JPS6028236B2 - braking device - Google Patents

Description

[Detailed Description of the Invention] When applying an instantaneous brake to a motor, one method that has been commonly used in the industry is to charge a capacitor with rectified direct current while the motor is rotating, and then use a stop signal to brake the motor. There is a method of discharging this charge to the motor windings and then applying DC excitation to stop the motor.

However, with this method, the stopping characteristics vary considerably depending on the stop timing, and in order to eliminate the variations, the capacitance of the capacitor must be made considerably large.
The possible cause of this is that the magnitude and phase of the current in the motor windings become a problem at the timing of applying DC excitation, and the net DC excitation current is the amount that overcomes the reaction of the secondary current. The present invention has been made in view of the above points, and is a braking device for stopping a motor operated by an AC drive signal applied to a winding, in which an AC drive signal to be applied to the winding is derived. A from the AC power source to the winding
control means for controlling application of the AC drive signal; and detection for detecting that the induced voltage generated in the winding has exceeded a predetermined value after the control means stops applying the AC drive signal to the winding. and a braking current supply means for supplying a braking current to the winding based on the detection output of the detection means.

Hereinafter, to explain one embodiment of the present invention according to the drawings, the reference numeral 11 in FIG. 1 is an AC drive signal having a signal waveform as shown by AV in FIG. 2 (however, the signal waveform at point A is ) is an AC power source that derives
3 and the winding 14, the armature 15 rotates.

Reference numeral 16 indicates a capacitor inserted to generate torque when starting the motor and to improve the power factor during motor operation.

Reference numeral 17 indicates an AC bidirectional control element commonly called a triac, which remains OFF as long as the gate 18 is open.

The gate 18 of this triax 17 is connected to the AC power source 11 via a switch 19 and a resistor R2, and the switch 19 is connected to the contact piece 19-1 contact 19.
The contact piece 19-1 is connected to the resistor 2, and the contact 19-2 is connected to the gate 18. Therefore, the rear piece 19 of the switch 19
-1 is connected to contact 19-2, and resistor R2 is connected to gate 18.
When an AC voltage is applied through the triac 17, the triac 17
Conducting through substantially all phase angles of the drive signal, motor 12 begins to rotate. Triack 17 is turned on like this
Then, the diode 25 connected in parallel with the motor 12 becomes conductive every half cycle of the AC disturbance signal, and the diode 25 is connected in parallel with the motor 12.
A capacitor 26 is charged via a resistor R and a resistor 25.
The final charging voltage Cv (potential at point C) of this capacitor 26 is equal to the maximum value of the AC power supply voltage. Note that the resistor R is a resistor for limiting rush current at the initial stage of charging the capacitor 26.

If you want to instantaneously stop the motor 12 rotating in this way, disconnect the bush piece 19-- of the switch 19 and the contact 19-2, and -3 is an idle terminal). When the switch 19 is turned OFF in this manner, the triac 17 is turned OFF at the same time as the half cycle in which it was applied at the moment of OFF is completed, and the supply of power to the motor 12 is stopped.

In this way, by stopping the supply of AC power, the motor 12 stops actively rotating.

On the other hand, in the embodiment of the present invention, a switch 20 is provided at one end of the winding 14, and a saddle piece 20-
1 to one end of the winding 14, and the degree point 20-2 and the winding 14
A series circuit consisting of a diode 21, a Zener diode 22, a resistor R4, and a light emitting diode 23 is connected between the other end of the switch 19 and the switch 19 is connected to the other end. -1 and the contact 19-2 are connected, the strand 20-1 of the switch 20 and the contact 20-3 are connected, and the strand 19-1 of the switch 19 and the strand 19-2 are connected.
The structure is such that when the switch 20 is connected, the hair piece 20-1 of the switch 20 and the contact 20-2 are connected.

Furthermore, in the embodiment of the present invention, the capacitor 2
A photothyristor 24 is provided at one end of the winding 6 and the winding 14 via a resistor R3, and the photothyristor 24 and the light emitting diode 23 are optically coupled. Therefore, when the triac 17 is OFF, the contact piece 20-1 and the contact point 20-2 are in contact with each other.

As mentioned above, after the triax 17 is turned off, the motor 12 continues to rotate due to inertia, so the motor 12 performs a power generation operation, and the winding 14 at point B has the voltage BV shown in FIG.
An induced voltage as shown in is generated.

Note that this FIG. 2 is drawn using point D in FIG. 1 as a reference potential.

The polarity of the induced voltage of this winding 14 is in the forward direction of the diode 21, and its magnitude is that of the Zener diode 22.
When the voltage drop exceeds (E, V in Figure 2), the resistance R4
The current limited by the current flowing through the light emitting diode 23, (second
Shaded area in the figure) The light emitting diode 2
3 emits light. Since the light emitted from the light emitting diode 23 is applied to the photothyristor 24, the photothyristor 24 is in a state where it can conduct. However, in order for this thyristor 24 to be conductive, the anode potential must be lower than the cathode potential. Therefore, conduction starts in the hatched period other than the double hatched area in FIG. 2. The electric charge stored in the capacitor 26 due to this conduction is discharged through the resistor R3, the thyristor 24, and the winding 14, and a current as shown in FIG. Perform braking.

If constructed in this way, braking will start only at a specific phase of the induced voltage, and the braking characteristics will also be improved.

That is, in FIG. 2, BI indicates the winding 14 during braking.
The negative current in this current waveform acts to cancel the discharge current of the capacitor 26.

With the device shown in Fig. 1, even if braking starts at the specified time in Fig. 2, this cancellation will only work during the rise of the discharge current DV, so the discharge supplied for braking will be It does not have any adverse effect on the peak value of current. On the other hand, if the present invention were not used, the discharge of the capacitor 26 would start at an arbitrary time regardless of the induced voltage or current, so the peak of the signal DV and the negative peak of the signal BI would be -. Naturally, this may occur, and in such a case, the peak value of the discharge current flowing through the winding 14 is substantially reduced, resulting in a reduction in braking efficiency.

Diodes 21 and 22 connected in parallel to the winding 14
, 23 is much higher than that of the winding 14, and is of the order of magnitude that can be ignored as a loss due to discharge of the capacitor C. In this way, by detecting the phase of the induced voltage in the motor windings that are DC-excited for braking and determining the braking timing, it is possible to reduce variations in the DC-exciting current waveform, thereby stabilizing the braking characteristics. .

In addition, the anode-cathode potential gap of the thyristor 24 when it is conductive changes from approximately 0 (V) to C(V) - V2 (Zener voltage of the Zener diode 22), and since no high voltage is applied, the reliability of the photothyristor 24 also increases. It is something.

Incidentally, the delay in the stop timing for matching the phases is about 10-odd milliseconds with the AC power source for the five-plate Z, and is hardly a problem.

As described in detail above, according to the present invention, the discharge current of the capacitor 26 can be used almost effectively as a DC excitation current for braking, and there is no variation.
The capacity of No. 6 also eliminates the need to prepare a large capacity one in advance.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a braking device according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the braking device of FIG. 1. Here, 11 is an AC power supply, 12 is a motor, 13 and 14 are windings, 17 is a triac, 21 and 22 are diodes,
23 is a light emitting diode, 24 is a photothyristor, 26
is a capacitor. Dropping figure 2

Claims (1)

[Claims] 1. A braking device for stopping a motor operated by an AC drive signal applied to a winding, including an AC power source for deriving an AC drive signal to be applied to the winding, and an AC power supply from the AC power source to the winding. A control means for controlling the application of a drive signal, and a detection means for detecting that the induced voltage generated in the winding becomes equal to or higher than a predetermined value after the control means stops applying the AC drive signal to the winding. and a braking current supply means for supplying a braking current to the winding based on the detection output of the detection means.