JPH0537676Y2 - - Google Patents

Description

[Detailed description of the invention] A. Field of industrial application The present invention relates to a stationary Servius device, and in particular, it simplifies the momentary power outage countermeasure circuit that enables continued operation even in the event of a momentary power outage (instantaneous power outage). It concerns stationary Servius devices.

B. Summary of the invention In a stationary Servius device that controls the speed of a wound induction motor, in order to enable the motor to continue operating without stopping in the event of a momentary power failure, the inverter is constructed with a self-extinguishing element, and the Momentary power failure countermeasure circuits having DC and AC residual energy absorbing circuits each using a self-arc-extinguishing element as a control element are provided on the primary and secondary sides of the inverter, and when a momentary power failure occurs, the power failure prevention circuit on the primary side of the inverter Based on the DC overcurrent, the inverter is cut off and at the same time, each of the residual energy absorption circuits is turned on to perform overcurrent control. The system is designed to simplify the process, improve reliability, reduce storage space, and save energy.

C. PRIOR TECHNOLOGY A static Servius device converts the secondary slip power of a wound induction motor that drives a load into direct current using a forward converter made up of diodes, etc., and converts this direct current into direct current using an inverse converter made up of thyristors. The power is returned to AC power at the power supply frequency, and the speed of the wound induction motor is controlled by controlling the firing phase of the inverter. In such stationary Servius devices, commutation failure occurs during a power outage, which is an essential flaw in separately excited converters, and overcurrent can flow and damage the elements. ) is stopped, and after the power is restored, it is started using a starting resistor, accelerated, and then enters Servian operation, which is a complicated procedure, and it takes a very long time to return to the desired operating state after a power outage occurs. Ta.

In order to solve this problem, in addition to preventing element failure due to commutation failure when a momentary power outage occurs, it is also possible to automatically switch to Cerbius operation as soon as power is restored without having to temporarily stop equipment operation. A thyristor Servian device with a configuration as shown in Figure 3 is used, which is equipped with a pulse commutation circuit.
Overcurrent attenuation control when commutation fails in the pulse commutation circuit 20 is performed according to a time chart as shown in FIG. That is, when the power supply 1 momentarily stops, a power failure countermeasure control circuit (not shown) backed up by an uninterruptible power supply detects a voltage drop in the power supply voltage E, and sends a signal to an automatic speed control circuit (not shown). The circuit controls and disconnects the inverter 11, and controls the current in the inverter 11 in a direction to prevent commutation failure. However, if a commutation failure occurs despite the current throttling of the inverter 11, the power failure countermeasure control circuit detects by the current detector 14 that the DC current Id exceeds a predetermined overcurrent value. (commutation failure), a commutation command is given to the pulse commutation circuit 20 to perform turn-off control (forced commutation control) of the thyristor of the inverse converter 11 and opening control of the charging electromagnetic contactor 21. In order to perform turn-off control of the thyristor of the inverse converter 11, first, the pulse commutation circuit 2 is
0 is charged to the polarity shown in the figure through the rectifier _D6 to the commutation capacitor _C1 prior to commutation. It is assumed that the Y-phase and U-phase thyristors of the inverse converter 11 are conducting during pulse commutation, and a current _I1 is flowing from the Y phase to the U phase, and the commutation of the inverse converter 11 is caused by a drop in the power supply voltage. When a failure occurs and the DC current Id reaches a predetermined overcurrent, the commutating thyristor _S1 is fired as described above, and the commutating capacitor _C1 is discharged by the flow of the pulse current _I2 , causing a reverse current to flow into the U-phase thyristor. The thyristor is turned off by applying the conductive voltage. The ignition of the commutation thyristor _S1 is caused by the commutation capacitor
Following the discharge of C ₁ , the current I ₃ flows to charge the commutating capacitor C ₁ in a polarity opposite to that shown in the figure, and at the same time, the energy stored in the DC reactor 9 is released. When the reverse charging voltage of the commutating capacitor _C1 exceeds the anode voltage of the Y-phase thyristor, a reverse voltage is applied to the thyristor and it is turned off. When the Y-phase thyristor is turned off, the residual energy on the DC side is released through the path of the current _I4 . Note that the power outage countermeasure control circuit also controls the starting electromagnetic contactor 5 to close at the same time as commutation failure is detected, so that the electric motor 3 and 2
The next output is passed through the starting resistor 6 at the starting position to attenuate the current.

The above circuit operation attenuates the charging current due to commutation failure.

After implementing such attenuation control of the failed commutation current, when the rotation speed N of the electric motor 3 is within the Cerbius control range at the time of power recovery (power restoration), the above-mentioned control interruption is canceled and Cerbius operation is resumed. On the other hand, if the rotation speed N of the electric motor 3 has fallen below the Servian control range when power is restored, the electric motor 3 is accelerated to the Servian control range speed under the control of the starting resistor 6, and the Servian operation restart control is started. .

D Problems to be solved by the invention A thyristor equipped with the pulse commutation circuit 20 as described above. Inverter 11 in the Salvian device
is a separately excited inverter operation, and commutation may fail depending on the mode at the time of momentary power failure, and as shown in Figure 5, the inflow DC current component _IMS from the motor 3 side and the inverter 1
The inflow DC current component I _TS from the power conversion transformer 12 side on the secondary side of the power converter 1 may be superimposed, and a large DC overcurrent Id may occur. Therefore, the pulse commutation circuit 20 needs to supply the pulse current I ₂ that cuts off the DC overcurrent Id = I _MS + I _TS from the current capacitor C ₁ , and therefore the capacitance of the commutating capacitor C ₁ is large. This occupies 25 to 30% of the volume of the storage board, and since the pulse commutation circuit 20 has a large number of parts and a complicated configuration, the overcurrent processing procedure is also complicated, unreliable, and expensive. Furthermore, once the pulse commutation circuit 20 is activated, the commutation thyristor S ₁ does not have a self-extinguishing ability, so it is also necessary to perform a cutting operation on the Serbius input magnetic contactor 7 and the charging magnetic contactor 21.

The present invention was developed in view of the above-mentioned drawbacks, and the inverter is configured with self-arc-extinguishing elements, and the self-arc-extinguishing elements are used as control elements on the primary and secondary sides of the inverter, respectively. The purpose of this design is to provide an instantaneous power failure countermeasure circuit that includes DC and AC residual energy absorption circuits to simplify the circuit, reduce its size, improve reliability, and save energy.

E Means and Effects for Solving Problems The stationary Servius device of the present invention includes an inverter configured with self-arc-extinguishing elements, and a self-arc-extinguisher connected in parallel to the primary side of the inverter. It has a DC residual energy absorbing circuit consisting of a series circuit of a control element and a resistor, and an AC residual energy absorbing circuit consisting of a series circuit of a rectifier, a self-extinguishing control element, and a resistor installed in parallel on the secondary side of the inverter. The momentary power failure countermeasure circuit is one element of the configuration.

A power supply voltage drop due to a momentary power failure is detected and the inverter 1
When the DC overcurrent flowing to the next side exceeds a predetermined value,
At the same time as the inverter is gated and disconnected, each control element of the instantaneous power failure countermeasure circuit is gated on, and the DC overcurrent on the primary side of the inverter flowing in due to the residual energy on the secondary side of the motor is reduced to the DC overcurrent. On the other hand, the AC overcurrent flowing due to the residual energy of the power conversion transformer on the secondary side of the inverter is passed to the AC residual energy absorption circuit, and each overcurrent is rapidly attenuated.

F. Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a block diagram of a stationary Servius device equipped with a circuit to prevent instantaneous power outages, and FIG. 2 is a time chart for overcurrent control during instantaneous power outages. In FIGS. 1 and 2, the same symbols as those in FIGS. 3 and 4 indicate the same or equivalent components. In Figure 1, 30
is a momentary power outage countermeasure circuit, and the power outage countermeasure control circuit (not shown) includes two residual energy absorption circuits 3.
01 and 302, 301 absorbs the residual energy from the motor 3 side, and 302 absorbs the residual energy from the inverter 2.
Absorbs residual energy from the next-side transformer 12. In addition, in these residual energy absorption circuits,
R ₃ and R ₄ are resistors for instantaneous power outage protection, CB ₂ is a breaker for instantaneous power outage protection, S ₂ and S ₃ are GTO thyristors for instantaneous power outage protection,
_D7 is a rectifier for momentary power outage countermeasures. Further, 31 is an inverse converter, which is composed of a GTO thyristor.

Next, the overcurrent attenuation control operation by the momentary power failure countermeasure circuit 30 when a momentary power failure occurs will be described.

During normal operation, the power failure countermeasure circuit
GTO thyristors S ₂ and S ₃ are kept in a de-energized state. When a momentary power outage occurs, the power outage countermeasure control circuit detects the voltage drop in the power supply voltage E and detects the power outage. Since the inverter 31 is composed of a GTO thyristor, commutation failure does not occur, but residual energy is released from the secondary power conversion transformer 12 of the inverter 31 at the same time as a momentary power failure occurs. The alternating current I _AC to the inverter 31 begins to increase. on the other hand,
As the AC side voltage of the inverter 31 decreases, the voltage Ed proportional to the residual energy from the motor 3 side becomes short-circuited through the circuit impedance, so that the voltage Ed from the forward converter 8 toward the inverter 31 A current close to the current I _MS shown in the figure flows, and the DC current Id (=Id') begins to increase. This direct current
When the power outage countermeasure control circuit detects through the DC current detector 14 that Id = (Id') has reached a predetermined overcurrent value, it sends a gate-off command to the inverter 31 and simultaneously turns off the inverter 31. The power outage countermeasure control circuit consists of residual energy absorption circuits 301 and 302.
Send gate-on command to GTO thyristors S ₂ and S ₃
Make GTO thyristors S ₂ and S ₃ conductive.

Therefore, the DC current Id flowing into the inverter 31
= 0, and the DC current Id flowing out from the forward converter 8 is absorbed by the resistance of the DC residual energy absorption circuit 301.
It flows through _two paths: R ₃ - breaker CB ₂ - GTO thyristor S, residual energy is absorbed, and DC current Id begins to decrease according to the circuit time constant.

On the other hand, the AC current I _AC on the secondary side of the inverter is connected to the rectifier D ₇ -GTO of the AC residual energy absorption circuit 302.
The remaining energy on the AC side flowing through the thyristor S ₃ and the resistor R ₄ is absorbed, and the AC current I _AC begins to decrease according to the circuit time constant. Since the AC side circuit time constant is smaller than the DC side time constant, the AC current I _AC decays faster.

The AC rated current of the inverter 31 is I ₀ , and I _AC ≦
When the AC side comparator of the constant voltage countermeasure control circuit detects the I ₀ state, the AC residual energy absorption circuit 3
A gate-off command is sent to GTO thyristor _S3 of 02, and GTO thyristor _S3 is cut off. after that,
The DC rated current corresponding to the motor secondary rated current is
When the DC side comparator of the power failure countermeasure control circuit detects a state where Id≦I _dN , a gate-off command is sent to the GTO thyristor S ₂ of the DC residual energy absorption circuit ₃₀₁ , and the GTO thyristor S ₂ is cut off.

With the above control, the operation when the power is restored after the overcurrent caused by an instantaneous power failure has attenuated is similar to that of a conventional thyristor. The rotational speed N of the electric motor 3 as in the Servius device
Depending on whether it is within the Cerbius control range or below the Cerbius control range, control for restarting Cerbius operation is entered according to the corresponding sequence.

In this example, a case was explained in which a GTO thyristor was used as a component of an inverter and a control element of an instantaneous power failure countermeasure circuit, but the same control operation can also be performed using a transistor, which is a self-extinguishing element. Of course it can be done.

G. Effect of the invention As described above, the present invention consists of the inverter of the Cerbius device using self-arc-extinguishing elements, the DC side residual energy absorption circuit is installed on the primary side of the inverter, and the DC side residual energy absorption circuit is installed on the secondary side of the inverter. A residual energy absorption circuit is installed on the AC side,
Since it is a self-arc-extinguishing Cervius device equipped with an instantaneous power failure countermeasure circuit in which these control elements are self-arc-extinguishing elements, the conventional pulse commutation circuit and charging circuit, which have a large number of parts, are eliminated and the circuit is simplified. Therefore, the overcurrent control procedure is also simplified and reliability is improved. Also,
In particular, since large capacity capacitors are no longer required, the space required for the instantaneous interruption board is greatly reduced (40%), making it compact and
Fixed price becomes possible.

In addition, in the past, a large pulse current was required to be directly cut off due to overcurrent, but this can be handled by gate control of the GTO thyristor, resulting in energy savings. Furthermore, conventionally, it was necessary to utilize the main circuit bus in constructing a pulse commutation circuit, but this momentary power failure countermeasure circuit has excellent effects such as not having to do so.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a stationary Servius device which is an embodiment of the present invention, FIG. 2 is a time chart of overcurrent control during momentary power failure of the embodiment, and FIG. 3 is a block diagram of a conventional stationary Servius device. FIG. 4 is a pulse commutation operation time chart of the conventional example, and FIG. 5 is an overcurrent characteristic diagram when commutation fails in the conventional example. 1 is a power source, 2, 13 is a wire cutter, 3 is a wound induction motor, 4 is a speed detector, 5 is a starting electromagnetic contactor, 6 is a starting resistor, 7 is a Servius starting electromagnetic contactor, 8 is a forward converter, 9 is a DC reactor, 1
0 is a high-speed shield breaker, 11 is an inverter (thyristor), 12 is a power conversion transformer, 14 is a DC current detector, 20 is a pulse current circuit, 21 is a charging magnetic contactor, 22 is a charging R ₁ is a bypass resistor, CB ₁ is a bypass circuit breaker, D ₁ to _{D 4} are bypass rectifiers, S ₁ is a commutation thyristor, C ₁ is a commutation capacitor, L ₁ and L ₂ are commutation capacitors. Commutation reactor,
D ₅ is a commutation rectifier, D ₆ is a charging rectifier, R ₂ is a charging resistor, 30 is a momentary power failure countermeasure circuit, 301 is a DC residual energy absorption circuit, 302 is an AC residual energy absorption circuit, 31 is an inverter ( GTO thyristor), R ₃ and R ₄ are resistors to prevent instantaneous power outages, CB ₂ is a circuit breaker to prevent instantaneous power outages, S ₂ and S ₃ are GTO thyristors to prevent instantaneous power outages, D ₇ is a rectifier to prevent instantaneous power outages, E is the power supply voltage, Id,
Id' is the DC current, I _MS is the DC inflow from the motor side when commutation fails, the current component, I _TS is the DC current component flowing from the secondary side of the inverter when commutation fails, I AC is the inflow DC current component from the secondary side of the inverter when commutation fails, I _AC is the inflow DC current component from the motor side when commutation fails AC current based on residual energy on the secondary side of the device.

Claims (1)

[Claims for Utility Model Registration] Secondary power of a wound induction motor is converted to DC power by a forward converter, this DC and inverse converter converts it to AC power, the power is returned to the power source, and the ignition phase control of the inverse converter is performed. A stationary Servius device that performs speed control by: an inverter configured with self-arc-extinguishing elements; a DC residual energy absorption circuit connected in parallel to the primary side of the inverter and having the self-arc-extinguishing elements as control elements; A momentary power failure countermeasure circuit is installed in parallel on the secondary side of the inverter and has an AC residual energy absorbing circuit having a self-arc-extinguishing element as a control element, and is provided with an instantaneous power failure countermeasure circuit that is installed in parallel on the secondary side of the inverter to prevent DC current on the primary side of the inverter when a momentary power outage occurs. A stationary Servius device characterized in that the inverse converter is turned off based on overcurrent detection and at the same time the instantaneous power failure countermeasure circuit is turned on to perform overcurrent attenuation control.