JPH0334312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC elevator control system, and more particularly to a DC elevator control system using a three-phase full-wave thyristor bridge.

FIG. 1 shows an elevator control device that obtains a variable DC voltage from a three-phase AC power source and applies it to the armature of a DC motor. 3 phase AC power supply
Apply the three-phase voltages U, V, and W from E _a to the AC terminals of a three-phase full-wave thyristor bridge consisting of six thyristors U ₁ , U ₂ , V ₁ , V ₂ , W ₁ , and W ₂ . The output voltage E _L of the three-phase full-wave thyristor bridge when
The direct current is controlled by controlling the phase of generating the gate pulse of each thyristor, and by rotating the sheave S, drives the counterweight CW and the cage C suspended in a spiral shape through the rope R. It is applied to the armature M of the electric motor.

Phase for generating gate pulse (thyristor U ₁
can be expressed as a delay in electrical angle from the point in time when the voltages of the U and W phases switch to positive, and this is hereinafter referred to as a control delay angle. ) is α, the DC output voltage E _L is expressed as E _L = 3√2/π・E _a・cos α (1) However, when the control delay angle α is zero, the DC output voltage E _L is maximum and when α = 90°, the DC output voltage is
Output voltage waveform when E _L is zero, U-phase voltage waveform,
The relationship between the U-shaped current waveforms is as shown in FIGS. 2a and 2b. Fig. 2 a assumes that the time constant of the armature M of the DC motor is sufficiently longer than the period of the power supply, and
This is the waveform assuming that the DC voltage E _O of the load, that is, the back electromotive force of the DC motor, is slightly lower than the output voltage E _L , and the waveform is U _V , V _V , W _V
is the phase voltage, E _L is the output voltage, and U _I is the U-phase current.

When the output voltage E _L is maximum, the center value of the U-phase current U _I matches the center value (maximum value) of the U-phase voltage U _V , and the phase of the fundamental wave component of the U-phase current U _I is
It matches the U-phase voltage _UV , and the power factor is the highest for this type of control method.

However, as shown in Figure 2b, the output voltage E _L
When is zero, the center of the U-phase current U _I is the zero point of the U-phase current U _V , and the fundamental wave component of the U-phase current U _I lags the U-phase voltage U _V by 90°, It can be said that the power factor is zero. In this way, by controlling the firing angle of the three-phase full-wave thyristor bridge, the output voltage
The method of controlling E _L has the disadvantage that the power factor deteriorates particularly in a range where the output voltage E _L is low.

In addition, the output voltage E _L of a three-phase full-wave bridge circuit includes a ripple component whose fundamental wave is a frequency six times the power supply frequency, but this ripple component decreases as the output voltage E _L increases. , is maximum when the output voltage E _L is zero, and U in Fig. 2 a and b
As can be seen from the pulsations in the phase current U _I , the output voltage E _L
When is low, the ripple component of the output current becomes large. Therefore, when the average values of the output currents are equal, the electromagnetic noise of the DC motor tends to increase as the output voltage E _L decreases.

This electromagnetic noise propagated not only in the machine room but also in the elevator hoistway and was transmitted not only to cage C but also to rooms near the elevator, which was a problem unique to elevators.

Therefore, in the past, a method was adopted in which a DC reactor LD was inserted into the output of the AC-DC converter to smooth out the ripples in the output current, thereby suppressing the generation of electromagnetic noise. In addition, a contactor CTT is used to cut off the output circuit when a failure occurs in the rectifier circuit and the output current increases.
This contactor has a time delay. For this reason, if the output current suddenly increases, it may exceed the breakdown current of the thyristor element before the contactor CTT can shut off the circuit, so a DC reactor LD is inserted at the output of the rectifier circuit to suppress the increase in output current. As described above, in the conventional circuit, a contactor CTT, a DC reactor LD, etc. were inserted into the output of the rectifier circuit, and the disadvantage was that the equipment was large and expensive, and the losses generated in these devices were large.

The present invention has been made in view of the above, and its purpose is to make it possible to eliminate or downsize the DC reactor inserted in the output circuit, thereby reducing the size and cost of the device. The object of the present invention is to provide a control device for a DC elevator that can perform the following functions.

The present invention is characterized in that the armature of a DC motor is controlled by a full-wave rectifier circuit, and a controllable opening/closing means having a current interrupting function is connected to each of the positive side or negative side arm of the rectifier circuit. The opening/closing means is controlled to open/close at a high frequency with a desired flow time width,
By circulating the output current without passing it through the power supply circuit during the open period and reducing the low frequency ripple of the output current, it is possible to directly feed the rectified output to the armature without going through a large DC reactor.

Hereinafter, the present invention will be explained based on examples.

When obtaining the output voltage shown in Figure 2 a and b, the six thyristors can be obtained by using thyristors that do not have a current cutoff function, but they can be obtained by using a thyristor that does not have a current cutoff function, but can be obtained by flowing a pulsed reverse current through the gate. If a thyristor (hereinafter referred to as GTO), which has the function of cutting off the current flowing in the Power factor can be improved.

In Fig. 1, conventionally the load current I _L always flows through the power source E _a , but in contrast, for example, thyristors U ₁ and U ₂ are fired simultaneously to By creating a period in which the current I _L does not flow through the power source E _a , the current flowing through the power source E _a can be reduced, and the low frequency ripple component of the output current can be reduced.

For example, when _the output voltage E _L is zero, during the period T shown in _FIG . ₁ and V ₁ are firing, but at this time GTO is used as thyristor U ₁ and V ₁ to open and close at a frequency 30 times the power frequency, and GTOV ₁ is made conductive while GTOU ₁ is disconnected. In this case, the waveform of the output voltage E _L and the waveform of the U-phase current U _I during the period T are as shown in FIGS. 3d and 3e, respectively.
In this way, during the period when GTOU ₁ is firing,
As shown in group c in Figure 3, a current flows and a load current flows to the power supply, but when GTOU ₁ is turned off and V ₁ is turned on, the current flows in a loop and does not pass through the power supply. Output voltage at this time
E _L becomes zero. The output current I _L decreases with a time constant due to the load inductance LL and resistance RL, but generally this time constant is about several hundred ms, so the output current changes during the period when GTOV ₁ is on (approximately 1 ms or less). is sufficiently small, and the generation of electromagnetic noise by the motor can be reduced without inserting an external DC reactor.

Furthermore, when generating a small output voltage E _L , if the phase α is controlled to zero to generate a high positive voltage, and the period T during which GTOU ₁ is conductive is made sufficiently short, the output voltage can be increased. The voltage E _L can be made sufficiently small. The output current waveform and U-phase current waveform in this case are shown in FIGS. 4b and 4c, respectively. Note that FIG. 4a shows the phase voltage waveform.

The center value of the U-phase current U _I almost coincides with the maximum value of the U-phase current U _V , and the fundamental wave component of the U-phase power supply is the V-phase voltage.
Since it is in the same phase as V _V , the power factor approaches 1, and the current flowing through the power supply is also pulsed and sufficiently small.

On the other hand, by making the positive side, negative side, or all control elements of a full-wave rectifier circuit a controllable switching means with a current interrupting function, DC reactors LD and contactors, which were conventionally inserted for the purpose of protecting the elements,
CTT may be removed.

For example, if the output current I _L suddenly increases due to a failure such as a power outage when the motor is in regenerative operation, the output circuit has conventionally been shut off using a DC contactor CTT.

Therefore, the contactor operation delay time (approximately 100m)
In order to prevent the output current I _L from becoming a breakdown current of the element, a DC reactor LD was inserted to suppress the rise of the current.
If a fault occurs at t ₁ and the fault is detected, the contactor
A signal to cut off the CTT is issued, but time t ₂ elapses before the contactor CTT can be cut off, and the output current I _L becomes I _L1 and is cut off. On the other hand, the present invention can control the positive side, negative side, or all control elements of a full-wave rectifier circuit.
Configure with GTO and use fault detection signals to detect all
The output current is reduced by giving an arc-extinguishing pulse to the GTO.
Since I _L can be shut off almost instantly, the output current can be reduced without inserting an external DC reactor to suppress current rise.
I _L is the output current at the time of failure as shown in Figure 5 B.
Although the rise in I _L is rapid, the maximum value I _L2 can be kept to a sufficiently smaller value than the maximum value I _L1 in the conventional case.

In this way, according to this embodiment, the externally inserted DC reactor LD and contactor that were conventionally used can be
Since CTT can be removed, the device can be made smaller and lighter, and the cost can be reduced. Moreover, since the loss consumed by the DC reactor is eliminated by removing the DC reactor, the power saving effect of the apparatus can also be obtained.

Next, another embodiment according to the present invention will be described.

In the method described above, when trying to continuously control the output voltage E _L to a sufficiently small value,
The on-time of GTOU ₁ ~ W ₁ must be made very short, and such control is difficult. In particular, it is extremely difficult to continuously control the output voltage E _L to 1/10 or less. .

By the way, in a high-speed elevator driven by a DC motor, it is necessary to continuously control the elevator to a speed of 1/1000 or less of the rated speed, but in such a case, conventional methods cannot control the elevator.

In order to use the output voltage E _L continuously to a sufficiently small value, first set the control delay angle α to zero and reduce the conduction rate to about 1/10, then control α and increase α. This can be achieved by continuously lowering the angle from 0 to 90 degrees.

Therefore, one method of controlling the gate signal will be explained here. However, it is assumed that the output current I _L always flows continuously, and each pulse is expressed as follows.

The firing signals of CTOU ₁ , V ₁ , W ₁ are connected to GU ₁ , GV ₁ ,
GW ₁ , and the firing signals of thyristors U ₂ , V ₂ , W ₂ are
Let GU ₂ , GV ₂ , and GW ₂ . In addition, the ignition signal GU ₁
There are two modes, so when GTOU ₁ fires, the firing signal GU _{1 during the period when the load current flows into the power supply (the period when the output voltage is generated) is set to GU 11 ,}
The period when the load current does not flow into the power supply (the period when the output voltage is zero) is defined as GU ₁₂ , and the other ignition signals GV ₁ ,
Similar saphics shall be attached to GW ₁ as well.

FIG. 6b shows the period during which each firing signal pulse occurs when the control delay angle is α. ignition signal
GU ₁ is at a positive voltage during the period when GTOU ₁ is conductive;
It is sufficient that the signal has a non-conducting period of zero, and the ignition signal GU ₂ only needs to be a positive narrow-width pulse for ignition, provided that the load current is continuous.

The source signal for generating such a signal may be one that generates one gate signal for each thyristor in one cycle, such as the gate signal of a conventional three-phase full-wave thyristor bridge circuit. If the gate signal corresponding to each thyristor is GU ₁₃
If expressed as follows, GU ₁₃ to GW ₂₃ become a pulse train as shown in FIG. 6c. As can be seen, GU ₂ = GU ₂₃ , GV ₂ = GV ₂₃ , and GW ₂ = GW ₂₃ . In other words, the gate pulses of thyristors U ₂ , V ₂ , and W ₂ may be the same as those of the conventional ones.

By passing this group of pulses through a flip-flop circuit, it is possible to obtain a pulse GU ₄ that turns on from the pulse of the signal GU ₁₃ to the pulse of the signal GU ₂₃ .
The pulses obtained in this way GU ₄ , GV ₄ ,
GW ₄ is shown in Figure 6d. Furthermore, the signal GU ₁₁ ,
The conduction pulses of the pulse C chopper operation that occur when GV ₁₁ and GW ₁₁ are on are shown as P for period T only in FIG. 6e. At this time, the logical formula for the gate pulses to be applied to GTOU ₁ , V ₁ , and W ₁ is as shown below.

GU ₁₁ = GU ₄ , GV ₄ , P GV ₁₁ = GV ₄ , GW ₄ , P GW ₁₁ = GW ₄ , GU ₄ , P GU ₁₂ = GU 4, GV ₄ , P _{GV 12 =} GV ₄ , GW ₄ , P GW ₁₂ = GW ₄・GU ₄・P ...(2) GU ₁ = GU ₁₁ + GU ₁₂ = GU ₄・GV ₄・P + GU ₄
・GV ₄・P GV ₁ = GV ₄・GW ₄・P=P+GV ₄・GW ₄・P GW ₁ =GW ₄・GU ₄・P+GW ₄・GU ₄・P ...(3) Generate these gate pulses An example of an actual circuit for this purpose is shown in FIG. In Figure 7, T _r is a △-Y transformer whose secondary neutral point is grounded, and PU, PV, and PW are phase shifters similar to conventional ones, each of which is ignited by a phase shift signal S _a . Signal pulse GU ₁₃ ,
Generates GU ₂₃ etc. Firing signal GU ₂₃ , GV ₂₃ ,
GW ₂₃ can be used as GU ₂ , GV ₂ and GW ₂ respectively.

These pulses are transferred to the flip-flop circuit PU ₁ ,
In addition to PV ₁ and PW ₁ , pulses GU ₄ , GV ₄ and GW ₄ are obtained. On the other hand, the conduction angle phase shifter PP generates a pulse _P according to the conduction rate command SP. These signals are applied to the 3-gate NAND circuit P 3 through the knot circuit P ₂ so that the logical formula (2) is satisfied, and are further applied to the 2-gate NAND circuit P ₃ so that the output satisfies the formula (3).
Added to NAND circuit P ₄ . In this way, pulses GU ₁ , GV ₁ and GW ₁ are obtained.

Next, a method of controlling the control delay angle α and the pulse P will be explained. When controlling the positive output voltage,
First, while keeping the conductivity of P constant at 0.1, α
When changing the angle from 90° to 0, the output voltage E _L (see Figure 1) changes from 0 to 0.1×3√2/π·E _a . Subsequently, when P is changed from 0.1 to 1, the output voltage E _L increases to a maximum of 3√2/π·E _a .

When controlling negative output voltage, set α from 90°.
When changing the angle up to 180°, the output voltage E _L changes from 0 to -0.1・
It changes to 3√2/π・E _a . Then, when P is changed from 0.1 to 1, the negative output voltage increases to a maximum of 3√2/
Increases to π・E _a .

In order to obtain the α command S _a and the P command S _P from the output voltage command S _i , a function generator with the characteristics shown in Fig. 8a is used.
F _a and F _P may be connected as shown in Figure 8b.

FIG. 9 shows an embodiment of a circuit for controlling a DC motor using the above-described circuit system according to the present invention.
In FIG. 9, M is the armature of the DC motor, F is its field, th is a push-pull thyristor amplifier that controls the field current, and PS is its phase shifter.
Further, PC is the gate circuit shown in Fig. 7, PA is a comparator that compares the output of the DC current transformer CT that detects the armature current and the armature current command S _C , and U ₁
~ _W1 , _U2 ~ _W2 are thyristors, and as described above, GOTs are used as the thyristors _U1 ~ _W1 .

The armature current is controlled to be constant according to the armature current command S _C , and the speed is determined by comparing the speed command S _S and the speed detected by the speed generator PG using a phase shifter PS. By controlling the current in the negative direction, the torque is controlled in the positive and negative directions, thereby controlling the motor to follow the speed command S _S.

Such a control system has a feature that even if the armature current is unidirectional, four-quadrant operation of forward/reverse rotation, power running, and regeneration is possible. Moreover,
Since the armature current is controlled in a constant and continuous state, the gate pulses for the thyristors U ₂ , V ₂ , and W ₂ may be narrow pulses, and the gate circuit can be simplified.

As described above, according to other embodiments of the present invention, the output voltage can be controlled continuously from positive to negative or from negative to positive, which is effective in applications that require high precision control such as elevators. There is.

As described above, according to the embodiments of the present invention, the power factor is improved, the capacity of the power source can be reduced, and a DC reactor and contactor are not required, which has great engineering effects.

In addition, in the above embodiment, U ₁ , V ₁ , W ₁ are
Although it is assumed that U ₂ , V ₂ , and W ₂ are GTO,
U ₁ , V ₁ , W ₁ are thyristors, U ₂ , V ₂ , W ₂
The same effect can be obtained by opening and closing using high frequency.

In addition, as a control method for a DC motor, a case is shown in which the armature current is controlled at a constant level, but full-wave rectification is also used, in which controllable switching means with a current cutoff function is applied to the positive side or negative side and all control elements. If the elevator equipment uses a circuit to control a DC motor, two pairs of forward and reverse full-wave rectifier circuits are used to control the armature voltage,
It may be a method of controlling the current, and the AC power source is not limited to a three-phase power source.

As explained above, according to the present invention, since the output current is output in pulses, it is possible to reduce ripples in the output current, especially in the low frequency range, so that no noticeable electromagnetic noise is generated, and therefore the rectifier circuit In addition to eliminating the need for a direct current reactor to cause combustion, it is possible to continuously output voltage according to the phase angle and current according to the current rate according to the load of the elevator, allowing smooth operation of the elevator. This has the effect of making it possible to downsize the device and save power.

[Brief explanation of drawings]

Figure 1 is the main circuit diagram of a general three-phase to DC converter.
Figure 2 is a waveform diagram for a conventional three-phase to DC converter, Figures 3 and 4 are waveform diagrams for a three-phase to DC converter of the device of the present invention, and Figure 5 is an output current waveform diagram at the time of failure. , FIG. 6 is a waveform diagram of the gate pulse in the device of the present invention, FIG. 7 is a circuit diagram showing an embodiment of the gate circuit of the device of the present invention, and FIG. 8 is the input of the phase shifter of the device of the present invention. FIG. 9, which is a diagram for explaining a function generator employed in the circuit, is a circuit diagram showing an embodiment in which a DC elevator is controlled by the apparatus of the present invention. E _a …3-phase AC power supply, U ₁ ~ _{W 1} … GTO, U ₂ ~ _{W 2}
…Thyristor, M…DC motor armature, S…Sheep, C…Cage, T _r …Transformer, PU to PW…Phase shifter, PU ₁ to PW ₁ …Flip-flop circuit, PP…
Flow angle phase shifter, P ₂ … knot circuit, P ₃ , P ₄ …
NAND circuit, F〓, F _P ...Function generator, PA...Comparator, PC...Gate circuit, th...Push-pull thyristor amplifier, PS...Phase shifter, CT...DC current transformer,
PG…Speed generator.

Claims (1)

[Scope of Claims] 1. A control device for a DC elevator driven by a DC motor, including an AC power source, and a current source connected to the AC power source, which is connected to at least one of the positive side and the negative side of the DC output side. A rectifier circuit configured by connecting a thyristor equipped with a switching means having a function, the armature circuit connected to the DC output side of the rectifier circuit, and a phase angle according to an output voltage command is determined. A control device for a DC elevator, comprising means for opening and closing the opening/closing means of the thyristor according to a phase angle, and means for determining an opening/closing pulse of the opening/closing means of the thyristor according to a conduction rate command. 2. The control device for a DC elevator according to claim 1, wherein the current pulse is kept constant at a minimum when the phase angle changes from 0 to 180 degrees. 3. Claim 1 that changes the conduction pulse from the minimum to the maximum when the phase angle is constant at 0 or 180°
The control device for a DC elevator according to item 1 or 2.