other words, after the smoothing capacitor 16 has shifted to a steady state in which the rush current has dropped below the predetermined level, the current suppressing resistor 13 and the reverse connection are connected. Both ends of the series circuit of the protection diode 14 are connected to the normally open contact 20a.
As a result, short-circuiting occurs, thereby preventing the occurrence of power loss in the current suppressing resistor 13 and the reverse connection protection diode 14 in a steady state.

A series circuit of a light emitting diode 21 (corresponding to a light emitting element in the present invention) and a resistor 22 having opposite polarities is connected to both ends of the reverse connection protection diode 14. Specifically, the light emitting diode 21 has an anode connected to the cathode side of the reverse connection protection diode 14 and a cathode connected to the anode side of the reverse connection protection diode 14 via the resistor 22. The resistor 22 serves to limit the current flowing through the light emitting diode 21, and may be a resistor having a high resistance and a small capacity.

According to the above configuration, when the positive input terminal P and the negative input terminal N of the inverter device 11 are connected to the DC power supply 12 with the normal polarity, the short-circuit relay 20 The light emitting diode 21 is in the reverse bias state until the open contact 20a is turned on. After that, when the normally open contact 20a is turned on, the voltage application to the light emitting diode 21 is stopped. Therefore, the light emitting diode 21 is not turned on.

On the other hand, a state in which the positive input terminal P and the negative input terminal N of the inverter device 11 are connected to the DC power supply 12 with a polarity opposite to the normal state (the positive input terminal P is connected to the DC power supply 12). Is connected to the negative output terminal 12b and the negative input terminal N is connected to the positive output terminal 12a), the reverse connection protection diode 14 is reverse biased (reverse voltage applied). ). For this reason,
While charging the smoothing capacitor 16 is prevented,
A forward current is supplied from the DC power supply 12 to the light emitting diode 21 via the flywheel diode 17b, the resistor 22, and the current suppressing resistor 13 in the inverter main circuit 17, whereby the light emitting diode 21
Will be lit.

That is, the inverter device 11 is connected to the DC power source 1
When the LED 2 is connected to the normal state with a polarity opposite to that of the normal state, the lighting of the light emitting diode 21 gives an alarm for the reverse connection state, which is very convenient in practical use. In addition, since it is not necessary to separately provide a power source to obtain such an alarm output, there is no possibility that the cost will rise.

FIG. 2 shows a second embodiment of the present invention. Only the portions different from the first embodiment will be described below. That is, in this embodiment, the light emitting diode 21
And a phototransistor 23 constituting a photocoupler
By providing both ends (emitter and collector) of the phototransistor 23 to the output terminals 11a and 11b, a contact capable of outputting a contact signal through the output terminals 11a and 11b is provided. The signal output circuit 24 is configured.

According to the present embodiment configured as described above,
When the light emitting diode 21 is turned on, that is, when the inverter device 11 is connected to the DC power supply 12 with a polarity opposite to the normal state, the phototransistor 23 in the contact signal output circuit 24 is turned on and the output terminal 11a is turned on. And 11b output contact signals. Therefore, when a contact signal is output from the output terminals 11a and 11b, for example, if an external sequence circuit that performs a process of cutting off the output of the DC power supply 12 is provided, the inverter device 11 When the connection is made with the polarity opposite to that of the state, the DC power supply 12 is automatically cut off, so that an improvement in safety can be expected.

In the above embodiment, a light receiving element such as a photodiode, a photothyristor, or a CdS photoelectric cell may be used in place of the phototransistor 23.

FIG. 3 shows a third embodiment of the present invention. Only the parts different from the first embodiment will be described below. The inverter device 11 'in this embodiment is
The configuration includes a failure output circuit 25. The fault output circuit 25 includes a fault output relay 26 that is operated by a command from a well-known protection circuit (not shown) provided for overload protection and the like in the inverter device 11 ′, and output terminals FLA, FLB, FLC is provided. The output terminals FLA and FLC are always in a cut-off state, and are bridged via the normally open contact 26a when the normally open contact 26a of the relay 26 is turned on. In addition, the output terminal FLB and FLC are always in a bridged state via the normally closed contact 26b of the relay 26, and have a configuration in which the normally open contact 26b is turned off when the normally open contact 26b is turned off. ing.

In this case, although not specifically shown, when the connection between the output terminals FLB and FLC is cut off, the DC power supply 12 is cut off, and the connection between the output terminals FLA and FLC is bridged. In this state, a failure indicator (not shown) is operated by the output of the DC power supply 12 to display a failure. Accordingly, when the fault output relay 26 is operated by the protection circuit, the DC power supply 12
Is interrupted, and the normally open contact 26a of the relay 26 is
Is turned on, a failure display operation is performed.

In this embodiment, instead of the series circuit of the light emitting diode 21 and the resistor 22 in the first embodiment, an auxiliary relay 27 (switching means according to the present invention) is provided at both ends of the reverse connection protection diode 14. And resistance 2
8 connected in series. The auxiliary relay 27 includes a normally open contact 27a and a normally closed contact 27b. The normally open contact 27a is connected to the output terminals FLA and FLC.
And the normally closed contact 27b of the failure detection relay 26 is connected in parallel with the output terminal FLB.
And the FLC is connected in series with the normally closed contact 26b of the failure detection relay 26.

According to the present embodiment configured as described above,
When the positive input terminal P and the negative input terminal N of the inverter device 11 ′ are connected to the DC power supply 12 with the correct polarity, the normally open contact 2 of the short-circuit relay 20 starts immediately after the connection.
In the period until 0a is turned on, the auxiliary relay 27
, Only a low level voltage corresponding to the forward voltage level of the reverse connection protection diode 14 is applied. When the normally open contact 20a is turned on thereafter, the voltage application to both ends of the auxiliary relay 27 is stopped, and the auxiliary relay 27 is not operated.

On the other hand, when the positive side input terminal P and the negative side input terminal N of the inverter device 11 'are connected to the DC power supply 12 with the polarity opposite to the normal state, the reverse connection protection diode 14 is connected. Because it becomes reverse biased state,
The DC relay 12 supplies a flywheel diode 17b and a resistor 2
2. A relatively large voltage is applied via the current suppressing resistor 13, whereby the auxiliary relay 27 is operated. Note that the magnitude of the voltage applied to the auxiliary relay 27 is determined by the resistance values of the current suppressing resistor 13 and the resistor 28.
The voltage applied to the auxiliary relay 27 is
Of course, it is set so as to be equal to or higher than the operating voltage of

When the auxiliary relay 27 is operated as described above, the connection between the output terminals FLB and FLC is cut off by the normally closed contact 27b of the auxiliary relay 27, so that the DC power supply 12 is cut off. , And at the same time,
Since the output terminals FLA and FLC are bridged by the normally open contact 27a of the auxiliary relay 27, a failure indicator (not shown) is operated.

Therefore, when the inverter device 11 'is connected to the DC power supply 12 with the polarity opposite to the normal state,
In response to the operation of the auxiliary relay 27, the DC power supply 12 is automatically cut off, and the fault indicator is operated to output an alarm. This makes it practically convenient and improves safety. Can be enhanced. Of course, also in this embodiment, it is not necessary to provide a separate power supply for the above-mentioned alarm, and it is only necessary to add the auxiliary relay 27 and the resistor 28, so that there is no possibility that the cost will rise.

[0033]

As is apparent from the above description, according to the power converter of the first aspect, when the power converter is connected to the DC power supply in the opposite polarity to the normal state, the reverse connection protection diode is connected to the DC power supply. Since the light emitting elements connected in parallel were configured to be turned on by the output from the DC power supply, an alarm when the DC power supply was connected in the opposite polarity to the normal state,
This can be generated without using a separate power supply.

According to the power converter of the present invention, since the contact signal output circuit for outputting a contact signal in accordance with the lighting of the light emitting element is provided, the DC power supply has a polarity opposite to that of a normal state. The contact signal can be obtained in the connected state, and the range of application can be expanded.

According to the third aspect of the present invention, when the DC power supply is connected to the DC power supply in a polarity opposite to the normal state, the failure output circuit is switched to the operating state through the switching means, thereby providing the DC power supply. Since the shut-off operation and the failure display are performed, the safety can be improved, and the alarm in the case of erroneous connection as described above can be issued without using a separate power supply.

[Brief description of the drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is a view corresponding to FIG. 1, showing a third embodiment of the present invention;

FIG. 4 is a diagram corresponding to FIG. 1 for explaining a conventional example.

[Explanation of symbols]

In the drawings, 11 and 11 'are inverter devices (power conversion devices), 12 is a DC power supply, 13 is a current suppressing resistor, 14 is a reverse connection protection diode, 16 is a smoothing capacitor, 17
Is an inverter main circuit (power conversion unit), 19 is a main circuit voltage detection circuit, 20 is a short-circuit relay (switch), 21 is a light emitting diode (light emitting element), 23 is a phototransistor (light receiving element), and 24 is a contact signal. An output circuit, 25 is a failure output circuit, 26 is a failure detection relay, and 27 is an auxiliary relay (switching means).

Claims (3)

[Claims] 1. A power conversion device which is used by being connected to a DC power supply and has a smoothing capacitor for smoothing an output current of the DC power supply and supplying the smoothed output current to a power converter. A current suppressing resistor for suppressing an inrush current flowing in, an output from the DC power supply when the connection state with the DC power supply is opposite to the normal state when the connection state with the DC power supply is opposite to the normal state; A reverse connection protection diode for blocking current; and turned on when the inrush current drops below a predetermined level in a steady state to short-circuit both ends of a series circuit of the current suppression resistor and the reverse connection protection diode. A switch, and a light-emitting element that is connected in parallel with the reverse connection protection diode and is lit when a reverse voltage is applied to the reverse connection protection diode. Power converter according to claim. 2. A contact signal output circuit which has a light receiving element constituting a photocoupler with the light emitting element and outputs a contact signal according to a light receiving state of the light receiving element. Power converter. 3. A power converter having a smoothing capacitor connected to a DC power supply and used for smoothing an output current of the DC power supply and providing the smoothed output current to a power converter. A current suppressing resistor for suppressing an inrush current flowing in, an output from the DC power supply when the connection state with the DC power supply is opposite to the normal state when the connection state with the DC power supply is opposite to the normal state; A reverse connection protection diode for blocking current; and turned on when the inrush current drops below a predetermined level in a steady state to short-circuit both ends of a series circuit of the current suppression resistor and the reverse connection protection diode. A switch, a failure output circuit that is operated by an output from a protection circuit for performing an overload protection operation or the like, and shuts off the DC power supply and displays a failure, and the reverse connection. It is connected in parallel with Mamoruyo diodes, power converter, characterized in that a reverse voltage to the diode for protection against reverse connection has a switching means for switching the operating state of the failure output circuit in a state of being applied.