JPS596594B2 - Generating brake device for AC commutator motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dynamic braking device for an AC commutator motor.

For electric motors for power tools such as circular saws, switch O
There is a regulation that states that the brake must stop within 10 seconds after the switch is turned off. Generally speaking, when the switch is turned off, the brake device operates by using the electric motor as a generator to convert the rotational energy of the armature into electrical energy. Generating brakes, which perform braking action using the armature's reverse rotational force, are often used.

There are two types of dynamic brakes: a separate excitation type in which the field is generated by a separate power source, and a self-excitation type in which the residual magnetism is utilized when the switch is turned off. When the above-mentioned self-exciting type dynamic brake device is used for a DC motor, no problem will occur in the braking action, but when used for an AC commutator motor, the dynamic brake will not work even if the switch is turned off. may not work. That is, the current is alternating current and the first
In order to draw a sinusoidal waveform as shown in the figure, the residual magnetism changes as the current changes, drawing a hysteresis curve. Even if the switch is turned off within this range, the residual magnetism is small or zero, so the motor does not function as a generator and does not function as a dynamic brake. In particular, in conventional AC commutator motors, the field windings of both poles are connected in series, so currents of the same phase do not flow in both field windings, and the residual magnetism changes at both poles simultaneously. When the switch is OFF, if the residual magnetism of one pole is small, the residual magnetism of the other pole is also small, making it impossible to perform a dynamic braking action. Also, the field windings of both poles have the same number of turns. Therefore, even if the field windings are connected in parallel, the impedance is the same and currents with the same phase flow, and similarly to the above, residual magnetism is small and dynamic braking cannot be performed. Something happened. As mentioned above, the self-excited dynamic braking device for AC commutator motors has the disadvantage that the brakes will not work once every few times, which is very dangerous. The reality is that it is sold as is because it is so rare.

The present invention was invented to solve the above-mentioned conventional drawbacks, and consists of an armature having windings, a field winding having a pair of magnetic poles, and a structure in which the armature and both field windings are normally During operation, the field windings of both poles are connected in series with the power supply, and when dynamic braking is applied, the field windings of the two poles are connected in parallel to each other. connection,
The connection configuration is such that a phase difference is created between the currents flowing in each pole, so that even if the residual magnetism due to the field winding of one pole is small, residual magnetism will be generated by the current flowing to the field winding of the other pole. The present invention is characterized in that the power generating brake can always be applied even if the switch is turned off at any point in time.

Next, embodiments of the present invention will be described with reference to the drawings.

In Figure 2, which shows the circuit diagram of an AC commutator motor, 10
is a power source, Ar is an armature with windings (hereinafter simply referred to as armature) 1} and 2 are field windings connected in parallel to one side of the power source 10, . L, , Rl are the inductance and resistance of one field winding 1, and L2 and R2 are the inductance and resistance of the other field winding 2. These field windings 1 and 2 are arranged at corresponding positions centering on the electric snore Ar as shown in FIG. 3, and have corresponding NS and NS poles. Sw is a changeover switch connected to the electric snore Ar, and when this changeover switch Sw is connected to the terminal 3 connected to the field windings 1 and 2 and the terminal 4 connected to the other side of the power source 10, When connected to side A in the figure, armature Ar and field windings 1 and 2 are connected in series to power supply 10 for normal operation, and changeover switch Sw is connected to power supply 10 and field windings 1 and 2 in series. When connected to the terminal 6 connected to the field windings 1 and 2 through the terminal 5 and terminal 3 provided between the field windings 1 and 2,
That is, when connected to the B side in the figure, a dynamic braking circuit is constructed in which the armature Ar and the field windings 1 and 2 are connected in series with the power supply 10 in a disconnected state, thereby performing a dynamic braking action. R is an external resistance for adjusting the braking time, and is provided to prevent the brake from being too effective and causing recoil when the resistance of the field windings 1 and 2 is used alone, which can be dangerous when dynamic braking is applied. . Therefore, the present invention provides a phase difference between the currents flowing in the field windings 1 and 2 of the corresponding two poles, and specifically, for example, By setting the number of turns to 100 turns and setting the number of turns of field winding 2 of the other pole to 80 turns, and changing the number of turns of both field windings 1 and 2, the impedance is made different and a phase difference is created in the current flowing in each. It is something that causes something to happen.

Alternatively, as shown in the circuit diagram in Figure 4, by connecting a special reactance or capacitor C to the field winding 1 of one pole, the impedances of both field windings 1 and 2 are made different. A phase difference can also be provided to the V1 current.

The phase difference θ is set so that the ranges Tl and t2 in which the residual magnetism created by the respective field windings 1 and 2 are so small that they cannot contribute to the dynamic braking action or are zero do not coincide.

Note that providing a phase difference between the currents flowing in the field windings 1 and 2 of both poles can be performed by other possible means in addition to the above embodiment.

The present invention is constructed as described above, and a phase difference θ is provided between the currents flowing through the field windings 1 and 2 of the corresponding two poles.
As shown in Fig. 5, the current a flowing through the field winding 1 of one pole
On the other hand, the field winding 2 of the other pole has a current b that lags behind this.
Therefore, even if the point in time when the switch is turned 0FF is within the range T, where the residual magnetism created in one field winding 1 is small or zero and cannot contribute to the dynamic braking action, the remaining magnetism in the other field winding 1 is The residual magnetism created by winding 2 can sufficiently contribute to making the motor work as a generator.
The dynamic braking action can be performed reliably and the brakes can be applied completely.

Contrary to the above, even when the switch is turned off in range T2 where the residual magnetism created by the field winding 2 cannot contribute to the dynamic braking action, the residual magnetism created by the other field winding 1 is used. Therefore, it is possible to reliably perform the electric braking action in the same manner as above. As described above, the present invention provides a phase difference between the currents flowing to the corresponding poles, so that even if the residual magnetism from the field winding of one pole is small or zero, the field winding of the other pole The flowing current can generate enough residual magnetism to cause the motor to act as a generator, so at what point should the switch be turned off?
This invention is an excellent invention that can eliminate all the drawbacks of the conventional electric braking device for AC commutator motors, such as being able to always apply a complete brake even when the brakes are turned off and being safe.

[Brief explanation of the drawing]

Fig. 1 is a waveform diagram of alternating current, Fig. 2 is a circuit diagram showing an embodiment of the present invention, Fig. 3 is a layout diagram of field windings, Fig. 4 is a circuit diagram showing another embodiment, Figure 5 shows a waveform diagram of the current flowing through the field windings of both poles. Ar...armature, 1, 2...field winding, Sw...
Changeover switch, Tl, t2...A range in which residual magnetism cannot contribute to power generation braking.

Claims (1)

[Claims] 1. An armature having a winding, a field winding of a pair of magnetic poles, and the armature and both field windings connected in series with a power supply during normal operation. In addition, in a dynamic braking device for an AC commutator motor, which is equipped with a changeover switch that is disconnected from the power source and connected to form a dynamic braking circuit when dynamic braking is applied, the field windings of the two poles are connected in parallel with each other. , a dynamic braking device for an AC commutator motor, characterized in that the connection configuration is such that a phase difference is provided between the currents flowing through each of the motors. 2. A dynamic braking device for an AC commutator motor according to claim 1, wherein the impedances of the field windings of the two poles are different to provide a phase difference. 3. A dynamic braking device for an AC commutator motor according to claim 2, wherein the impedance is made different by changing the number of turns of the bipolar field windings. 4 Claim 2 in which a reactance or a capacitor is connected to the field winding to make the impedance different.
A dynamic braking device for an AC commutator motor as described in Section 1.