JPS59110392A - Speed control circuit for commutatorless motor - Google Patents

Abstract

PURPOSE:To improve the low speed operating performance of a synchronous motor in the speed control of the motor by applying the output of a power reactor through a DC reactor to a power inverter by obtaining a feedback command signal to the converter by detecting the current flowed to the reactor. CONSTITUTION:The output of a 3-phase AC power source 1 is applied through a power reactor 2 and a DC reactor 3 to a power inverter 5, and a synchronous motor 6 is driven by the output of the inverter 5. A current detector 9' is connected in series with the reactor 3. A speed control circuit 8 inputs a set rotating speed signal N*, and the fed back rotating speed signal N frequency-to- voltage-converted by a converter 7' from the output of a distributor 7 and outputs a speed control signal NC to a current control circuit 10. The circuit 10 controls the converter 2 through the output of the detector 9 and a phase controller 11. The signal output NR of the distributor 7 fires the thyristor of the converter 5 through a phase controller 11'. A low/high speed discriminator 12 discriminates by the signal N to control the controller 11 and a circulating thyristor 4. In this manner, the low speed operating performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a speed control circuit for a commutatorless motor that can obtain DC reactor current, improve current control characteristics, and significantly improve low-speed operation performance.

Conventionally, in the operation control of non-commutated motors, the DC voltage applied to the inverter in the low rotational speed range such as during startup is intermittently passed as zero voltage every 60 degrees of electrical angle of the motor. Generally, a combination method is used in which two types of commutation methods are used: one is commutating the silicate, and the other is so-called load commutation, in which the silicate of the inverter is commutated by the back electromotive voltage of the motor in the high speed range. .

Figure 1 shows a typical configuration of 11 circuits for conventional non-commutated dL motor speed control.
is an IIU converter for converting three-phase alternating current to direct current, 3 is a direct current reactor to reduce the current pulsation of the forward converter 2 output, 4 is a cyrisk for circulation, and 5 is for converting direct current to three-phase alternating current. 6 is a synchronous motor. Further, 7 and 7' are a frequency-voltage converter that converts the output of the 2-distributor 7 into a signal, which is connected directly to the rotating shaft of the synchronous electric Isochiki to detect the rotor position, 8 is a speed control circuit, and 9 is a main circuit. a current detector for detecting the input terminal; 10 is a current control circuit;
11°11' is a forward converter 2. Phase control circuits for driving the thyristors, which are the main control elements of the inverter 5, 12 a low/high speed discrimination circuit, and 13 a gate circuit for the free-circulation thyristor 4.

Such a circuit configuration is well known and detailed explanation will be omitted, but its speed control system is as follows. In other words, the speed control circuit 8 converts the set rotational speed signal N5 output from the divider 7 into the frequency-voltage converter 7. The feedback rotational speed signal N converted into a DC voltage via The control circuit 10 inputs the main circuit current signal Is of the speed control circuit 8 output and the current detector 9 output, and the phase control (H number 8o) of the current control circuit 10 output is given to the phase control circuit 11. That is, by controlling the phase of the forward converter 2 according to the set rotation speed, the DC voltage of the forward converter 2 is obtained to control the rotation speed.

Also, the signal output NR of the distributor 7 is
1' becomes an input signal, and by controlling the set control advance angle, the side risk of the inverter 5 is ignited. Here, as mentioned above, it is impossible to commutate the iris 41 of the reverse variable J converter 5 using the back electromotive voltage of the motor at low rotational speeds such as during startup. For this reason, the frequency voltage converter 7
'The low/high speed discrimination circuit 12 is activated depending on the level of the output. In other words, the low/high speed discrimination circuit 12 obtains the feedback rotation speed signal N and discriminates the low speed region or the high speed region. Especially in the low speed region, the signal output NB of the distributor 7 indicates that the synchronous motor 6 is The signal is passed through the phase control circuit 11 to make the current voltage negative and commutate the sirisk of the inverter 5. At this time, the forward converter 2 is fired because the set control advance angle is close to 180°.

Furthermore, the effect of the DC reactor 3A and the return current cyrisk 4 connected in parallel to the DC reactor 3 will be explained with reference to FIGS. 8+42 to 4.

Here, 2C is a simplified representation of the main circuit part in Figure 1, E8 is a DC voltage source, L is a reactance,
EM indicates the leakage reactance, and EM indicates the visiting voltage source. FIG. 2 shows a state in which a 7if flow flows through one phase of the inverter 5 and the synchronous motor 6.

In addition, this is the inverter 5 and the synchronous voltage! I? Although the resistance of JI machine 6 has been omitted, it does not lose its lethality. Based on the following simplified circuit diagram, we will now explain the case where the gate signal Pa of the forward converter 2 is fired near 1800 as described above, and the reflux thyristor 4 is made conductive at the same time. , consider the current flowing through the DC reactor 3, that is, the reactance L filj.

First, the current ID is as shown in Figure 3, and its waveform is set to 4 periods (1, 1, 1, This is the period until it decays to zero, and J! ill″jJ
I is the zero period of the current In, and period 2 is a period until the current II3 rises and becomes equal to the current IL. 1112 can be expressed as shown in Figure 41 (a), (b), and (c) by the signal flow between these Jt'J.

Here, during the period (2), equation (1) is established as a circuit equation from FIG. 4 (a). This current ID flows through the DC reactor 3 and the synchronous motor a6.

Then, for the period, that is, in FIG. 4 (0), the gate control on the forward converter 2 side is set to close to 1800, so the negative power is turned on, and the reflux thyristor 4 becomes conductive, so the DC reactor 3 part becomes short-circuited. be. The current ID at this time is expressed as follows. However, the value ID is the main circuit current value at the moment when the game Ha PG is turned on, and the current ID is the value In.

will be reduced over time. moreover,
In the period mark, the current ID is zero.

Also, in period ■, that is, in FIG. 4 (c), the forward converter 2 side changes to a positive voltage (4), (
! It is shown as equation 31.

1'+B EM = 212 ・ID --
-.(41t) Furthermore, since the current IL is passed by the free-wheeling thyristor 4 (7!), the potential difference ΔV across the reactance L becomes zero, as shown in FIG. 4). That is, the current IL flowing through the DC reactor 3 is kept at a constant value ID, ignoring the forward voltage drop of the freewheeling thyristor 4. Note that the current ID in equation (5) above is (ID
> IDO), the reflux thyristor 4
is extinguished and DC reactor 3 is inserted (
1) The process of establishing the formula is repeated. Further, in the high speed region, the reflux thyristor 4 remains non-conductive.

In this manner, in the non-commutator motor operation, the waveform of the detected current differs due to the system that changes the commutation of the inverter 5 depending on the speed of the motor. This is shown in FIG.

FIG. 5 shows the waves of the raw circuit power current of the equipment shown in FIG. 1, and I8L*Isu is the main circuit current signal in the low speed region and high speed region. In other words, since the main circuit current at low speeds commutates the inverter 5, it is in the intermittent current mode as described above, and there is a zero level for several milliseconds every 60 degrees of electrical angle of the motor. The main circuit current has a continuous waveform with no dips at low speeds. The main circuit current is the same when viewed from the long sword side of the forward converter 2. Note that the gate signal P shown in FIG.

To obtain this, the rising edge is assumed to be synchronized with the signal from the distributor 7, and the falling edge is selected by determining the energization time after a certain period of time has elapsed from the rising edge, or after detecting that the main circuit current reaches a peak. It was supposed to be done.

Therefore, according to such commutatorless motor operation,
It can be said that it has the following problems.

In other words, in the conventional system, a speed control system that obtains detection currents with different waveforms depending on the high and low rotational speeds as shown in No. 115<1 is used, and at low rotational speeds, a book return input of 19F continuous current is obtained. Assuming that the set rotational speed signal N'', the feedback rotational speed signal N, and the speed control signal Nc are constant values at the time of speed command, since the main circuit's current flow rate I3 is given by the continuous current value rJi, the current In principle, the control circuit 10 was supposed to receive a command that could not be delivered as the deviation input. Therefore, due to fluctuations in the main circuit current, in extreme cases, the thyristor Aoi of the inverter 5, etc. It was a cause of destruction.

In view of the above-mentioned points, the present invention provides a device that allows the same control in the low-speed range as in the high-speed range to be effective. To further summarize its main point, it is based on the technical concept of feeding back the current signal flowing through the DC reactor section to the current control circuit section.

And, with this cut out, the first illustration is a one-pointed hi similar to bamboo.
An example of li is shown in FIG. That is, 7'r
In the diagram, 9' is a current detector connected in series with the DC reactor 3, and the main circuit current signal s' output from the current detector 9' can be input to the current control circuit 10. The features of this device will be described below with reference to the waveform diagram shown in FIG.

That is, in the case shown in Fig. u56, the main circuit current signal Is' is obtained as the main circuit current signal st at low speeds, as shown in Fig. 7, and is obtained as the main circuit current signal l5ffi at high speeds. becomes. In this manner, the waveform of the feedback 61U during low-speed rotational speed operation can be obtained as being significantly modified compared to the conventional main circuit type 61 signal I8L shown in FIG. This is remarkable when considering the difference in the operation of the current control circuit 10.

Now, considering the effects of the current control circuit 10,
(No - Is) or (N
The purpose is to obtain a phase control signal So as a result of signal adjustment, so-called proportional, fractional, integral, etc. calculations for the Is) value. This means that, as is clear from the waveform of the main circuit current signal sL', there is no dip period 2 that appears in the main circuit current signal I8L, so the function of the current control circuit 10 can be sufficiently performed. means. Further, this will be explained in detail using FIG.

Fig. 8 is shown to explain the difference in the current control circuit section, in which (a) shows the waveform obtained by the first fixed device method, and (b) shows the waveform obtained by the sixth fixed device method. Toy No. 3 Pd is shown.

In Fig. 8, if we consider the sections A, B, and C that are divided into one cycle of Pd (K) (d),
Between the waveforms shown in Fig. 8(a) and (b), there is an interval A.
, I3 are different and the interval C is the same. In section A, the gate signal pd is on, and the current command value during this period is ultimately rejected by the phase control circuit 11, so that no actual difference in control occurs.

Here, what should be noted is the difference in section 0, which is the key to the command of the phase control circuit 11.

It is clear that the current level in section C is the current value of the current feedback signal, and that the command is at a fairly high level in section B in FIG. 8(a). Therefore, as a result of sending out a command with a large current value, problems such as increased operating noise occur. Furthermore,
It becomes impossible to improve the control accuracy of the rotational speed, resulting in torque fluctuations and thyristor failure. On the other hand, in the case shown in FIG. 8(b), there is almost no level difference between sections B and C, and the above-mentioned problem does not occur.

The gist of this approach is that in a DC non-commutated electric motor, the change in main circuit current due to thyristor commutation in the inverse converter is not essential information for speed control, but the information is used in low speed operation IMI. The reason lies in the realization of a circuit configuration that does not incorporate

As explained above, according to the present invention, it is possible to provide an exceptional device with improved current control characteristics and significantly improved low-speed operation performance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing four typical components of the conventional example, and FIGS. 2, 3, and 4 are simplified circuit diagrams shown to explain the effects of the DC reactor and reflux thyristor.
Waveform diagrams and flow charts for each part, Figure 5 is a main circuit current waveform diagram during low-speed operation 114 and high-speed operation according to Figure 1, Figures 6 and 7 are 4i'7 configuration of an actual hhi example according to the present invention. Block lt, I and its main circuit current waveform diagram showing 8th
The figures are waveform diagrams to explain the differences in the current control circuit parts.
Freewheeling thyristor, 5...Inverse converter, 6...Synchronous motor, 8-... -Speed control 1 circuit, 9,9'-
Current detector, 10-Current control circuit, 11.11' ・
Phase control circuit, 12...Low/high speed discrimination circuit, 13
Gate circuit, Is e I8L r ■81 (+ i
s't ILL * l811"' - Main circuit current flow permit applicant Toyo type (r ≧ Manufacturing Co., Ltd. Representative Atsutame Doi 1 Figure Kay 2 Drama 31st child"i-- P etc.

Claims (1)

[Claims] It includes at least a forward converter for converting an AC input type υ1 into DC, and a synchronous motor connected to the forward converter and the inverse converter, and outputs the speed deviation between the target rotational angle and the motor rotation speed. In a speed control circuit for a non-commutator motor that includes a speed control system using a current feedback loop as a command signal for the output current of a forward converter, a current detector for detecting the current flowing through the DC reactor is provided, and the current detector is configured to detect the current. A speed control circuit for a non-commutator motor, characterized in that the motor output is obtained as a current feedback signal.