JP2638870B2 - Contact point determination device for variable speed operation system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for determining a contact point in a variable speed operation system.

B. Summary of the Invention The present invention relates to a grounding point judging device for a system in which a plurality of motors are operated at a variable speed by one inverter device, wherein a high-speed switch is provided on an electric path between the inverter device and the motor to prevent one Detecting with the detector, it is possible to determine which phase of the grounding accident occurred in which phase, so that the occurrence of the grounding accident can be found quickly.

C. Conventional technology Fig. 5 shows a single inverter unit INV and multiple motors M
_1, M _2, in the circuit configuration diagram of a system for variable speed operation of ... Mn, the system shown in FIG. 5, is referred to as normal multidrive system. This type, motor M ₁ of the plurality of the multi-drive system, M _2, ... 1 single motor M ₁ of the Mn
When an accident occurs, an overcurrent flows to the inverter INV. Then, an overcurrent detector in the inverter INV operates to take measures to protect the system from overcurrent.

Although the protection of the system can be achieved by such a protection operation, the operation of sound motors M ₂ , M ₃ ,... Mn is also stopped. Applying such a protection operation to a process for producing spindles in parallel, such as in the textile industry, would halt the operation of the entire system, resulting in significant losses. Therefore, it is necessary to avoid such a protection operation.

D. Problems to be Solved by the Invention It is not preferable to provide an overcurrent detector in the inverter device in order to protect the system from overcurrent as described above. Therefore, protection can be ensured if the accident motor can be separated from the inverter device before the overcurrent occurs.
For this reason, it has been found through experiments and the like that when analyzing the details of the motor fault up to the overcurrent, a ground fault at the outlet of the motor occurs first, followed by an overcurrent due to an interphase short circuit. For this reason, it is demanded to detect a grounding accident so as not to cause an overcurrent.
In order to satisfy this demand, there is one in which the judgment of the ground contact point is performed by a sequencer (see Japanese Patent Application No. 61-50850). If the sequencer determines the grounding location, the switch needs to be opened only for a time during which the sequencer can determine the presence or absence of the ground current. When the switch is opened, no voltage is applied to the load motor for the open time, and the motor freely decelerates. 10 ms is the time when it is considered that there is no effect on the motor speed even if the load GD ² etc. are not expected
It has been found from test results that the time is of the order. However, the scan time of the sequencer is not
There is a problem that the above condition cannot be satisfied because the maximum is about 100 ms. In addition, if a sequencer that satisfies this condition is used, there is a problem that the apparatus becomes extremely expensive and becomes economically disadvantageous.

E. Means for Solving the Problems The present invention relates to a system for controlling the operation of a plurality of motors by one inverter device, a switch inserted between electric circuits between the inverter device and each motor and opened and closed in a very short time. And a zero-phase current transformer provided on the input or output side of the inverter device, and a comparator that compares the detected output of the current transformer with a set value and, when the output is equal to or greater than the set value, outputs as ground. When an output is sent to the comparator, the oscillator starts oscillating after a predetermined time, oscillates at a preset time interval, and stops oscillating when the output is exhausted. A counter whose count output is held when the oscillation is stopped, and the switch when an AND condition between the output of the counter and the output of the oscillator is satisfied. A first output unit for outputting an output for sequentially turning off the counter at a fixed time interval, a ground phase discriminating display element which is lit when the output of the counter is in a holding state so that a ground phase can be discriminated, and the display element is lit. And a second output section for transmitting the lighting output when the state is reached.

F. Operation When the output is sent to the comparator, the oscillator starts operating. This oscillator is configured to oscillate about every 1 second, and the oscillation output is counted by a counter. When the AND condition between the output of the counter and the output of the oscillator is satisfied, an output is output from the first output unit to sequentially turn off the switches at an interval of about 1 second for a very short time. When the switch is turned off and the ground current decreases and the output of the comparator disappears, the oscillator stops oscillating. As a result, the output of the counter is held, and the ground phase determination display element is turned on, and it can be determined that the motor circuit whose switch is turned off is grounded.

G. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1A,
In B, CT is a current transformer for detecting a zero-phase current of the output of the inverter INV. The secondary side of the current transformer CT is input to the comparator CP via the amplifier A. This comparator
When the zero-phase current becomes equal to or greater than a preset set value (shown in FIG. 2), the comparator CP operates and its output changes from “H” to “L” (see FIG. 2). ). When the comparator CP operates and outputs its output, the transistor Tr is turned off. When the transistor Tr is turned off, the oscillator T outputs the oscillation shown in FIG. 2 about every 1 second.
The output of the oscillator T is "L" level for a time determined by _{T 0 = 0.7 · R 1 ·} C 1. CUT is a counter, this counter C
The UT sends the output shown in FIG. ₂ to its output terminals CUT- ₃ , CUT- ₂ , which are counted when the output of the oscillator T falls. Each output of the counter CUT is supplied to one end of a NAND circuit NA,
When the condition with the output of the oscillator T supplied to the other end matches, the signal is supplied to the first output unit FT composed of a photocoupler. From the output terminals TB _1-2 , TB _3-4 … of the first output unit FT, the second
The pulse outputs of TB _1-2 , TB _3-4 ... Shown in the figure are given to the transistors TR ₁ , TR ₂ ... Of the high-speed switch SW ₁ shown in FIG. Transistors TR _1, TR ₂ ... are turned off only between the T ₀ at approximately 1sec intervals sequentially by the pulse output. The T ground current during the off _zero is reduced, the output of the comparator CP becomes "H" level, the operation of the oscillator T transistor Tr is turned on is stopped. Since the clock stops being input to the counter CUT due to the stoppage of the operation of the oscillator T, the output of the output terminal CUT- ₂ of the counter CUT becomes the holding state, that is, the "H" level as shown in FIG. Counter output of CUT is HD ₃ out of the ground phase discrimination display device (light emitting diode) HD ₂ ~HD ₅ becomes "H" level is illuminated. By this display device HD ₃ is turned, for example, a motor circuit of the transistor TR ₁ can determine that is grounded. Further, when the display device HD ₃ is turned on, this is sent to the operation unit PC consisting sequencer via the second output unit I / O.

Even if the off detection level all the output T ₀ between 1sec interval to be defective in the comparator CP may grounding current does not fall below the level of detection. When such a ground failure occurs, the flip-flop circuit FF is operated when the count value of the counter CUT becomes equal to or more than the rotation speed of the load motor, and the transistor Tr is turned off. This causes the oscillator T to stop oscillating. Only comparator CP at the time of this state is operated, device failure display device HD ₁ is turned on.
When this HD ₁ is lit, the ground phase discriminating display elements HD _{2 to} HD ₅
Does not light.

FIG. 3 is a semiconductor switching circuit diagram showing an example of a high-speed switch SW _1. In FIG. 3, between the DC buses P and N,
Smoothing capacitor C ₁ and the inverter INV are connected in parallel. The path connecting the U-phase output side and the motor M ₁ of the inverter INV, the diode _{D 1U, D 2U, D 3U} , bridge circuit bridge connected as shown polarity D _4U is inserted. A common connection point 1 _U connecting the cathodes of the diodes D _1U and D _{3U and} a common connection point 2 _U connecting the anodes of the diodes D _2U and D _3U
Semiconductor switching element, for example a power transistor TR ₁ is connected as shown polarity between. Wherein the common connection point 1 path connecting the _U and the positive DC bus P freewheeling diode D _PU illustrated polarity are inserted. The common connection point 2 _U
The path connecting the negative DC bus N freewheeling diode D _NU illustrated polarity is inserted as. The path connecting the V-phase output side and the motor M ₁ of the inverter INV, the diode _{D 1V, D 2V, D 3V} , D
A bridge circuit in which _{4 V} is bridge-connected as shown in the figure is inserted. A semiconductor switch element is provided between a common connection point 1 _V connecting the cathodes of the diodes D _1V and D _{3V and} a common connection point 2 _V connecting the anodes of the diodes D _2V and D _4V .
For example, a power transistor TR ₂ is connected as shown polarity. Wherein the common connection point 1 _V and path connecting the positive side DC bus line P freewheeling diode D _PV illustrated polarity are inserted. Wherein the common connection point connecting the 2 _V and the negative DC bus N path connecting the W-phase output side and the motor M ₁ of the inverter INV to reflux diode D _NV illustrated polarity is inserted path, the diode D _1W , D _2W , D _3W , and D _4W are connected via a bridge circuit as shown in FIG. Diode D _1W , D
1 _W common connection point between _{3 W} cathodes and diode D
_2W, the semiconductor switching element between the common connection point 2 _W connecting the anode to each other of D _4W, for example, a power transistor TR ₃ are connected as shown polarity. A return diode D _PW having the illustrated polarity is interposed in an electric circuit connecting the common connection point 1 _W and the positive DC bus P. Wherein the path connecting the common connection point 2 _W and the load DC bus N freewheeling diode D _NW illustrated polarity are inserted.

Next, the operation of the circuit configured as described above will be described. If path connecting the inverter INV and the motor M ₁ is closed (i.e. the power transistor TR _1, TR _2, TR ₃ are in an on state), for example, a current flowing between the U-V-phase positive-side DC bus P → inverter INV → Diode D _1U → Power transistor TR ₁ → Diode D _4U → Motor M ₁ → Diode D
_3V → Power transistor TR ₂ → Diode D _2V → Inverter INV → Negative DC bus N Pass through the path. In reverse mode, positive DC bus P → Inverter INV → Diode D _1V → Power transistor TR ₂ → Diode D _4V → Motor M ₁ → Diode D _3U → Power transistor TR ₁ → Diode D _2U → Inverter INV → Negative DC bus N U-W phases of paths connecting the inverter INV motor M _1, also the current flowing between the V-W phase flowing in the same manner as described above. When the power transistor TR ₁ (TR ₂ , TR ₃ ) is turned off, the energy stored in the motor M ₁ and the surge energy applied by the line inductance are supplied to the return diode D
_PU (D _PV , D _PW ) → smoothing capacitor C ₁ → freewheeling diode D _NU
(D _NV , D _NW ) and flows through the smoothing capacitor C ₁
Is absorbed by Therefore, the power transistor TR ₁ (TR ₂ , T
When R ₃ ) is turned off, the voltage applied to the transistor TR ₁ (TR ₂ , TR ₃ ) can be clamped to the DC voltage of the inverter INV.

According to the semiconductor switching circuit as described above, by utilizing the fact that the V _BE voltage of the power transistor shown in FIG. 4 is changed by the collector current Ic and detects an overcurrent, one bidirectional current flowing through each phase The power transistor can cut off at a high speed, and a surge voltage absorbing circuit dedicated to the power transistor is not required, thereby reducing the size of the circuit.

H. Effects of the Invention As described above, according to the present invention, the determination of the grounding location can be determined from the lighting state of the display element before the motor grounding fault is detected and the overcurrent does not occur. Can be quickly detected, maintenance is easy, and an apparatus which is extremely economically advantageous is obtained.

[Brief description of the drawings]

1A and 1B show an embodiment of the present invention. FIG. 1A is a block diagram, FIG. 1B is a detailed circuit diagram of main parts, and FIG. 2 is an operation of FIGS. 1A and 1B. A time chart to explain the
FIG. 3 is a circuit diagram showing a specific configuration of a semiconductor switch circuit applied to the present invention, and FIG.
V _BE -Ic characteristic diagram, FIG. 5 is a block diagram showing a conventional device. A: Amplifier, CP: Comparator, T: Oscillator, CU
T ...... counter, FT ...... first output unit, I / O ...... second output, HD ₂ ~HD ₅ ...... ground phase discrimination display device, TR ₁ ~TR ₃ ...... power transistor, M _1, M ₂ …… Motor, CT …… Zero-phase current transformer.

Claims (1)

(57) [Claims] In a system for controlling the operation of a plurality of motors by one inverter device, a switch inserted between electric circuits between the inverter device and each motor and opened / closed in a very short time, an input of the inverter device or A zero-phase current transformer provided on the output side, a detection output of the current transformer is compared with a set value, and when the output is equal to or greater than the set value, a comparator that outputs a ground is provided. Oscillation is started after a certain period of time when transmitted, oscillation is continued at a preset time interval, and an oscillator that stops oscillation when the output is exhausted, and an oscillation output of this oscillator is counted and oscillation is stopped. And a counter in which the count output is held, and when the AND condition between the output of the counter and the output of the oscillator satisfies the condition, the switches are sequentially turned over at fixed time intervals. A first output unit for transmitting an output to be turned off, a ground phase discrimination display element that is lit when the output of the counter is in a holding state to enable a discrimination of a ground phase, and when the display element is lit, And a second output unit for transmitting a lighting output.