JPS61203892A - Motor drive device - Google Patents

Abstract

PURPOSE:To smoothly control a motor at recovery time by using the speed detection signal of the motor as a speed command at momentary power interruption time. CONSTITUTION:When a momentary power interruption occurs, the output signal Ts of an input voltage detector 27 is turned OFF. A switching circuit 34 blocks a speed signal Ss therefor and outputs a speed control signal Sx with a speed detection signal Tx from a speed detector 33. This signal Sx is inputted to a voltage/frequency setter 10. Thus, the output of an inverter 6 is decelerated proportionally to the speed of an induction motor 8. This control is advanced at the input side of a gate circuit 2 during the momentary power interruption. Thus, the motor 8 can be risen while synchronizing the output of the inverter 6 with the speed of the motor 8 when the input power source is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a motor drive device, and more particularly to a variable voltage variable frequency power supply device (hereinafter referred to as VVV) that controls the speed of a variable speed motor.
In a system equipped with VVVF (referred to as F), if the VVVF input power supply experiences a momentary power outage, it stabilizes so that the VVVF does not trip by preventing overcurrent when the momentary power outage recovers. The present invention relates to an electric motor drive device suitable for performing 1lIII control.

[Technical background of the invention and its problems]

Generally, variable speed control is performed using VVVF.
As m, an induction motor is often used. The rotational speed of an induction motor, more specifically the synchronous speed, can be expressed by: synchronous speed=(120xfrequency)/number of poles. Therefore, when controlling the speed of an induction motor, it is possible to do this by changing the frequency of the power supply or by changing the number of poles, but usually the method of changing the frequency of the power supply is used. There is. However, if only the frequency is changed while keeping the voltage of the power supply supplied to the induction motor constant, the windings of the induction motor will become over-excited. Therefore, in order to keep the excitation constant, not only the frequency but also the voltage is generally varied. In order for the excitation to be constant in an induction motor, voltage/frequency (hereinafter referred to as V/F) is required.
A constant power supply is required. In this way, a VVVF is a power source that can change the voltage and frequency in order to generate an AC power source with a constant V/F.

A conventional motor drive device using a VVVF will be explained based on the block diagram of FIG. As shown in the figure, the induction motor 8 includes a rectifier 3 that converts commercial AC power into DC, a DC reactor 4 and a filter capacitor 5 that smooth the DC output, and converts the DC thus obtained into a variable frequency variable voltage converter. A VVV consisting of an inverter 6 that converts into alternating current, and an output transformer 7 that converts the output alternating current voltage of the inverter 6.
Driven by F system. The output current feedback signal To and the output voltage feedback signal Vo to the induction motor 8 are supplied to the current transformer 2 connected to the secondary side of the output transformer 7.
0 J3 and transformer 9. The speed setting device 1 generates a speed signal S8 that determines the speed of the induction motor 8, and also controls the speed of the inverter 6 based on the input current 11 of the induction motor 8 or the input voltage detection signal T8 detected by the input voltage detector 27. It performs a protective action and prevents the pollutant effect. The voltage frequency setter 10 generates a voltage reference signal vR and a frequency base signal @V in accordance with the speed signal s8. 'V/F
The converter 11 generates a clock pulse C3 proportional to the output frequency by the frequency reference signal V.
I is the voltage reference signal V8. Output voltage feedback signal @
Combined with Vo, the voltage is 1IIIJIl! Generates signal vX. The frequency dividing circuit 12 divides the frequency of the zero clock pulse C3 to generate a reference pulse fs. The frequency dividing circuit 13 divides the frequency of the 0 clock pulse Cp to obtain a desired clock pulse and sends it to the phase circuit 15. The phase shift circuit 15 receives the reference pulse fs
It has the effect of giving a time delay corresponding to the energization phase width. The output pulse signal of the phase shift circuit 15 is frequency-divided by the frequency dividing circuit 14 and sent out as a phase control pulse fR. Gate circuit 2
receives the reference pulse fS and the phase control pulse fR, amplifies them, and supplies them to the switching elements forming the inverter 6. The input voltage detector 27 detects the voltage of the commercial AC power supply of the rectifier 3, and turns off the input voltage detection signal T8 when a power outage occurs. On the other hand, the speed setter 1 has the function of setting the speed signal S3 to 0% and stopping the induction motor 1f18 when this input voltage detection signal T8 is not input for a period of 100 to 200 msec or more.

The operation of this configuration will now be described with reference to the circuit diagram of FIG. 6 and the waveform diagram of FIG. 7.

As shown in FIG. 6, the inverter 6 includes switch elements GU to GY such as GTOs which are connected in a ψ-phase bridge, and diodes DLI-GY connected in antiparallel to each switch element.
It is composed of DY. On the other hand, FIG. 7(A) shows the reference pulse f8. (B) is the phase control pulse fR2 (C), (
D), (E), (F) are switch elements GU, GV, GX
, GY, and (G) indicate the output voltage vo1 of the inverter 6, respectively.

Now, as shown in the time chart of FIG. 7, the switching elements GV and GY are switched by the pulse train of the switching elements GU, GX&, and one reference pulse fs, and the pulse train of the phase control pulse fR.

When the reference pulse f8 is fixed and the phase of the pulse train of the phase control pulse fR is shifted, the output voltage V of the inverter 6. 1
The pulse width θ changes, and the inverter output voltage V. 1 or change. In other words, the phase control pulse fR and the reference pulse f8
■ Output voltage by controlling the phase difference of. 1 voltage control can be performed.

The current transformer 20 detects the output current 11 from the output transformer 7 and outputs an output current feedback signal r□ to the speed setting device 1. When the output current 11 exceeds the rated value, the speed setting device 1 trips the VVVF in order to protect each element constituting the inverter 6.

However, the control method for the motor drive device having the configuration shown in FIG. 5 has a problem in that even if an instantaneous power outage of several hundred milliseconds occurs in the commercial AC power source, the induced lightning Wb I 8 will stop. Here, the operation when an instantaneous power outage of several hundred milliseconds occurs will be explained using the time chart of FIG. Figure 8 (A> is the input voltage detection signal T8 of the commercial AC power supply, (B) is the speed signal S3, (C) is the voltage reference signal vR1, (D) is the output current 11, and (E) is the output voltage Each indicates a VOI.

Suppose now that a momentary power outage occurs at time t. In this case, since no power is supplied to the inverter 6, the output voltage VOI and the output current 11 of the inverter 6 decrease, and the rotational speed of the induction motor 8 decreases. At the same time, the output voltage feedback signal V. However, since the speed signal SS is constant, the voltage reference signal VR is kept constant. Therefore, the voltage reference signal 1 is constant and the output voltage feedback signal Vo decreases, which inevitably leads to the voltage control signal VX
will rise.

Also, since the speed signal S8 is constant, the frequency reference signal (2) is kept constant, and therefore the clock pulse C
P does not change, and the output frequency of the inverter 6 also remains constant.

At this time, if the commercial AC power supply is restored, the output frequency of the inverter 6 will be the same as before the instantaneous power outage. On the other hand, the output voltage V of the inverter 6. 1, the voltage control signal vx has an upper limit, so that the energization phase width is increased so that a higher voltage can be outputted than before the instantaneous power outage.

However, since the speed of the induction motor 8 has decreased due to the instantaneous power outage, there is a difference between the output frequency of the inverter 6 and the speed of the induction motor 8, and the phases are also not synchronized. Therefore, the inverter 6 controls the induction motor 8 so that the output frequency and the speed and phase of the induction motor 8 are synchronized.
try to increase the speed of However, induction motor 1f
In order to increase the speed of the i8, it is necessary to provide a strong acceleration torque, and for this purpose the inverter 6 needs to supply the induction motor 8 with an output current 1 that is higher than the rated value.

However, if a current exceeding the rated value is passed through the inverter 6, the overcurrent will cause the inverter to rip.

In other words, the current flowing through the inverter 6 is the output of the inverter 6:! ! This is determined by the magnitude of the speed deviation of the S electric motor 8, and this deviation is proportional to the instantaneous power outage time t.

Therefore, if the instantaneous power outage time is long, the output current (1) becomes an overcurrent, and the overcurrent output current feedback signal IO is sent to the speed setter 1, causing the speed setter 1 to trip VVVF.

As mentioned above, in the conventional electric motor drive system, depending on the duration of the momentary power outage, the VVVF may trip, and as a result, the electric motor may stop and the continued operation of the system may be hindered. This was a major problem in terms of system configuration and operation.

[Purpose of the invention]

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, suppress overcurrent after power is restored even if an instantaneous power outage occurs in the input power supply, prevent VVVF from tripping, and improve the motor system. An object of the present invention is to provide a highly reliable electric motor drive device that allows continuous operation.

[Summary of the invention]

In order to achieve the above object, the present invention provides a variable voltage variable frequency power source that drives a motor by controlling the ratio of output frequency and output voltage to a constant value, and a momentary power failure in the input power source of the variable frequency power source in this variable voltage cylinder. switching means that stops the variable voltage variable frequency power source when the input power source is restored, detects the speed of the motor, and holds this as a speed control signal; The present invention provides an electric motor drive device equipped with a control means that restarts control using a speed control signal held by a switching means and gradually returns to normal operation after a certain period of time.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a motor drive device according to an embodiment of the present invention. In the figure, the phase detection circuit 31 detects the output voltage V of the inverter 6. 1 phase is output from the quadrature transformer 7. Voltage V. 2 and outputs a phase detection signal α. Gate block circuit 32 sends gate block signal GB to gate circuit 2 based on phase detection signal α from phase detection circuit 31 and input terminal detection signal T8 from input voltage detector 27. Speed detector 33 outputs voltage feedback signal V. The actual speed of the induction motor 8 is detected based on the frequency of , a speed feedback signal Tx is generated, and this is applied as a speed control signal to the voltage frequency setter 10 via the signal switching circuit 34, and the speed of the induction motor 1fi8 is When the speed falls below a certain level, a stop signal TV is generated and sent to the speed setter 1.

In other words, the phase detection circuit 31 outputs the output voltages of output 1 to lance 7 (■). The gate block circuit 32 detects the phase of 2 and outputs the phase detection signal α having a phase of O'' to the gate block circuit 32. The gate block circuit 32 is connected to output the block signal G8 to the gate circuit 2. On the other hand, the gate block circuit 32 is configured to turn off the gate block signal GB when the phase detection signal α is input. When the gate circuit 2 inputs the block signals G1 to G, it turns off all the switch elements GU to GY of the inverter 6. On the other hand, when the gate block signal G8 turns off, the switch elements GU turn off when the reference pulse is input. Each switch element GU to GY is configured to perform a switching operation from the time when the switch is turned on.

Note that the switching n-path 34 is configured as shown in the block diagram of FIG. As shown in the figure, the switching circuit 34 is composed of analog switches 40, 41, 42, an inverter 43, a -order delay circuit 44, and a comparator 45. Note that the analog switches 40 and 41 are input voltage detectors g T s
It can be turned on/off by On the other hand, the comparator 45 turns off the bus signal TR when the input voltage detection signal T8 rises from off to on, and the analog switch 4
2 is connected to turn off. Further, the comparator 45 outputs a bypass signal TR when the speed command signal SA and the speed control signal SX match. - The next delay circuit 44 is connected to output the speed command signal SA by applying a first-order delay when the bus signal T1 is not input to the analog switch 42 and the speed command signal S is blocked.

The operation of this configuration will now be explained with reference to the waveform diagrams of FIGS. 3 and 4. In FIG. 3, (A) is the input voltage detection signal Ts, (8) is the speed feedback signal Tx, and (C) is the speed signal S81. (D) is the speed control signal SX. On the other hand, in FIG. 4 (A> is the reference pulse f
, (B) is the phase control pulse fR1 (C), (D),
(E).

(F) is the switching state of switch cables GU, GX, GV, GY, and (G) is the input voltage detection signal T1 (H
) is the gate block signal G1-S
B(1) is the phase detection signal α, the same L
l) is the output voltage V of the inverter 6. It is 1.

Assume that the induction motor 8 is now being driven at approximately 100% speed. At this time, if a momentary power outage occurs in the input power supply, the input voltage detection signal TS, which is the output of the input voltage detector 27, is turned off. When the input voltage detection signal TS is turned off, the gate block circuit 32 outputs the gate block signal G to the gate circuit 2. The gate circuit 2 turns off the switch elements GU to GY all at once using the gate block signal G.

On the other hand, in the switching path 34, when the input voltage detection signal T8 is turned off, the analog switch 40 is turned off and the speed signal S8 is blocked. The analog switch 41 has the input voltage detection signal T3 inverted by the inverter 43 and given to the control input. Therefore, when the input voltage detection signal T8 turns off, the inverted signal TC turns on and is input, so it is turned on. The speed detection signal Tx from the speed detector 33 is unblocked. Then, before the power failure of the input power supply, the speed signal SS is used as the speed command signal SA by the analog switch 42,
- The speed detection signal TX was input to the next delay circuit 44 and the comparator 45, but at the same time as the power outage, the speed detection signal TX was switched to the speed signal S8, and the analog switch 42, - the next delay circuit 44,
The signal is input to a comparator 45. When the input voltage detection signal TS rises from off to on, the comparator 45 is reset by this rising signal and turns off the bypass signal TR, so the speed command signal SA is outputted as the speed control signal SX through the analog switch 42.

Therefore, when a momentary power outage occurs in the input power source, the speed command is switched from the speed signal SS to the speed detection signal TX, and is outputted to the voltage frequency setter 10 as the speed control signal SX.

When the input rKi ffA experiences a momentary power outage, the switching element GLI-GY is turned off, so that the speed of the induction motor 8 is reduced. As the speed of the induction motor 8 decreases, the speed control signal Sx sent from the switching circuit 34 based on the speed detection signal Tx decreases, and the reference pulse f
8. The synchronization of the phase control pulse fR increases, and the phases of the reference pulse f8 and the phase control pulse fR decrease.

Therefore, each pulse signal is controlled in the direction of decreasing the output of the inverter 6. By the way, switch element G U
~Assuming GY is not turned off, the reference pulse f
If the period of 8 becomes large, the switching element GU-GY
The switching period of the inverter 6 increases, and the output frequency of the inverter 6 decreases. Also, phase & IJ111 pulse fR and M
When the phase difference of the quasi-pulse fS decreases, the output voltage phase width θ
As a result, the output of the inverter 6 decreases in proportion to the speed of the induction electric motor v18. but,
In reality, when a momentary power outage occurs, the gate block signal GB is input to the gate circuit 2, so switching of the switching elements GLI-GY is not performed. is progressing on the input side.

Assume that the input power is restored after such a state.

When the input power is restored, the input voltage detection signal T is turned on.
The signal is input to a gate block circuit 32 and a switching circuit 34.

As shown in FIG. 4, even if the input voltage detection signal TS is input to the gate block circuit 32, the gate block signal G,
does not turn off.

On the other hand, when the phase detection circuit 31 detects phase 0'', the phase detection signal α is output to the gate block circuit 2. When both this phase detection signal α and the input voltage detection signal T8 are input, the gate block signal G8 is turned off, and the gate block of the gate circuit 2 is released.In the gate circuit 2, when the gate block signal GB is turned off, the switch element G is turned off.
The switch element GU is turned on in a cycle that turns it on from U.
Switch GY. As a result of such control, the output of the inverter 6 and the phase of the induction motor 8 are synchronized when the power is restored. The reference pulse fs and the phase control pulse fR are F! Jden! Since it is proportional to the speed of IXIIm 8,
The output of the inverter 6 and the induced lightning vJ are connected to the input power source 1111.
The induction motor 118 can be started up while the speed of the machine 8 is synchronized.

However, if the speed detection signal air of the induction motor 8 is left as the speed command signal SA, speed control after the input power supply is restored will not be possible, so it is necessary to switch to the speed signal S8. Therefore, the switching circuit 34 unblocks the analog switch 40 when the input voltage detection signal Ts is turned on. The analog switch 41 outputs an inverted signal T when the input voltage detection signal T8 is turned on. is turned off, and the speed control signal Tx
block. As a result, the speed signal SS is sent to the analog switch 42 as the speed command signal SA, and then to the second delay circuit 44.
, are input to the comparator 45. Since the input voltage detection signal T8 rises from off to on, the comparator 45 is reset and turns off the bypass signal T. By turning off the bypass signal TR, the analog [1 switch 4
2 is blocked. Therefore, the speed command signal SA is outputted as the speed control signal Sx via the first-order delay circuit 44. In this case, the speed command signal SA is the speed signal @Ss and is 100% output. Therefore, the speed command signal S
8 is input to the first-order delay circuit 44, the speed control signal S
X gradually increases to 100% with a first-order lag. As the speed control signal Sx rises, the output of the inverter 6 increases and reaches 100% after a predetermined period of time. When the speed control signal Sx reaches 100%, the comparator 45 compares the speed command signal S and the speed control signal Sx, and when the speed m command signal SA and the speed control signal SX match, the bus pass signal TR is output.
Output. Ana[] switch 42 is bypass signal T
By inputting R, the speed command signal S is bypassed without going through the first-order delay circuit 44, and is made into the speed control signal SX. Thereafter, the inverter 6 will be controlled by the speed signal Ss.

Note that if the power outage of the input power source is too long and the speed of the induction motor 8 becomes lower than the minimum speed, the speed detector 33 outputs a stop signal TV. The speed setter 1 sets the speed signal Ss to 0% by inputting the stop signal TV, and puts the induction motor 8 in a stopped state even if the input power is restored.

Note that the comparator 45 outputs the speed command signal SA and the speed control signal S.
The speed command signal S does not have to be 100% because it is configured to output the bypass signal TR if x matches. In other words, the speed signal S is sent from the speed setting device 1 at instantaneous stop and heavy contact.
8, the speed fli! can be increased without increasing the speed control signal SA to 100%. In can be implemented.

〔Effect of the invention〕

As described above, according to the present invention, even when there is a momentary power outage in the input power supply, the speed detection signal of the motor is set as the speed command, the speed command is decreased to match the speed of the motor, and when the power is restored, the inverter is activated. By controlling the output of the motor to match the speed of the motor, the m
It is possible to obtain an electric motor drive device that enables smooth control of the electric motor during power operation, improves operational reliability of the electric motor system, and enables stable operation.

[Brief Description of the Drawings] Fig. 1 is a block diagram of a motor drive device according to an embodiment of the present invention, Fig. 2 is a block diagram showing details of the switching circuit shown in Fig. 1, and Fig. 3 is a block diagram of a motor drive device according to an embodiment of the present invention. A waveform diagram explaining the operation of the circuit during a momentary power outage. Figure 4 is a waveform diagram that does not show the timing when the block signal to gate 1 input to the gate circuit is turned off. Figure 5 is a waveform diagram of a conventional motor drive device. 6 is a circuit diagram showing details of the inverter in Fig. 5, Fig. 7 is a waveform diagram showing inverter switching and output voltage timing, and Fig. 8 is a circuit diagram showing details of the inverter in Fig. 5. FIG. 2 is a waveform diagram showing transient characteristics of an output voltage, an output current, a voltage control signal, and a speed signal when a momentary power outage occurs. DESCRIPTION OF SYMBOLS 1... Speed setting device, 2... Gate circuit, 6... Inverter, 8... Induction motor, 10... Voltage frequency setting device, 11... V/F converter, 15... - Phase shift circuit, 27... Input voltage detector, 31... Phase detection circuit, 32... Gate block circuit, 33... Speed detector, 34... Switching circuit. Applicant's agent Kiyoshi Inomata 51 Guchi 62 Figure 53 Figure (C) Ss 64 Figure (J) Vo+ et al. 5 Figure 6 Figure t5 tR

Claims (1)

[Claims] 1. When a momentary power outage occurs in a variable voltage variable frequency power source that drives a motor by controlling the ratio of output frequency and output voltage to a constant value, and in the input power source of this variable voltage variable frequency power source. switching means for stopping the variable voltage variable frequency power source and detecting the speed of the motor and holding it as a speed control signal; and when the input power source is restored, the switching means holds the variable voltage variable frequency power source. 1. A motor drive device comprising: control means for restarting control in response to a speed control signal that has been in use for a certain period of time and gradually returning to normal operation after a certain period of time. 2. A patent claim characterized in that the control means includes means for detecting the phase of the motor when the input power supply is restored, and restarting the operation of the variable voltage variable frequency power supply in accordance with the phase of the motor. The electric motor drive device according to item 1.