JPH0444515B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a commutation margin angle control method for a commutatorless motor.

In the control method of a commutatorless motor, a synchronous motor is energized by a cycloconverter consisting of multiple switching elements, and a commutation margin angle is required in principle to prevent commutation failure. Become. Conventionally, this has been expected to have a sufficient margin, since the failure of commutation may cause an accident such as a short circuit in the power supply, and for example, the set control advance angle has been set to about 60°. However, according to such a method of operating a commutatorless motor, the commutation margin angle becomes excessive at light loads, which causes a decrease in the apparent power factor and efficiency of the synchronous motor. For this reason, a method has been considered in which the setting control advance angle is controlled so that the commutation margin angle is always a constant value that is the minimum necessary value.

However, as mentioned above, delaying the set control advance angle may improve the apparent power factor, but the induced voltage may increase, causing a balance operation with the power supply voltage and reducing the motor speed. will result in This will be explained using a conventional example.

Figure 1 shows the general configuration of a conventional non-commutator motor, in which 1 is an AC power supply, 2 is a cycloconverter section, 3 is a synchronous motor, 4 is a speed detector, and 5 is a speed setting device. , 6 is a speed control circuit,
7 is a phase control circuit, 8 is a gate control circuit, 9 is a commutation margin angle detection circuit, and 10 is a setting control advance angle control circuit.

That is, in such a circuit configuration, the cycloconverter section 2 that energizes the synchronous motor 3 from the input of the AC power source 1 is an element section that performs switching operation from the gate control circuit 8 at the final output stage of the control circuit section. This is to obtain control commands for the this is,
Speed command signal from speed setter 5 and speed detector 4
The speed feedback signal of is given to the speed control circuit 6, a phase control angle command signal is generated from a calculation example of PID adjustment by the speed control circuit 6, and the phase control circuit 7 synchronizes with the power supply to adjust the phase control angle. A gate command signal is given at the corresponding timing.
Although a detailed explanation of the gate control circuit 8 will be omitted here, the switching element of the cycloconverter section 2 is controlled based on the rotor position signal of the synchronous motor 3 obtained by calculation from input signals such as a distributor and armature back electromotive force. It has a logic circuit section for selecting a switching element and a driving circuit section for a switching element, and sends a control command for driving a selected switching element to the cycloconverter section 2. Furthermore, in the commutation margin angle control, the setting control advance angle control circuit 10 that obtains the output signal of the commutation margin angle detection circuit 9 sends a setting control advance angle command signal so that the commutation margin angle is always within a certain range. is provided to the gate control circuit 8.

In such conventional commutation margin angle control, the margin angle is usually controlled to be as small as possible. Here, it is known that, assuming that the voltage induced at the motor terminals is V _M and the internal induced voltage is B _M , and ignoring the voltage drop due to internal resistance, the following equation holds.

V _M ∝E _M・cos(βo−μ/2)・cosμ/2 (1) where βo is the setting control advance angle and μ is the overlap angle. Therefore, according to the commutation margin angle control as described above, the value of βo is smaller than when the set control advance angle βo is fixed with a margin in advance, and the value of the induced voltage V _M is large. Become something. Note that the value of the overlap angle μ depends on the load current. In addition, in the electric power supplied to the synchronous motor 3, from the power supply voltage V _s and the phase control angle α,
The following relationship is known.

V _M ∝V _s・cosα …(2) In this way, when the induced voltage V _M increases with a decrease in the set control advance angle βo, the power supply voltage V _s is increased or the phase It is necessary to reduce the control angle α. However, the power supply voltage V _s usually cannot be changed freely. Also, the value of (cosα) can be increased by advancing the phase control angle α, but it cannot be made larger than 1, and if the phase control angle α advances to around 0°, the voltage supplied to the motor cannot be increased any further. . Note that field weakening, which reduces the field current of the motor, is used as a general method for controlling the induced voltage of the motor.

However, this method causes problems such as a decrease in output torque, an increase in motor speed at light loads, no reduction in induced voltage, and a lack of stability in control operation.

The present invention has been made with attention to the above-mentioned points, and in order to reduce the induced voltage without reducing the motor speed, the set control advance angle βo as shown in the relationship of equation (1) is advanced and cos ( This invention provides a special control method that reduces the value of βo-μ/2).

FIG. 2 is shown to facilitate understanding of the technical idea of the present invention, and shows the general configuration of a device similar to the device shown in FIG. 1, in which 10' is a setting control advance angle control circuit; 11 is a phase angle detection circuit. In the figure, the same reference numerals as in FIG. 1 indicate parts having the same function.

That is, the device shown above particularly includes a phase angle detection circuit 11 and a setting control advance angle control circuit 10' which obtains the output of the phase angle detection circuit 11 and operates to effectively advance the setting control advance angle. It is composed of Here, the principle method of commutation control and the method of driving the motor 3 of the same machine are as explained in FIG. Then, it is detected from the phase control angle command signal that the phase control angle α has reached its limit, and a signal is generated to the setting control advance angle control circuit 10'. The setting control advance angle control circuit 10' changes and sends a signal so as to advance the setting control advance angle command when the phase angle detection circuit 11 generates a signal, for example, when the phase control angle α reaches around 0°. Therefore, from the relationship in equation (1), the set control advance angle βo effectively becomes a large value, and an increase in the induced voltage of the synchronous motor 3 can be suppressed. In addition, in normal times when the phase angle detection circuit 11 does not generate a signal, the commutation margin angle detection circuit 9
This is similar to the apparatus shown in FIG. 1 in that the commutation margin angle is controlled to be within a constant range as small as possible based on the output. Here, the amount by which the set control advance angle βo is advanced must be prioritized between the amount to be advanced by the commutation margin angle control and the amount to be advanced by the aforementioned phase angle detection. This is important in preventing failure.

Therefore, a device based on this technical idea can be used without impairing the drive function of the motor by simply adding a simple phase detection circuit without providing a circuit for detecting induced voltage or field current. Furthermore, this circuit configuration makes it possible to effectively deal with a drop in power supply voltage and variations in the generation coefficient of induced voltage during motor manufacturing, thereby reducing the difficulty in designing and manufacturing specifications for commutatorless motors. It has the advantage of being relaxed.

As described above, according to the present invention, it is possible to provide a control method that can realize a simple device that monitors the power supply side phase control angle and changes the set control advance angle when the power supply side phase control angle reaches a predetermined value.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a general configuration of a conventional non-commutator motor, and FIG. 2 is a block diagram shown to facilitate understanding of the technical idea of the present invention. 2...Cycloconverter section, 3...Synchronous motor, 6...Speed control circuit, 7...Phase control circuit,
8... Gate control circuit, 9... Commutation margin angle detection circuit, 10, 10'... Setting control advance angle control circuit,
11...Phase angle detection circuit.

Claims (1)

[Claims] 1 In a method of operating a non-commutator motor in which a synchronous motor is energized by a cycloconverter that has the function of adjusting the commutation margin angle, when the power supply side phase control angle reaches a predetermined value near 0° in the power running region, A commutation margin angle control method for a commutatorless motor, characterized in that a set control lead angle is made larger than a current value.