JPS649831B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pre-excitation device for starting and braking a DC series motor.

FIG. 1 shows a DC series motor equipped with a conventional pre-excitation device. In the figure, 1 is a DC power supply, 2 is a main circuit on/off switch that closes only during power running, 3 is a main circuit on/off switch that is closed during power running and braking, 4 is a side switch for current reducing resistor 5, and 6a , 6c is a forward rotation switch, 6b, 6d
6 is a reverse switch, and 6a to 6d collectively form a forward/reverse switch circuit. Also, 7 is the series field winding of the motor, 8 is the armature of the motor, and 9 is the motor's armature.
is the main resistor, 10 and 11 are brake closing switches,
12 is a field shorting switch, 13 is a pre-excitation switch, 14a to 14d are rectifying elements, 15 is a pre-excitation insulating transformer whose primary side is connected to an AC power supply, and 16 is a pre-excitation current limiting resistor.

When the electric motor rotates in the forward direction, the forward rotation switches 6a, 6 are activated, regardless of whether it is during power running or during braking.
c is closed. On the other hand, when reversing, regardless of whether it is powering or braking, the reversing switch 6
b, 6d are closed.

Consider the case where the switches 6a and 6c are closed for normal rotation. During power running, switches 2, 3, and 4 are closed, as shown in FIG. The field shorting switch 12 is a normally closed contact and is also closed. On the other hand, switches 10, 11, 13
is open.

To stop the motor, first, the current reducing resistor bypass switch 4 is opened, then the main circuit on/off switches 2 and 3 are opened, and the motor is disconnected from the DC power supply 1. At the same time, the field short circuit switch 12 is opened. Next, the brake closing switches 10 and 11 are closed. Subsequently, the pre-excitation switch 13 is closed,
Pre-excitation is started. The purpose of pre-excitation is to improve the rise of the dynamic braking torque. Switches 3 and 4 are turned on after a predetermined time from the start of pre-excitation.
is closed and dynamic braking begins.

When the rotational speed of the motor is reduced to a predetermined value by dynamic braking, the field shorting switch 12 is closed and field shorting is started. As a result, the dynamic braking force rapidly decreases. This procedure is effective in reducing the shock associated with the transition from dynamic braking to pneumatic braking when the motor is used as the main motor of an electric vehicle or the like.

When the braking is finished, the field shorting switch 13 and the main circuit switches 3 and 4 are opened. When starting the next power running operation, the brake closing switches 10 and 11 open,
Next, switch 4 is closed, followed by switches 2 and 3.

The operation of each switch as described above is controlled by a known control device.

Since the forward/reverse switching circuits 6a to 6d are used not only during power running but also during dynamic braking, the number of switches can be reduced. In other words, the usage rate of the switch increases.

However, in the above circuit configuration, if the pre-excitation switch 13 closes due to welding or malfunction during power running, an excessive current flows from the power supply 1 to the armature 8 through the switch 13 and the rectifier circuits 14a to 14d, causing the motor to flash. This may lead to further accidents such as overflow or destruction of the rectifier.

SUMMARY OF THE INVENTION An object of the present invention is to provide a pre-excitation device that does not cause flashover of the motor or destruction of the rectifying element.

FIG. 3 shows an embodiment of the pre-excitation device of the present invention. The difference from the pre-excitation device shown in FIG. 1 is that the outputs of the rectifier circuits 14a to 14d are supplied to the field winding 7 not only through the pre-excitation switch 13 but also through the brake closing switch 11. The point is that it is becoming more and more common. That is, as shown in the figure, the negative DC output terminal N of the rectifier circuit is connected to the connection point of the switches 11 and 12 via the switch 13. A series circuit of switches 11 and 12 is connected between the connection points of switches 6a and 6b and between the connection points of switches 6c and 6d, and the positive DC output terminals P of rectifier circuits 14a and 14d are connected through a current limiting resistor 16. The fact that it is connected to the connection point of the switches 6a and 6d is the same as in the case of FIG. Although not shown in Fig. 3, the power supply 1, switches 2 to 4, 10, current reducing resistor 5, armature 8, and main resistor 9 in Fig. 1 are the same as in Fig. 1. It is connected.

If the connection shown in Fig. 3 is adopted, even if an accident such as closing of the pre-excitation switch 13 due to welding or malfunction occurs during power running, the switch 11 for closing during braking will remain open, so that the switch 11 shown in Fig. 1 An excessive current (flowing from the DC power supply 1 to the armature via the rectifier circuit) as in the case does not flow. Therefore,
There is no risk of causing further accidents such as flashover of the electric motor or destruction of the rectifying element.

According to the present invention, the output terminal of the rectifier circuit is connected to the field winding via the pre-excitation switch and the closing switch during braking, so that even if the pre-excitation switch is used during power running, there is no possibility of welding or malfunction. Therefore, even if the circuit is closed, the rectifier circuit is prevented from being connected to the circuit, thereby preventing flashover of the motor and destruction of the rectifier circuit.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of a DC series motor equipped with a conventional pre-excitation circuit, Fig. 2 is a time chart showing the operation of each switch in Fig. 1, and Fig. 3 is an implementation of the pre-excitation device of the present invention. FIG. 3 is an example wiring diagram. 6a to 6d...Forward/reverse switching circuit, 7...
...field winding, 8...armature, 11...braking closing switch, 12...field short circuit switch, 13...
... Pre-excitation switch, 14a-14d... Rectifier circuit, 15... Pre-excitation power supply transformer, 16...
...Current limiting resistor.

Claims (1)

[Claims] 1 Pre-excitation device for a DC series motor in which a series circuit of a braking closing switch that closes during pre-excitation and dynamic braking and a field short-circuit switch that closes when a field short-circuit is connected in parallel to the field winding. , one of the pair of output terminals of the rectifier circuit whose input terminal is connected to the AC power source is connected to the midpoint side of the connection between the field short circuit switch and the brake closing switch via the pre-excitation switch. The preliminary excitation device is connected to one end of the field shorting switch located at the field shorting switch, and the other of the pair of output terminals is connected to the other end of the field shorting switch.