JPS5836191A - Contactless relay for 3-phase ac motor - Google Patents

Abstract

PURPOSE:To eliminate the production of counterelectromotive force at the time of starting and stopping an AC motor by performing the starts and the stops of triacs of the respective phases R, S, T at the zero crossing points of AC current. CONSTITUTION:When a control command is inputted to an input terminal 4, zero crossing trigger pulses is generated when zero volt is initially generated between the respective phase and the next order phase from zero passing logic circuits 20-1-20-3 which include constant voltage diodes 9-1-9-3 connected in reverse direction between the phase. Thus, light emitting diodes 23-1-23-3 generate light, and gate circuits 24-1-24-3 operate. Accordingly, the phases R, S, T sequentially become ON at the phase difference of 120 deg. in the vicinity of the zero volt. When a stop command for contactless relay for 3-phase AC motor is dispatched, the phase which initially becomes zero becomes zero sequentially of the respective phases.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contactless relay for a three-phase motor.

Currently, electromagnetic contact relays are mainly used to control electric motors used in machine tools. A back electromotive force is generated between the contacts of an electromagnetic relay due to the inductive load when the motor starts and stops, which causes spark discharge and malfunctions in electronic control equipment. The time spent can't be ignored.

In addition, relays need to be replaced every one to three years due to poor contact due to melting, welding, or oxidation of contacts due to spark discharge, and the cost of this, as well as the need to stop operating semi-automatic equipment due to failure discovery and replacement, cannot be ignored.

Currently, zero-cross contactless relays are in practical use for single-phase alternating current, and many three-phase phase control devices have been manufactured, but contactless relays for three-phase power have not been put into practical use.

On the other hand, in recent years, electronic control has come to be widely used to control machine tools, and malfunction of electronic control devices due to noise generated by contact relays has become a problem.

This also applies to large machines such as No and ONO. Further, even in the case of control using only electromagnetic relays, there is a problem in that it is time-consuming to replace the relay due to contact welding, melting, poor contact, etc.

All of these adverse effects occur when a large current is suddenly applied or interrupted, and in the present invention,
When an ON or OFF command is received, it is not executed immediately, and if it is ON, the voltages of the R phase, S phase, and T phase, which have a phase difference of 120 degrees, are sequentially changed from the phase that first became zero. O
If the switch is set to N, and if it is set to OFF, the R phase, S phase, and T
This is logical control so that the phase current is sequentially cut off starting from the phase where it first becomes zero.

Therefore, according to the present invention, there is no back electromotive force generated during 0N1OFF, and there is no adverse effect on the electronic control device.
Since it is non-contact control, it has a semi-permanent lifespan and is highly reliable.

That is, the purpose of the present invention is to eliminate vibratory surges when starting and stopping a three-phase motor, and to eliminate the influence of the external atmosphere and external magnetic field, especially in the electronic control of machine tools.
In addition, the aim is to eliminate malfunctions caused by external vibrations and shocks, shorten operation adjustment time, reduce material costs such as spark killers, improve reliability, and reduce maintenance and repair costs due to semi-permanent life. do.

The present invention will be explained below with reference to the drawings.

1 is a command input for controlling a three-phase non-contact relay, which is supplied to a full-wave rectifier via a voltage drop resistor l. The (+) side of the aftereffect rectifier is connected to the smoothing circuit 3 and the protective resistor n-i.
And light emitting diode 2 for triac ignition? -/ is connected to the open collector of the OR circuit x-i.

On the other hand, the (-) side of the full-wave rectifier is connected to the GND of the OR circuit -/ via the diode -/.

The R phase j, S phase 6, and T phase 7 of the three-phase AC power supply are connected to the inputs T-1/ of the triacs B-/, B-λ, and 25-3, respectively.
Connect to T2-2 and Tno3, and its output T/-/, T/
- and Tl-3 are connected to the three-phase motor l, respectively.

Between the R phase and the SS phase≦7, there are constant voltage diodes connected in series in opposite directions through a voltage drop resistor 1-/, 9-
Connect /, /θ-7. These constant voltage diodes 9
The anode sides of reversely connected diodes // -/ and /2- / are connected between the cathodes of -/ and /θ-/, respectively, and the cathodes of diodes // -/ and /2- / are connected with smooth The other end is connected to the vOa input terminal of the OR circuit 20-/. A smoothing capacitor /4- / is installed at both ends of the smoothing resistor /4- /
, /7- / are connected, and the other ends of these capacitors are
The above-mentioned I constant voltage diodes connected in series in opposite directions? Connect the anode sides of -/ and /θ-7. Further, this point is connected to the GND of the OR circuit -/, and further connected to the (-) side of the full-wave rectifier through a diode -7. On the other hand, the anode sides of diodes /J-/, /4I-/ are separately connected to the cathode sides of the constant voltage diodes 9-t and to-i, which are connected in series in opposite directions. The cathode side of the diode is connected to the input terminal of the OR circuit〃-/, and the resistor/
g −/ , /? The operation of the preferred embodiment of the present invention shown in the first diagram will now be described.

AC 200 V is constantly applied between each phase.

Considering that R phase j and S phase 6 are connected, AC OOV is also applied between these R phase j and S phase 6, and they are connected in opposite directions through voltage drop resistors ri. Constant voltage diode Day 7, /θ-/ is R phase! Considering the case where S phase 6 becomes (-), the forward and reverse characteristics of the constant voltage diode shown in Fig. 2 are ma-a' and b-
As is clear from b/, the constant voltage diode 9-/ is t
Connected in the opposite direction to the source, with the cathode side as (+),
Generates an intermittent DC constant voltage with the anode side (-). The other constant voltage diode 10-/ is connected in the forward direction, and its voltage drop is extremely small.

Is the anode side of diode l/-/ a constant voltage diode? -7 is connected to the cathode side of the diode //
The cathode side of −/ is a smooth resistor /! -/ from the voo (+ terminal) and GND terminal of the OR circuit XI-/ to the constant voltage diode 1. /θ−l is connected to the anode side (one side in terms of DC), so the cathode side is connected to (+
), constant voltage diode 9-/ with the anode side as (-)
The diode /I − / is forward connected to
It becomes ON state. On the other hand, die 1-F/2-/ is the constant voltage diode? - / and also the constant voltage diode /θ-7 whose anode side is (10) and cathode side (-) are connected in the opposite direction, and are in an OFF state.

Therefore, the intermittent constant DC voltage generated in the constant voltage diode 9-/ is logically converted into a constant DC voltage through the diode //-/, the smoothing capacitors /, /7-/, and the smoothing resistor B-7. Added to vcc of sum circuit -/.

During the next half cycle, S phase t becomes (+) and R phase j becomes (→
becomes. Therefore, the constant voltage diode lθ-7 is connected in the opposite direction, with the cathode side being (10) and the anode side being ←
) generates an intermittent DC constant voltage.

On the other hand, the constant voltage diode is connected in the forward direction,
This results in a very small voltage drop. Therefore, contrary to the above explanation, diode /2-1 is turned on, and diode //
-/ is in the OFF state, and the constant voltage diode 10-
The intermittent DC constant voltage generated at / is smoothed by the capacitor l≦-/, /7-/ and the resistor /K-/ of the smoothing circuit, and then VOO is applied to the OR circuit -/ in the same manner as described above.
Added as input.

On the other hand, the anode side of the diode /J-/, /Glu is
Each is connected to the cathode side of the constant voltage diode 9-/, /θ-/, and the other is connected to the resistor /I-/, /9-/
Since it is connected to the anode side of the constant voltage diode 9-/S/θ-7 through When ≦ is (+) and R phase j is (-), diode l is on and /3-/ is off, and these are added as zero-cross logic detection inputs of the OR circuit -/. . That is, R phase triac B-/
It is used for zero-cross detection.

Similarly, the zero cross for triggering triac B-co of S phase 6 is detected by S phase 6 and T phase 7, and the triggering zero cross of triac B-3 of T phase 7 is detected by T phase 7 and R phase j. zero crossing is detected.

The timing of zero cross trigger between each phase will be explained with reference to FIG. 1 and FIG. 3.

In Fig. 3, □ indicates R phase, 1 ---- indicates S phase, 1 ---- indicates T phase, M indicates each phase voltage curve of three-phase AC, and B mainly indicates R phase. When current flows from the S phase to the S phase, the cathode of the constant voltage diode 9-/ is a DC current waveform. (The waveform is as follows: D is the trigger pulse of R-phase triac B-7, E is
Mainly, when the current flows from the S phase to the T phase, the cathode of the constant voltage diode λ is DC (+), and F is the waveform of the constant voltage diode 10-J when the current flows from the T phase to the S phase. Waveform with cathode as DC (+)) G is the trigger pulse of S-phase triac B-λ, ■ is,
A waveform in which the cathode of the constant voltage diode 3 is DC (+) when the current mainly flows from the T phase to the R phase, and J is the cathode of the constant voltage diode 10-J when the current flows from the R phase to the T phase. is a DC (+) waveform, and K is the trigger pulse of the T-phase triac B-3.

Furthermore, the zero cross trigger of the R-phase triac B-/ will be explained in detail. When an alternating current voltage is applied between the R phase, j1, and S phase, as explained above, the constant voltage diodes 9-/, 10-/, dioton/, -/, /2
− / , smoothing circuit /j−/ , /4−/, /7−/
A constant DC voltage is created, and these voltages are added to the OR circuit as an operating power source.

When the R phase is (+), the diode n-t causes the R phase to become (-) during the 0th half cycle, which is applied to the 0th side, due to the diode /l -/, as shown in Figure 3C. is applied to the other input side of the OR circuit 21)-1.

Therefore, as is clear from the functional diagram of the OR circuit in Fig.
The output of the OR circuit -/ becomes L level, and a waveform as shown in the third figure is obtained, and near zero of the relative voltage between the R phase, S phase, and each other is detected, and becomes a zero cross trigger timing pulse.

S phase, T phase triac 2s-2, B-,! The zero cross trigger timing pulse is also generated by a similar logic circuit.

Now, consider the case where a control command is issued for a three-phase power non-contact relay. Although the control command may be either a DC voltage or an AC voltage, this example will be explained using an AC voltage.

The control command enters the input shown by the line in FIG. 7, becomes an appropriate voltage by the voltage drop resistor l, enters the aftereffect rectifier 2, undergoes full-wave rectification, and then is converted into a DC voltage by the smoothing circuit 3 and sent to the protective resistor 2.
2-/, 22-2.22-J through the light emitting diode n-no, n-2,2? -3 is connected to the anode side, and the cathode side is connected to the OR circuit z-i, x-co of each phase, and the open collector of -3; 7% When the open collector of J7-2, , J-2 and 21-3 do not operate. In other words, even if a control command is issued, the R phase, S
If the voltage between each phase and T phase is high, use TRIAC B.
-/SB-λ, control of 25-3 is withheld, and among the R phase, S phase, and T phase, the phase where the relative voltage between each phase and the next phase is near zero volts, e.g. S-T when looking at S phase ≦
When the voltage between the two voltages reaches zero volts for the first time, the waveform shown in Figure 3G becomes the L level, and the protective resistor ッ-1 and light emitting diode
λ, the open collector and diode I-gate circuit 24I-2 of the logical homology W62D-2 is activated, the triac 15-2 is turned on, the S phase is turned on near zero volts, and the T phase is further delayed by 720 degrees of phase difference. But another 00
After a delay, the R phase turns ON.

In addition, when a non-contact relay stop command for three-phase AC motor is issued, the first phase of each phase where the current becomes zero will be turned OFF.
becomes. For example, if the current in the T phase becomes zero first, the T phase, R phase, and S phase are turned off in this order. Therefore, when a drive control command is issued, do not immediately turn on the R phase, S
Among the phases and T-phases, turn on the phase that first reached near zero volts, and turn it off immediately if a stop command is issued.
It is possible to provide a contactless relay for three-phase AC motors that does not generate back electromotive force due to the inductive load, regardless of whether it is turned on or off, since the current is turned off sequentially from the phase where the current becomes zero first. .

According to the present invention, as described above, the induction disturbance caused by spark discharge can be reduced to almost zero.

[Brief explanation of the drawing]

FIG. 2 is a curve diagram showing the characteristics of a constant voltage diode, FIG. 3 is a waveform diagram for explaining the logical operation of the circuit of the present invention, and FIG. 9 is a logical operation chart of the circuit of the present invention. ? −/ , De − , 2 , De −
3, lθ −/, 10-2, 1
0-3... Constant voltage diode, 21-/, 211-ko, 21-3... Gate, 2-/, B-2, 25-3
...Tochiiatsuk. Patent applicant Yutaka Seimitsu Kogyo Co., Ltd.

Claims (1)

[Claims] A non-contact relay that controls starting and stopping of a three-phase AC motor from a three-phase AC power supply having each phase of L, R, S, and T through a triac provided in each phase. (R-8,
A zero-crossing detection logic circuit including a constant voltage diode connected in series in the opposite direction between S-T, T-R) is provided, and when a zero potential first occurs between each phase and the next phase, the corresponding phase is detected. Generates a zero cross trigger pulse from the logic circuit, activates the triac gate of the corresponding phase according to the operation command,
A contactless relay for a three-phase AC motor, which controls the operation of the three-phase AC motor by starting or stopping each triac. 2. The logic circuit for detecting zero passing of each phase is connected to the anode side of one diode connected in series in the reverse direction between each cathode of a constant voltage diode connected in series in the reverse direction. Contactless relay. 3. The non-contact relay according to claim 2, wherein zero crossing of the constant voltage generated by one of the constant voltage diodes is detected by an OR circuit.