JPH08194017A - Electric current sensor of direct current servo motor - Google Patents

Abstract

PURPOSE: To provide an electric current sensor which detects grounding of a power line of a direct current servo motor and protects a transistor of a servo amplifier. CONSTITUTION: This electric current sensor is constituted of coils N1 , N2 wound around a core of a magnetic body forming a magnetic circuit and a Hall element H provided on the same core to detect an electric current flowing in these two sets of the coils N1 , N2 , Respective both ends of these two sets of the coils N1 , N2 are connected to output terminals (c), (d) of a servo amplifier and connecting terminals (a), (b) of a direct current servo motor in directions where magnetic fields in the core are strengthened each other and an output terminal of the Hall element H is connected to a feedback circuit of the servo amplifier and an excess current detection circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a current sensor for a DC servo motor.

[0002]

2. Description of the Related Art FIG. 4 shows a control circuit for a positioning DC servo motor. As shown, commercial three-phase AC
The four transistors Q ₁ , which are converted into direct current by the rectifier circuit 1 and the smoothing capacitor C and are assembled in the bridge,
The voltage and polarity (direction of current for forward / reverse rotation of the motor) are controlled by the servo amplifier 3 composed of Q ₂ , Q ₃ , Q ₄ and commutation diode, and then the direct current servomotor is passed through the current sensor 5 ′. Is supplied to M.

The control of the output voltage and the polarity of the servo amplifier 3 corresponds to the position command by the pulse train corresponding to the rotation angle of the encoder E directly connected to the servo motor M and the feedback of the output voltage of the current sensor. Then, after operating the reversible counter, the D / A converter, the F / V converter, the speed comparator 7, the amplifier A, the current comparator 9, etc., the PW
This is performed by applying the output voltage of M (pulse width modulation circuit) to the bases of the four transistors Q ₁ , Q ₂ , Q ₃ and Q ₄ of the servo amplifier 3.

As shown in FIG. 5, a conventional current sensor 5'is provided with a winding N through which a motor current flows, on one side of a core of a magnetic body forming a magnetic circuit, and the ends of the winding N are output from the servo amplifier 3. The terminal c or d is connected to the connection terminal a or b of the DC servomotor M, and the hall element H is provided on the other side,
A control current is supplied to this to obtain a voltage proportional to the current flowing on the winding side, and this is output to the current feedback and overcurrent detection circuit.

[0005]

As described above, the conventional current sensor is provided with one winding, and when the power line of the servomotor falls from the connection terminal b as shown in FIG. 6, for example, a ground fault occurs. , The current passing through the transistor Q _{1 of the} servo amplifier flows through the servo motor M, but the current sensor 5 '
Since the current does not flow to the current, the current increases more and more. However, since the overcurrent detection circuit does not operate, the transistor Q ₁ is burned out.

Further, the power line of the servomotor is connected to the connection terminal a.
When it falls from the ground and has a ground fault, the current passing through the transistor Q _{2 of the} servo amplifier is the current sensor 5 ′ and the servo motor M.
As it flows through, the overcurrent detection circuit and the alarm are activated, and the transistor Q ₂ is protected.

As described above, when the power line of the servo motor falls from the connection terminal and is grounded, the conventional current sensor is
The transistor (Q _{1 in the} above case) of the circuit that does not pass the current sensor will be burnt out. The present invention has been made focusing on such a problem, and by improving the current sensor, even if any one of the power lines of the servo motor falls from the connection terminal and is grounded, it can be reliably detected. However, it is an object of the present invention to provide a current sensor capable of preventing burning of a transistor of a servo amplifier.

[0008]

In order to achieve the above object, a current sensor for a DC servo motor according to the present invention comprises two sets of windings wound around a core of a magnetic material forming a magnetic circuit,
It consists of a Hall element provided in the same core that detects the current flowing through these two sets of windings, and both ends of each of the above two sets of windings are connected to the output terminal of the servo amplifier and the connection terminal of the servo motor, It is characterized in that they are connected to each other in a direction in which the magnetic field in the core is strengthened, and the output terminal of the Hall element is connected to the feedback circuit and the overcurrent detection circuit of the servo amplifier.

[0009]

Since it is configured as described above, when this current sensor is inserted between the servo amplifier and the DC servo motor, even if any one of the power lines of the servo motor falls from the connection terminal and is grounded, This is surely detected to operate the overcurrent detection circuit and the alarm to prevent burning of the transistor of the servo amplifier.

[0010]

EXAMPLES Next, examples of the present invention will be described.
FIG. 1 is a configuration diagram of a current sensor of the present invention. Two sets of windings N ₁ and N ₂ having the same number of turns, in which a motor current flows, are provided on one side of a core of a magnetic body forming a magnetic circuit, and the other side of the core is provided. A Hall element H is provided on the side, a control current is supplied to the Hall element, and a voltage proportional to the current flowing on the winding side is obtained as an output voltage.

The two sets of windings are wound in the same direction as shown in FIG. 2, and both ends of each winding are output terminals c and d of the servo amplifier.
Also, the connection terminals a and b of the servo motor are connected in a direction in which the magnetic field in the core of the magnetic material is strengthened.

In such a configuration, when the power line of the servo motor drops from the connection terminal b and is grounded as shown in FIG. 3, the current passing through the transistor Q ₁ of the servo amplifier is the current from the output terminal c of the servo amplifier. Since it flows through the winding N ₁ of the sensor 5 to the servomotor M, the overcurrent detection circuit and the alarm are activated, and the transistor Q ₁ is protected.

Further, the power line of the servomotor is connected to the connection terminal a.
Even if it falls from the ground to a ground fault, the current passing through the transistor Q ₂ of the servo amplifier flows from the output terminal d of the servo amplifier to the servo motor M through the winding N ₂ of the current sensor. Are activated and the transistor Q ₂ is protected.

As described above, even if any one of the power lines of the servo motor falls from the connection terminals a and b to the ground fault, the current sensor can detect this and protect the transistor of the servo amplifier.

[0015]

As will be understood from the above description, the current sensor of the present invention has the structure described in the claims. Therefore, when this is inserted between the servo amplifier and the DC servo motor, Even if one of the power lines of the servo motor falls from the connection terminal and is grounded, this can be detected reliably and the overcurrent detection circuit and alarm can be activated, preventing the servo amplifier transistors from burning out. It becomes possible to do.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a current sensor of the present invention.

FIG. 2 is a connection circuit diagram of a current sensor, a servo amplifier, and a servo motor according to the present invention.

FIG. 3 is an explanatory diagram of the operation of the current sensor when one of the power lines of the servo motor in FIG. 2 falls from the connection terminal and is grounded.

FIG. 4 is a control circuit diagram of a positioning DC servomotor using a conventional current sensor.

FIG. 5 is a configuration diagram of a conventional current sensor.

FIG. 6 is an explanatory diagram of the operation of the current sensor when one of the power lines of the servo motor in FIG. 4 falls from the connection terminal and is grounded.

[Explanation of symbols]

3 the servo amplifier 5 a current sensor 5'conventional current sensors M DC servo motor to Q ₁ the present _{invention, Q 2, Q 3, Q} 4 windings N ₁ of the transistor N conventional current sensors constituting the servo amplifier, N ₂ this Winding H Hall element of current sensor of the invention

Claims (1)

[Claims] 1. A set of two windings wound around a magnetic core forming a magnetic circuit, and a Hall element provided on the same core for detecting a current flowing through the two windings. DC servo motor current sensor.