JP4178588B2 - Induction motor braking method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a braking method for an induction motor that performs braking electrically.
[0002]
[Prior art]
Conventionally, in an induction motor, a method of stopping rotation by applying a DC voltage between terminals is well known as a dynamic brake. This is because when the rotating rotor is placed in a fixed magnetic field, an eddy current is generated in the rotor, and the magnetic flux newly generated in the rotor by this current is in a direction opposite to the rotation of the rotor. It uses the generation of torque. In practice, a half-wave rectified DC voltage is often applied to the induction motor by opening and closing the control triac for the induction motor without providing a separate DC voltage circuit.
[0003]
FIG. 5 is a circuit diagram showing a conventional induction motor braking method. FIG. 5 shows a circuit described in Japanese Patent Laid-Open No. 3-212181 as a braking method for an induction motor that applies a half-wave rectified DC voltage. Of the single-phase induction motor 1 in which the main winding 2 and the auxiliary winding 3 form a stator winding, a pulsating voltage obtained by rectifying an AC power supply 7 using a triac 6 is supplied to the main winding 2. As a result, the magnetic flux generated from the main winding 2 acts on the rotor 4 to restrain the rotation of the rotor 4 and apply braking. However, when braking is performed by applying a half-wave rectified voltage to the induction motor, the induction motor may continue to rotate without stopping. The reason is as follows.
[0004]
In general, induction motors are started by creating a rotating magnetic field with a main winding and an auxiliary winding whose directions are different by 90 degrees. At this time, since an eddy current is generated in the rotor, a magnetic pole is also formed. Due to this influence, the rotor generates torque in the rotating direction of the rotating magnetic field. After the rotation starts, the auxiliary winding for starting is disconnected and driven by an alternating magnetic field generated every 180 degrees generated only by the main winding.
[0005]
Here, in the circuit having the configuration as shown in FIG. 5, the AC power supply 7 is turned on while measuring the terminal voltage of the main winding 2 in the induction motor 1 after it is already rotating and the auxiliary winding 3 is disconnected by the relay 5. When the triac 6 is cut, a waveform as shown in FIG. 6 is obtained. FIG. 6 is a voltage waveform diagram between the main winding terminals when the AC power supply is cut off in the conventional induction motor. The power supply is cut off at the time point of waveform a, and the circuit current i is zero. A voltage v is generated at the terminal of the main winding 2 and decays with time. This is because the induction motor is generating power by the action of the magnetic poles of the rotor 4 formed by the eddy current remaining in the rotor and the rotation of the fly of the rotor 4. Therefore, it can be seen that the magnetic pole is maintained in the rotor 4 rotated by the AC power source 7.
[0006]
When a half-wave rectified voltage is applied to the stator winding in a state where the power supply has just been cut off, the rotor magnetic pole formed by the eddy current remaining in the rotor and the stator winding generated every 360 degrees Interaction with the magnetic field of the wire works. Furthermore, if a torque sufficient to keep the rotation speed is applied to the rotor, the rotor can continue to rotate even if the direction of the magnetic field does not rotate.
[0007]
As described above, in the conventional braking method in which a half-wave rectified DC voltage is applied to the induction motor, there is a possibility that the rotation of the rotor is reversed, and the braking cannot be reliably performed.
[0008]
Therefore, the following technique has been proposed as an improvement of this braking method. That is, this technology is configured to apply a half-wave rectified voltage after a predetermined time after the eddy current remaining in the rotor is attenuated to a predetermined value after the power source is disconnected from the stator winding. The brake is surely performed.
[0009]
[Problem to be Solved by the Invention]
However, although the above-described conventional braking method can reliably perform braking, after the power is cut off from the stator winding, the eddy current remaining in the rotor is attenuated to a predetermined value and is rotated by inertia. For example, when a quick braking is required as a safety device with a disposer or the like in a short time, there is a problem that the eddy current remaining in the rotor cannot be stopped without being attenuated.
[0010]
Therefore, the present invention solves the above-mentioned conventional problems, and in an induction motor that can reliably generate sudden braking by generating braking torque without continuation of rotor rotation in braking by half-wave rectified voltage. An object is to provide a braking method.
[0011]
[Means for Solving the Problems]
The present invention includes a rotor, a stator winding composed of a main winding and an auxiliary winding, a relay connected to the auxiliary winding for switching the rotation direction, power supply to the stator winding, and In an induction motor including a control circuit for controlling the relay, after a power source is cut off from the main winding, a half-wave rectified voltage is applied to the main winding after a predetermined time after the auxiliary winding is short-circuited. A method of braking an induction motor that brakes the rotor, wherein at least one of a predetermined time after the auxiliary winding is short-circuited and a time during which a half-wave rectified voltage is applied to the main winding is supplemented. A signal output from a current detecting means for outputting a signal corresponding to the current value of the induced current flowing through the auxiliary winding connected to one end of the winding, or a current value in which the induced current value flowing through the auxiliary winding is set in advance Has an LED that lights up when A braking method for an induction motor, characterized by determining using a photocoupler that.
[0012]
In this configuration, the rotational energy due to the eddy current remaining in the rotor is actively consumed as the induced current to the auxiliary winding, and then the half-wave rectified voltage is applied. As a result, the inertial rotation time can be significantly shortened, and the braking time can be shortened by reliably generating the braking torque.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 is a rotor, a stator winding composed of a main winding and an auxiliary winding, a relay connected to the auxiliary winding for switching the rotation direction, and the stator winding. In an induction motor comprising a control circuit for controlling the power supply to the relay and the relay, after cutting off the power from the main winding and short-circuiting the auxiliary winding, a half wave is applied to the main winding after a predetermined time. A method of braking an induction motor that brakes the rotor by applying a rectified voltage, wherein at least a predetermined time after the auxiliary winding is short-circuited and a time during which a half-wave rectified voltage is applied to the main winding One side is determined from the signal output from the current detection means that outputs a signal corresponding to the value of the induced current flowing through the auxiliary winding connected to one end of the auxiliary winding. According to a second aspect of the present invention, there is provided a rotor, a stator winding composed of a main winding and an auxiliary winding, a relay connected to the auxiliary winding for switching the rotation direction, and the stator In an induction motor comprising a power supply to a winding and a control circuit for controlling the relay, after disconnecting the power from the main winding, a short time after the auxiliary winding is short-circuited, the main winding A method of braking an induction motor that brakes the rotor by applying a half-wave rectified voltage, wherein a predetermined time after the auxiliary winding is short-circuited and a time during which the half-wave rectified voltage is applied to the main winding At least one of the above is determined using a photocoupler having an LED that lights up when the value of the induced current flowing in the auxiliary winding becomes equal to or greater than a preset current value.
[0014]
With this configuration, braking can be performed reliably and braking time can be shortened.
According to a third aspect of the present invention, in the first or second aspect of the present invention, when the auxiliary winding and the switching relay are connected, the auxiliary winding is provided by a resistor arranged to be a closed circuit. In this way, an excessive current is prevented from flowing through.
[0016]
( Reference Example 1)
FIG. 1 is a circuit diagram showing a braking method for an induction motor according to Reference Example 1 related to the present invention , and FIG. 2 is a voltage waveform diagram between main winding terminals during the braking.
[0017]
In FIG. 1, an induction motor 1 is composed of a rotor 4, a stator winding composed of a main winding 2 and an auxiliary winding 3, and via relays 5a and 5b and triacs 6a and 6b as control elements. It is connected to an AC power source 7.
[0018]
The relays 5a and 5b are connected to a capacitor 8 for changing the phase of the 90 ° auxiliary winding with respect to the auxiliary winding 3 and the main winding 2, and are applied to the auxiliary winding 3 by turning on one of them. The direction of rotation of the rotor 4 is switched by reversing the phase of the AC voltage to be rotated by 180 °. When both are OFF, the auxiliary winding 3 is short-circuited.
[0019]
A control circuit 9 detects the zero potential of the AC power supply 7 and controls the relays 5a and 5b and the triacs 6a and 6b. When starting rotation, first, the relay 5a or 5b is turned on to determine the rotation direction, and the main winding driving triac 6a and the auxiliary winding driving triac 6b are turned on, so that the main winding is 90 degrees different in direction. The auxiliary winding creates a rotating magnetic field and starts up. At this time, the rotor 4 generates torque in the rotating direction of the rotating magnetic field generated by the eddy current. Therefore, after the rotation starts, the auxiliary winding driving triac 6b is turned off to disconnect the auxiliary winding 3, and the auxiliary winding 3 is driven by an alternating magnetic field generated by only 180 degrees.
[0020]
The operation of the induction motor braking method configured as described above will be described below with reference to FIG. When the AC power supply 7 is disconnected from the rotating induction motor 1, a magnetic flux is generated in the rotor 4 due to an eddy current, and an induced electromotive force is generated between the terminals of the stator winding due to the power generation action by the rotating magnetic flux. . At this time, when both the relays 5a and 5b are turned OFF, the auxiliary winding 3 is short-circuited, and the electromotive force induced in the auxiliary winding 3 flows in the auxiliary winding 3 as an induced current, and the auxiliary winding 3 It becomes a heat energy by the resistance component of and decays rapidly. The time for which the induced current of the auxiliary winding 3 decays to half or less is T1.
[0021]
After the decay time T1 has elapsed, as shown in FIG. 2, the control circuit 9 detects the zero potential of the AC power supply 7, and turns on the triac 6a only in one cycle of positive or negative. Then, a half-wave rectified voltage is applied to the terminal of the main winding 2 of the induction motor 1. After the time T2 when the rotation of the induction motor 1 is stopped, the triac 6a is turned off. As described above, the rotational energy due to the eddy current remaining in the rotor is actively consumed as the induced current to the auxiliary winding, so that rapid braking can be performed in a short time.
[0022]
( Reference Example 2)
FIG. 3 is a circuit diagram showing a braking method for an induction motor according to Reference Example 2 related to the present invention. 3 having the same reference numerals as those in FIG. 1 have basically the same functions as those of the reference example 1, and thus detailed description thereof will be omitted. Reference numeral 10 denotes a resistor, which is arranged so as to be a closed circuit when the auxiliary winding 3 and the resistor connection relay 11 are connected.
[0023]
With the above configuration, when the AC power supply 7 is disconnected from the rotating induction motor 1, the induction current flowing in the auxiliary winding 3 is prevented from flowing excessively, the relay element is prevented from being destroyed, and the auxiliary winding 3 The abnormal heat generation can be suppressed.
[0024]
(In the form state of implementation)
Figure 4 is a circuit diagram showing a braking method for an induction motor in the form status of the present invention. 4 having the same reference numerals as those in FIG. 1 have basically the same operations as those described above, and thus detailed description thereof will be omitted. In FIG. 4A, the current detection means 12 is connected to one end of the terminal of the auxiliary winding 3 of the induction motor 1, and a signal corresponding to the current value of the auxiliary winding 3 is output from the current detection means 12. .
[0025]
The current detecting means 12 divides the voltage generated at both ends of the resistor 10 as shown in FIG. 4B by a voltage dividing circuit 13 composed of a high resistance and the like and rectifies it by the smoothing circuit 14. Alternatively, the potential may be detected by smoothing. Further, in a circuit using the photocoupler 15 as shown in FIG. 4C, when the current more than the current value set in the auxiliary winding 3 flows, the LED of the photocoupler 15 is turned on and the output is turned on. You may catch it.
[0026]
Hereinafter, the operation of the induction motor braking method configured as described above will be described with reference to FIG. After the AC power supply 7 is disconnected from the rotating induction motor 1, when both the relays 5a and 5b are turned off, the auxiliary winding 3 is short-circuited and flows in the auxiliary winding 3 as an induced current, which is rapidly attenuated. go. The induced current of the auxiliary winding 3 is detected by the current detection means 12 and converted into a signal corresponding to the current value. When this signal is attenuated to a predetermined value or less, the control circuit 9 determines that the eddy current of the rotor 4 has attenuated, detects the zero potential of the AC power supply 7, and in a positive or negative cycle. Only turn on the triac 6a. Then, a half-wave rectified voltage is applied to the terminal of the main winding 2 of the induction motor 1. As a result, the magnetic flux generated from the main winding 2 can restrain the rotation of the rotor 4 and brake it. At this time, an induced current flows through the auxiliary winding 3 again and gradually attenuates as the rotation of the rotor 4 slows down. When this induction current is detected by the current detection means 12 and the signal output from the current detection means 12 is attenuated to a predetermined value or less, the control circuit 9 determines that the rotation of the induction motor 1 has stopped, Turn off the triac 6a.
[0027]
As described above, at least one of the predetermined time after the auxiliary winding 3 is short-circuited and the time during which the half-wave rectified voltage is applied to the main winding 2 is determined from the induced current value flowing through the auxiliary winding 3. Therefore, it is possible to brake suddenly in a short time.
[0028]
【The invention's effect】
As apparent from the above description, according to the braking method of the induction motor of the present invention, the rotational energy due to the eddy current remaining in the rotor is actively consumed as the induced current to the auxiliary winding, so that the rapid You can brake.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a braking method for an induction motor of Reference Example 1 of the present invention. FIG. 2 is a voltage waveform diagram between main winding terminals during braking of Reference Example 1 of the present invention. circuit diagram showing a braking method of the circuit diagram FIG. 5 conventional induction motor showing a braking method for an induction motor in the form status of implementation of the induction motor in the circuit diagram of a braking process [4] the present invention of example 2 [ Fig. 6 Voltage waveform diagram between main winding terminals when AC power is cut off in a conventional induction motor
DESCRIPTION OF SYMBOLS 1 Induction motor 2 Main winding 3 Auxiliary winding 4 Rotor 5a, 5b Relay 6a, 6b Triac 7 AC power supply 8 Capacitor 9 Control circuit 10 Resistor 11 Connection relay 12 Current detection means 13 Voltage dividing circuit 14 Smoothing circuit 15 Photo coupler

Claims (3)

A rotor, a stator winding composed of a main winding and an auxiliary winding, a relay connected to the auxiliary winding to switch the rotation direction, power supply to the stator winding and control of the relay In the induction motor comprising a control circuit, the rotor is configured to apply a half-wave rectified voltage to the main winding after a predetermined time after the auxiliary winding is short-circuited after the power source is disconnected from the main winding. A method of braking an induction motor that brakes at least one of a predetermined time after the auxiliary winding is short-circuited and a time during which a half-wave rectified voltage is applied to the main winding is set at one end of the auxiliary winding. A method for braking an induction motor, comprising: judging from a signal output by a current detecting means for outputting a signal corresponding to a current value of an induced current flowing through an auxiliary winding connected to the auxiliary winding. A rotor, a stator winding composed of a main winding and an auxiliary winding, a relay connected to the auxiliary winding to switch the rotation direction, power supply to the stator winding and control of the relay In the induction motor comprising a control circuit, the rotor is configured to apply a half-wave rectified voltage to the main winding after a predetermined time after the auxiliary winding is short-circuited after the power source is disconnected from the main winding. A method of braking an induction motor that brakes at least one of a predetermined time after the auxiliary winding is short-circuited and a time during which a half-wave rectified voltage is applied to the main winding is applied to the auxiliary winding. induction motor method of braking you characterized by determining using a photocoupler having a LED that lights up when the induced current value becomes a preset current value or more flows. 3. An overcurrent is prevented from flowing through the auxiliary winding by a resistor arranged to be a closed circuit when the auxiliary winding and the switching relay are connected. Braking method for induction motors.

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