JPS60141187A - Set control lead angle controlling method of commutatorless motor - Google Patents

Abstract

PURPOSE:To prevent the commutation failure of a cycloconverter type power converter by setting the value of a set control lead angle to the prescribed fixed value when the output frequency of a synchronous motor is operated near one divided by an integer number of the frequency of a power source. CONSTITUTION:When the output frequency of a motor is operated near one divided by an integer number of the frequency of a power source in the operation of the motor, the set control lead angle is set to the prescribed value under no condition. Thus, it prevents the effective control lead angle from being set to small value more than required. The detection of the output frequency of the motor can be readily obtained from the rotating speed of the motor, and the value of one divided by an integer number can be simply calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a setting control advance angle control method based on the minimum commutation margin angle setting of a cycloconverter type power converter in commutatorless WaS operation.

Conventionally, in the operation of an AC non-commutator motor that drives a synchronous motor using a cycloconverter type power converter, the commutation margin angle is set to the necessary minimum in order to improve the motor's power efficiency and torque efficiency. It is well known to employ a method of narrowing down the settings to the limit, and in order to realize setting control advance angle control of this type of commutatorless motor, means for detecting the commutation margin angle in the operating state of the motor is used.

However, in the case of AC non-commutator motor operation,! # In addition to load commutation using the back electromotive force of the machine, IjLg! from the conditions on the AC 'Ia source side! , Since the commutations are superimposed, it is usually difficult to detect the commutation margin angle at the full speed of the motor.

In view of the above-mentioned points, the present invention provides a method that can realize a device that can particularly prevent commutation failure without obtaining accurate detection of commutation margin angle. Hereinafter, the present invention will be explained in detail based on the drawings.

Figures 1 and 2 show the relationship between the t source voltage and the motor induced voltage. Figure 1 shows an example when the power supply frequency and motor output frequency match, and Figure 2 shows the relationship between the motor output frequency and the motor output frequency. An example that is different from - for an integer number of frequencies is shown. In the figure, s VRe Vs + VT is the phase voltage s v of the three-phase power supply.
ow #vuv' is the line voltage of the motor induced voltage, β is the effective control advance angle, μ is the overlap angle, and r is the commutation margin angle. Here, a state is shown in which commutation is performed from 8 phases to 8 phases on the power supply side during a period when load commutation is performed from U phase to V phase.

In addition, since the power source impedance is generally extremely small compared to the internal impedance of the motor, the commutation time due to power source commutation is short and the overlap angle (μ2) required for load commutation is short.
) Of course, the commutation can be completed with a smaller overlap angle (μX) than in the case of

Now, when the motor output frequency, that is, the motor rotation speed, and the power supply frequency match, as shown in Fig. 1, if the power supply commutation is performed continuously during the load commutation, the commutation margin angle γ1 due to the power supply commutation is larger than the commutation margin angle r for only load commutation due to the above-mentioned relationship between the overlap angle μm and -:.

For this reason, if commutation margin angle control is executed that detects the commutation margin angle and sets the set control advance angle based on that value, the commutation margin angle detection value must be checked several times in succession. This means that even if the commutation margin angle γ1 is detected, the set control advance angle is set to a small value. It is clear that this effect is similar even when the motor output frequency is an integer fraction of the power supply frequency.

In addition, when the motor output frequency differs by an integer of the power supply frequency, as shown in Figure 2 (the overlap angle due to power supply commutation is smaller than the overlap angle μ due to load commutation, the commutation margin is The angle rl has a value larger than the commutation margin angle r!, and therefore the commutation margin angle r2 due to load commutation cannot be detected correctly.

However, if we now consider the case where the motor output frequency is not operated near an integer fraction of the power supply frequency, the probability that power supply commutation will occur during load commutation in the next cycle is significantly reduced. In the commutation margin angle control by detecting the commutation margin angle, the set control advance angle is normally operated after checking several times in succession, so commutation failure does not occur due to the influence of power supply commutation.

Here, regarding such a conventional setting control advance angle control method, a case where power commutation is performed during load commutation and commutation fails because the setting control advance angle is made small will be explained with reference to FIG. do.

FIG. 3 shows the state of each motor induced voltage and represents the relationship between the commutation margin angle and the effective control advance angle 9 overlap angle.

Fig. 3(a) shows an example of a state in which there is no influence of power supply commutation, where the commutation margin angle r) is narrowed down to the minimum necessary value, and the effective control advance angle β0 is smaller than the overlap angle μ0. This shows a state in which the commutation margin angle r is maintained.

Figure 3(b) shows an example of a state in which power supply commutation is performed during load commutation, and the effective control advance angle is set to β8 in order to maintain the commutation margin angle r. Overlapping angle μ
It is clear that S is smaller than the overlapping angle μ· shown in FIG. 3(a).

FIG. 3(C) shows an example in which power commutation is no longer performed during load commutation from the state shown in FIG. 3(b), for example. In other words, this is an example in which the overlap angle is increased instantaneously and transferred from the overlap angle μS to the overlap angle μ0, and as a result, the commutation margin angle γ0 is reduced to the commutation margin angle r8, causing a commutation failure. It is clear that this will happen.

The present invention has been made with this point in mind, and the technical idea of the present invention can be summarized as follows.

In other words, when the motor is operated with the motor output frequency close to an integer fraction of the power supply frequency, the set control advance angle is set to the minimum necessary small value based on normal commutation margin angle detection. The purpose is to solve this problem and set a fixed value of, for example, 60', which allows commutation even at maximum load.

The present invention is based on the biased technical concept, and by detecting the integer fraction of the motor output frequency and unconditionally setting the set control advance angle to a predetermined value, the effective control advance angle is increased more than necessary. This prevents it from being set to a small value.

Here, detection of the motor output frequency can be easily obtained from the motor rotation speed, and the negative value of the integer can be easily calculated. In general, commutatorless motors that perform commutation margin angle control are equipped with a device that can detect the rotational speed P7 of the motor, and are further equipped with a control system that operates the set control advance angle. Therefore, it is clear that it is possible to easily add a fixed value setting control advance angle command as described above.

As explained above, according to the present invention, it is possible to provide a control method that can realize a simple device that utilizes a novel setting control advance angle control that can prevent the occurrence of commutation failure.

[Brief explanation of the drawing]

Figures 1, 2 and 3 are shown to facilitate understanding of the present invention; Figures 1 and 2 are waveform diagrams showing the relationship between power supply voltage and motor induced voltage; is a waveform diagram showing the relationship between the commutation margin angle and the effective control advance angle 1 overlap angle. ■R9v8. vT... Phase voltage of three-phase power supply, vu
v t VUV' +■υVl e VUV* l v
U ys・・・Line voltage of motor induced voltage, β・
...Effective control advance angle, μ...Overlap angle,
r... Commutation margin angle. Fan 1 Figure 2 Figure 3

Claims (1)

[Claims] A cycloconverter type power converter, which is made up of a plurality of switching elements connected to the armature windings of a synchronous motor with A bias, minimizes the commutation margin angle that energizes the armature windings of the synchronous motor. In a setting-based lead angle control method for a non-commutated motor that controls the setting control lead angle to 1. A setting control lead angle control method for a non-commutated motor, characterized in that commutation failure of the cycloconverter type power converter is prevented by setting the value to a predetermined fixed value.