JPS5854755B2 - Generating brake device for AC series-wound commutator motor - Google Patents

Description

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

For electric motors for power tools such as circular saws, switch O
There is a legal requirement that the brake system must stop within 10 seconds after FF, and when this switch is set to 011, the brake system generally uses an electric motor as a generator to convert the rotational energy of the armature into electrical energy. , a dynamic brake that performs a braking action using the armature reverse rotation force at that time is 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 at the time of switch 011 is utilized.

When the above self-exciting type dynamic brake device is used in an AC commutator motor, the dynamic brake may not function even if the switch is turned off.

In other words, since the current is alternating current and draws a sinusoidal waveform as shown in Figure 1, the residual magnetism changes as the current changes, drawing a hysteresis curve, and becomes centered around the zero of the sinusoidal waveform of the current. In the phase range t1, the residual magnetism cannot contribute to the braking action or is zero. Therefore, even if the switch is turned OFF and the power is cut off in this phase range t1, the motor does not function sufficiently as a generator, and the motor cannot function as a dynamic brake. It serves no purpose.

In particular, in the case of a multi-phase series-wound commutator motor, currents of the same phase flow through each field winding, so if the residual magnetism in the - field winding is small, the residual magnetism in the other field windings also increases. Similarly, the number of brakes was small, and it was not possible to perform a dynamic braking action.

As mentioned above, the self-excited dynamic braking device used in AC series-wound commutator motors has the disadvantage that the brake does not work once every few times, and although it is extremely dangerous, The reality is that it is sold commercially as it is because there is little of it.

The present invention aims to eliminate the above-mentioned conventional drawbacks, and therefore detects the operating current of the electric motor, and detects the phase in which residual magnetism cannot contribute to the braking action by detecting the operating current of the motor and communicating from the phase detection means when the switch is 011. A brake circuit is formed by cutting off the power supply outside the range t1, so that the power generating brake can always be applied no matter when the switch is set to 0FFt.

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

The circuit diagram in Figure 2 shows an embodiment of the present invention in the basic type of an AC series-wound commutator motor.
To explain using the block diagram shown in the figure, 1 is an armature winding of a motor, 2 is a field winding, and 3 is a power source.

Reference numeral 4 denotes a phase detection means provided to detect the phase of the operating current of the motor, and this phase detection means 4 may be constructed using a well-known phase detection circuit or the like.

Reference numeral 5 denotes a brake circuit forming means, and the brake circuit forming means 5 and the phase detecting means 4 are connected so that the phase detected by the phase detecting means 4 can be communicated to the brake circuit forming means 5.

When the switch (not shown in FIG. 2) is turned OFF, the brake circuit type means 5 receives the communication from the phase detection means 4 and detects that the residual magnetism is outside the phase range t1 in which the residual magnetism cannot contribute to the braking action. It is configured to form a brake circuit by cutting off the power source 3 within a phase range t2 that can contribute to the action.

This brake circuit type means 5 may be constructed from a well-known control circuit, changeover switch, and other electronic components.

In the present invention having such a configuration, the phase of the operating current of the motor is detected by the phase detection means and communicated to the brake circuit forming means.

Then, when the switch is set to 0FFL to stop the electric motor, the brake circuit type means receives communication from the phase detection means, and when the phase at the time of switch OFF is within the phase range t1 in which residual magnetism does not contribute to the braking action, ,
At the same time, the current is passed for a moment without turning off the power,
When the phase is outside the phase range t1, that is, when the phase reaches the phase range t2 in which the residual magnetism can contribute to the braking action, the power is cut off and a brake circuit is formed.

Furthermore, the time during which the current continues to flow when the switch is OFF is as follows:
This is a very short time until the residual magnetism reaches a phase outside the phase range t1 that does not contribute to the braking action.

Further, if the phase when the switch is turned off is outside the phase range t1 in which no braking action can be performed, the power is cut off at the same time as the switch is turned off, and a brake circuit is formed.

As described above, the present invention detects the phase of the operating current of the motor using the phase detection means, and when the switch is turned off, the brake circuit forming means is operated outside the phase range in which residual magnetism does not contribute to the braking action to cut off the power supply to the brake circuit. Therefore, no matter at what point the switch is turned OFF, the residual magnetism at the time of actual power shutoff can sufficiently contribute to making the motor work as a generator, causing a dynamic braking action. It can be done reliably, the brakes can always be fully applied, and it is highly safe.

As described above, the present invention is an excellent invention as a dynamic braking device for an AC series-wound commutator motor, which can solve the conventional drawback that the brake sometimes does not work.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram of an alternating current, FIG. 2 is a circuit diagram showing an embodiment of the present invention in a basic type of electric motor, and FIG. 3 is a block diagram of the device of the present invention. DESCRIPTION OF SYMBOLS 1... Armature winding of electric motor, 2... Field winding, 3... Power supply, 4... Phase detection means, 5... ...brake circuit forming means, tl...
...Phase range in which residual magnetism does not contribute to power generation braking, t2 ...Phase range in which residual magnetism can contribute to power generation braking.

Claims (1)

[Claims] 1 In a dynamic braking device for an AC series-wound commutator motor that performs dynamic braking using residual magnetism generated in a field winding, a phase detection means for the operating current of the motor and a switch 011 are used.
and means for forming a brake circuit by cutting off power outside the phase range in which residual magnetism cannot contribute to braking action in response to a communication from a phase detection means.