JPS614489A - Protecting device of dc motor controller - Google Patents

Abstract

PURPOSE:To perform protecting function capable of preventing an overvoltage with less current capacity by inserting a protecting circuit having a Zener diode, a thyristor and a current limiting resistor between the collector and the base of a transistor. CONSTITUTION:When transistors of a field chopper are all turned OFF so that induced voltage by a field coil F generates the polarity as shown, a field current flows in a closed circuit of a field coil F, a diode D3, a fuse Fu, a switch SW, a DC power source EB, a diode D2 and the coil F. At this time, when a regenerative current to a DC power source is interrupted due to melting of the fuse, the induced voltage of the field exceeds a Zener voltage. Thus, a thyristor CR is fired. Thus, a transistor Tr1 is turned ON, and the induced voltage of the field drops.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a protection device for preventing destruction of a switching transistor from surge voltage caused by an inductive load in a DC motor control device.

(Prior Art and Background of the Invention) Figure 1 shows the wiring of a conventional DC shunt motor.
B represents a DC power supply, 3w represents a switch, and Fu represents a fuse, which are connected to the armature A and field F of the motor via a transistor chopper. Transistor Tr
The field chopper consisting of l=Tr4 has a circuit configuration in which the polarity of the magnetic flux, that is, the field current, can be switched to enable forward and backward movement of the vehicle, and when energized, the combination of transistors Trl and Tr4 or Tr2 and Tr3 is used. In this case, the transistor Tri or Tr 3 connected to the + side of the DC type mEe is made fully conductive, and the transistor Tri or Tr 3 - the diode DI or D
3-field'coil F--makes the closed circuit of transistor Trl or Tr3 act as a freewheeling circuit;
An example of the DC power supply EB is a transistor Tr2 or Tr
The field current is controlled to a predetermined value by switching the field chopper 4.The field has a very large inductance value and a long time constant, so when switching the vehicle forward or backward 2, that is, reversing the polarity of the field current, all of the field choppers are switched. Transistors Tri to Tr4 are turned off, and magnetic energy is generated in the closed circuit of field coil F, diode 'D1 or D3, fuse Fu, switch Sw, DC power supply E8, diode D2 or D4, and field cobble F, to generate magnetic energy back into DC power supply E8. Rapid decay methods are used. In this case, fuse Fu and switch SW
The diode Do connected in parallel with the diodes Do enables regeneration to the DC power supply E8 even when the fuse Fu is blown or the switch SW is opened.
It has a protection function of clamping the surge voltage applied to Tr4 to the voltage value of DC power supply E8 to prevent application of excessive voltage. Moreover, when the fuse Fu blows out or the switch SW becomes open during dynamic braking due to the strong field at high rotational speeds of the morph, the large current of the armature is regenerated to the DC power supply via the diode Do.
O needs to have a large current capacity. In addition, from the viewpoint of protection function in case of fuse melting, since the DC source 0 and the load are connected directly to the diode Do without going through the fuse, the diodes D and O require high reliability. There are some drawbacks.

(Object of the present invention) In view of the above points, an object of the present invention is to provide a protection device for a DC motor control device that has a small current capacity and can realize a protection function.

(Structure of the present invention) The present invention provides a protection circuit consisting of a Zener diode for determining overvoltage, a thyristor as a switching element, a resistor for limiting current, and a capacitor for absorbing current to prevent erroneous firing of the thyristor. It is configured to be inserted between the collector and base of the Tri.゛(Example) Hereinafter, an example of the present invention shown in the drawings will be described. Second
The figure is an electrical circuit diagram of a protection device for a DC shunt motor control device showing an embodiment of the protection device for a DC motor control device according to the present invention. Zener diode and switching element size for determining overvoltage 〉Iris Risk CI'? , a resistor R1 to limit the current, and a surge absorbing capacitor R21 to prevent erroneous firing of the thyristor.
It is inserted between the collector of the transistor Tri and the source.

To explain the case where the induced voltage by the field coil F has a polarity as shown in Fig. 2, the field current flows from the field coil F to the diode D3 to Fuse Fu-Sui Nochi SW-DC power supply IF
, 13 - diode D2 - closing 1 of field coil F
ijl t/it flows. In this case, the transistor Tr
The voltage VCE between the collector and emitter of L is almost equal to the voltage EB of the DC power supply. Therefore, the transistor T
1111 inserted between the collector bases of r 1
A voltage equal to the DC power supply is also applied to the protection circuit 1.

Since the set voltage of the Zener diode Z is a little lower than the maximum collector-emitter voltage Vce5, which is the transistor standard, the Zener diode Z is turned off during normal operation, so the thyristor CR does not fire. However, when the regenerative current to the DC power supply is cut off due to a fuse blowout, the induced voltage in the field increases, that is, the bias towards the Zener diode Z of the protection circuit 1 increases, and when the Zener voltage is exceeded, the current flows through the Zener diode Z. flows. This triggers the gate, so the thyristor CR fires and automatically supplies the base current of the transistor Tr1 through the diode D6, turning on the transistor Tr1. As a result, field coil F - diode D
3-Transistor Tri-Field' Since the magnetic energy of the field flows through the closed circuit of the coil F, the induced voltage is reduced and the destruction of the transistor due to overvoltage is prevented. In addition, since the thyristor CR will not extinguish unless the current drops below the holding current, a 1-run risk base current will flow while the field induced voltage is generated, the aforementioned closed circuit will be maintained, and the protection function will operate. .

When returning to normal operation from such an abnormality, the 1-run risk Trl for driving the base of the transistor Tri
When turned on, the current is commutated to the transistor Tr6 side, so that the thyristor CR is turned off and the protection function can be reset.

Above, we have explained the case where the induced voltage by the field coil F has the polarity shown in Figure 2, but if it has the opposite polarity, the diode is changed from D6 to Dl, from Dl to D3, and the transistor is changed from Tri to Tr3. Then, the same protection function as described above can be achieved.

The present invention can be applied not only to a bridge circuit of transistors in which diodes are connected in antiparallel as shown in FIG. 2, but also to a three-phase transistor inverter. D) The same protection function can be achieved by simply adding one I. In addition, in FIG. 3, 1 is a protection circuit consisting of a Zener diode Z and a thyristor CR, and within the protection circuit 1 shown by the dotted line in FIG. It does not include D7, and 2 indicates an inductive load such as a motor.

Further, the protection circuit 1 is connected to the DC power supply EBO+ side.
As mentioned above, as shown in Fig. 3, the protection circuit 1 including the diodes D9 to Dll is connected to the DC power supply P.
It can be provided on one side of B to provide the same protection function as described above.

(Effects of the present invention) As described above, in the protection device for a DC motor control device according to the present invention, the resistors R, , R2, which limit the current of the thyristor CR1 of the Zener diode Z1 switching element that determines overvoltage, and the thyristor CR A protection circuit consisting of a surge absorbing capacitor to prevent false ignition is inserted between the collector and base of the transistor Tri, so it detects the induced voltage in the field and automatically turns on the transistor, reducing current capacity. can prevent overvoltage.
It is very effective in preventing overvoltage by triggering the thyristor and keeping the transistor on while the above voltage is being generated. Also, by combining a single detection circuit and a diode, it can be used in bridges and three-phase or more inverters. It also has the effect that it can be applied to normal operations, and it also has the effect that the protection circuit can be easily installed when returning to normal operation from a field lightning.

[Brief explanation of drawings]

Fig. 1 is an electrical wiring diagram of a protection device for a conventional DC shunt motor control device, Fig. 2 is an electrical circuit diagram of a protection device for a DC motor control device according to the present invention, and Fig. 3 is an electrical circuit diagram of a protection device for a conventional DC shunt motor control device. FIG. 2 is an electrical circuit diagram of an example. Es...DC power supply, SW...switch, Fu...
fuse, F...field coil, Trl~Tr4
...Transistor, D1-D4...Diode, 1
・・・Protection circuit, Z...Zener diode, CR・
...Thyristor, R'l+R2...Resistor, C...Capacitor, D6 +D7...Diode

Claims (1)

[Claims] Consists of a Zener diode (Z) that determines overvoltage, a thyristor (CR) as a switching element, resistors (R_1, R_2) that limit current, and a surge absorption capacitor (C) that prevents erroneous firing of the thyristor (CR). A protection device for a DC motor control device, characterized in that a protection circuit is inserted between the collector and base of a transistor (Tr1).