JPS6143957B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for emergency operation of a stationary Servius device.

Speed control methods for induction motors can be broadly divided into primary control and secondary control, and among these secondary control methods, the Cerbius method has become widely adopted, especially since it provides constant torque characteristics. The Servian method is generally classified into the MG Servian method and the static Servian method, but the stationary method has no consumable parts and is easy to maintain, so it is easy to control pump pressure, flow rate, or water level. As such, its fields of use are extremely wide-ranging. As shown in FIG. 1, a stationary Servius device for realizing the static Servius system usually includes a wound induction motor 2 and a forward converter 4 that converts the secondary side slip power of this motor 2 into DC. , a reactor 6 that smoothes the DC output of the forward converter 4, and an inverse converter 10 that converts the smoothed DC output into AC and regenerates it to the power source 8. In a stationary Servius device with such a configuration, the induction motor 2
The speed control is performed by changing the control advance angle of the converter 10, and the inverse converter 10 performs commutation operation by using the power supply voltage. However, on the power supply side (commercial power system)
In the event of a short circuit accident, grounding fault, or switching operation of the power supply system, the power supply voltage may drop by 0 to 70% for several cycles to several minutes, or a power outage may occur, or the frequency may fluctuate or the voltage waveform may be distorted. may occur. As a result, the inverse converter 10 constituted by a thyristor inverter becomes unable to commutate, resulting in failure of commutation, and the protective fuse of the thyristor blows out within the inverter 10.
Such commutation failure does not only cause the thyristor's protective fuse to blow out as described above, but also causes operational problems to the entire plant including the thyristor.

In order to eliminate these inconveniences, the applicant has
In particular, by focusing on the drop in power supply voltage and shifting the control advance angle of the inverter to the minimum allowable value using the output signal of a detector that constantly monitors the power supply voltage and detects abnormal voltage drops or voltage loss. At the same time, we developed an emergency operation method for a stationary Servius device by firing thyristor switches attached to both ends of the DC reactor, and filed a patent application. According to this method, the current that continues to flow due to the energy stored in the DC reactor circulates through the thyristor switch and does not flow into the inverter, so the inverter quickly returns to a no-current state. This makes it possible to prevent accidents caused by failure of commutation in the inverse converter. Furthermore, after the inverter has entered the no-current state, the firing pulse for the thyristor of this inverter can be effectively blocked without any hindrance, and furthermore, the energy of the DC reactor is transferred to the thyristor switch. attenuates through. On the other hand, when the power supply voltage is restored to its original state, the output signal of the detector returns to its original normal state, thereby returning the inverter to normal operation again. In this case, the thyristor switch will be automatically deactivated by the output of the rectifier connected to the secondary side of the motor. By using the above method, it was possible to continue operating the motor without damaging the inverter in the event of an abnormal drop or loss of power supply voltage.

However, commutation failure in the inverter cannot be avoided only by monitoring the current and voltage as described above. For example, in a mode where the frequency changes rapidly and the voltage drop of the power supply voltage is delayed, the detection of a power outage condition by the detector is delayed, and commutation failure may occur due to frequency fluctuations or voltage waveform distortion. isn't it. In particular, if a large phase advance capacitor is connected to the secondary power return system, or if a relatively small generator etc. is connected in parallel to the system capacity, the above mode will be activated when the system is disconnected. This caused the inconvenience of a failure in commutation.

Therefore, as a result of various studies to overcome the above-mentioned problems, the inventors have developed a method of constantly monitoring power supply frequency fluctuations or power supply voltage waveforms in addition to the above-mentioned emergency operation method of a stationary Servius device by monitoring the power supply voltage. Moreover, if the power supply frequency fluctuates within a certain range, it is possible to prevent commutation failure due to power supply frequency fluctuation by compensating for it. It has been found that if an abnormal condition that changes beyond the range occurs, if this is detected instantaneously and reliably, the stationary Servius device can be easily stopped instantaneously, and the entire plant can be protected.

Accordingly, the general object of the present invention is to monitor the power supply voltage and power supply frequency introduced into the induction motor in a stationary Servius device for speed control of an induction motor, and to detect variations in the power supply frequency within a certain range. In addition to compensating for this and ensuring the operation of the stationary Serbius device, when the power supply voltage fluctuates or the power supply frequency fluctuates beyond a predetermined range, it is detected and the stationary Serbius device is instantly and reliably operated. The objective is to stop the stationary Servius equipment, protect the stationary Servius equipment itself, and further increase the reliability of the entire plant including this equipment.

In order to achieve the above object, in the present invention, a forward converter is connected to the secondary side of a wound induction motor to convert this secondary side slip power into DC, and the DC output of the forward converter is smoothed. A DC reactor is connected, and an inverter for converting the DC output to AC is connected to the DC reactor to supply AC output to the primary side of the induction motor, thereby controlling the speed of the induction motor. In the stationary Servius device, a power frequency tracking circuit is provided to compensate for fluctuations in the power frequency introduced to the induction motor within a certain range, and to constantly monitor the power supply voltage and power frequency introduced to the induction motor. If one of the detected values fluctuates beyond a certain range, a thyristor switch for circulation provided between both ends of the DC reactor is activated, and the control advance angle of the inverter is phase-shifted to the minimum allowable value. do.

Other objects and advantages of the present invention will become more apparent from the detailed description below.

Next, a preferred embodiment of the emergency operation method for a stationary Servius device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 shows an embodiment of the present invention in a single line diagram. According to this embodiment, the primary side of the three-phase wound induction motor 20 is connected to a three-phase AC power source 24 via a disconnect switch 22, while the secondary side is connected to a switch 26.
It is connected to the starting resistor 28 via. After the induction motor 20 has been started, another switch 30 is turned on and the switch 26 is opened. Due to this operation, the secondary side slip voltage of the induction motor 20 is reduced by the switch 3
It is converted into a DC voltage by a forward converter 32 connected to 0. The DC output terminal of the forward converter 32 is connected to the thyristor type inverse converter 3 via the DC reactor 34.
The AC output terminal of the inverter 36 is connected to a power source (the primary side of the induction motor 20) via a transformer 38.
The DC side voltage Em of the forward converter 32 and the DC side voltage Es of the inverse converter 36 are configured to match in a DC intermediate circuit including the DC reactor 34, so that the control advance angle of the inverse converter 36 If γ is changed, the DC voltage Es on the inverter 36 side will also change, and the induction motor 20 will be operated with a slip voltage commensurate with the amount of change.

The speed regulator 40 is connected to the induction motor 20 to adjust the motor 20 to a desired speed. The actual speed value of the speed generator 44 connected to the child is introduced. Therefore, the speed regulator 40 sets a current target value according to the deviation between the speed target value and the actual speed value, and sets the current target value according to the deviation between the speed target value and the actual speed value, and sets the current target value to the current controller 4 connected to its output side.
6. On the other hand, a current target value detection signal from a current target value current detector (current transformer) 48 connected to the output side of the inverter 36 is introduced into the current regulator 46, and An output signal corresponding to the deviation between the value and the detection signal is generated and this signal is introduced into the ignition control device 50. The ignition control device 50 receives the power supply voltage taken out via the transformer 52 connected to the primary side of the induction motor 20 as a synchronization signal, and reverses it at a control advance angle according to the output signal of the current regulator 46. The firing pulses for the individual thyristors making up the transducer 36 are formed.

Next, according to the present invention, a control device 54 and a thyristor switch 56 connected in parallel to the DC reactor 34 are provided for emergency operation in the event of voltage or frequency fluctuations in the power supply 24.
That is, this control device 54 is connected to the power supply line 24 via a transformer 58, receives a voltage proportional to the power supply voltage or power frequency, and determines whether the power supply voltage or power frequency is normal during operation of the device. Determine. For example, 2 of transformer 58
When the next winding is a six-phase winding, this six-phase secondary voltage is full-wave rectified in the input circuit of the control device 54, and this rectified voltage is led to a comparator and compared with a predetermined value. Alternatively, the secondary frequency of the transformer 58 is once waveform-shaped and then converted into a voltage, and this voltage is introduced into a comparator and compared with a predetermined value to determine whether or not there is an abnormal state. In addition, in the present invention, as mentioned above,
In particular, for fluctuations within a certain range of power supply frequency,
Since this is compensated for by shaping the waveform, there is no risk of commutation failure. However, fluctuations in the power supply frequency exceeding a predetermined amount will deviate from the compensation range. Therefore, when the control device 54 detects a fluctuation of the power supply frequency by a predetermined amount or more or a fluctuation of the power supply voltage by a predetermined amount, an output signal is sent to the ignition control device 50 and the ignition device 60 that fires the thyristor switch 56. is given. As a result, the ignition control device 5
0 is the control advance angle γ of the inverse converter 36 to the minimum allowable value γ
At the same time, the ignition device 60 ignites the thyristor switch 56. The control advance angle γ of the inverter 36 is the minimum allowable value γ min
As a result of the shift, the DC side voltage E _s of the inverse converter 36 becomes larger than the DC side voltage Em of the forward converter 32, and furthermore, due to the ignition of the thyristor switch 56, the current of the DC reactor 34 increases. , is commutated to this thyristor switch 56 and does not flow into the inverter 36. As a result, the inverter 36 quickly reaches a no-current state. The control device 54 constantly monitors the current state of the inverter 36 using a current detector 48, and when the no-current state of the inverter 36 is confirmed, it provides a pulse-off command signal to the ignition control device 50. In this way, the inverter 36 can be stopped without commutation failure, and the current due to the remaining energy of the DC reactor 34 can be circulated through the thyristor switch 56. In the above case, the electronic control devices 40, 46, 48, 50, 54 and 6
The control power supply to be supplied to the power source must be an uninterruptible power supply, or must be configured to maintain a normal voltage at least until the control device 54 generates a pulse-off command signal. In addition, the control device 5
4 is the control advance angle γ of the inverter 36, which is the minimum allowable value γ.
min, and the speed regulator 40 and current regulator 46 can be simultaneously held at zero by the firing signal of the thyristor switch 56. As the means for generating the ignition pulse at the minimum permissible value γ min of the control advance angle, it is advantageous to provide dedicated means separate from the regulator-dependent means for determining the control advance angle in normal conditions. That is, the residual voltage on the primary side of the motor during a power outage changes from normal values in both amplitude and frequency, and the changes also depend on the situation at each time. Therefore, in the case of a three-phase bridge type inverter, the voltage zero passing point of _{the synchronizing signal for thyristor Th 2 ,} which is 60° in phase with respect to thyristor Th ₁ , is
When converted to the control advance angle γ, it becomes γ=60°. Therefore, by combining the voltage zero crossing point detector and the transfer device, it is possible to easily form the ignition pulse at a desired minimum permissible control advance angle, for example around 45°. Therefore, in the event of a power outage, it is only necessary to switch from the formation of ignition pulses depending on the regulator during normal conditions to the formation of ignition pulses based on the voltage zero crossing point detector as described above.

Next, when the Serbius device returns to the normal state, the control device 54 automatically shifts to normal operation. The control device 54 determines that the "normal state" has returned when the power supply voltage introduced via the transformer 58 exceeds a predetermined value for a predetermined time or more and the power supply frequency reaches the predetermined value. do.

As a result, the control device 54 outputs a pulse-off command, a control advance angle γ min command, and a speed regulator 4
0 and cancels the zero hold command of the current regulator 46. As a result, the inverter 36 is again controlled by the regulation loop of the two regulators 40 and 46 via the ignition control device 50, and the control advance angle γ min gradually increases, so that the induction motor 20 is in a normal operating state. ensure that On the other hand, an additional input signal from the speed generator 44 is also introduced into the control device 54 . This signal is particularly useful during extended power outages when the motor speed decreases enough to require accelerated operation via the starting resistor 28. That is, the control device 54
After confirming that the power has returned to normal,
If the motor speed is below the specified value, the control advance angle γ
The switch 26 is switched on instead of the switch 30 without releasing the min command. As a result, the motor speed increases via the starting resistor 28, and when it exceeds the specified value, the switch 26 opens and the switch 3
0 is switched on and the control advance angle γ min command is released. After the command is released, normal operation is resumed using the control loop including the regulators 40 and 46, as described above.

FIG. 3 shows a specific embodiment of the control device 54 for emergency operation according to the present invention. This control device 54 has a voltage proportional to the power supply voltage taken out through the transformer 58 as described above, a voltage proportional to the current of the inverter 36 taken out through the current detector 48, and a speed control device 54. A voltage proportional to the motor speed drawn via the generator 44 is introduced as an input signal. The input signal from transformer 58 is rectified by rectifier G1 and then sent to comparator CP.
1, while the input signal is introduced into a waveform shaper SC, and then into a frequency voltage converter FV.
After being converted into a voltage proportional to the frequency, the voltage is introduced into a computing unit PX, and then led out to the ignition control device 50 and a comparator CP4 through this computing unit PX. By the way, as shown in FIG. 5, when the power supply is suddenly interrupted, the frequency of the power supply changes, and accordingly, the frequency of the synchronizing signal also changes [FIG. 5 1]. On the other hand, since the generation level of the ignition pulse outputted from the ignition control device 50 to the inverter 36 is constant, the generation position of the ignition pulse is fixed at _t1 [Fig. 5 3], Therefore, there is a phase shift between the synchronization signal and the ignition pulse, which causes commutation failure. Therefore, the power supply frequency is introduced into the waveform shaper SC to be waveform-shaped, and further voltage-converted by the frequency-voltage converter FV.
The amount of deviation from the reference level for generating the ignition pulse is detected by the calculator PX, and this is detected by the ignition control device 50.
is introduced as a correction amount. As a result, the slope of the integral waveform in the ignition control device 50 changes (FIG. 5, 2), and the time to reach the ignition pulse generation level is correspondingly delayed, so that the ignition pulse generation position ends up at t ₁ will be corrected to t ₂ . Next, on the output side of the comparator CP1, there is a delayed action instantaneous return type time element T1 and an instantaneous action delayed return type time element T2.
The signal output from the instantaneous operation delay recovery type timer T2 is introduced into one input terminal of the OR circuit OR1 connected to the output side of the timer T2. Since the output side of the comparator CP4 is also connected to the other input terminal of the OR circuit OR1, the signal of the comparator CD4 is introduced into the OR circuit OR1. Furthermore, a NOT circuit NOT1 and a NOR circuit NOR1 are sequentially connected to the output side of the OR circuit OR1. Therefore, the output signal of the NOR circuit NOR1 is the zero hold command signal of the speed regulator 40 and the current regulator 46, and the control advance angle γ of the ignition control device 50 as described above.
It will be used as a min shift command signal and an ignition command signal to the ignition device 60 (see FIG. 2). On the other hand, the signal from the current transformer 48 enters the rectifier G2 constituting the control device 54, and after being rectified, is introduced into the comparator CP2. and leads the NOR circuit NOR2 to one input terminal. Note that the NOR circuit NOR
The configuration is such that the output signal of the OR circuit OR1 is introduced into the other input terminal of the logic circuit OR1. Then,
The output signal of the NOR circuit NOR2 is introduced into the input terminal of the NOT circuit NOT3, and the output signal of the NOT circuit NOT
The output signal No. 3 is introduced into the ignition control device 50 and used as a pulse-off command signal. The output signal of the speed generator 44 is introduced into a comparator CP3, and the output signal of this comparator CP3 is also introduced into the other input terminal of the NOR circuit NOR1, and also controls the switches 26 and 30 (not shown). guided by the device.

FIG. 4 is an explanatory diagram of the operating state of the control device 54 shown in FIG. 3, where reference numeral A indicates the case where the motor speed is in the Servius region when returning to the normal state, and reference numeral B indicates the normal state. This shows a case where the motor speed is in the starting region when the state is restored.

First, when the power supply voltage drops below the specified value at time t ₁ , comparator CP1 operates and its output signal changes from "0" to "1" [see Figure 4 ₁ ]. At time _t2 , when the time _T1 for confirming a power outage has elapsed, the timer T1 operates, and its output signal changes from "1" to "0" (see FIG. 4, 2). As a result, the timer T2 also immediately generates a "1" signal, and this signal is introduced into the OR circuit OR1. Furthermore, when the power supply frequency fluctuates at time _t1 , if the degree of fluctuation falls within a certain range, the waveform is shaped by the waveform shaper SC as described above, converted into voltage by the frequency voltage converter FV, and then output to the arithmetic unit. PX detects the amount of deviation from the reference level. Therefore, the output signal of the arithmetic unit PX corresponding to this deviation amount is introduced into the ignition control device 50 as a correction amount, but on the other hand, as can be easily understood from the circuit diagram shown in FIG. is introduced into the comparator CP4, and when the correction amount exceeds the predetermined value, the comparator CP4
4 and is introduced into one input terminal of the OR circuit OR1. In this way, when the power supply voltage fluctuates by a predetermined amount or the power supply frequency exceeds a predetermined amount, the output signal of the OR circuit OR1 becomes "1", and the output signal "1" of the OR circuit OR1 is negated. The signal reaches the circuit NOT1, is converted into a signal "0" by the NOT circuit NOR1, and is introduced into the NOR circuit NOR1. The NOR circuit NOR1 converts the output signal "0" of the NOT circuit NOT1 into an output signal "1", as shown in FIG.
Command to immediately hold the speed regulator 40 and current regulator 46 at zero, shift the control advance angle of the inverter 36 to a predetermined minimum value γ min, and fire the thyristor switch 56 (logic signal "0") occurs. This quickly brings the inverter 36 into a currentless state. Due to this no-current state of the inverter 36, the output signal of the comparator CP2 changes to the output signal "1" at time _t3 (see FIG. 4). This signal is guided to the timer T3, and the timer T3 operates at time _t4 , which is delayed from time _t3 by the time _T3 for checking the no-current state, and generates an output signal "1". See Figure 4.5]. The output signal "1" is then converted into an output signal "0" by the NOT circuit NOT2 and guided to one input terminal of the NOR circuit NOR2. Since the output signal "1" of the OR circuit OR1 is led to the other input terminal of the NOR circuit NOR2, the output signal of this NOR circuit NOR2 changes to "1" at time _t4 , and this output signal "1"
is converted into an output signal "0" by the inverting circuit NOT3 (see FIG. 4, 6) and gives a pulse-off command to the ignition control device 50, thereby causing the ignition control device 5 to
The ignition pulse from 0 to the inverter 36 is blocked, resulting in a complete shutdown of the inverter 36. After this, the electric motor 20 continues to rotate due to inertia, but the speed gradually decreases as shown in FIG. 4 and 8. When the power supply voltage or power supply frequency returns to its normal state, the operation is A when the motor speed is above the specified value N ₁ and in the Servian region, and B when the motor speed is below the specified value N ₁ and is in the starting region. differs as follows. In case A, comparator CP1 returns when the power supply voltage exceeds a predetermined value, and comparator CP1 returns when the power supply frequency returns to the normal state.
CP4 returns, and as a result, timing element T1 also returns (time _t5 ). However, in order to confirm the return to the normal state, the timer T2 does not return immediately but returns after a predetermined time _T2 (time _t6 ). As a result, the pulse off command, the γ min shift command, and the regulator zero hold command are all canceled. As a result, the regulators 40 and 46 start operating according to the speed control deviation, and accordingly, the control advance angle of the inverse converter 36 given from the ignition control device 50 is γ
It gradually increases from min and returns to normal state. However, in case B, the motor speed fell below the specified value _N1 during the abnormal condition, so the comparator
The output signal of OP3 changes to “1” [Fig. 4 7],
As a result, the switch 26 is closed instead of the switch 30. Even if the output signal of NOT1 becomes a “0” signal at time t ₆ , the output signal of NOR1 remains unchanged from the comparator.
It remains at "0" and does not change due to the "1" signal from CP3. Therefore, the inverter 36 is only given a firing pulse with a control advance angle of γ min and no current flows. However, when the motor 20 returns to its normal state, it will be accelerated by secondary resistance starting.
When the motor speed reaches the specified value N ₁ (at time t ₇ )
Then, the output signal of comparator CP3 is switched to “0” signal, and as a result, the NOR circuit NOR is activated for the first time.
The output signal of 1 is switched to a "1" signal. As a result, the zero hold command of regulators 40 and 46 and γ
The min shift command is canceled. Regulator 40, 4
6 operates according to the speed control deviation, and the control advance angle of the ignition pulse from the ignition control device 50 to the inverter 36 gradually changes from γ min, returning to normal operation. .

As described above, according to the present invention, when the power supply frequency fluctuates, the inverter operates in accordance with the frequency fluctuation within a certain range, that is, within the range in which the fluctuation amount of the power supply voltage does not hinder operation. Shifting the control advance angle and thus compensating for its fluctuations, while detecting any of these fluctuations in the event of fluctuations in the power supply frequency over a predetermined range or fluctuations in the power supply voltage over a predetermined range. As a result, the inverter could be automatically protected without causing a commutation failure of the inverter. Furthermore, when the power supply voltage and frequency return to normal, the induction motor can also return to normal operation, which has the effect of increasing the safety and reliability of the entire plant.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments. Of course, various modifications can be made without departing from the spirit of the present invention, such as application to devices.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram showing an example of a stationary Servius device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram showing a specific embodiment of the main part of the present invention. 4 is a waveform diagram showing the operating state of the circuit of FIG. 3, and FIG. 5 is a waveform diagram showing the state in which the ignition pulse is generated with a delay by the circuit of FIG. 3. 20...Wound induction motor, 22...Shin breaker, 2
4...Power source, 26...Switch, 28...Starting resistor,
30... Switch, 32... Forward converter, 34... DC reactor, 36... Inverse converter, 38... Transformer, 40...
Speed regulator, 42...setting device, 44...speed generator,
46... Current regulator, 48... Current detector (current transformer), 50... Ignition control device, 52... Transformer, 54
...Control device, 56...Thyristor switch, 58...
Transformer, 60... Ignition device, G1, G2... Rectifier,
CP1~CP4...Comparator, T1~T3...Time element, FV...Frequency voltage converter, NOT1~NOT3
...Negation circuit, NOR1~NOR2...NOR circuit, OR1
...OR circuit, SC...waveform shaper, PX...calculator,
In addition, in FIG. 4, when A... the motor speed is in the Servian region when returning to the normal state, B...
When the motor speed is in the starting region when returning to the normal state, a...the rotation rate of the induction motor in the Servian region, and b...the rotation rate of the induction motor in the starting region.

Claims (1)

[Claims] 1. A forward converter for converting this secondary side slip power into DC is connected to the secondary side of a wound induction motor, and a DC reactor is connected for smoothing the DC output of the forward converter, and In a stationary Servius device configured to control the speed of the induction motor by connecting an inverter that converts the DC output to AC to the DC reactor and supplying the AC output to the primary side of the induction motor, A frequency tracking circuit is provided to compensate for fluctuations in the frequency of the power supply introduced into the induction motor within a certain range, and the power supply voltage and frequency introduced into the induction motor are constantly monitored to ensure that either one of the detected values is An emergency feature of a stationary Servius device characterized in that when the fluctuation exceeds a certain range, a thyristor switch for circulation provided between both ends of the DC reactor is fired, and the control advance angle of the inverter is phase-shifted to the minimum allowable value. how to drive. 2. In the method described in claim 1,
An emergency operation method for a stationary Servius device, which comprises detecting fluctuations in the power supply frequency within a predetermined range using a detector, and igniting an inverter in accordance with the amount of fluctuation. 3. In the method described in claim 2,
The power supply frequency within a predetermined range detected by the detector is converted into voltage and compared with the reference level for ignition pulse generation in the inverter, the amount of fluctuation in the power supply frequency is detected as a deviation amount, and this is used in the ignition control device. A method for emergency operation of a stationary Servius device, which comprises introducing the inverter into the inverter and controlling the ignition of the inverter. 4. In the method described in claim 1,
A thyristor switch connected in parallel to a DC reactor is ignited based on an output signal of a detector that detects a fluctuation in a predetermined power supply voltage or a fluctuation in a power supply frequency, and the current of the DC reactor is commutated to the thyristor switch. An emergency operation method for a stationary Servius device consisting of the following. 5. In the method described in claim 1,
A method for emergency operation of a stationary Servius device, comprising blocking the ignition pulse of an inverter after the inverter has reached a no-current state. 6. In the method described in claim 4,
A method of emergency operation of a stationary Servius device, characterized in that the ignition of the thyristor switch is carried out by means of a normal voltage which is maintained at least until generating a blocking signal for the ignition pulse of the inverter. 7 In the method described in claim 5,
When it is detected that the power supply voltage and power supply frequency have recovered to predetermined values, the command to prevent the firing pulse of the inverter is released, a firing pulse is generated, and the control advance angle of this inverter is controlled. An emergency operation method for a stationary Servius device, which consists of gradually increasing the size and returning to a normal operating state. 8. In the method described in claim 5,
When it is detected that the power supply voltage and power frequency have recovered to the predetermined values, if the actual speed value of the induction motor is below the predetermined value, the secondary resistance starting is performed by switching and connecting the motor secondary side to the starting resistor. After the motor speed is accelerated until the actual speed value reaches the predetermined value, the secondary side of the motor is switched to the Serbius device side again, and after this switching is completed, the control advance angle of the converter is gradually increased to resume normal operation. A method of emergency operation of a stationary Servius device consisting of returning it to the state. 9 In the method recited in claim 7,
An emergency operation method for a stationary Servius device in which the ignition pulse is generated by detecting the voltage zero crossing point and adjusting the phase shift of the inverter based on this detection signal.