JPS639228Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is a reversible Leonard device that drives a DC motor using a thyristor power converter in which thyristors are connected in antiparallel, and also regenerates power and applies a brake. It is related to protection circuits.

[Conventional technology]

Generally, a reversible Leonard device is a forward converter (hereinafter referred to as a converter) that converts an AC power source to a DC power source.
The converter is equipped with a thyristor power converter consisting of an inverse converter (hereinafter referred to as an inverter) that regenerates the energy of a DC motor (hereinafter simply referred to as the motor) into an AC power supply, and the thyristor configurations of the converter and the inverter are connected in antiparallel. It consists of In addition, since the commutation of the thyristor in both these converters and inverters is separately excited, that is, by commutation of the power supply, if a power outage occurs while the inverter is operating, the thyristor cannot be turned off, and the motor is The load will be short-circuited through. It is known that this short-circuit current can lead to the destruction of thyristor elements or the melting of protective fuses.
Normally, a high-speed circuit breaker is inserted in series with the motor to protect the thyristor power converter from fault current during a power outage, and the high-speed circuit breaker is opened when a power outage occurs during regenerative operation.

FIG. 1 shows an example of the main circuit configuration of a conventional circulating current type reversible Leonard device, in which 1 is a molded circuit breaker, 2 is a transformer, 3 is a thyristor power converter consisting of a converter 3a and an inverter 3b, 4,
4' is a current detector, 5 and 5' are reactors for suppressing circulating current, 6 is an electric motor equipped with a speedometer generator 7,
8 is a contactor, and 9 is a high speed circuit breaker. In FIG. 1, when the electric motor 6 is in power running with the illustrated polarity, electric power is supplied to the electric motor 6 from the AC power source, and the circuit breaker 1, the transformer 2, the contactor 8, the converter 3a, and the current detector 4. Voltage is applied to the electric motor 6 via the circulating current suppressing reactor 5 and the high-speed circuit breaker 9. In addition, during regenerative operation, the AC power is supplied from the motor 6 via the high-speed circuit breaker 9, the circulating current suppressing reactor 5', the current detector 4', the inverter 3b, the contactor 8, the transformer 2, and the molded circuit breaker 1. Electric power is regenerated. In the main circuit configured in this manner, as described above, during a power outage or a power outage, during overcurrent when the current value in power running or regenerative operation exceeds a predetermined level, and during commutation failure, etc. A protection is provided in which the high-speed circuit breaker 9 is opened when a fault current flows. This will be explained with reference to FIG.

FIG. 2 shows an example of a speed control circuit comprising the protection circuit section of the reversible Leonard device shown in FIG.
12 is a speed control amplifier, 13 is a polarity inverter, 16
17, 18 are current control amplifiers, 19, 20 are converter 3a, inverter 3
a gate circuit that applies an upper gate signal to each thyristor of b, which is converted into a firing pulse synchronized with an alternating current voltage;
21 is a power failure overcurrent protection signal generator.

That is, during power running, the setting signal 101 from the setting device 10 and the speed signal 102 sent from the speedometer generator 7 are computationally amplified by the speed control amplifier 12, and the signal output from the speed control amplifier 12 is 103 is an input signal of the current control amplifier 17 which uses the current signal 105 from the current detector 4 on the power running side as feedback;
A signal 108 output from the current control amplifier 17 is converted into a pulse by a gate circuit 19, and a signal 111 is applied to the gate of each thyristor of the converter 3a. Furthermore, during power running, the signal 103 is passed through the polarity inverter 13 to the current control amplifier 18 which returns the current signal 106 output from the current detector 4' on the regenerative side.
is input. However, the current control amplifier 17,
18 is a circulating current command 10 from the circulating current command device 16
7 is input, even in the power running mode, the current on the regenerative side is controlled by the current control amplifier 18 so that it has a constant regeneration amount, and the signal 109 output from the current control amplifier 18 is sent to the gate circuit 20. A signal 112 is applied to each thyristor of the inverter 3b via the inverter 3b. Similarly, circulating current control is performed during regenerative operation, and at the same time a regenerative gate pulse is applied as a signal 112 to each thyristor of the inverter 3b, a current control amplifier 17 and a gate circuit are applied to each thyristor of the converter 3a. A circulating current gate pulse is applied as signal 111 via 19 .

Next, in the power outage overcurrent protection signal generator 21, regarding overcurrent, the signal 118 of the output of the current detection circuit 21b which inputs the current signals 105, 106 from the current detectors 4, 4' exceeds a certain value. When the overcurrent detector 21e is activated. From the signal 119 output from this overcurrent detector 21e, the OR circuit 2
A gate shift signal 110 is sent through the signal 1g to shift the gate circuits 19 and 20 to the maximum delay angle so as to throttle the current, and operate the DC cutoff circuit 21h to turn on the high speed circuit breaker 9 by the signal 120. The thyristor power converter 3 is protected from the fault current by opening the terminal. Next, regarding power outages, even if a power outage occurs during power running, there is usually no problem and restarting operation is possible after the power is restored by simply blocking the gate.If a power outage occurs during regenerative operation, regeneration will occur due to failure of thyristor commutation. The current flows through the thyristor, causing the load to short-circuit, causing an excessive current to flow. Therefore, a rectified power supply signal 114 is generated in the power supply detection circuit 21b which receives the AC power supply signal 113 as input, and the signal 115 output from the power failure detector 21c is sent to the gate circuits 19, 20 regardless of power running or regeneration at the time of power failure.
is applied as a gate block signal. Furthermore, the signal 10 of the current control amplifier 17, 18 output
Regeneration mode detector 21a with input 8,109
This signal 116 and signal 115 generate a signal 117 output from an AND circuit 21f, which is passed through an OR circuit 21g to control only the gate block during power running. The signal 120 is generated from the DC cutoff circuit 21h only when a power failure occurs during regeneration.

[Problem that the invention attempts to solve]

However, in the circulating current control type reversible Leonard device as shown in FIG. 1, the circulating current flows through the inverter 3b even during power running.

When a gate block signal is applied to the thyristor during a power outage, if the powering side current is sufficiently large compared to the regenerative side current, the regenerative circulating current disappears first compared to the powering side, resulting in a commutation failure phenomenon. No worries. However, since the armature current flowing through the electric motor 6 during no-load powering operation is small, the detected values of the current signal 105 on the powering side and the current signal 106 on the regeneration side are almost the same, so that if a power outage occurs during operation, Even if a gate block signal is applied to the thyristor, the regeneration side thyristor does not necessarily turn off earlier than the powering side thyristor. Therefore, when commutation fails, a DC short-circuit current flows from the motor 6 through the thyristor of the inverter 3b, and the overcurrent detector 21e detects the fault current and operates the high-speed circuit breaker 9.

Moreover, in the circulating current type reversible Leonard device, there is a high probability that commutation failure will occur when a power outage occurs during no-load power running. As described above, in the conventional power failure overcurrent protection signal generation, there was a risk of damaging the thyristor because an excessive short-circuit current flows through the thyristor during a power failure during frequently operated no-load operation.

[Means for solving problems]

In view of the above-mentioned points, the present invention is equipped with a differentiation circuit and a discriminator for the output of a current detector that receives the output currents of both the power running side and regeneration side thyristor power converters as input, and distinguishes it from the power failure detector output. The present invention has realized a device that utilizes the output signal of an AND circuit or the output signal of an overcurrent detector whose input is the output of the overcurrent detector.

[Effect]

Therefore, even if a power outage occurs during power running and commutation fails, the present invention quickly detects the flow of fault current and opens the high-speed circuit breaker before a large current occurs. To provide a protection circuit device which blocks a gate during a power outage when the current attenuates and disappears after a power outage, and makes the device capable of restarting operation after the power is reliably restored.

〔Example〕

FIG. 3 shows an embodiment of the protection signal generator part according to the present invention, where 21' is a power failure overcurrent protection signal generator. In the figure, the same reference numerals as in FIG. 2 indicate parts having the same functions. In Figure 3,
21i is a differentiating circuit, 21j is a discriminator that outputs a signal 122 when the signal 121 output from the differentiating circuit 21i is above a certain value, and 21f' is a signal 115 and a signal 122.
It is an AND circuit with input. Next, the operation of this embodiment will be explained using FIGS. 4 and 5.

First, regarding the fault current that occurs during normal operation, a gate shift signal 1 is sent from the current detection circuit 21d to the gate circuits 19 and 20 via the overcurrent detector 21e and the OR circuit 21g in the same manner as explained in FIG.
10 is generated, and the DC cutoff circuit 21h is operated to open the high speed circuit breaker 9 and protect it. Next, waveforms of various parts when a power outage occurs during power running are shown as shown in FIG. That is, when the output level of the power supply signal 114 output from the power supply detection circuit 21b falls below a certain value, the power failure detector 21c, which determines a power outage, generates a signal 115 as illustrated. Note that signal 115 is set to 10 when the power is restored.
The ~20 ms time delay ensures that the reversible Leonard device is returned to service after power has been restored. Further, a signal 121 and a signal 122 of the output of the differentiating circuit 21i for the signal 118,
In this way, a power failure is detected at time _T0 , a signal 115 is generated, and the gate is immediately blocked, and even if the signal 118 is attenuated, the signal 1
21 only changes in the negative direction, the gate block continues without changing the signal 122, and if the power is restored before the contactor 8 is turned off at time _T1 , the time
Press T ₂ to release the gate block and restart operation.

In addition, Figure 5 shows the waveforms of various parts when a power outage occurs during operation when the power running current is near zero, and then the circulating current flowing in the inverter section does not turn off and commutation fails. be. That is, when the power supply signal 114 becomes below a certain value at time T ₀ ', the signal 115 is generated and the gate is blocked as explained in FIG. However, signal 118
As an example, the short-circuit current rises rapidly through the thyristor and transformer 2 of the inverter 3b shown in FIG. At this time, the signal 12 of the differentiating circuit 21i
1 increases in the positive direction as shown, and at time T ₀₁ ', the discriminator 21j operates and the DC cutoff circuit 21h is operated via the AND circuit 21f' and the OR circuit 21g. As a result, the fault current can be cut off before the current increases significantly as at time t ₀₂ '. The acceleration detection circuit portion consisting of the differentiating circuit 21i and the discriminator 21j that can act in this way is
Since the gate block and DC cutoff commands are generated through the AND circuit 21f' only during a power outage, the accelerating current during normal operation will not have any adverse effect.

As described above, the reversible Leonard device to which this embodiment is applied is protected by quickly detecting an abnormal condition when a fault current begins to flow in either power running or regeneration mode, and is immediately protected by detecting a power failure during regeneration. Compared to conventional circuit systems that cut off direct current, this circuit can operate without any difference in time delay, and the regeneration mode detection section that was conventionally provided can be removed. Furthermore, its reversible Leonard device is MG
This has the effect of bringing us one step closer to meeting the need for continuous operation without stopping in the event of a momentary power outage, similar to power supply drive or induction motor drive. Of course, it is also possible to easily open the high-speed circuit breaker immediately in response to a power outage during regeneration by using the regeneration mode detection section in combination.

[Effect of idea]

As explained above, according to the present invention, it is possible to provide a protection circuit for a reversible Leonard device that specifically detects a fault current during a power outage and effectively opens a high-speed circuit breaker to protect against power outage and overcurrent. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the main circuit configuration of a conventional circulating current type reversible Leonard, and FIG. 2 is a diagram showing an example of a speed control circuit comprising a protection circuit section of the device shown in FIG. 1.
FIG. 3 is a diagram showing an embodiment of the protection signal generator portion according to the present invention, and FIGS. 4 and 5 are explanatory diagrams of the present invention showing waveforms of each part of FIG. 3. 3... Thyristor power converter, 6... Electric motor,
9... High-speed circuit breaker, 21, 21'... Power outage overcurrent protection signal generator, 21i... Differential circuit, 21j...
...Discriminator, 114...Power supply detection circuit 21b output,
115...Power failure detector 21c output, 118...Current detection circuit 21d output.

Claims (1)

[Scope of utility model registration request] A current detector that obtains the output current of both the power running side and regenerative side thyristor power converters, an overcurrent detector that operates above a certain value based on the output signal of the current detector, and a power failure detector that detects a power outage of the input power source. In a protection circuit for a reversible Leonard device that protects a thyristor power converter by opening a high-speed circuit breaker inserted in series with a DC motor in the event of a power outage or overcurrent, a differential circuit is connected to the output of the current detector. and a discriminator for discriminating whether the output of the differential circuit is greater than or equal to a positive predetermined value, and an AND circuit receiving the output signal of the power outage detector and the output signal of the discriminator as input, the output of the AND circuit or A protection circuit for a reversible Leonard device, characterized in that the high-speed circuit breaker is opened by an output of an overcurrent detector.