JPH01185182A - Inverter apparatus - Google Patents

Abstract

PURPOSE:To prevent surely accidents of overheating and burning by a short- circuit current, by detecting a short-circuit current flowing through a regenerative energy absorbing resistor and by actuating a breaker when an inverter circuit is in a stopped state. CONSTITUTION:AC power of an AC power source 2 is converted into DC power by a rectifier circuit 3 and said AC power is converted again into AC power by an inverter circuit 6 and supplied to a motor 1. When abnormality occurs in a switching element 7 and a short-circuit current continues to flow through a resistor 9 in the stopped state of inverter operation, protective operation circuits A-C are actuated to cut off a breaker for a power line leading from the AC power source 2 to the rectifier circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) This invention relates to an inverter device for driving an AC motor.

(Prior Art) In recent years, inverter devices for driving AC motors have become widespread not only in the general industrial field but also in elevators and home appliances.

FIG. 4 shows a conventional example of a voltage type inverter device that is most widely used among such inverter devices for driving an AC motor. In this conventional voltage type inverter device, in order to drive an AC motor 1, a single-phase or three-phase AC power supply 2 is converted into DC by a rectifier circuit 3 composed of diodes, etc., and a smoothing capacitor 5 of a DC bus 4 is charged. The output of the smoothing capacitor 5 is used as a DC power source, which is reconverted into a variable voltage, variable frequency (VVVF) AC power source by an inverter circuit 6, and then supplied to the motor 1 to drive it.

And a rectifier circuit 3 for converting the AC power supply 2 to DC.
In the case of a voltage-type inverter device configured with a diode rectifier, if the load is such that the motor 1 operates in the regenerative region, it is impossible to regenerate the regenerative energy to the power supply 1, so generally the DC bus 4 A circuit is installed to absorb and consume regenerative energy.

In FIG. 4, in such a circuit, when the voltage of the DC bus 4 increases due to regenerative energy, it is detected and used as a voltage to turn on and off the switching element 7 constituted by a self-extinguishing semiconductor element. A detection circuit 8 and a regenerative energy absorbing resistor 9 are provided for consuming regenerative energy by the current flowing when the switching element 7 is turned on and off.

Therefore, the switching element 7 does not operate when the motor 1 is in the regenerative operation mode, and when the DC bus 4 rises above a certain voltage due to regenerative energy, the voltage detection circuit 8 operates and turns on the switching element 7. , resistor 9
A current is passed through to prevent the voltage from increasing, and when the voltage drops below a certain value, the switching element 7 is turned off, and by repeating this operation, the regenerated energy is consumed by the resistor 9.
An attempt is made to prevent a voltage rise on the DC bus 4.

(Problem to be Solved by the Invention) However, in such a conventional inverter device, if an abnormal mode occurs such as damage to the switching element 7 due to a short circuit or failure of the voltage detection circuit 8 to the switching element ON mode, , a problem occurs where a short circuit current flows continuously in the regenerative energy absorbing resistor 9, and if this abnormal mode continues, overheating will occur exceeding the capacity of the resistor 9, which may lead to burnout. was there.

This invention was made in view of such conventional problems, and when an abnormal mode occurs and short-circuit current continues to flow through the regenerative energy absorption resistor, power supply from the AC power supply or It is an object of the present invention to provide an inverter device that can cut off the supply of DC power from a rectifier circuit and perform a protective operation for the device.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes an AC power supply, a rectifier circuit that rectifies the AC power into DC, and a rectifier circuit that reconverts the DC into AC and supplies it to an electric motor. an inverter circuit, a resistor connected between the positive and negative poles of the DC bus to absorb and consume regenerative energy during regenerative rotation of the motor, and a switching circuit that turns on and off the current to this resistor. An inverter device further comprising: a power supply breaker provided between the AC power source and the rectifier circuit or at an output end of the rectifier circuit; and a current detection circuit that detects the current flowing through the resistor. The device further includes a protection operation circuit that turns off the s1gi device when the current detection circuit detects a current value equal to or higher than a set value when the inverter circuit stops operating.

(Function) The inverter device of the present invention uses a rectifier circuit to convert AC power into DC, and the DC by the rectifier circuit is reconverted into AC by the inverter circuit and supplied to the electric motor. When the motor is in regenerative operation, the regenerative energy is absorbed and consumed by a resistor connected between the positive and negative electrodes of the DC bus. The current flowing from the DC bus to the resistor is detected by the current detection circuit, and if the current value is greater than the set value, it is determined that an abnormality has occurred in the DC circuit, and the current breaker is turned off. The circuit can be protected by cutting off the power supply from the AC power source or cutting off the DC output of the rectifier circuit.

(Example) Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

FIG. 1 shows an embodiment of the present invention, in which the basic configuration circuit of an inverter device is a motor 1, an AC power supply 2,
The rectifier circuit 3, the DC bus 4, the smoothing capacitor 5, the inverter circuit 6, the switching element 7, the voltage detection circuit 8, and the regenerative energy absorbing resistor 9 have the same configuration as in the conventional example shown in FIG. 4.

In the embodiment of this invention, for this inverter device,
Further, between the AC power supply 2 and the rectifier circuit 3, a main contactor contact M-MC, an auxiliary contactor contact AUX-MC and a current limiting resistor 1 are connected.
A parallel circuit with 0 is provided as a current breaker, and a parallel circuit for detecting the current flowing through the DC bus 4 is provided at a position between the smoothing capacitor 5 provided at the output end of the rectifier circuit 3 and the voltage detection circuit 8. A current detection circuit 11 is provided.

Furthermore, as a circuit protection operation circuit, a series circuit of the main contactor M-MC and the time-limiting relay contact TLR, and an auxiliary contactor AU
A series circuit of the X-MC and a start-up premature ejaculation completion relay contact STR is provided in parallel, and a circuit A is provided in series with these parallel connection circuits to which an abnormality detection relay contact ERR is connected.

Further, the start-ready relay 5TR1 turns on and off the start-ready relay contact STR1, and the main contactor M-
Main contactor contact M-MC that turns on and off depending on the operation of MC
, a series circuit B of auxiliary contactor contacts AUX-MC operated by said auxiliary contactor ALIX-MC is also provided.

Further, for the current detection circuit 11, a circuit C for detecting the regenerative operation state of the motor 1 includes a comparison current value setter 12, a comparator 13, a latch circuit 14, and AND circuits 15, 16, 17. , an inverting circuit 18, and an abnormality detection relay ERR.

The operation of the inverter device having the above configuration will be explained next.

When the startup preparation command STR is input, first the auxiliary contactor A
UX-MC operates and this auxiliary contactor contact AUX-MC
is turned on, and the smoothing capacitor 5 is connected via the current limiting resistor 10.
Charging starts, and after a certain period of time the time-limiting relay TLR
is turned on, the main contactor M-MC in circuit A is also turned on, and the start-up ready II electric appliance STR in circuit B is turned on, and the start-up preparation of the inverter circuit 6 is completed.

When the inverter operation signal STP becomes 1'' in response to an elevator operation command (not shown), the N motor 1 is driven by the inverter circuit 6, and a current flows through the current detector 11 according to the operating state of the inverter circuit 6.

During inverter operation, the current signal may become a large current exceeding the current setting value set by the comparison current value setter 12, and the comparator 13 may output a detection signal ``'1''.
．． Since the output of the A N D circuit 16 is "O" while the inverter operation signal STP is "1", the output of the A N D circuit 16 is
7 is also "0", the abnormality detection relay ERR is inoperative, no abnormality detection operation is performed, and the inverter circuit 6 continues its normal operation.

Before the inverter operation signal STP is output, or when the inverter operation signal STP becomes 0'' due to a stop command, the output of the AND circuit 16 becomes 1'', but since the inverter circuit 6 itself is in an operation stopped state, Each device,
If there is no abnormality in the sensor, no current flows to the current detector 11, and no abnormality detection operation is performed.

In this inverter stopped state, if a short circuit mode occurs due to an abnormality in the voltage detector 8 or due to an abnormality in the switching element 7 itself, a short circuit current flows through the DC bus 4.

At this time, the inverter operation signal SPT is "OP!" and the start-up preparation completion signal STR is "1", so the signals inputted to the AND circuit 16 via the inverting circuit 18 are both "1", and The output also becomes "1" and is input to the AND circuit 17.

Here, when the current detector 11 detects a short circuit current and detects a current value larger than the current value set by the comparison current value setting device 12, the output of the comparator 13 becomes "1", and the A
The output of the ND circuit 17 also becomes "1", and the latch circuit 14 latches the abnormal signal.

This causes the abnormality detector ERR to operate, turning off its normally closed contact ERR and turning off the auxiliary contactor AUX-MC.
, main contactors M-MC are both turned off, and these contacts A
tJX-MC and M-MC are turned off, the AC supply from the AC power supply 2 to the rectifier circuit 3 is cut off, the short circuit current stops flowing to the regenerative energy absorption resistor 9, and the circuit protection operation is performed. be exposed.

In this way, when the inverter circuit 6 is in the operating state, the protective operation circuit A-C does not operate, and the necessary current is supplied to the motor 1.

Then, when an abnormality occurs in the switching element 7 and the short circuit current continues to flow through the resistor 9 while the inverter is stopped, the protective operation circuit A-C is activated, and the power line leading from the AC power supply 2 to the rectifier circuit 3 is activated. It is possible to cut off the circuit breaker and prevent the short circuit current from continuing to flow through the resistor 9, thereby preventing the resistor 9 from overheating and burning out.

Note that the latch circuit 14 is configured such that the output of the AND circuit 17 is
If the input 1111+ is set to operate for a certain period of time by setting a certain delay time instead of operating instantly when the signal becomes negative, malfunctions can be reliably prevented.

Note that the present invention is not limited to the above-described embodiment, and the logic circuit (2) in the abnormal current detection circuit C in FIG. 1 can be changed to the circuit configuration shown in FIG. 2.

The logic circuit shown in FIG. 2 has a start-up ready signal STR.
Even if the inverter operation signal STP is in a stopped state and the input is "0", it is input directly to one input terminal of the AND circuit 17 without passing through the AND circuit 16 shown in FIG. This is how it was done.

In the case of this embodiment, the current detection circuit 11 detects a short circuit current in the entire range when the inverter operation is stopped, that is, when the inverter operation stop signal STP is "0", and performs a circuit protection operation.

In this embodiment, when the auxiliary contactor AIJX-MC is turned on, the current limiting resistor 10 is inserted into the circuit, so the current I 5hort due to the short circuit of the switching element 7 is equivalent to 1 When the limiting resistance value of is R1, rshort=Vdc/(R+2R+).

Therefore, the set value of the comparison current value setter 12 is set to be smaller than the short circuit current of the first embodiment shown in FIG.

The embodiment shown in FIG. 3 is a modification of the circuit part (2) including the AC power supply 2, the rectifier circuit 3, and the smoothing capacitor 5 in the first embodiment shown in FIG. An auxiliary contactor contact AUX-MC is connected between the two, and a time-limiting relay TLR is also provided between the rectifier circuit 3 of the DC bus 4 and the smoothing capacitor 5, and a current-limiting resistor 10 and a main contactor contact M-MC are connected between the rectifier circuit 3 of the DC bus 4 and the smoothing capacitor 5. This is a configuration in which a parallel circuit is connected with the

Also in the case of this embodiment, when the start preparation completion signal is output from the elevator control device side, the auxiliary contactor ALJX-M
C is turned on, and the DC from the rectifier circuit 3 passes through the current limiting resistor 10.
It will be input to the smoothing capacitor 5 via. Then, after the delay time caused by the time-limited relay T and R has elapsed,
The main contactor contact M-MC is also turned on, and direct current from the rectifier circuit 3 is supplied to the smoothing capacitor 5 through the main contactor contact M-MC, allowing a transition to a steady operating state.

Then, an abnormal short circuit current is detected and the auxiliary relay ΔUX
-MO is turned off and the contact AIJX-MC is turned off, the power supply from the AC power supply 2 to the rectifier circuit 3 is cut off, and a protective operation is performed.

[Effects of the Invention] As described above, according to the present invention, when an abnormality occurs in which the switching element is constantly in a conductive state and a short circuit current flows through the regenerative energy absorption resistor, the current detection circuit detects the short circuit current. However, if the inverter circuit is in a stopped state, when the detected current exceeds the set value, the circuit breaker is activated to supply power from the AC power supply to the rectifier circuit, or from the output end of the rectifier circuit to the DC bus. The output of the regenerative energy absorbing resistor can be cut off to perform circuit protection, and accidents such as overheating and burnout caused by short-circuit current flowing continuously to the regenerative energy absorbing resistor can be reliably prevented.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram showing a modification of the part ``■'' in FIG. 1, FIG. 3 is a circuit diagram of the part ``■'' in FIG. 1, and FIG. FIG. 2 is a circuit diagram of a conventional example. 1... Electric motor 2... AC power supply 3... Rectifier circuit 4... DC bus 5... Smoothing capacitor
6... Inverter circuit 7... Switching element
8... Voltage detection circuit 9... Regenerative energy absorption resistor 10... Current limiting resistor 11... Current detection circuit 12
... Comparison current value setter 13 ... Comparator 14 ... Latch circuit 15.
16.17...AND circuit '18...Inverting circuit M-MC...Main contactor ALIX-MC...Auxiliary contactor STR...Ready to start relay ERR...Abnormality detection Relay S'TP...Inverter operation signal

Claims (1)

[Claims] An AC power supply, a rectifier circuit that rectifies the AC power into DC, an inverter circuit that reconverts the DC by the rectification circuit into AC and supplies it to the motor, and regeneration during regenerative operation of the motor. In an inverter device comprising a resistor connected between positive and negative electrodes of a DC bus bar in order to absorb and consume energy, and a switching circuit that turns on and off electricity to the resistor, the AC power supply further comprises: a power supply breaker provided between and the rectifier circuit or at the output end of the rectifier circuit; a current detection circuit that detects the current flowing through the resistor; and a current detection circuit that detects the current flowing through the resistor when the inverter circuit stops operating. An inverter device comprising: a protection operation circuit that turns off the circuit breaker when a current value greater than a set value is detected.