JPS5845261B2 - Overcurrent detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overcurrent detection circuit for detecting an overcurrent in a motor connected to the ground side from the backflow blocking element in an electric vehicle equipped with a power regenerative brake having a backflow blocking element. It is.

Fig. 1 shows the circuit configuration of a conventional electric car with a power regeneration brake using a backflow prevention element, and Fig. a is a circuit diagram when the vehicle is running;
Figure b is a circuit diagram during braking.

In the figure, 4 indicates main motors 13a, 13b, and 13c.

13d is a DC current transformer for detecting current in the main motor circuit; 13a', 13b', 13c', and 13d' are field coils of the main motors 13a to 13d; 10 is a panda graph; 11 is a main circuit disconnection 12 is an overcurrent detector, 1
41d Main circuit resistor, 15 is a reverse current blocking diode, 1
6 is a cam switch for the main circuit, 1T is a reversing device, and 18 is a power source for field excitation.

Due to the circuit configuration having such a backflow blocking diode 15, overcurrent detection when the main motor circuit is connected to the ground during power regenerative braking is performed on the ground side of the backflow blocking diode 15, that is, the main motor 13c.

Since overcurrent detection of 13d is impossible, it was necessary to provide an overcurrent detector 19 exclusively for power regenerative braking between main motor 13d and ground.

The present invention provides an overcurrent detection circuit that can detect overcurrent in the main motors 13c and 13d connected to the ground side from a reverse current blocking element without using such a dedicated overcurrent detector. It is.

An embodiment of the present invention shown in FIG. 2 will be described below.

The difference in Figure 2 from Figure 1 is that the primary windings 1 and 2
A DC current transformer 4 consisting of an i- and secondary winding 20 is further provided with a primary winding 3, and this secondary winding 3 is connected to the secondary windings 1 and 2.
The point is that the main motor 13d is connected only during power regeneration so that the current direction is reversed.

Fig. 3 shows a controller 5 and an overcurrent detector 61 in addition to the above Fig. 2.
This is an example in which a control device consisting of a control transformer 7 and a rectifier 8 is combined.

When the main motors 13a to 13d are running, the DC current transformer 4 detects the current of the main motors 13a to 13d and passes through the rectifier 8 to obtain a direct current proportional to the current. , that is, performs constant acceleration control of the electric vehicle.

When the power regenerative brake is normal, primary windings 1 and 2 are primary winding 3.
If the current direction is reversed, the current value flowing through the primary winding 1.2.3 is the same, and moreover, the ampere turns due to the current in the − secondary winding 1.2 and the ampere turns due to the current in the − secondary winding 3 are equal. Therefore, the output of the DC current transformer 4 is zero.

Considering the case where the main motor 13c is damaged, the primary winding 3
The current value of is larger than the current value of the primary windings 1 and 2, and this difference current value operates the overcurrent detector 6, opens the main circuit disconnector 11, and reduces the output of the field excitation power source 18. The main circuit current breaker 11 that carries the voltage is opened.

As described above, according to the present invention, it is possible to detect overcurrent without using an overcurrent detector dedicated to electric power regenerative braking as in the past, and since it is detected by the difference current, the fault current detection value Since the detection time delay can be set lower than that of the conventional method, it is possible to shorten the detection time delay.

This makes it possible to shorten the circuit open time in the event of an accident and keep the maximum value of the fault current low, which has various effects such as reducing damage to electrical equipment due to the fault current.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional overcurrent detection circuit, and FIGS. 2 and 3 are circuit diagrams showing an embodiment of the present invention. In the figure, 1.2.3 is the primary winding, 4 is the current transformer, and 13
A to 13d are main motors, and 15 is a backflow blocking diode. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 A current transformer consisting of first and second motor circuits connected by a reverse current blocking element, a first primary button and a secondary winding for detecting the currents of the first and second motor circuits. a second primary winding in said current transformer, said current transformer having a second primary winding in which current flows in the opposite direction to said first primary winding, and having the same number of windings as said second primary winding; When the number of turns is set to 1, the button is pressed during power regenerative braking, the second motor circuit is connected to ground through this second primary winding, and the second motor circuit is connected to ground through this second primary winding.
An overcurrent detection circuit characterized in that an overcurrent in the second motor circuit is detected by a differential current flowing between the primary winding and the second primary winding.