JPH0452078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an abnormality detection device for a transistor motor used, for example, as a fan motor for an air conditioner.

[Prior art]

Conventionally, single-phase induction motors have been mainly used as fan motors for air conditioners. Detection of abnormalities in this motor, such as detection of a locked state, is performed using a temperature switch that responds to the internal temperature of the motor, focusing on the fact that the windings etc. become hot as the motor current increases. A method was used to cut off the main circuit of the motor. FIG. 1 shows the main circuit configuration of this system.

The circuit shown in FIG. 1 is a circuit that supplies power from an AC power supply 1 to a single-phase induction motor 3 via a temperature switch 2. The temperature switch 2 is provided to accurately detect the temperature of the windings, etc. of the electric motor 3. The electric motor 3 has a main winding 3M and an auxiliary winding 3A, and a running capacitor 4 is connected in series to the auxiliary winding 3A. The temperature switch 2 is closed when the temperature of the electric motor 3 is within a normal range, and opens when the temperature exceeds the normal range to cut off the motor main circuit.

[Problems with conventional technology]

By the way, recently, as more fine-grained speed control has been performed in air conditioning systems, for example, as a fan motor,
Transistor motors, which are easy to control, have come into use. If the above-mentioned abnormality protection method using a temperature switch is adopted for this transistor motor, there are the following disadvantages. That is,
Since this type of transistor motor performs speed control by changing the manual voltage, the current for the same speed does not necessarily have the same value depending on the voltage. Therefore, if overload detection is performed simply based on the current value, it is not possible to distinguish between normal load and overload. In any case, it is necessary for the transistors in the transistor motor to maintain the time-integrated value of the current within a predetermined value, so it is desirable to accurately detect and protect against this type of overload.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an abnormality detection device that can reliably detect abnormal conditions such as overload due to binding of a transistor motor without delay.

[Structure of the invention]

In order to achieve the above object, the present invention provides a transistor for detecting overload of a transistor motor consisting of a bridge type transistor inverter that is supplied with power from a DC power source via a voltage regulating means and a motor body connected to its AC output terminal. The motor abnormality detection device includes a first means for detecting an instantaneous value of a load current flowing to a DC side of a transistor inverter, and an instantaneous value of the load current detected by the first means when the instantaneous value of the load current reaches a predetermined value. a second means for measuring the overtime for each pulse when the overtime is exceeded; and a third means for outputting an abnormality detection signal when the overtime measured by the second means reaches a predetermined value. This constitutes an abnormality detection device for a transistor motor.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention.
The upper half of Fig. 2 is the main circuit, and the AC power supply 10
In order from rectifier 11, smoothing capacitor 12, switching regulator 13, smoothing capacitor 1
4, and a transistor motor 15. A switching regulator 13 is provided as voltage adjustment means for speed control. The transistor motor 15 includes a three-phase bridge-connected transistor inverter 16 and a motor body 17 connected to its AC output terminal. The inverter 16 has a built-in position detector (not shown) that detects the rotor position of the motor body 17, and is driven and controlled by a control device (not shown) in synchronization with the detection signal thereof.

A current detection resistor 20 is inserted on the DC input side of the transistor motor 15. The voltage Va of the current detection resistor 20 is inputted to the comparison input terminal of the comparator 21 as a signal representing the motor current, and the reference input terminal of the comparator 21 is inputted to the reference power supply 2.
2, the reference voltage V _s1 is input. The comparator 21 outputs an "H" signal when the voltage V _a representing the motor current input to the comparison input terminal is below the voltage V _s1 (V _a <V _s1 ), and when the voltage V _a is above the voltage V _s ( When V _a > V _s1 ), an “L” signal is output.
The output V _b of the comparator 21 is integrated by the integrator 23, and the integrated output V _c is
The signal is input to the comparison input terminal 24 of No. 4. A reference voltage V _s2 is input from a reference power supply 25 to a reference input terminal of the comparator 24 . Output of comparator 24
V _d is “L” when V _c >V _s2 and “H” when V _c <V _s2 . Output of comparator 24
_Vd is input to the set input terminal of RS flip-flop 26. Resetting flip-flop 26 is accomplished by closing reset switch 27 and providing a reset signal. The regulator control circuit 28 is controlled by the Q output of the flip-flop 26.
The switching regulator 13 is controlled to be turned off via.

A specific circuit example of the comparator 21, integrator 23 and comparator 24 is shown in FIG.
The circuit in FIG. 3 includes two sets of operational amplifiers 31 and 3 as main circuit elements constituting each comparator.
Contains 2. An operating voltage bus 30 is provided for the entire circuit. The voltage V _a of the current detection resistor 20 through which the motor current I _M flows is input to the inverting input terminal of the operational amplifier 31, and the limit value for overcurrent identification is input from the reference power supply 22 via the resistor 33 to the non-inverting input terminal. The voltage V _s1 is input as the voltage V s1. A feedback resistor 34 is connected between the output terminal and the non-inverting input terminal of the operational amplifier 31. A resistor 35 is connected between the output terminal of the operational amplifier 31 and the operating voltage bus 30.
and 36 are connected in series, a series connection body of a resistor 37 and a diode 38 is connected in parallel to the resistor 35, and a capacitor 3 is connected to the resistor 36.
9 are connected in parallel. These circuit elements 3
5 to 39 constitute the integrator 23 for time measurement shown in FIG. The voltage at the connection point between the resistors 35 and 36 is input as the integrator output voltage V _c to the inverting input terminal of the operational amplifier 32, and the reference voltage is input from the reference power supply 25 through the resistor 40 to the non-inverting input terminal.
V _s2 is input. A feedback resistor 41 is connected between the output terminal and the non-inverting input terminal of the operational amplifier 32. Output from the output terminal of the operational amplifier 32
V _d is obtained.

Next, the circuit operation of the apparatus shown in FIGS. 2 and 3 will be explained with reference to the waveform diagrams shown in FIGS. 4 and 5.

As shown in FIG. 4, a voltage V _a representing the _magnitude of the motor current _I
(operational amplifier 31) compares and in the range of V _a <V _s1
V _d = “H” signal, V _b = “L” in the range of V _a > V _s1
Output a signal. As long as the motor 15 is rotating normally, the section where V _a < V _s1 or V _a > V _s1 within each pulse section becomes narrower (fourth pulse section).
Since the integrated output V _c of the integrator 23 (circuit elements 35 to 39) does not fall below the reference voltage V _s2 , the comparator 24 (operational amplifier 32) continues to output an "L" signal. Therefore, the switching regulator 13 continues to be driven and controlled by the control circuit 28 without the flip-flop 26 producing a set output.

Next, when the motor 15 is in a locked state, the current waveform in this case is as shown in the voltage _{V a} in FIG. _{The s1} section becomes longer. Correspondingly, the output V _b of comparators 21 and 31
As the "H" signal section becomes shorter, the "L"
The signal section becomes longer. Therefore, the output of the integrator 23
V _c gradually becomes lower than the reference voltage V _s2 , and the comparators 24 and 32 set V c = V _c in the range of V _c > V _s2 .
However, in the range of V _c <V _s2 , the flip-flop 26 is set by the V _c =“H” signal. The set output Q turns off the switching regulator 13 via the control circuit 28. In this way, the transistor motor 15 is protected.

As described in detail above, the present invention uses, in addition to the overcurrent detection element, the speed reduction detection element of measuring the overcurrent time per pulse based on the DC current of the transistor inverter. Even if the input voltage of the transistor inverter changes to control the speed of the motor, it is possible to quickly detect an overload by distinguishing the current increase due to the change in input voltage. In that case, one feature of the present invention is that the speed reduction factor is also based on the detected current.

After confirming the abnormal condition and removing the cause, the flip-flop 26 may be reset by the reset switch 27 in order to resume operation. Note that when the motor is started, a larger starting current flows than during normal operation, which may lead to the power being cut off. To prevent this, it is sufficient to use a timer or the like to lock the above-mentioned abnormality detection device from operating depending on the starting current. Abnormality detection signal, that is, flip-flop 26
The output signal may be used not only to shut off the power but also to indicate an abnormality.

〔Effect of the invention〕

As described above, according to the present invention, even if the input voltage of the transistor inverter changes for speed control of the motor by adopting the structure described in the claims, the change in input voltage It is possible to quickly detect an overload by distinguishing the increase in current caused by the current increase, and to accurately protect the transistor inverter, which is sensitive to overload, from thermal damage.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of a conventional abnormality detection device, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a connection diagram showing a specific example of the main part of Fig. 2, and Figs. FIG. 5 is a signal waveform diagram for explaining different circuit operation examples of the devices shown in FIGS. 2 and 3. 15...Transistor motor, 20...Current detection resistor, 21, 24...Comparator, 22,2
5...Reference power supply, 23...Integrator, 26...Flip-flop.

Claims (1)

[Scope of Claims] 1. Abnormality detection of a transistor motor that detects overload of a transistor motor consisting of a bridge type transistor inverter that is supplied with power from a DC power source via a voltage adjustment means and a motor body connected to its AC output terminal. The apparatus comprises: a first means for detecting an instantaneous value of a load current flowing on the DC side of the transistor inverter; and when the instantaneous value of the load current detected by the first means exceeds a predetermined value. , a second means for measuring the excess time for each pulse, and a third means for outputting an abnormality detection signal when the excess time measured by the second means reaches a predetermined value.
An abnormality detection device for a transistor motor, comprising means for detecting an abnormality in a transistor motor.