JP4304735B2 - Induction motor failure detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a failure detection method for an induction motor that electrically switches the direction of rotation.
[0002]
[Prior art]
Conventionally, induction motors with rotational direction switching control have been used as power sources such as disposers and pumps, and relays have been widely used as rotational direction switching means.
[0003]
A conventional induction motor with rotation switching control will be described below. FIG. 1 is a circuit diagram showing a conventional induction motor braking method, wherein 1 is an induction motor, 2 is a main winding, 3 is an auxiliary winding, 4 is a rotor, 5a and 5b are attached to the auxiliary winding 3 6 is a triac attached to the main winding 2 and the auxiliary winding 3, 7 is an AC power source, 8 is a capacitor, 9 is a control circuit, and 10 is a current detection means.
[0004]
The operation of the conventional induction motor with the rotation direction switching control configured as described above will be described below. As shown in FIG. 1, when the relays 5a and 5b are OFF (the relay contacts are connected to the NC side), no current flows through the auxiliary winding 3 even if the triac 6b is turned ON. Next, when the relay 5a is ON (the relay contact is connected to the NO side) and the relay 5b is OFF (the relay contact is connected to the NC side), if the triac 6b is turned ON, a current is supplied to the auxiliary winding 3. Flows. At this time, when the triac 6a is also turned on and a current is passed through the main winding 2, the rotor 4 rotates. If this rotation direction is normal rotation, the operation explanation when reverse rotation is as follows. When the relay 5b is ON (the relay contact is connected to the NO side) and the relay 5a is OFF (the relay contact is connected to the NC side), a current flows through the auxiliary winding 3 when the triac 6b is turned ON. . At this time, when the triac 6a is also turned on and a current is passed through the main winding 2, the rotor 4 rotates. This direction of rotation is reversed.
[0005]
[Problems to be solved by the invention]
However, in the above-described conventional method and configuration, if the induction motor is started when the relay has failed, the induction motor is not rotating, and therefore, processing is performed as a false detection as a rotor lock. There was no means to detect as a failure of the relay.
[0006]
SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a failure detection method for an induction motor that can detect relay contact welding and relay malfunction.
[0007]
[Means for Solving the Problems]
The present invention provides a rotor, a stator winding comprising a main winding and an auxiliary winding, the main winding being inserted between both ends of the AC power source, and one end of the auxiliary winding at both ends of the AC power source. Fault detection of an induction motor comprising a pair of relays that selectively connect the other end of the winding to both ends of the AC power source and a control circuit that controls the pair of relays and switches the energization direction of the auxiliary winding. a method, current flowing through the current detection means for detecting a current value, attached to a position where it can detect the current flowing to both the main winding and auxiliary winding in the induction motor, the main winding detected by the current detector If the total current value of the current flowing through the auxiliary winding is larger than the current value during normal operation and smaller than the current value during rotor lock, it is determined that a failure has occurred.
[0008]
The present invention having the above configuration uses the difference in the current value flowing through the induction motor when the rotation direction switching relay is welded at the time of starting the induction motor, thereby welding the relay contact of the induction motor, A malfunction can be detected.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
According to the first aspect of the present invention, there is provided a rotor, a stator winding comprising a main winding and an auxiliary winding, the main winding being inserted between both ends of the AC power source, and one end of the auxiliary winding connected to the AC power source. And a pair of relays that selectively connect the other end of the auxiliary winding to both ends of the AC power source, and a control circuit that controls the pair of relays to switch the energization direction of the auxiliary winding. a failure detection method for an induction motor, a current detecting means for detecting a current value, attached to a position where it can detect the current flowing to both the main winding and auxiliary winding in the induction motor, the main detected by the current detector If the total current value of the current flowing through the winding and the current flowing through the auxiliary winding is larger than the current value during normal operation and smaller than the current value during rotor lock, it is determined that a failure has occurred. To do.
[0010]
According to this configuration, it is possible to detect relay welding and malfunction when the induction motor is activated.
[0012]
Further, it is possible to detect a malfunction of the relay that occurs during the rotation of the induction motor.
[0013]
(Embodiment 1)
FIG. 1 is a circuit diagram showing a method of braking an induction motor according to Embodiment 1 of the present invention, and FIG. 2 is a voltage waveform diagram converted from a current by the current detection means. FIG. 2 shows voltage waveforms obtained by converting the current detected by the current detection means when the induction motor is 1) when the rotor is locked, 2) when the auxiliary winding is short-circuited and not rotating, and 3) during normal operation.
[0014]
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.
[0015]
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.
[0016]
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. At the start of rotation, first, the relay 5a or 5b is turned on to determine the direction of rotation, and the main winding 2 having a 90 ° direction difference is determined by turning on the main winding 2 driving triac 6a and the auxiliary winding driving triac 6b. The auxiliary winding 3 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. Reference numeral 10 denotes current detection means, which is attached at a position where the current flowing through both the main winding 2 and the auxiliary winding 3 can be detected.
[0017]
How to use the current detection means 10 when starting up the induction motor 1 configured as described above will be described. When the induction motor 1 starts normal rotation, current flows only through the main winding 2, and the voltage waveform obtained by converting the detected current becomes a waveform as in 3) normal operation of FIG. When the rotor 4 is locked, the triac 6b is kept turned on, the rotating magnetic field is strengthened by energizing the auxiliary winding 3, and the induction motor 1 is given a high torque to avoid the lock. The voltage waveform obtained by converting the detected current at this time is the waveform shown in FIG.
[0018]
However, when the relay 5a is welded to the NO side, when the relay 5b is turned on and the triacs 6b and 6a are turned on to start the induction motor 1, the auxiliary winding 3 is short-circuited. Even if the triacs 6a and 6b are turned on while the auxiliary winding 3 is short-circuited, the rotor 4 does not rotate, and a larger current flows through the main winding 2 than during normal operation. The voltage waveform obtained by converting this current is shown in FIG. 2 and 2) when the auxiliary winding is short-circuited and not rotated. When the relay 5b is welded to the NO side, the auxiliary winding 3 is also short-circuited when the relay 5a is turned on and the triacs 6b and 6a are turned on to start the induction motor 1. Even if the triacs 6a and 6b are turned on while the winding 3 is short-circuited, the rotor 4 does not rotate, and a larger current flows through the main winding 2 than during normal operation. The voltage waveform obtained by converting this current is also shown in FIG. 2 when 2) the auxiliary winding is short-circuited and not rotated. Even when the triac 6b is turned on when the auxiliary winding is short-circuited, the auxiliary winding 3 is not energized, and the current detected by the current detection means 10 is lower by the amount of current flowing through the auxiliary winding 3 than when the rotor 4 is locked. Therefore, it is possible to easily distinguish between when the rotor is locked and when the auxiliary winding is short-circuited, that is, when the relay is welded.
[0019]
(Basic forms of state)
Figure 3 is a circuit diagram showing a braking method for an induction motor according to the shape condition of the base of the present invention. In FIG. 3, the 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.
[0020]
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.
[0021]
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. At the start of rotation, first, the relay 5a or 5b is turned on to determine the rotation direction, and the main winding 2 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. Reference numeral 10 denotes current detection means, which is attached at a position where the current flowing through the auxiliary winding 3 can be detected.
[0022]
Even in the induction motor configured as described above, it is possible to distinguish between lock and relay welding. The usage of the current detection means 10 will be described below with reference to FIG. If the induction motor is to be started when the rotor 4 is locked, a larger current flows through the auxiliary winding 3 than during normal operation. However, when the induction motor is started in a state where the relay 5a or the relay 5b is welded and the auxiliary winding 3 is short-circuited, current cannot flow through the auxiliary winding even if the triac 6b is turned on. Absent. Therefore, by confirming the current value of the auxiliary winding 3 by the current detection means 10, it is possible to easily distinguish between when the rotor is locked and when the auxiliary winding is short-circuited, that is, when the relay is welded.
[0023]
(Embodiment 2 )
FIG. 4 is a voltage waveform diagram converted from the current by the current detection means according to the second embodiment of the present invention, where the induction motor is 1) when the rotor is locked, and 2) when the auxiliary winding is short-circuited and rotating. 3) A voltage waveform obtained by converting the current detected by the current detection means during normal operation. The configuration of the induction motor is the same as the first embodiment shown in FIG.
[0024]
How to use the current detection means 10 when the relay malfunctions during rotation of the induction motor configured as shown in FIG. 1 will be described. When the induction motor is rotating normally, a current flows only through the main winding 2, and the voltage waveform obtained by converting the detected current becomes a waveform as in 3) normal operation of FIG. When the rotor is locked, the triac 6b is turned on again and the auxiliary winding 3 is energized to strengthen the rotating magnetic field, and the lock is avoided by applying a high torque to the induction motor. The voltage waveform obtained by converting the detected current at this time is a waveform as in FIG. 4 1) when the rotor is locked.
[0025]
However, if the relay malfunctions during normal operation of the rotor, that is, when the relay 5a is connected to the NO side and the relay 5b is connected to the NC side, the relay 5a is connected to the NC side. Or when the relay 5a is in contact with the NO side, or when the relay 5a is connected to the NC side and the relay 5b is connected to the NO side and the normal operation is being performed. The auxiliary winding 3 is short-circuited when a malfunction occurs such as contact with the relay side or contact of the relay 5b with the NC side. Then, the magnetic flux generated by the eddy current generated in the rotor 3 causes an induced electromotive force in the short-circuited auxiliary winding 3, and the induced current flows through the auxiliary winding 3. Since the load corresponding to the induced current increases, a larger current flows through the main winding 2 than during normal operation. The voltage waveform obtained by converting this current is shown in FIG. 4 when 2) the auxiliary winding is short-circuited and rotated. When these auxiliary windings are short-circuited, the auxiliary winding 3 is not energized even if the triac 6b is turned on, so that there is no change in the waveform before and after the triac 6b is turned on. Therefore, it is possible to easily distinguish between when the rotor is locked and when the auxiliary winding is short-circuited, that is, when the relay malfunctions, depending on the difference in the waveform of the detected current after the triac 6b is turned on.
[0026]
Also in the induction motor configured as shown in FIG. 3, it is possible to detect a short circuit of the auxiliary winding 3 due to a malfunction of the relay 5a or the relay 5b. Hereinafter, the usage of the current detection means 10 will be described with reference to FIG. When the auxiliary winding 3 is short-circuited, the magnetic flux generated by the eddy current generated in the rotor 3 causes an induced electromotive force in the auxiliary winding 3, and the induced current flows through the auxiliary winding 3. However, during normal operation, no current flows through the auxiliary winding 3, and even when the rotor 4 is locked, the auxiliary winding 3 is energized until the auxiliary winding 3 is energized to increase the torque of the induction motor. No current flows through 3. Therefore, by confirming that a current flows through the auxiliary winding 3 while the rotor 4 is rotating, it is possible to detect a short circuit of the auxiliary winding 3, that is, an operation failure of the relay 5a or the relay 5b.
[0027]
In relay failure detection and malfunction detection as described above, the torque of the induction motor is increased when starting or locking with devices that have a high locking frequency, such as a disposer, or that have a forward / reverse rotation mode, or an auxiliary winding. This is especially useful for devices that are equipped. In addition, when comparing the current values, it is better to take into account the amplitude and frequency of the input voltage.
[0028]
【The invention's effect】
As described above, according to the present invention, in this type of induction motor, when a relay for switching the rotation direction is welded or malfunctions, it can be detected separately from when the rotor is locked or during normal operation. It can be used for devices with high locking frequency, such as a disposer, with forward / reverse rotation mode, and for devices that use an auxiliary winding to increase the torque of the induction motor when starting or locking. It can be performed.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a method of braking an induction motor according to the prior art and Embodiments 1 and 2. FIG. 2 is a voltage waveform diagram converted from current by current detection means according to Embodiment 1 of the present invention. voltage waveform diagram obtained by converting the current at a current sensing means according to a second embodiment of a circuit diagram showing a braking method for an induction motor according to the basic form state [4] the present invention of the present invention description of Reference numerals]
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 Current detection means

Claims (1)

A rotor, a stator winding composed of a main winding and an auxiliary winding, the main winding being inserted between both ends of the AC power supply, one end of the auxiliary winding at both ends of the AC power supply, and the other of the auxiliary winding A failure detection method for an induction motor comprising a pair of relays whose ends are selectively connected to both ends of the AC power source, and a control circuit that controls the pair of relays to switch the energization direction of the auxiliary winding. ,
A current detection means for detecting a current value is attached at a position where the current flowing in both the main winding and the auxiliary winding can be detected in the induction motor,
If the total current value of the current flowing in the main winding and the current flowing in the auxiliary winding detected by the current detection means is larger than the current value during normal operation and smaller than the current value during rotor lock, it is a failure. A method for detecting a failure in an induction motor, characterized in that:

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