JP3328728B2 - Motor power detection device and overload protection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor power detecting device for detecting power supplied to a motor and a motor power detecting device for protecting the motor and a device driven by the motor from overload. The present invention relates to an overload protection device.

[0002]

2. Description of the Related Art The value of AC power supplied to a motor can be obtained by time-averaging the result of multiplying AC voltage and AC current supplied to the motor. The AC power supply of the motor includes a noise component such as a high-voltage pulse generated in various electric devices connected to the power supply line,
In order to protect the power detection circuit from the aforementioned noise components and high voltage, it is necessary to electrically insulate the power detection circuit. In a conventional motor power detection device, a voltage signal is insulated using a transformer, a current signal is insulated using a current transformer, and these insulated voltage and current signals are separated from an analog multiplier or an operational amplifier. To obtain a power value.

[0003]

As described above, in the conventional motor power detecting device, when the current and the voltage are detected by using the current transformer and the transformer, the current transformer and the transformer are connected by a coil and an iron core. It has the advantages of being easy to manufacture and handle, and being inexpensive, because of its structure, but has a large inductance, so that in the low frequency region where the frequency of the AC current and AC voltage to be detected is 20 Hz or less, the phase is low. Since an error occurs and a magnetic flux change hardly occurs in a frequency range of several Hz or less, a voltage corresponding to an AC current and an AC voltage to be detected cannot be accurately obtained. Therefore, when the power supply frequency range is wide such as a servo motor and an inverter control motor, there is a problem that the supplied AC voltage cannot be detected with high accuracy.

In order to detect power, three components, a voltage detection unit, a current detection unit, and a voltage / current multiplication unit, are required.
The present invention has been made in view of the circumstances as described above, in the first shot bright, the power supplied to the motor can be accurately detected regardless of the frequency, the motor power can be inexpensively manufactured in small It is an object to provide a detection device.
In the second invention, an object to provide an overload protection device provided with a motor power detection apparatus according to the first shot bright.

[0005]

A motor power detection device according to a first aspect of the present invention detects a voltage applied to a motor, and outputs a current corresponding to the detected voltage. the current circuit is output as a control current, and a Hall element that outputs a Hall voltage subjected to magnetic flux generated by current flowing through the motor, a Hall voltage which the Hall element is output, output as the supply electric power value to the motor
A motor power detection device for detecting the motor voltage.
The output circuit is interposed between the input terminals of the motor.
The first photocoupler and the second
A photocoupler, the first photocoupler and the second photocoupler;
A first voltage generator for generating a voltage corresponding to the secondary current of the plastic
Generating means and the voltage generated by the first voltage generating means
A differential amplifier provided to an input terminal;
The primary side is to be connected in anti-parallel
Third and fourth photocouplers, and a third photocoupler.
Current corresponding to the secondary current of the photocoupler and the fourth photocoupler.
And a second voltage generating means for generating a voltage.
The voltage generated by the generating means is applied to the other input terminal of the differential amplifier.
A third photocoupler and a fourth photocoupler
Characterized in that the primary side current is output.

In this motor power detection device, a motor voltage detection circuit detects a voltage applied to the motor and outputs a current corresponding to the detected voltage. The Hall element uses the current output by the motor voltage detection circuit as a control current, receives a magnetic flux generated by the current flowing through the motor, outputs a Hall voltage, and outputs the output Hall voltage as a power supply value to the motor .

[0007]

In the motor voltage detection circuit , when a voltage is applied to the input terminal of the motor, a current corresponding to the voltage and the polarity flows to the primary side of the first photocoupler or the primary side of the second photocoupler. On the secondary side of the first photocoupler, a current corresponding to the current on the primary side flows, and on the secondary side of the second photocoupler, a current corresponding to the current on the primary side flows.
These currents flow to the first voltage generating means, and the first voltage generating means generates a voltage related to the voltage applied to the input terminal of the motor. When the voltage generated by the first voltage generating means is input to one input terminal of the differential amplifier, the differential amplifier outputs a voltage according to the voltage input to one input terminal, and outputs a voltage according to the voltage and the polarity. Current flows through the primary side of the third photocoupler or the primary side of the fourth photocoupler.

A current corresponding to the current transmission ratio and the primary current flows on the secondary side of the third photocoupler, and the current transmission ratio and the primary side current flow on the secondary side of the fourth photocoupler. And the currents flow through the second voltage generating means, and the second voltage generating means generates a voltage related to the voltage input to one input terminal of the differential amplifier. When the voltage generated by the second voltage generating means is input to the other input terminal of the differential amplifier, the differential amplifier compares the voltage input to the other input terminal with the voltage input to one input terminal. A voltage corresponding to the difference voltage is amplified, and a current corresponding to the voltage and the polarity output from the differential amplifier flows to the primary side of the third or fourth photocoupler. A current compensating for the current transmission ratio of the third and fourth photocouplers flows through the primary side of the first photocoupler.

Therefore, if the current transfer ratio of the first photocoupler, the second photocoupler, the third photocoupler, and the fourth photocoupler is made substantially the same and the same temperature condition is set, the two photocouplers of the first photocoupler and the second photocoupler are obtained. The voltage corresponding to the secondary current can be compensated for by the same current transmission ratio of the third and fourth photocouplers as the current transmission ratio of the first and second photocouplers. Then, the primary current of the third and fourth photocouplers matches the voltage applied to the input terminal of the motor. Hall element is the third
A primary current of the photocoupler and the fourth photocoupler is used as a control current, a Hall voltage is output by receiving a magnetic flux generated by the current flowing through the motor, and the output Hall voltage is output as a power supply value to the motor. Thus, the motor power detection device can detect the power supplied to the motor with high accuracy regardless of its frequency, and can be manufactured small and inexpensively.

An overload protection device according to a second aspect of the present invention is described in claim
1. A motor power detection device according to claim 1, wherein a current supplied to the motor is cut off based on an output of the motor power detection device.

The overload protection device includes the motor power detection device according to claim 1, and cuts off the current supplied to the motor based on the output of the motor power detection device. It can be detected with high accuracy irrespective of the frequency of the power supplied to the device, and can be manufactured small and inexpensively.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. Embodiment 1 FIG. FIG. 1 is a circuit diagram showing a configuration of an embodiment of a motor power detection device according to the present invention. One input terminal a of the motor M is connected via a resistor R1 to the anode of the light emitting diode LED1 which is the primary side of the photocoupler PC1 (motor voltage detection circuit) and the primary side of the photocoupler PC2 (motor voltage detection circuit). Light emitting diode LE
It is connected to the cathode of D2. The other input terminal b of the motor M is connected to the anode of the light emitting diode LED2 of the photocoupler PC2 and the photocoupler PC via the resistor R2.
It is connected to the cathode of one light emitting diode LED1.

The collector of the phototransistor PT1, which is the secondary side of the photocoupler PC1, is connected to a + 15V DC power supply. The emitter of the phototransistor PT1 is connected to the phototransistor PT2 on the secondary side of the photocoupler PC2 via a series circuit of a resistor R3 and a resistor R4.
Connected to the collector. Phototransistor PT
The emitter No. 2 is connected to a -15 V DC power supply. The connection midpoint between the resistors R3 and R4 is grounded. The series circuit of the resistors R3 and R4 includes a variable resistor VR1 for offsetting an output voltage of a differential amplifier OP1 described later.
(First voltage generating means) are connected in parallel. This variable resistor VR1 can be replaced with a simple resistor.

The variable resistance terminal of the variable resistor VR1 is connected to the inverting input terminal of the differential amplifier OP1. The output terminal of the differential amplifier OP1 is connected to the cathode of the light emitting diode LED3 that is the primary side of the photocoupler PC3 (motor voltage detection circuit) and the anode of the light emitting diode LED4 that is the primary side of the photocoupler PC4 (motor voltage detection circuit). Is connected to The anode of the light emitting diode LED3 and the cathode of the light emitting diode LED4 are commonly connected and connected to the current input terminal I (+) on the positive side of the Hall element IC1.

The collector of the phototransistor PT3, which is the secondary side of the photocoupler PC3, is connected to a +15 V DC power supply. The emitter of the phototransistor PT3 is connected to the collector of the phototransistor PT4, which is the secondary side of the photocoupler PC4.
It is connected to a 15V DC power supply. A connection intermediate point between the emitter of the phototransistor PT3 and the collector of the phototransistor PT4 is connected to a non-inverting input terminal of the differential amplifier OP1, and is grounded via a resistor R6 (second voltage generating means). Photocoupler PC1, PC2, PC
3 and PC4 are selected to have substantially the same value.

The current input terminal I on the negative side of the Hall element IC1
(-) Is grounded, the positive voltage output terminal O (+) is connected to the inverting input terminal of the differential amplifier OP2 via the resistor R7, and the negative voltage output terminal O (-) is connected to the resistor R8. Is connected to the non-inverting input terminal of the differential amplifier OP2 via The non-inverting input terminal of the differential amplifier OP2 is connected to a resistor R10
, And the output terminal thereof is negatively fed back by a resistor R9, and is connected to one output terminal c of the motor power signal. The other output terminal d of the motor power signal is grounded.

As shown in FIG. 2, a current I flowing through the light emitting diodes LED3 and LED4 is provided in the Hall element IC1.
_V flows from the positive side current input terminal I (+) to the negative side current input terminal I (−), and the magnetic flux generated by the current supplied to the motor M is converged by the magnetic body m. The Hall element IC1 is installed in the middle of the magnetic circuit to apply the magnetic flux B, and the electromotive force generated in the direction perpendicular to the direction in which the current _IV flows is taken out by the voltage output terminals O (+) and O (-).
At this time, the Hall voltage V _H generated between the voltage output terminals O (+) and O (−) is represented by the following equation (1) due to the Hall effect. V _H = K _H · I _V · B cos θ (1) where K _H is a proportional constant of the Hall element, and θ is a gradient of the magnetic flux B with respect to a direction perpendicular to the current (control current) I _V and the Hall voltage V _H. is there.

Here, the current _IV is a value related to the voltage supplied between the input terminals a and b of the motor M, and the magnetic flux B
Is a value related to the current supplied to the motor M. Therefore, from the equation (1), the Hall voltage V _H is a value related to the power supplied to the motor M = (supply voltage to the motor M) × (supply current to the motor M), and the Hall voltage V _H is detected. By doing so, the power supply to the motor M can be detected.

Hereinafter, the operation of the motor power detection device having such a configuration will be described. The AC voltage ACV applied between the input terminals a and b of the motor M becomes low voltage due to the voltage drop by the resistors R1 and R2, and
It is applied to the light emitting diodes LED1 and LED2 of C2.

Then, from the input terminals a and b of the motor M,
Currents I and I, which are limited by the resistors R1 and R2 and correspond to the positive and negative voltages V and V of the AC voltage ACV, flow through the light-emitting diodes LED1 and LED2 and
1, LED2 emits light alternately. Light emitting diode PD
1, PD2 emits light to the phototransistor PT1,
PT2 receives light, phototransistors PT1 and PT2 are turned on alternately, currents i and bar i flow from DC power supplies + 15V and -15V to resistors R3 and R4 through phototransistors PT1 and PT2, and to the variable resistance terminal of variable resistor VR1. a current i, the positive voltage V _R corresponding to the bar i, the negative-side voltage bar V _R occurs.

[0022] That is, the positive-side voltage V _R of the AC voltage corresponding to the AC voltage ACV to be detected, a negative-side voltage bar V _R occurs.
By the way, the current i and the bar i flowing through the phototransistors PT1 and PT2 change as the current transmission ratio of the photocouplers PC1 and PC2 is shifted left and right depending on the ambient temperature. L
The current I and the bar I of the ED2 do not match, and the voltage corresponding to the current of the phototransistors PT1 and PT2 does not match the AC voltage ACV input between the input terminals a and b of the motor M.

[0023] However, the voltage V _R of the resistance variable terminal of the variable resistor VR1, bar V _R is inputted to the inverting input terminal of the differential amplifier OP1, a differential amplifier OP1, a voltage input to the inverting input terminal voltage outputs in accordance with, the voltage V _R, a current corresponding to the bar V _R I ', bar I' is, light emitting diode LED3 of the photocoupler PC3, PC 4, LE
It flows through D4 to the Hall element IC1. Then, the light emitting diodes LED3 and LED4 emit light alternately according to the current I 'and the bar I'.
T3 and PT4 are turned on alternately, and DC power supply + 15V,-
A current flows from 15 V to the resistor R6 through the phototransistors PT3 and PT4, and the terminal voltage of the resistor R6 is set to the positive side voltage V _F and the negative side voltage bar corresponding to the output current I ′ and the bar I ′ of the differential amplifier OP1. It becomes V _F, the voltage V _F, V bar
_F is input to the non-inverting input terminal of the differential amplifier OP1.

The differential amplifier OP1 amplifies the difference between the voltage input to the non-inverting input terminal and the voltage input to the inverting input terminal, and according to the voltage output from the differential amplifier OP1, the photo-coupler PC3 The current I _V compensated for the current transmission ratio of PC4 passes through the light-emitting diodes LED3 and LED4 of the photocouplers PC3 and PC4 from the current input terminal I (+) on the positive side of the Hall element IC1 to the current input terminal I on the negative side.
It flows to (-).

Therefore, the photocouplers PC1, PC2, P
If the current transmission ratios of C3 and PC4 are selected to be substantially the same value, the light emitting diodes LE of the photocouplers PC3 and PC4 can be used.
The current flowing through D3 and LED4 is equal to the photocoupler PC1,
The current which compensates the current transmission ratio of PC2 and the current which compensates the current transmission ratio of photocouplers PC1 and PC2 is the same as the current flowing to Hall element IC1.
1 matches the AC voltage ACV input between the input terminals a and b of the motor M.

By using the photocouplers PC1, PC2, PC3, and PC4 having the same current transmission ratio and arranging them under the same temperature condition, the current transmission ratio of the photocouplers PC1 and PC2 is compensated. A current is obtained, and the voltage supplied to the motor M can be detected with high accuracy.

On the other hand, as shown in FIG. 2, a magnetic flux B generated by concentrating a magnetic flux generated by the current supplied to the motor M by the magnetic material m is applied to the Hall element IC1, and the current _IV is generated by the Hall effect. An electromotive force is generated in the direction perpendicular to the flowing direction, and is extracted from the voltage output terminals O (+) and O (-). As described above, the Hall voltage V _H generated between the voltage output terminals O (+) and O (−) is represented by the equation (1). V _H = K _H · I _V · B cos θ (1) where K _H is a proportional constant of the Hall element, and θ is a gradient of the magnetic flux B with respect to a direction perpendicular to the current (control current) I _V and the Hall voltage V _H. is there.

Here, the current _IV is, as described above, the AC voltage ACV input between the input terminals a and b of the motor M.
And the magnetic flux B is a value related to the current supplied to the motor M. Thus, equation (1), the Hall voltage V _H is a value related to the power supplied motor M = (voltage supplied to the motor M) × (current supplied to the motor M), the Hall voltage V _H By amplifying and detecting by the differential amplifier OP2, power supplied to the motor M (motor power signal) can be detected from between the output terminals c and d. Further, since the circuit of the above-described motor power detection device (excluding the windings L1 and L2 of the motor M) does not include an inductance component, no phase error occurs between the AC voltage and the AC current. In addition, since a transformer is not used, it can be configured to be small and lightweight.

Since the motor power signal is a sine wave having a cycle twice as long as the power supply frequency, the motor power value can be obtained by averaging the sine wave with a smoothing circuit including a resistor and a capacitor (not shown). The motor power signal is digitized by an A / D converter instead of a smoothing circuit using a resistor and a capacitor, and the digitized motor power signal is sampled by a microcomputer at predetermined intervals, and the sampled value is calculated. The motor power value may be obtained by integrating for a period corresponding to the power supply frequency and dividing the integration result by the number of samples. In the above-described embodiment, the case where the motor M is a single-phase motor has been described. However, the same effect can be obtained even if the motor M is a three-phase motor or a DC motor.

Embodiment 2 FIG. FIG. 3 is a block diagram showing the configuration of the second embodiment of the overload protection device according to the present invention. In this overload protection device, a single-phase power is supplied to a single-phase motor M that drives a drive mechanism (not shown), for example, a conveyor, via a circuit breaker 1 and an electromagnetic contactor 2. A thermal relay 3 is interposed in a line connecting the electromagnetic contactor 2 and the single-phase motor M.

The voltage supplied to the single-phase motor M is input to the motor power detection device 10 described in the first embodiment via the input terminals a and b.
The output voltage of 0 is averaged by an averaging circuit 10a such as a smoothing circuit, and is input to each positive input terminal + of a comparator 11 for starting detection and a comparator 13 for detecting overload. The voltage of the control power supply CE is connected to the negative input terminal
The start detection reference voltage E11 divided by the resistor 22 and the resistor 22 is input. An overload detection reference voltage E13 obtained by dividing the voltage of the control power supply CE by the variable resistor 23 is input to the negative input terminal − of the comparator 13.

The output signal V11 of the comparator 11 is input to a start timer 12, and the output signal V13 of the comparator 13 is input to an overload timer 14. The start timer 12 is an on-delay timer for preventing the start current of the single-phase motor M from being erroneously recognized as an overload so as not to cut off the motor current, and measures a set time T1 longer than the start time of the single-phase motor M. Is completed, an output signal V12, which is a start end signal, is output.

The overload timer 14 is an on-delay timer for measuring the duration of the overload so as not to interrupt the motor current due to an instantaneous overload. The overload timer 14 measures a set time T2 shorter than the set time T1. Is completed, an output signal V14 is output. Start timer 12
Is input to one input terminal of the OR circuit 34, and the output signal V12 is input to one input terminal of the AND circuit 15. The output signal V14 of the overload timer 14 is input to the other input terminal of the AND circuit 15.

The output signal V11 of the comparator 11 is NA
The signal is input to one input terminal of each of the ND circuit 31 and the NAND circuit 32. The output signal V13 of the comparator 13 is NAN
The signal is input to one input terminal of the D circuit 30. An output signal of the NAND circuit 30 is input to the other input terminal of the NAND circuit 31 via a series circuit of the capacitor 35 and the resistor 36. The connection point between the capacitor 35 and the resistor 36 is grounded via the resistor 37.

The output signal V31 of the NAND circuit 31 is N
The other input terminal of the AND circuit 30 and the NAND circuit 33
Is input to one of the input terminals. The output signal of the NAND circuit 32 is input to the other input terminal of the NAND circuit 33, and the output signal V33 of the NAND circuit 33 is input to the other input terminal of the NAND circuit 32 and the other input terminal of the OR circuit 34. . AND circuit 15 and NAND circuit 3
0, 31, 32, 33, a capacitor 35, and a resistor 3
6 and 37 constitute a transient operation end detection circuit 300 that detects the end of the transient operation of the single-phase motor M.

The output signal V15 of the AND circuit 15 is input to the base of the transistor 16 whose emitter is grounded. The collector of the transistor 16 is the overload trip relay 1
8 and a control power supply CE. The flywheel diode 17 is connected to the overload trip relay 18 in parallel. A series circuit of the normally closed contact 18b of the overload trip relay 18, the stop push button switch 7, the start push button switch 6, the electromagnetic coil 2c of the electromagnetic contactor 2, and the normally closed contact 3b of the thermal relay 3 AC power supply AC
Is interposed between one terminal and the other terminal. The self-holding normally open contact 2 a of the electromagnetic contactor 2 is connected in parallel to the starting push button switch 6.

Then, the motor power detecting device 10, the averaging circuit 10a, the resistors 21 and 22, the variable resistor 23, the comparator 1
1, 13, start timer 12, overload timer 14, AND
Circuit 15, transistor 16, overload trip relay 1
8, flywheel diode 17, normally closed contact 18b and transient operation end detection circuit 300
0 is configured.

The operation of the overload protection device having such a configuration will be described below with reference to the timing chart of FIG. When the starting pushbutton switch 6 is closed with the circuit breaker 1 closed, the electromagnetic coil 2c is excited to close the electromagnetic contactor 2, and a single-phase motor current I _S flows through the single-phase motor M, thereby causing a single-phase motor current IS to flow. The motor M starts. As a result, the motor power detection device 10 outputs a DC output voltage V10 that is proportional to the motor power. The comparator 11 outputs the output voltage V10 and the voltage divided by the resistors 21 and 22 in FIG.
The magnitude is compared with the start detection reference voltage E11 shown in FIG.
When V10> E11, the output signal V11 of the comparator 11
Attains the H level, and the start of the single-phase motor M is detected.

[0039] The output signal V11 is a period during which the motor current I _S flows becomes the H level as shown in FIG. 4 (c). Then, the start timer 12 starts timing when the output signal V11 becomes H level, and when the set time T1 is measured, the output signal V12 of the start timer 12 becomes H level as shown in FIG. 4D. On the other hand, if an excessive starting current flows when the single-phase motor M starts, the output signal V13 of the comparator 13 goes to the H level as shown in FIG. Upon completion, the level becomes L level. Then, when the output signal V13 becomes L level,
The output signal of the NAND circuit 30 becomes H level, and the output signal is differentiated by the capacitor 35 and the resistor 37 to generate a sawtooth pulse V36 shown in FIG.
It is input to the D circuit 31.

The output signal V3 of the NAND circuit 31
1 indicates that the single-phase motor M goes to the H level after starting.
Due to the logic of the output signal V11 shown in FIG. 4 and the sawtooth pulse V36, a negative pulse shown in FIG. The output signal V31 of the NAND circuit 31 is output from the NAND circuit 32 and the NA
Transient operation end detection circuit 3 composed of ND circuit 33
At 00, the output signal V11 is held during the H level. Accordingly, as shown in FIG. 4 (i), the output signal V33 of the NAND circuit 33 starts at the time when the output voltage V10 corresponding to the starting current of the single-phase motor M becomes equal to or lower than the overload detection reference voltage E13. The level is at the H level until I _S is cut off. Then, after the single-phase motor M starts, N
Whether the output signal V33 of the AND circuit 33 becomes H level,
Alternatively, the output signal V12 of the start timer 12 is set to the set time T1.
Becomes high after the clocking, the output signal V34 of the OR circuit 34 becomes high as shown in FIG. 4 (j).

Thus, the output signal V of the AND circuit 15
15 is that when both the output signal V34 of the OR circuit 34 and the output signal V14 of the overload timer 14 become H level, it becomes H level, the transistor 16 is turned on, and the coil of the overload trip relay 18 is excited, The normally closed contact 1
8b opens. The normally closed contact 18b is opened when the electromagnetic contactor 2 electromagnetic coil 2c is demagnetized, the electromagnetic contactor 2 is opened to cut off the motor current I _S of the single-phase motor M, single-phase motor M is stopped, The drive mechanism driven by the single-phase motor M is protected from overload.

The period (A) in FIG. 4 is a timing chart when the overload OL occurs after the single-phase motor M starts and after the set time T1 of the start timer 12 is measured. After the occurrence, when the overload timer 14 finishes measuring the set time T2, as shown in FIG. 4 (k), the overload trip signal V15 becomes H level and the motor current I _S of the single-phase motor M is increased. Cut off.

The period (B) is a timing chart when the single-phase motor M is overloaded when it is started. When the start timer 12 measures the set time T1, the timing chart shown in FIG. ), The overload trip signal V15
There becomes H level, to cut off the motor current I _S of the single-phase motor M.

The period (C) is a timing chart in the case where an overload OL occurs while the set time T1 of the start timer 12 is being measured after the start of the single-phase motor M. In this case, the start is started. Regardless of the timing operation of the timer 12, the output signal of the NAND circuit 33 of the transient operation end detection circuit 300 is at the H level as shown in FIG.
Since the output signal V34 of the circuit 34 is at the H level as shown in FIG. 4 (j), the overload timer 14 finishes the timekeeping operation and the time when the output signal V14 becomes the H level, that is, the timekeeping operation of the start timer 12. within the period, the overload trip signal V15 as shown in FIG. 4 (k) is at the H level, to cut off the motor current I _S of the single-phase motor M.

As described above, the protection operation similar to that of the conventional overload protection device is performed in the periods of FIGS. 4A and 4B, but the protection operation of the present invention is performed in the period of FIG. Such an overload protection device can control the overload trip signal V15 during the clocking operation period even when the start timer 12 is performing the clocking operation.
Becomes H level, the motor current I _S can be cut off. Therefore, when the overload OL occurs as in the period (C), the motor current cannot be cut off until the timer operation of the start timer 12 ends in the related art. By shutting off, the drive mechanism driven by the single-phase motor M can be protected from overload at an early stage. still,
In the present embodiment, a drive mechanism driven by a single-phase motor is targeted for overload protection, but a drive mechanism driven by a three-phase motor or a DC motor may be used, and the type of motor is limited. Not something.

[0046]

[0047]

According to the motor power detection device of the first invention, the AC power supplied to the motor can be detected with high accuracy regardless of the frequency, and the motor can be manufactured small and inexpensively.

According to the overload protection device of the second invention,
The overload state can be detected with high accuracy regardless of the frequency of the electric power supplied to the motor, and the overload state can be manufactured at a small size and at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of a motor power detection device according to the present invention.

FIG. 2 is an explanatory diagram for explaining a Hall element.

FIG. 3 is a block diagram showing a configuration of an embodiment of an overload protection device according to the present invention.

FIG. 4 is a timing chart showing the operation of the embodiment of the overload protection device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Comparator (for start detection) 12 Start timer 13 Comparator (for overload detection) 14 Overload timer 15 AND circuit 18 Overload trip relay 18b Normally closed contact 30, 31, 32, 33 NAND circuit 34 OR circuit 300 Transient Operation end detection circuit a, b Input terminal B Magnetic flux c, d Output terminal IC1 Hall element L1 Main winding L2 Auxiliary winding LED1 to LED4 Light emitting diode M Motor OP1, OP2 Differential amplifier PC1 to PC4 Photocoupler (motor voltage detection circuit PT1 to PT4 Phototransistors R1 to R4 Resistance R6 (second voltage generation means) VR1 Variable resistance (first voltage generation means)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-194394 (JP, A) JP-A-7-23557 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 21/08 G06G 7/162

Claims (2)

(57) [Claims] 1. A motor voltage detecting circuit for detecting a voltage applied to a motor and outputting a current corresponding to the detected voltage, and a current flowing through the motor as a control current using the current output by the motor voltage detecting circuit. and a Hall element that outputs a Hall voltage subjected to the magnetic flux due to the Hall voltage which the Hall element is output, output as the supply electric power value to the motor
A motor power detection device, wherein the motor voltage detection circuit is provided between input terminals of the motor.
Interposed, and the first transformer whose primary side is connected in anti-parallel.
And a second photocoupler and the first photocoupler
And a voltage corresponding to the secondary current of the second photocoupler
First voltage generating means for causing the first voltage generating means to generate
Differential amplifier in which the applied voltage is applied to one input terminal,
The output current of the differential amplifier should be input.
Third photocoupler and fourth photocoupler connected in parallel
Plastic and the secondary of the third and fourth photocouplers
Second voltage generating means for generating a voltage corresponding to the side current.
The voltage generated by the second voltage generating means corresponds to the differential amplification.
To the other input terminal of the third photocoupler and
A motor power detection device for outputting a primary current of a fourth photocoupler . 2. A motor power detecting device according to claim 1.
And a motor based on the output of the motor power detection device.
Characteristic to cut off the current supplied to the
And overload protection device.