JPS589582A - Electric motor control device - Google Patents

Abstract

PURPOSE:To prevent the flow of excessive transient current at the contact point for a reverse rotation switching relay by performing the operation of the reverse rotation switching relay under the state a power source relay is restored. CONSTITUTION:When a forward rotation switch 8 is closed, a voltage comparator 44 becomes a low level, a comparator 45 becomes a high level, and transistors 49 and 53 are turned ON. Then the power source relay 7 is operated and the motor M is rotated in the forward direction. When the forward rotation switch 8 is released and a reverse rotation switch 9 is closed, the power source relay 7 is restored. When the switch 6 is closed, a thyristor 26 is turned ON. After a timer T2 is operated, a voltage comparator 31 becomes a low level, a transistor 35 is turned ON, and the reverse switching relay 4 is operated. After a timer T3 is operated, the voltage comparator 45 becomes a high level, a transistor 53 is turned ON, the power source relay 7 is operated, and the motor M is rotated in the reverse direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for an electric motor used in a shredder, etc., and an object of the present invention is to obtain a control device for an electric motor that can reliably rotate the motor in reverse even when there is inertia of the rotor of the electric motor. Another object of the present invention is to provide a control device for a motor that can reduce the overload applied to the contacts of the reverse switching relay even when the motor is automatically reversed when it is overloaded.

Conventional motor control devices require that when rotating the motor in reverse, the power to the motor must be cut off, the motor rotates at an extremely low speed, and then the reverse rotation switch must be used to turn on the power to the motor again. However, due to the inertia of the motor's rotor, the motor had the disadvantage that it could not be reversed. Moreover, when automatically reversing the motor when it is overloaded, the reversing switching relay is switched when the motor is close to locking, so a transient current due to the excessive back electromotive voltage of the motor flows to the relay contacts. Therefore, it has the disadvantage that it cannot be put into practical use unless the contact capacity of the relay is made extremely large or a contact protection circuit is provided.

The present invention solves these conventional drawbacks, and one embodiment thereof will be described in detail with reference to FIG. 1.

In the figure, 1 is an auxiliary coil of a capacitor-started induction motor, 2 is a centrifugal force switch, and 3 is a starting capacitor, which are connected in series, one end of which is connected to one movable contact of the reverse switching relay 4, and the other end of which is connected in series. , are connected to the other movable side contact of the relay 4, respectively. Reference numeral 6 denotes a main coil of the induction motor, which is connected in parallel to the fixed contact side of the relay 4 so that the motor can rotate in reverse when the movable side contact of the relay 4 is switched. 6 is a power supply, one end is connected to the point where the normally open fixed contact of the power supply relay γ and one end of the forward rotation switch 8 and the reverse rotation switch 9, which are capable of holding operation, are connected, and the other end is for voltage step-down. transformer 1
o and one end of the primary coil of the overcurrent detection transformer 11 are connected to each other. The other end of the transformer 10 is connected to the other ends of the switches 8 and 9. A movable contact of the power relay 7 is connected to one end of the main coil 6, and a normally closed fixed contact of the power relay 7 is connected to the other end of the main coil 5 via a resistor 12. The secondary coil of the transformer 10 is connected to the AC terminal of the bridge diode 13, and together with the smoothing capacitor 14 constitutes a DC power source for the control circuit. The secondary coil of the overcurrent detection transformer 110 is connected to obtain a half-wave rectified power supply through a diode 15, and is configured to charge a capacitor 17 via a resistor 16 from the half-wave rectified power supply. . A resistor 18 has one end connected to the cathode side of the diode 15 and the other end connected to the negative polarity side of the capacitor 17. 19 is a voltage comparator whose (G) side is connected to the anode side of the capacitor 17;
5 bases are connected to the connection point of 1. The output terminal is also connected to the positive side of a capacitor 26 via a diode 23° resistor 24. The negative polarity side of the capacitor 25 is connected to the (→ side) of the DC power supply for the control circuit. 26 is a thyristor whose cathode is connected to the negative polarity side of the capacitor 26.
A resistor 27 is connected between the gate and the cathode. 28
．． 29 are resistors connected in series, one end of which is connected to the (+) side of the DC power supply for the control circuit, and the other end of which is connected to the thyristor 26.
connected to the anode of the 30 is a capacitor connected in parallel with the resistor 29, and the negative polarity side is connected to a voltage comparator 31.
32 is a resistor connected to the gate of the thyristor 26 and the positive side of the capacitor 26. Both ends of the resistors 33 and 34 connected in series are connected to the DC power supply for the control circuit. connected in parallel with the resistor 33.3
The connection point 4 is connected to the (→ side) of the voltage comparator 31. 36 is a PIP transistor whose emitter is connected to the (+) side of the DC power supply for the control circuit, and whose collector is connected to the excitation coil of the reverse switching relay 4. The base 6 is connected to one end of the voltage comparator 31 through a resistor 37. 38 is a resistor connected to the PNP) range meter 3.
50 is connected between base and emitter. A diode 39 is connected in parallel with the excitation coil 36, and its cathode is connected to the collector side of the PNP transistor 36. The anode is connected to the cathode of the thyristor 26. 40 and 41 are resistors connected in series, and both ends are connected in parallel to a DC power supply for the control circuit. Both ends of the resistors 42 and 43 connected in series are also connected in parallel to the control circuit DC power supply.

44 and 45 are voltage comparators (the → sides are connected to each other).
, and the ←) side is connected to the cathode of the diode 46, respectively. The (→ side of the voltage comparator 46 is connected to the connection point of the resistors 40 and 41, and the (T) side is connected to the other end of the resistor 47, one end of which is connected to the cathode of the thyristor 26, and the cathode of the diode 48. 49 is a PNP transistor whose emitter is the emitter 7, -9 of the PNP transistor 36, the base is connected to the output terminal of the voltage comparator 44 via the resistor 6o, and the collector is connected to the cathode of the diode 62. are connected to each. 53 is an NPN transistor,
The emitter is connected to the cathode of the thyristor 26, the base is connected to the output terminal of the voltage comparator 45 via a resistor 64, and the collector is connected to the anode of the diode 62.

A resistor 55 is connected between the base and emitter of the NPN resistor 3. 56 is the power supply relay 7
The excitation coil is connected in parallel with the diode 52. A capacitor 57 is connected in parallel to the resistor 42. 58 and 59 are resistors connected in series, and both ends thereof are connected in parallel to the control circuit DC power supply.

The anode of the diode 6° and one end of each of the resistors 61 and 62 are connected to the connection point of the resistors 58 and 59. The other end of the resistor 61 is connected to the anode of the diode 48, the other end of the resistor 62 is connected to the cathode of the diode 63, and the cathode of the diode 60 is connected to the anode of the thyristor 26. A capacitor 64 has its positive polarity connected to the anode of the diode 48.63, and its negative polarity connected to the cathode of the thyristor 260. 66 is a switch that operates in conjunction with the reversing switch 9; one end is connected to the (→ side) of the DC power supply for the control circuit, and the other end is connected to the anode of the diode 66 and one end of the resistor 67.The cathode of the diode 66 is connected to the It is connected to the positive side of the capacitor 25, and the other end of the resistor 67 is connected to the anode of a diode 68. The cathode of the diode 68 is connected to the ←) side of the voltage comparator 44. A resistor 69 and a diode 7o are connected in parallel with the resistor 69, and have an anode connected to the anode of the diode 46 and a cathode to the cathode of the diode 39, respectively. A capacitor 71 has its positive polarity connected to the anode of the diode 7o, and its negative polarity connected to the anode of the diode 39.

The resistors 61, 62. The capacitor 649 and the diode 63 constitute a timer T1, and the resistor 69. The diode 70 and the capacitor 71 constitute a timer T3. In the figure, M is an electric motor, W is a driving section, R is a reverse rotation command section, and V is an overload detection section.

To explain the operation of the motor control device configured as above, when the forward rotation switch 8 is turned on, a DC power source for the control circuit is generated, the voltage comparator 19 becomes low level, and the thyristor 26 remains in the off state. . The voltage comparator 31 is at a high level, the PNP transistor 35 remains off, and the reverse switching relay 4 does not operate. The voltage comparator 44 is at a low level, the PNP transistor is on, and the voltage comparator 45 is at a high level (NPN).
Since the power supply relay 7 is also turned on, the power supply relay 7 operates and the motor starts rotating in the normal direction. Next, in order to reverse the motor, when the forward rotation switch 8 is released, the power relay 7 returns to its original state.
The power to the motor is cut off, but due to inertia, the motor's rotor continues to idle in the forward rotation direction. When the reversing switch 9 is turned on, the DC power for the control circuit is generated again, and the switch 65 is also turned on in conjunction with the reversing switch 9, so a gate current is applied to the thyristor 26 through the diode 66 and the resistor 32. , and the thyristor 26 turns on. The voltage comparator 44 is connected through the resistor 67° diode 68 (→The level is raised and the output terminal becomes low level, so P
NP ) transistor 49 is in the on state, but the (G) level of the voltage comparator 45 continues to be low level by turning on the thyristor 26 while the timer T1 is operating, so the output terminal of the voltage comparator 45 becomes low level and NPN ) Ranjistaro 3 is turned off.

Therefore, the power supply relay 7 maintains a non-excited state.

Further, by turning on the thyristor 26, the (T) level of the voltage comparator 31 is lowered to the - level after the operation of the timer T2, and its output terminal reaches the low level. Then, the PNP transistor 36 turns on, the reverse rotation switching relay 4 operates, and the motor is connected for reverse rotation. PIP)
When the transistor 35 is turned on, the timer T3 turns the (+) level of the voltage comparators 4511, . Therefore, the NPN transistor 53 is turned on, the power supply relay 7 is operated, and power is supplied to the motor.

At this time, the rotor of the electric motor is at a sufficiently low speed, so
The electric motor starts rotating in reverse.

By matching the operating time of timer T3 to the inertia of the rotor of the electric motor, reversal can be ensured. Furthermore, by changing the resistance value of the resistor 12, it is possible to adjust the time it takes for the rotor of the motor to reach a low speed state in which rotation can be reversed, and with a resistance value of 0 to several ohms, the time can be shortened to just a fraction of the time.

When the motor is in an overload state during normal rotation, a large voltage is generated in the secondary coil of the overcurrent detection transformer 11, the output terminal of the voltage comparator 19 becomes high level, and the thyristor 26 is turned on. Timers T1 and T2 operate, and first the voltage comparator 45 (→ level becomes low level, so its output terminal goes to low level, NPN) transistor 5
3 is turned off, the power supply relay 7 returns to its original state, and the power to the motor is cut off. Next, after the timerarch 2 operates, the output terminal of the voltage comparator 31 becomes low level, and the PNP l-transistor 35
turns on and the reverse rotation switching relay 4 operates.

Then, the timer T3 starts operating, and after a certain period of time, the output terminal of the voltage comparator 45 returns to high level, so the power supply relay 7 operates again and the motor starts rotating in reverse. When the timer T3 completes its operation, the output terminal of the voltage comparator 44 becomes high level, so the power supply relay 7 is reset again, and the motor rotates in reverse for a certain period of time and then stops. In this manner, the operation of the reverse switching relay 4 is always performed with the power supply relay 7 restored and the power to the motor cut off, so that no excessive transient current flows through the relay contacts.

As described above, when the present invention reverses the electric motor, it is possible to reliably reverse the electric motor even if there is inertia of the rotor of the electric motor. Moreover, even when it is necessary to automatically reverse the rotation when an overload occurs, such as in a shredder, excessive transient current does not flow through the contacts of the reverse switching relay, so there is no need to increase the contact capacity of the relay. This is extremely useful as there is no need to provide a contact protection circuit.

13,,-,・

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2 is a circuit diagram showing the main parts of the condenser run type motor. M...Electric motor, W...Driving section, R...
... Reverse command detection section, ■... Overload detection section, T1. T2. T3... Timer, 1...
... Motor auxiliary coil, 3 ... Motor capacitor, 4 ... Reverse switching relay, 5 ...
...Electric motor main coil, 6...Power supply, 7...
...Power supply relay, 11...Overcurrent detection transformer, 12...Resistor.

Claims (1)

[Scope of Claims] (1) A motor is connected to the power supply through the contacts of the stain source relay, and the motor is connected so as to be capable of forward and reverse rotation through the contacts of the reverse switching relay, and the reverse switching relay is energized. It consists of a reversal command detection section composed of a coil, a transistor, etc., and an excitation coil of a power supply relay, a transistor, etc., and has a timer T3 so that the power to the motor can be cut off for a certain period of time according to the signal from the detection section. A control device for an electric motor equipped with a driving section. @) The electric motor control device according to claim 1, wherein the reverse rotation command detection section is provided with a timer T1 and a timer T2 whose operating time is longer than that of the timer T1. (3) The electric motor control device according to claim 1 or 2, further comprising an overload detection section that detects overload of the electric motor. ←) One end of page 2 of the main coil of the motor is connected to the movable contact of the power relay, and the other end is connected via a resistor or directly to the normally closed side fixed contact of the power relay. - The electric motor control device according to any one of Items 3 to 3.