JPS62178189A - Instantaneous-stoppage reclosing device for inverter - Google Patents

Abstract

PURPOSE:To conduct reclosing positively with high precision by uniting motor revolution detected by the residual voltage of a motor on instantaneous-stoppage reclosing and output frequency from an inverter and performing reclosing. CONSTITUTION:An output voltage-frequency command circuit 1 brings a switch SW1 to an OFF state on instantaneous-stoppage reclosing, turns a switch SW2 ON, and outputs the signal of command voltage corresponding to the number of revolution of a motor IM. A micro-computer 3 computes the actual number of revolution of the motor IM from a zero-cross detecting signal from a zero- cross detector 2, conducts necessary correction or the decision of erroneous pulses or the like, and sets the value of command voltage corresponding to the number of revolution of the motor to a D/A converter.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an inverter that restarts the inverter by matching the motor rotational speed detected from the motor whistle pressure when the inverter is stopped and turned on, and the output frequency of the inverter. The present invention relates to an instantaneous power failure re-powering device for an inverter, and more particularly to a momentary power failure re-powering device for an inverter that has been improved so as to be able to reliably re-power the inverter with high accuracy.

[Background of the invention]

Conventional inverter instantaneous power failure restart devices predict the drop in motor rotation speed during a momentary power failure and restart the motor at an output frequency based on that prediction after recovery. The present invention is based on the following improvements: counting the number and re-injecting the power at the output frequency determined based on the total 1111i.

FIG. 3 is a block diagram illustrating a conventional inverter instantaneous power failure restart scissor. In Figure 3, C0NV is a converter that converts the three-phase main current of the power supply into direct current, CNV is an inverter that converts direct current to alternating current of any ridge and frequency, and I
A is the inverter I based on the external speed command of 6 feet.
A V/F command circuit that outputs voltage and frequency signals to NV.
These constitute a general inverter, where M is a motor. 2A is a zero cross detector that measures the rising pressure between the terminals of the motor M and generates a pulse signal when the voltage between the terminals becomes 0, and 3A is a zero cross detector that measures the interval between pulses from the two motor M 3B is a V/F control means that controls the V/F command circuit lAt1 to output a voltage/frequency signal commensurate with the output of the rotation speed calculation means 3A. , r, etc., constitute a circuit section necessary for restarting the power supply after an instantaneous power failure.

FIG. 4 is a time chart of an example of the operation waveforms of each part in FIG. 3. In Fig. 4, when an instantaneous power failure occurs during the period Ta of the motor M during constant speed operation with the rotation number Na, V/
The output voltage Va of the F command (b) path 1 becomes 0, the inverter NV stops outputting, and the motor M becomes free-run. During this free running of the motor IM, a sinusoidal residual voltage is generated between the terminals of the motor IM. The zero cross detector 2A detects the zero cross point of this IA distillation pressure and generates a pulse signal. Number of rotations? ) The 1 arithmetic and ten step 3A measures the interval 711 of these pulses and outputs the rotational speed f,', JK of the motor M at that time. V/F?
The ff1J control means 3B uses this output to control the output 'voltage' of the v/pi command circuit IA or the motor I regardless of speed instruction from the outside.
After the fly control is completed, the power is turned on again when the power is restored so that the output voltages vb and Vc correspond to the number of rotations of the motor. By re-turning on the power after an instantaneous power failure, there is not much of a difference between the output frequency of the inverter NV and the rotational speed NbO of the motor M at the time of re-turning on, so that smooth re-throwing is possible.

However, in this conventional instantaneous power failure restart device, the motor I
By detecting the serocross point of the residual W [pressure of M with two serocross detectors, the rotation speed of the motor IM is calculated, and the (b) rotation speed is converted into the output frequency of the 11 inverter NV and recalculated. Because of this, errors in detection by two cello-cross detectors, detection difference due to characteristics such as the hynuteresis detake bias installed in the comparator of two cello-cross detectors, and a wide voltage range due to the accuracy of the zero-cross detector 2A may occur. Since no consideration has been given to the occurrence of erroneous pulses or detection errors when the residual voltage is extremely small, there are problems that may occur due to these, such as failure to turn on again, or overcurrent or overvoltage trips.

[Purpose of the invention]

Yumei Moto's purpose is to provide an inverter instantaneous restart device that solves the problems of the conventional technology described above, eliminates the risk factors that lead to restart failure, and ensures smooth recharging. .

[Summary of the invention]

The present invention calculates the rotational speed of the motor based on the cello-cross detection signal of the terminal dark residual voltage of the motor at the time of restarting the power after an instantaneous power failure, and when restarting the motor by adjusting the output frequency of the inverter to the rotational speed. A predetermined correction valve is added to the tanabata rotation speed calculated above, and it is determined whether or not the above-mentioned cello cross detection signal is an erroneous signal. If a normal zero-cross detection signal is not input, the rotation speed is assumed to be zero and the engine is re-input, allowing for reliable and smooth re-input.
This is a device for restarting an inverter after a momentary power failure.

[@Ming Example]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 4.

! Figure @1 is a block diagram showing an embodiment of the inverter instantaneous power failure restart device according to the present invention. In Figure 1, C
oMV is a converter that converts the three-phase alternating current of the power supply into blood flow.
The NV is an inverter that converts the direct current into alternating current of any voltage and frequency.

1 is a voltage-frequency command circuit of the inverter NV, which is half of the V/F command circuit IA in FIG. Resistors R1, R2, R3, capacitor C
It consists of switches SWI, SW2, etc. During normal operation, switch 8W1 is turned on to output a command 'M pressure signal according to the speed command for speed setting from the outside, and when a momentary power failure is restarted, switch SWI is turned off. The switch 8W2 is turned on to output a command voltage signal according to the rotation speed of the motor M. Reference numeral 1a denotes a V/F conversion circuit that varies the command voltage by a voltage-frequency ratio. 2 is a cello-cross detector for detecting the voltage between the terminals of the motor M, which is similar to the two cello-cross detectors in Fig. Comparator OP3 compares the divided voltage with a base value of approximately O, and if the divided voltage is higher than the reference value, it outputs 0", and if it is lower than the reference 1@, it outputs @1". By outputting , the output of the comparator OF3 is inverted at the zero cross point when the voltage between the terminals of the motor IM changes from negative to positive or from positive to negative, and becomes an inverted signal or a zero cross detection signal. '3
is a microcomputer roughly corresponding to the rotational speed calculation means 3A and V/F control means 3B shown in FIG.
cfi [CPU *Storage device ROM, input/output "interface 101. 102, etc., and arithmetic unit 1i1: (!PU performs calculations and control of each building by the program in the memory device TItROM, but the cello cross detector 2 through the interface E 101, measure the interval between the pulses, calculate the actual rotation speed of the motor M, and make any necessary corrections or errors.]
After making a judgment as to whether or not the rotation speed is high, a command voltage value corresponding to the rotation speed is set to the V/A converter D/A through the interface E 102, and at the same time, the value of the command voltage corresponding to the rotation speed is set to the V/A converter D/A through the interface E 101'ii. A control signal is output to turn off the switch SWI of the output voltage-frequency command circuit 1 and turn on SW2'i of the output voltage-frequency command circuit 1.
Control is performed to output voltage and frequency signals commensurate with the rotational speed of the motor.

Figure 2 (ale (b+), (c) shows the hysteresis of the comparator OP3 of the cello-cross detector 2 in Figure 1. FIG. 3 is an explanatory diagram of the operation of the measurement pulse interval in the case where the cello cross detector 2 (
Comparator OP3 of 2A) may not have hysteresis (or bias) characteristics as shown in Figure 2(a).
In this case, a stable detection pulse can be obtained when the terminal voltage (residual voltage) of the motor M is high, but becomes unstable when it is low. For this reason, it is common to provide a hysteresis (or bias) characteristic as shown in FIG. 2(b), in which case a more stable detection pulse can be obtained over the entire range. However, if hysteresis (or bias) is included as shown in FIG. 2 (cl), the zero-crossing detection point and the true zero-crossing point will be slightly different from each other, and therefore the pulse interval τ1.f of the measured zero-crossing point , and the pulse interval of the true zero crossing point' 10
T'! . There will be a slight deviation between the two and a measurement error will occur.

1 When an instantaneous power failure occurs during the period Ta of the power supply (Fig. 4) while the motor IM is operating at a constant speed Na with the speed set from the outside as shown in Fig. ) The output voltage Va of path 1 becomes 0, the inverter NV stops outputting, and the motor IM becomes free-running. During this free run of the motor M, a residual voltage of sine deviation is generated between the terminals of the motor M, and the cell cross detector 2 detects the cell cross point of this residual voltage and generates a pulse signal. When we include the processor C of the microcomputer 3 (
(Fig. 4), starts the timer in the microcomputer 3 and waits for the second cello cross detection pulse signal. When the signal of the second self-crossing detection pulse is input, the actual rotation speed Nl (rpm) of the motor M is calculated from the interval τ, (seconds) between the first and second self-crossing detection pulses using the following equation.

However, P is the number of poles of the motor M. Here, as shown in FIG. 2(C), when the cello cross detector 2 has a hysteresis bias characteristic, the interval f1 between the cello cross detection pulses will deviate somewhat from the true cello cross point interval too. The pulse interval f, which refers to some measurement error due to the following, is as follows.

Considering that an erroneous pulse is judged based on the magnitude of f, a predetermined positive correction amount ΔN1 of the rotation speed is added to this calculation result, and a command voltage vb corresponding to the corrected rotation speed N11=(1+Δ)・Nl, The value of D/ is passed through the interface 102.
Set the A converter to D/A. The rotation speed correction factor Δ is commensurate with the measurement error of the cello cross detector 2.
Set it to % or 3%. Also, the calculation result of PkiJi is stored in the storage device ROM. At the same time, the calculation unit rt
The CPU outputs a control signal through the interface 101 to turn off the switch SWI of the output voltage-frequency command circuit 1 of the inverter NV and turn on the switch 5W2t. As a result, the analog command voltage vb corresponding to the rotation speed Nil of the motor IM converted from digital to analog by the D/A converter D/A is inputted to the operational amplifier ○P2 through the switch SWZ of the output voltage-frequency command circuit l. From this operational amplifier OP2, first switch 8W1
is off, a command voltage Vb corresponding to the actual rotational speed of the motor M is output regardless of the speed setting value from the outside, and the voltage is converted to frequency by the V/F converter circuit V/F and sent to the inverter INV. is supplied as a control signal to Also, this output voltage −Ji! The output of the dtli number command circuit 1 is again passed through the interface device 101 to the arithmetic unit cp.
tt, and the D/A converter D/A is loaded again so that it becomes equal to the value previously stored in the storage device fliROM.
controlled through.

Next, when the signal of the 3rd - cycle cross detection pulse is input, the actual rotation speed N2 is calculated again from the interval τ between the 2nd (b) and 3rd cycle cross detection pulse, and the corrected rotation speed N21 =
(1 + △) Find N2, and if the current rotation speed N21 becomes larger than the previous (g1 rotation speed Nll), the rotation speed of the motor M during free running will inevitably decrease, so it will cross zero. It is determined that the detection 62 has generated an erroneous pulse, the current calculation result is invalidated, and the previous rotation speed N is set.
A command voltage vb corresponding to 11K is set to the viD/A converter D/A, but this time (gIi number N2
1 is smaller than the previous (b) rotation number Nil, it is determined that the rotation speed of the motor M has actually decreased, and the command voltage Vc corresponding to the current (b) rotation number N21 is set to the D/A converter D/A. Set to A to control the inverter NY'i. Here, as illustrated in FIG. 2(c), the pulse interval τ including the measurement error, and the calculated rotational speed N2 are the true pulse intervals t. (In this case f.

<τ, ) may be lower than the corresponding rotational speed N20, especially when the rotational speed of the motor M decreases or is gradual due to the load, the above pulse interval τ! ,vinegar! If we repeat the judgment of erroneous pulses based on the magnitude of
A positive correction valve ΔNl is applied to the rotational speed Nl, N2, etc. calculated by
, ΔN2 are added, and by controlling the inverter INV in accordance with the corrected rotational speed Nil, N21, etc., the above-mentioned inconvenience is eliminated, and correcting it to the positive side makes it easier to turn on the inverter NV again.

In addition, if the rotation speed of the motor M is too low and the cello cross detection pulse signal is not generated normally, a soft timer installed in the microcomputer 3 is used to
Measure the time at which the signal of the second cello cross detection pulse is input and the interval of the cello cross detection pulse.
If these values are larger than a certain value, the motor
It is determined that the rotation speed of the inverter has dropped extremely or has stopped, and the D/A converter D/A is set to set the output of the inverter NV's output voltage-frequency command circuit l to O, and then it starts from 0. let The limit rotation speed of this motor M is set to, for example, 20 Hz or less.

As described above, the problem in this embodiment is due to the hysteresis spanning bias characteristic for obtaining stable detection pulses of the zero-cross detector that detects the zero-crossing point of the residual voltage at which the motor rotation speed is to be calculated. In addition to correcting deviations in the number of revolutions, the system also takes into account cases where the number of revolutions drops extremely, thereby reducing the accuracy of calculation of the motor's revolutions and making it more accurate to the actual number of revolutions. It is possible to reinsert the inverter without the risk of mismatching failure.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an instantaneous power failure restart device f for an inverter that eliminates the risk factors that lead to restart failure and enables reliably smooth restart.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram showing an embodiment of an inverter instantaneous power failure 8 insertion device according to the present invention, and Fig. 2 (a+, (bt), (c) shows the self-crossing detection shown in Fig. 1). Fig. 3 is a block diagram illustrating a conventional inverter instantaneous power failure restart device, and Fig. 4 is a time chart showing an example of operation waveforms of each part in Fig. 3. 1...Inverter output' Voltage-frequency command circuit, 2
...Serocross detector for voltage between motor terminals, 3...
Now microcomputer performs calculation processing of 6 gods based on cello cross detection signal

Claims (1)

[Claims] Means for measuring the residual voltage between the terminals of a motor driven by an inverter during a momentary power failure and detecting the zero-crossing point of the residual voltage, and calculating the rotational speed of the motor by measuring the time interval of the zero-crossing detection signal of the means. At the same time, a predetermined correction amount is added to the calculated rotation speed, and if the rotation speed calculated this time is larger than the rotation speed calculated last time, the rotation speed calculated this time is invalidated, and the calculated rotation speed is set to the predetermined rotation speed. an inverter comprising a calculation means that considers the rotation speed to be zero if the rotation speed is less than or equal to the number of rotations; and a control means that controls the output frequency of the inverter according to the rotation speed calculated by the means to restart the inverter in the event of a momentary power failure. instantaneous power failure re-input device.