JPS6268094A - Detector for abnormality such as disconnection of motor and speed controller for motor - Google Patents

Abstract

PURPOSE:To eliminate the need for devices, such as an expensive voltage sensor and shunt by transmitting an abnormal signal when the combination of input signals from predetermined comparator circuits forms logics meaning the disconnection of a speed controller and the breakdown of an element. CONSTITUTION:In a disconnection detecting circuit 64, a non-inverting amplifier 67 monitors a current feedback signal If. A voltage comparator 66 monitors a thyristor-ignition phase-angle adjusting signal I. Both outputs V2, V3 from voltage comparators 66, 68 reach a H level. An output from a 2 input NAND logic IC28 reaches a L level and an output from an inverter logic IC29 at the next stage the H level and a transistor 71 is turned ON at that time, an alarm relay X is driven, and a contact 32 is closed, thus notifying disconnection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an abnormality detection device such as a disconnection of a motor and a motor speed control device.

[Background of the invention]

As a method for detecting disconnection using a purely electrical method, as described in Japanese Patent Application Laid-Open No. 166487/1982, a voltage comparator is used to detect an abnormality in the speed feedback system when the terminal voltage of the electric terminal exceeds a certain level. There is a method that makes a determination by determining the AND condition of the output and the output of a speed comparator that outputs a signal when the speed signal from the speed detector PG becomes less than a certain value, and by detecting overspeed of the speed comparator.

This conventional example has the characteristic that even though there is no speed feedback signal, it is recognized as abnormal when the motor terminal voltage is above a certain level, and that it is recognized as abnormal when the speed feedback signal exceeds a certain value, that is, in an overspeed state. There is. However, the disadvantage of this conventional example is that the presence/absence of speed, the presence/absence of terminal voltage, and the overspeed state are all determined by comparing the levels of detection signals, so it is necessary to set the detection level accurately. If this level is incorrectly set, malfunctions can easily occur. There is also the problem that it is not possible to determine whether the overspeed state is due to destruction of the semiconductor power device or due to improper adjustment of the speed feedback rate. Furthermore, if an overspeed condition occurs in the fourth curfew quadrant operating region, a stall condition is likely to occur, and there is also the drawback that overspeed prediction judgment cannot be made to prevent this.

Next, as another example, there is a disconnection detection method for automatic dynamic control used for crane operation, etc. First, an overview of this control will be explained to facilitate understanding.

Dynamic control is a method for generating braking force in a wound induction motor. This causes a dynamic current to flow through the motor's secondary winding, causing the magnetomotive force generated in the secondary winding to be consumed by the secondary resistor, thereby generating braking force. Automatic dynamic means that this dynamic current is controlled by a thyristor to adjust the braking force and control the speed. FIG. 8 is a control system block diagram of automatic dynamic control.

This automatic dynamic control system consists of fuses 1 and 2 for semiconductor protection, thyristor 3 for free circulation, main thyristor 4, current detector 5, magnetic contactor 7 for reverse rotation, magnetic contactor 81 for forward rotation, and magnetic contactor 9 for regenerative operation.
, winding type Sanwa induction motor 10, speed setting circuit 14A, speed control system error amplification device 111, current control system error amplification device 16, phase control circuit 17, drive circuit 18 to main thyristor gate 1, reflux Thyristor gate drive circuit 18A,
It consists of a current-voltage conversion circuit 21, a rectifier circuit 22, a secondary resistor and its short circuit 23, a speed detection alternator 24, a thyristor drive interlock circuit 25, and a dynamic operation command circuit 26.

The sequential movements in this figure are as shown in FIG. 9 depending on the operating state of the crane. Furthermore, its speed-torque characteristics are as shown in FIG.

In FIG. 9, there are two operating states: hoisting and hoisting, and during hoisting, the IMIO operates as a two-phase induction motor due to =3-ON of the contactor 8.

In dynamic operation during lowering, only the contactor 7 is turned on, and the IMIO operates as a single-phase induction motor. The power supply at this time is a single-phase half-wave rectified power supply. The equivalent circuit at that time is shown in FIG. Furthermore, during lowering, there is a regenerative operation, and during this operation, the contactor 7.9 is turned on. Figure 12 shows the waveforms of various parts during dynamic operation.

In the automatic dynamic control under the above operation, the system shown in Fig. 13 is used to detect the melting of the thyristor element, the melting of the thyristor protection fuses 1 and 2, and the disconnection of the electric wires and motor windings connected to the thyristor element. There have been conventional disconnection detection circuits. The main circuit configuration is the same as that shown in FIG. 8, and a shunt or instrument current detector 6, a voltage sensor 12, an over-input prevention device 11 for the voltage sensor 12, and an alarm contact 13 are newly added.

The disconnection detection method shown in this figure is that when current flows through the shunt 6, a minute voltage is generated across the shunt. This voltage is detected by the voltage sensor 12, and when the current falls below a certain value, the alarm contact 13 is closed. .

A drawback of this circuit is that the current value for determining a disconnection must be set to the same minimum current value as required during dynamic control. For this reason, if the detection level is lowered too much, the voltage generated at both ends of the shunt will also become small, resulting in a value that cannot be detected by the voltage sensor. In order to be able to detect this with a voltage sensor, a control method must be used that allows a small amount of dynamic current to flow even when the motor is stopped. As a result, the speed control performance during light loads deteriorates, and furthermore, the speed control range becomes narrower.

Other disadvantages include the expensive voltage sensor and shunt.

[Purpose of the invention]

An object of the present invention is to detect a disconnection between a speed control board having a semiconductor power element and a motor whose speed is controlled by this control board by purely electrical means, without having to worry strictly about the detection level of current or speed. An object of the present invention is to provide an abnormality detection device such as a wire breakage that does not adversely affect speed control performance and does not use expensive voltage sensors or shunts.

[Summary of the invention]

A solution to the problems of conventional circuits could be found by the principle of thyristor phase control in automatic dynamic control circuits. Based on this discovery, semiconductor devices were developed and 1. It was also found that all speed control devices with current feedback loops are effective.

FIG. 2 is a diagram showing the speed control principle of automatic dynamic control. 14 is a variable resistor for speed setting. The operation is as follows.

Rectifier circuit 2 converts the speed reference N* and speed generator PG24 signals.
The difference between the speed feedback signal Nf rectified by 2 (N" - N
r) is amplified by the amplifier 15 and becomes a signal ■α for adjusting the firing phase angle of the thyristor in the phase control circuit 17. The signal output from the phase control circuit 17 is sent to a power circuit for driving the gate of the thyristor, and is sent to a pulse transformer 18.1.
8A and becomes the gate signal for the thyristor. When a signal lj is applied to the gate of the thyristor, the switching action of the thyristor causes a dynamic current as shown in FIG. 12 to flow through the circuit as shown in FIG. 11.

Now, when the speed feedback signal N' is larger than the speed reference Nx, the control delay angle α of the firing phase angle becomes large, the conduction angle of the thyristor becomes large, the dynamic current increases, and it works in the direction of suppressing the speed of the motor. .

Further, when the feedback speed N (is smaller than the speed reference N), the control delay angle α of the ignition phase angle becomes small, and the dynamic current decreases, working in the direction of increasing the motor speed.

When the feedback speed Nf becomes approximately equal to the speed reference N*, the dynamic current becomes constant at a current commensurate with the load, resulting in a state of uniform motion. Figure 3 shows N”, Nf, and I*.

The state relationship of the If+α signal is shown.

The present invention solves the problem by utilizing the aforementioned characteristics of circuit operation, and focuses on the following points.

First of all, if the thyristor is destroyed or the wire is disconnected between the thyristor element and the motor winding, it means that there is no current fee 1 (back signal).Also, since no dynamic current flows, dynamic braking does not occur, and the motor rotation speed Nr increases. It is to be.

These relationships can be expressed as follows.

1 tree”Kc(Nr-N*) ・・・・・・(1)
However, the amplification factor Nf of the KG amplifier 15 is large → ■ Main University ...... (2) I α,
= KC(N*-N()= Kc-Ikyo(Nr=O)
= 13) However, according to the above formula for the amplification factor of the KC amplifier 16, if the wire is disconnected or the thyristor element is destroyed, the process α =
KCI* and reaches the saturation output value of the amplifier 16.

We are also focusing on the following points.

If there is no wire breakage or thyristor destruction and the thyristor firing angle adjustment signal α is saturated, the thyristor control delay angle α will be large and the thyristor conduction angle will be large, so an excessive current will definitely flow. It is.

We discovered that it is possible to detect wire breaks by using the above properties.

=81 In other words, it is sufficient to judge whether the firing phase angle adjustment signal ■α of the thyristor is at a saturated output or not, and then judge whether the current value is excessive or not.

If Iα is a saturated output and no excessive current flows at this time, the wire is disconnected. Therefore, in the conventional method, the presence or absence of current is determined near the lowest level at which the current can be detected to detect a disconnection, but according to the present method, the current can be determined anywhere as long as the current is not excessive.

It has also been found that the concept of the present invention can be applied to applications other than automatic dynamic control panels.

First, an example in which the present invention is applied to speed control using an eddy current joint is shown. FIG. 4 is a control block diagram when a wound induction motor and thin current joint control are adopted for hoisting and raising the crane. Here, eddy current control is used as a means of braking the wound induction motor, and the main circuit is a thyristor 29.30
, a mixing bridge combined with diodes 31 and 32, and a freewheeling diode 33, and the excitation current of the excitation coil 36 can be automatically adjusted. Note that 27 is a pulse transformer and 28 is a current detector.

If the speed feedback signal N is larger than the speed reference N*, the conduction angle of the thyristor becomes large, and the exciting current flowing through the exciting coil 36 of the eddy current joint increases.

The excitation coil is stationary, and the magnetic pole 37 itself that is magnetized is also stationary. Therefore, as the coupling force between the rotating drum 38, which is directly connected to the shaft of the wound Sanwa induction motor, becomes stronger, the braking force becomes stronger and the speed increases. can be suppressed. Further, when the speed feedback signal Nf is smaller than the speed reference N*, the excitation current becomes small, the coupling force between the magnetic poles and the rotating drum weakens, and the speed increases. When the speed reference N* and the speed feedback signal Nf substantially match, the excitation current matches the load, resulting in a uniform motion state. Considering the above, when comparing FIG. 2 and FIG. 4, the principle of adjusting the thyristor phase angle is the same as automatic dynamic control, only the main circuit configuration is different. Therefore, the present invention can be applied.

Next is an application example of vector control of a three-phase induction motor using a variable frequency inverter. FIG. 5 is a block diagram of slip frequency vector control. In this control, the main circuit is the converter section 39. Smoothing capacitor 40. It consists of power transistors 41 to 46, and the control configuration is also quite different from automatic dynamic control. Its configuration is the main circuit section 61. Speed detection unit 62, Baku1Hel calculation unit 53. PWM
Section 63. It consists of a switching circuit section 52. First, the main circuit 61 is a part that constitutes a speed control loop, including an error amplifier 56 and a V/F converter 54 . It has a full angular frequency calculation circuit 55.

The speed detection circuit 62 converts the pulses obtained from the pulse generator PLG50 into a voltage signal proportional to the speed and converts the pulses into the F/V converter 5.
This is the part to be converted in step 1.

The vector calculation circuit 53 receives the 1-herc current command signal j-, the excitation current signal jm*, and the -phrase frequency signal ω□ from the main circuit, performs vector calculation, and calculates the -th current command ]x
This is the part where u'+ 1tV trees and 11w trees are obtained.

I) The WM circuit 63 compares the primary current command with the actual primary current using the hysteresis comparator 58 to generate a PWM signal. 59.60 is the base end driver.

The switching circuit 52 is a circuit that switches between forward rotation and reverse rotation.

In the control circuit configured as described above, a current command and a current feedback signal can also be obtained.

If there is a disconnection between the power transistors 41 to 46 and the moder winding, speed control becomes impossible and the speed reference N* does not match the speed feedback signal. A signal representing the difference between N* and Nr is output from the error amplifier 56 and becomes six torque current command signals j, but the output in this case is in a saturated state or at the maximum output. Also, since no actual current flows at this time, the current feedback signal 1
2u+ 1- zV+ 12W is zero. Furthermore, if there is no wire breakage and the torque current command signal j- is in a saturated state, the primary current command liu'+ 1zV*+ ltW* will also be large, and therefore the current feedback signal j2LIt 12V
+12W is also large.

If we consider the above, we can find the following common points. The present invention can be applied to a speed control panel having a semiconductor power device whose circuit has both a current command and a current feedback signal, and disconnection can be easily detected.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. This figure shows the automatic dynamic control block diagram (Figure 2), which describes the invention in detail, and the disconnection detection circuit 64 of the present invention.
is added. The main configuration is a non-inverting amplifier 67
, voltage comparator 66, 68.2 human powered NAND logic IC
69, Inverter Logic IC70, l-Langistav 1. It consists of an alarm relay 72.

First, the non-inverting amplifier 67 monitors the current feedback signal If. The output V1 becomes the input voltage of the voltage comparator 68 which determines whether the current feedback signal If is large or small. Therefore, when the current is small, vl is small and is below the reference level v6 of the voltage comparator 68, and the output v3 of the voltage comparator 68 is at the H level, and when the current is large, V□ is large and the reference level v6 of the voltage comparator 68 is reached. As a result, the output (3) of 68 becomes L level.

Next, the voltage comparator 66 outputs the thyristor firing phase angle adjustment signal I
While monitoring α, it is determined whether this signal has reached the saturated output. In operation, the voltage comparator 660 becomes equal to or higher than the reference level 7 only when the signal of the output voltage α reaches the saturated output value, and its output v2 becomes H level.

However, the amplifier 16 may be provided with an output limiting function, and it is conceivable that the output limit will remain at the maximum output value before reaching the saturation value. In this case, it is not necessary to determine whether the saturation value has been reached, but whether the maximum value has been reached. Therefore, the operation of adjusting the reference level V7 of the voltage comparator 66 to this maximum output value is performed by the variable resistor VRI.

Next, the output V2 of the voltage comparators 66 and 68. V3 each becomes an input to the two-man NAND logic IC 28, and it is determined whether or not there is a disconnection. Figure 6 D I (1,
If+ V21 V3+ 2-person NANDO chic IC
28 shows the state relationship of output 4. As you can see from this figure, when the wire is broken, ■2. It can be seen that this is the case when both V3 are at H level, that is, in the I] mode. Therefore, at this time, the output of the two-man power NAND logic IC 28 is L level, the output of the next stage inverter logic IC 29 is H level, and the transistor 71 is turned on, driving the alarm relay X, closing the contact 32, and confirming that the wire is disconnected. It will end. The signal from this contact 32 becomes an abnormality signal on the system, and is used to release the main circuit breaker 7°8.9 shown in Fig. 8 and to stop the wound type Sanwa induction motor and its drive device. becomes.

As another embodiment, as shown in FIG. 7, instead of the thyristor firing phase angle adjustment signal α, a single current command signal that contributes to the thyristor firing may be used. ■The reason why the last signal can be used is as follows. If the thyristor is destroyed or disconnected, the dynamic current will not flow, so no braking force will be obtained, and the actual speed Nf will be greater than the speed reference N tree. Therefore, the output signal of the amplifier 15 which compares the difference between N* and Nf and amplifies and outputs the That is, the current command signal 11 always reaches the saturated output value or the maximum output value. Therefore, the L1 objective of disconnection detection can be achieved even if the operation signal shown in (1) is used instead of the operation signal α described above. However, since the polarity relationship between the single line and the input signal α is in a reciprocal relationship, an inverting amplifier 74 is provided. Also, since it works to increase the current only when one signal is a negative signal, the diode D3. D4 is provided so that the output (6) of the 1-inverting amplifier 74 is always treated as a positive signal.

Next, the attached functions shown in FIGS. 1 and 7 will be explained. Resistor R3
, capacitor C1 is provided to smooth the ripple component of current feedback. Also, resistor R6, capacitor C
2 is due to the provision of R3 and C1. This is provided to compensate for the time constant delay of the current feedback signal 1. In other words, R6,C
If 2 were not present, when the thyristor phase angle signal ■α momentarily becomes a dog, the output ■ would be at H level, but the signal ■ would be due to the time constant delay of R3 and C1, so there would be no current flowing. The situation is the same as that, and ■3 is set to H level. This is because as a result, the disconnection mode is erroneously determined. Also, the non-inverting amplifier 67 is provided to smooth the ripple of the current feedback signal by providing R3 and CI = 16-, but if R3 and C1 are provided without this non-inverting amplifier 67, the current feedback during normal dynamic control will be reduced. This is because the time constant of the signal is affected.

Further, resistor R18 and relay 65 are provided to prevent malfunction during dynamic operation stop. <When the dynamic operation is stopped, Jα becomes the saturation value or the maximum value, and at this time, If is always zero because it is in a stopped state. Therefore, the condition for disconnection mode is established. The relay 65 opens when the dynamic operation starts and closes when the dynamic operation stops.When closed, one output of the amplifier 15 becomes negative, so the thyristor phase angle command signal
Set to zero, and set ■2 to zero. Therefore, it is possible to avoid the condition of disconnection mode from being met.

The unique effects based on the above embodiments are as follows.

■ Voltage sensor is more expensive than conventional methods.

Devices such as shunts can be made unnecessary.

■ Current detection can be shared with the current detector required for dynamic control.

■ In the conventional method, in order to set the voltage generated by the shunt to a certain minimum level that can be detected by a voltage sensor, a small amount of dummy current had to be passed, which had a negative effect on control performance, but there is no need to worry about this kind of thing. .

〔Effect of the invention〕

According to the present invention, it is possible to minimize the number of components necessary for current detection in a circuit that is simpler than the conventional circuit, and therefore it is economically effective. In addition, since the determination of disconnection does not rely solely on the current detection level, but utilizes the operating characteristics of a single circuit,
There is no need to strictly set the current detection level. It also has a function that can predict overspeed conditions caused by wire breakage before reaching the overspeed level.

[Brief explanation of drawings]

Fig. 1 is an embodiment of the present invention, Fig. 2 is a diagram of the principle of automatic dynamic speed control, Fig. 3 is a diagram of the relationship between the load and various signals, and Fig. 4 is a diagram of the principle of speed control of eddy current joint control. Figure 5 is a speed control block diagram in variable frequency inverter vector control, Figure 6 is a diagram of the relationship between mode types and various types of signals, Figure 7 is a diagram of another embodiment of the present invention, and Figure 8 is an automatic dynamic Fig. 9 is a diagram showing the states of various elements under operating conditions, Fig. 10 is an automatic dynamic speed-torque characteristic diagram, Fig. 11 is an equivalent circuit when dynamic current flows, and Fig. 12 is a diagram showing the states of various elements under operating conditions. The figure is a current waveform diagram in an equivalent circuit, and FIG. 13 is a diagram showing a conventional disconnection detection method. 15, 16... Amplifier, 17... Phase control circuit, 1
8.18A... Pulse 1-Lance, 3, 4... Thyristor, 10... Induction motor, 64... Disconnection detection circuit.

Claims (1)

[Claims] An automatic speed control system that performs speed feedback control and current feedback control, and an automatic speed control system provided on the output side of the control system,
In a motor speed control device comprising a semiconductor power conversion device that controls the motor speed by phase control or variable frequency inverter control, it is determined whether a current command signal is a signal that causes the maximum current to flow. A first comparator, a second comparator that determines whether the feedback signal of the actual current is above a certain level, and the outputs of the first and second comparators are input, and the combination of these inputs is A device for detecting an abnormality such as a disconnection of a motor and a motor speed control device, comprising a logic operation circuit that outputs an abnormal signal when a logic indicating a wire breakage or element destruction occurs in a speed control device including a motor.