JP3627374B2 - Overheat protection device for electric motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an overheat protection device for an electric motor, and more particularly to detection of overtemperature.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an overtemperature protection device for an electric motor that detects an overtemperature of an electric motor and performs an overtemperature protection operation of the electric motor, as shown in FIG. 1, the rotational position of the magnetic pole 4a of the rotor is detected by a position detection element 4b. Use a thermal protector, such as a thermostat, in close contact with the rotor winding in a large-sized motor for a temperature detector that detects the temperature of an AC or DC motor whose rotational speed is controlled by In addition, the current is cut off by detecting an excessive temperature rise in the rotor winding.
[0003]
However, in a small electric motor such as a molded motor, since there is no space for storing the above-described thermal protector, a temperature detector is externally attached to the outer portion of the electric motor.
For this reason, the rotor winding temperature has reached the overheated temperature before the overheat protection operation is started by detecting the overheated temperature. In some cases, the windings were burned out.
[0004]
[Problems to be solved by the invention]
The present invention solves the above-described problems, detects an internal temperature rise of a small motor, and immediately performs an overtemperature protection operation even if there is a sudden temperature rise to prevent winding burnout and protect the motor. An object of the present invention is to provide an overtemperature protection device for an electric motor that can be used.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides an AC motor in which a rotor is provided with a rotational position detection magnet, and the position of the magnetic pole is detected by a position detection element to control the rotational speed. Compared to the reference voltage, a comparison means is provided to compare the output of the position detection element that detects the position of the same position detection magnet with a reference voltage. An overtemperature of the AC motor is detected by a signal, and an overtemperature protection operation is performed.
[0006]
Further, in a DC motor that controls the number of rotations by detecting the position of the magnetic pole of the field magnet provided in the rotor by a plurality of position detection elements, the magnetic field corresponding to the magnetic pole is provided in the field magnet provided in the rotor. Comparing means for outputting a comparison signal by comparing the output of the position detection magnet having a high temperature dependency of the density and the position detection element for detecting the position of the position detection magnet with a reference voltage is provided. The overheating of the DC motor was detected and the overheating protection operation was performed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Since it is configured as described above, in the overtemperature protection device for an electric motor according to the present invention, in the case of an AC motor, a rotor is provided with a position detection magnet having a high temperature dependence of magnetic flux density, and in the case of a DC motor, it is rotated. The field magnet provided in the child is provided with a position detecting magnet with high temperature dependence of the magnetic flux density corresponding to the same magnetic pole, and the position of the magnetic pole of the same position detecting magnet is detected by the rotational position detecting element and the number of rotations In addition, the motor overheat is detected by a comparison signal that is compared with the position detection signal and the reference signal, and the overheat protection operation is performed. An overtemperature protection operation is performed by detecting the internal temperature rise of the electric motor by monitoring the detection signal from the rotational position detection element, eliminating the need for the temperature detection element.
[0008]
【Example】
Hereinafter, an overheat protection device for an electric motor according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view of a main part of an electric motor 4 of an overheat protection device for an electric motor according to the present invention. FIG. 1 (A) shows an AC motor, and FIG. 1 (B) shows a DC motor.
In FIG. 1A, 4a is a rotation position detection magnet having a four-pole configuration, 4b is a Hall element that detects the position of the magnetic pole of the rotation position detection magnet 4a, a position detection element formed by a coil gap, etc., 4c is Rotor iron core.
In FIG. 1B, 4a is a four-pole rotational position detecting magnet provided corresponding to the field magnet 4d, and 4b is a hall element and coil for detecting the position of the magnetic pole of the rotational position detecting magnet 4a. The position detection elements 4d are configured by a gap or the like and arranged at intervals of 120 degrees, and the field magnet 4d has a four-pole configuration.
[0009]
FIG. 2 shows the temperature characteristics of the rotational position detecting magnet 4a used in the present invention. As shown in FIG. 2, the magnetic flux density decreases as the temperature T increases.
[0010]
FIG. 3 is a block diagram of a detection circuit for outputting a detection signal Ss from the detection voltage Vs detected by the position detection element 4b of the magnetic pole of the rotational position detection magnet 4a having the temperature characteristics shown in FIG. The circuit is integrally formed with the position detection element 4b as an integrated circuit.
In the figure, reference numeral 4b denotes the position detecting element, and in this example, a Hall element is used. An amplifier 4b1 amplifies the detection voltage Vs from the position detection element 4b. Reference numeral 4b2 denotes a comparison circuit, which compares the signal from the amplifier 4b1 with a predetermined detection level (reference voltage) and shapes the waveform to obtain a comparison signal -Ss. An output transistor 4b3 outputs a comparison signal Ss obtained by inverting the comparison signal -Ss from the comparison circuit 4b2.
[0011]
Next, the operation of the above configuration will be described.
FIG. 4 shows the detected voltage Vs waveform of the position detecting element 4b according to the present invention and the comparison signal Ss obtained by switching the waveform, the solid curve shows the detected voltage Vs waveform at the normal temperature, and the broken curve shows the overheated temperature. It is a detection voltage Vs waveform in FIG.
As shown in the figure, since the detection voltage Vs waveform exceeds the detection level (reference voltage) on the + side and − side at the normal temperature, the comparison signal Ss becomes a rectangular wave, and the indoor control unit is used as the magnetic pole position detection signal. 6 controls the rotation speed of the motor 4 and suppresses the overheat protection operation as an overheat detection signal.
In the case of excessive temperature, the detection voltage Vs waveform does not exceed the detection level on the + side, so the comparison signal Ss has the same DC waveform (Ss = constant) as when the motor is restrained, and this comparison signal Ss (= constant). Is received as an over-temperature detection signal, and the motor is stopped by the indoor control unit 6 for a certain period of time, and after a certain period of time has elapsed, an over-temperature protection operation is performed so as to resume normal operation.
[0012]
【The invention's effect】
As described above, according to the overheat protection device for an electric motor according to the present invention, a position detecting magnet having a large temperature coefficient of magnetic flux density is provided in the rotor in the case of an AC motor, and the rotor is provided in the case of a DC motor. The field magnet is provided with a position detection magnet having a large temperature coefficient of magnetic flux density corresponding to the same magnetic pole, and the rotational position is controlled by detecting the position of the magnetic pole of the same position detection magnet with the rotational position detection element. At the same time, a comparison signal comparing the same position detection signal and the reference signal is output, and the internal temperature rise of the motor is detected by the comparison signal, and the overheat protection operation is performed. Since the temperature detection element installed in the outer part is not required and the detection signal from the rotational position detection element is monitored, the internal temperature rise of the motor is detected and the overtemperature protection operation is performed. Small electric An overtemperature protection device for an electric motor that can detect an internal temperature rise of the machine and immediately perform an overtemperature protection operation even if there is a sudden rise in temperature to prevent winding burnout and protect the motor. can do.
[Brief description of the drawings]
FIG. 1 is a perspective view of a main part of an electric motor 4 of an overheat protection device for an electric motor according to the present invention, FIG. 2 (A) shows an AC motor, and FIG. 2 (B) shows a DC motor.
FIG. 2 shows a temperature characteristic of a rotation detecting magnet 4a of an overtemperature protection device for an electric motor according to the present invention.
FIG. 3 is a block diagram showing an embodiment of a detection circuit used in the overheat protection device for an electric motor according to the present invention.
FIG. 4 shows a detection voltage waveform and a detection signal of a position detection element 4b according to the present invention.
[Explanation of symbols]
4 Electric motor 4a Rotational position detection magnet 4b Position detection element 4b2 Comparison circuit 4d Field magnet

Claims (2)

In an AC electric motor having a rotor for detecting a rotational position and detecting the position of the magnetic pole by a position detecting element to control the rotation speed, the position detecting magnet of the rotor has a high temperature dependence of magnetic flux density. And comparing means for comparing the output of the position detecting element for detecting the position of the magnet for position detection with a reference voltage and outputting a comparison signal, and detecting an overtemperature of the AC motor by the comparison signal. An overtemperature protection device for an electric motor, characterized in that an overtemperature protection operation is performed. In a DC motor that controls the number of rotations by detecting the position of the magnetic pole of a field magnet provided in the rotor by a plurality of position detection elements, the field magnet provided in the rotor has a magnetic flux density corresponding to the magnetic pole. Comparing means for outputting a comparison signal by comparing the output of a position detection magnet having a high temperature dependency and a position detection element for detecting the position of the position detection magnet with a reference voltage is provided. An overtemperature protection device for an electric motor, wherein an overtemperature protection operation is detected and an overtemperature protection operation is performed.

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