JPS596157B2 - Control device for commutatorless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a commutatorless motor using an electric valve with control poles.

As is well known, a synchronous motor rotating at a synchronous speed generates a reverse induced voltage, so it is possible to perform load commutation as a separately excited inverter.However, at startup and at low speeds, the aforementioned reverse induced voltage is small, so commutation is not possible. Difficult to operate.

For this reason, an intermittent starting method is widely used in which the DC current is intermittent and the electric valve is switched during the zero current period.

Figure 1 shows a conventional continuous startup system. In Figure 1, 1 is a three-phase AC power supply, 2 is a synchronous motor, 3 is a rectifier in which electric valves with control poles are connected in a three-phase bridge, and 4 is a control pole. Inverter device with three-phase bridge connection with electric valve, 5
is a smoothing reactor, 6 is a starting circuit for the rectifier 3, T is a starting circuit for the inverter device 4, 8 is a speed generator that generates a signal according to the speed of the synchronous motor 2, and 9 is a position detector for the synchronous motor. 1 is an AC current transformer that detects the current flowing through the rectifier; 11 is a control circuit that controls the output of the rectifier; 12 is a signal from the position detector 9; This is a logic circuit that determines the ignition arm of the inverter device 4 in response to the following. That is, in the circuit configuration shown in FIG. 1, a variable voltage DC power source is created from the output of a three-phase AC power source 1 using a rectifier 3, and a position detector 9 detects the position of the field side rotor of the synchronous motor 2. This determines the ignition arm of the inverter device 4 and supplies AC power to the armature of the synchronous motor 2.

FIG. 2 is a diagram showing the current flowing through the DC circuit of this conventional device.

By controlling the phase of the rectifier 3, the current detected by the AC current transformer 10 is controlled in two stages: constant current and zero current, and this control method is widely known. During this zero current period, the ignition arm of the inverter device 4 is switched.
A so-called commutation is performed, but at this time, the current injected into the synchronous motor 2 becomes zero, so pulsation of the acceleration torque occurs and the acceleration force decreases, making it impossible to obtain rapid acceleration. Therefore, for example, in electric motors for steel rolling mills, rapid operation is required, so the intermittent starting method is not preferable.

Furthermore, in intermittent operation, there is a risk of resonance with the mechanical system due to pulsation of acceleration torque. The present invention was made in order to eliminate the drawbacks of the conventional ones as described above.
It is an object of the present invention to provide a control device for a commutatorless motor that can reduce pulsation in the acceleration torque of the motor and provide rapid acceleration. An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 3, 20 is a three-phase AC power supply, 21 is a synchronous motor, 22 is a power transformer, 23 is a primary winding of transformer 22,
24 and 25 are secondary windings of the transformer 22; 26 is a first rectifier device in which an electric valve with a control pole is connected in a three-phase bridge; 27 is a first inverter device in which an electric valve with a control pole is connected in a three-phase bridge; 28 is a smooth reactor.

UH, VH, WH, XH, YH, and ZH represent each arm of the first inverter 27. 26, 27, and 28 constitute a group of conversion devices similar to the conventional configuration shown in FIG. 1, and this will be referred to as the H group.

Reference numeral 29 denotes a second rectifier device in which an electric valve with a control pole is connected in a three-phase bridge connection, 30 is a second inverter device in which an electric valve with a control pole is connected in a three-phase bridge connection, and 31 is a smoothing reactor.

UL, L, WL, XL, YL, and ZL represent each arm of the second inverter 30. Similarly, converters 29, 30, and 31 constitute a group of conversion devices, which will now be referred to as L group.

32 is a speed generator, 33 is a position detector, and synchronous motor 21
34 is a pulse generator which generates a pulse signal every time the rotor rotates several degrees.

35 is a speed control circuit, 36 is a speed reference device, and 37 is an operational amplifier that matches the reference with the output of the speed generator 32.

18M is a speed relay which is demagnetized at startup and is energized when a specific speed level is reached after startup.

18M1, 18M2, 18M5, 18M6 are speed relays 18M0) b contact, 18M3, 18M4, 1aM7, 1
8M8 represents the a contact of the speed relay 18M.

38 is a first rectifier ignition circuit that controls ignition of the first rectifier 26; 39 is a first inverter ignition circuit that controls ignition of the first inverter 27; 40 is a position detection circuit during startup; This is a logic circuit that receives a signal from the inverter 33 and determines the firing arm of the first inverter 27.

54 is a logic circuit that receives a signal from the position detector 33 and determines the firing arm of the first inverter device 27 after completion of startup.

41 is an AC current transformer that measures the current in the H group, 42 is a current reference circuit for the H group at startup, and 43 is a current waveform that receives signals from the position detector 33 and pulse generator 34 at startup and flows through the H group. The first current pattern circuit 44 that determines the current pattern is a first multiplier that multiplies the output signal of the speed control circuit 35 by the current pattern from the first current pattern circuit 43.

45 is an arithmetic amplifier for current control, which uses the detected current value from the AC current transformer 41, the output of the first multiplier 44 at startup,
After the start-up is completed, each output is matched with the output of the speed control circuit 35.

Although the H group devices have been described above, the L group also has a similar device configuration.

That is, 46 is a second rectifier ignition circuit that controls ignition of the second rectifier 29, 47 is a second inverter ignition circuit that controls ignition of the second inverter 30, and 48 is an activation circuit. When the signal from the position detector 33 is received, the second inverter 30
This is a logic circuit that determines the ignition arm of the ignition arm. 55 receives the signal from the position detector 33 after the start-up is completed, and operates the second inverter 3.
This is a logic circuit that determines the firing arm of 0.

49 is an AC current transformer, 51 is an L group current reference circuit at startup, 51 is a second current pattern circuit at startup, 52
is the second multiplier.

53 is an operational amplifier for current control.

Next, the operation will be explained.

The AC voltage of the AC power supply 20 is transformed by a transformer 22,
is applied to the first and second rectifiers 26 and 29, and the first
Under the control of the second ignition circuits 38 and 46, direct currents 1d-H and Id-L flow to the output side of each rectifier 26, 29.

The DC currents Id-H and Id-L are further converted into a three-phase AC current IR- by the first and second inverter devices 27 and 30.
The current is converted into H, IR, and -L (only the R phase current is displayed) and supplied to the synchronous motor 21. The rotational position of the synchronous motor 21 is detected by a position detector 33, and the output signal thereof is converted by a pulse generator 34 into a pulse signal of a format that generates one pulse for each output of the rotation, and the first and second currents are generated. It is supplied to pattern circuits 43 and 51. On the other hand, the rotational speed of the synchronous motor 21 is detected by a speed generator 32 and supplied to an operational amplifier 37. The H group and the L group have the same configuration, and are only controlled so that the phases of the output currents are different from each other by 90 degrees. Therefore, the H group will be explained below.
The output signal of 3 and the pulse signal of the pulse generator 34 are used as Y- and X-axis address signals corresponding to the time axis, the internal memory is read out, and a current pattern consisting of an analog sine wave is generated from the read data. A signal is formed and provided to a first multiplier 44 . On the other hand, the operational amplifier 37 compares the output signal of the speed generator 32 and the speed reference signal of the speed reference device 36 and inputs the difference signal therebetween to the first multiplier 44 .

The first multiplier 44 multiplies the current pattern signal of the first current pattern circuit 43 and the difference signal of the operational amplifier 37,
The resulting signal is input to the first multiplier 44 . The first multiplier 44 multiplies the signal from the operational amplifier 37 and the current pattern signal from the first current pattern circuit 43, and inputs the resulting signal to the operational amplifier 45 via the b contact 18M1 of the speed relay 18M0). When the synchronous motor 21 reaches the rated speed of 1070, the b contact 18M1 is opened because the speed relay 18M is energized. Instead, since the a contact 18M3 is closed, the difference signal of the operational amplifier 37 is directly transmitted to the operational amplifier 45 via the a contact 18M3.
is input. The operational amplifier 45 takes the difference between the signal of the first multiplier 44 or the operational amplifier 37 and the output signal of the AC current transformer 41, and supplies the resulting signal to the first rectifier ignition circuit 38. This ignition circuit 38 includes an operational amplifier 37
The firing phase of each control pole electric valve of the first rectifier 26 is controlled according to the output signal of the AC current transformer 41 so that the signal becomes zero 5, and the DC current as shown in FIG. A current of 1d-H is applied. Similarly, the second rectifier 29 of the L group causes a direct current 1d-L shown in FIG. 4C to flow. Furthermore, the output signal of the position detector 33 is supplied to logic circuits 40, 48, 54 and 55.

As a result, the logic circuits 40, 48, 54 and 55 follow the output signal of the position detector 33;
, c outputs firing signals that sequentially fire the electric valves with control poles in the first and second inverters 27 and 30 in phase correspondence as shown in FIGS. During the period when the speed relay 18M is not energized, that is, during the starting period, the electric valve selection signals (FIG. 4B, d) of the logic circuits 40 and 48 are connected to the b contacts 18M2 and 48, respectively.
First and second inverter ignition circuit 3 via 18M6
9,47. After that, when the rotational speed of the synchronous motor 21 reaches 10% of the rated speed, the speed relay 18M
is energized, the B contacts 18M2 and 18M6 are opened, and the A contacts 18M4 and 18M8 are closed, so that from now on, the logic circuit 54,
The electric valve selection signal from 55 is supplied to the first and second inverter ignition circuits 39 and 47. This ignition circuit 39, 47 is thus connected to the logic circuit 40, 48 or 54, 5.
According to the selection result in step 5, an ignition signal is generated, thereby sequentially controlling the ignition of each electric valve with a control pole in the first and second inverters 27 and 30. In addition, during the starting period, the zero point T2 of the DC current 1d-H shown in FIG.
, t4, t6... and the direct current 1d- shown in FIG.
At the zero points Tl, t3, t, ... of L, the turn-off time of the thyristor of each inverter 27, 30 (approximately
0 psec 8 degrees) or more for a certain period (approximately 2 msec 8 degrees)
, the DC currents 1d-H and ld-L are controlled by the first and second rectifiers 26 and 29 to be completely zero, so the phase-to-phase commutation of the first and second inverters 27 and 30 is completely zero. It will be held in First and second inverters 27, 30
For example, the output currents of R-phase currents R-H and IR-
L is as shown in FIGS. 4e and 4f.

A current obtained by combining the R, S, and T phase currents of the inverters 27 and 30 is supplied to the R, S, and T phases of the armature of the synchronous motor 21. FIG. 4g shows the R-phase current of the synchronous motor 21, which is a combination of the currents shown in FIG. 4E and f. Next, to explain Fig. 4, a is H
It shows the temporal change in the DC current 1d-H of the group, b shows the ignition arm name of the inverter device 27 of the H group, c shows the temporal change in the DC current Id-L of the L group, and d is the ignition arm name of the inverter device 30 of the L group, and e is the R-phase current 1R-Hlf flowing out from the inverter device 27 of the H group. g is electric motor 2
The R-phase current IR of 1 indicates the combined current of IR-H and IR-L.

The time points t1 to T7 shown in FIG. g are separated by 60 intervals of motor voltage cycles. That is, time T,
is the time point when the polarity of the back electromotive force of the electric motor 21 is reversed due to the movement of the field rotor, time point T4 is the time point after half a cycle, and time point T7 is the time point after one cycle. These points are determined geometrically by the structure of the motor,
It can be easily detected by the position detector 33. Let us now consider the waveforms whose angular frequency on the motor side is ω and whose base point is time t1. Waveforms a and b repeatedly increase and decrease every 601 times, and waveforms a and c are out of phase.

That is, when the current in the H group is maximum, the current in the L group is zero, and when the current in the H group is zero, the current in the L group is maximum. This means that the power injected into the motor is continuous, but by arranging the current pattern and the firing arm of the inverter, the current injected into the motor 21 becomes a sine wave, with no torque ripple Tj. It can provide good acceleration torque.

From t1 to T2, the current of H group has a sinusoidal waveform of 120 to 1800, that is, 1sin(ω
t+1208), the waveform is controlled from ωt=00 to ωt=600. The current in the L group has a sinusoidal waveform of 60, i.e., ωt at SinO)t.
=06, it is controlled to ωt=600. This current is
Phase control of the rectifiers 26 and 29 allows the current to flow in accordance with the current pattern. The current pattern signal is from position detector 3.
3 and pulse generator 34, pattern generators 43 and 51 generate the patterns. The pulse generator 34 is a circuit that generates pulses in accordance with the rotation of the rotor, but if we consider a motor that generates 360 pulses in one cycle, one pulse is generated every time the motor rotates once. . Since the time point t1 is detected by the position detector 33, it is sufficient to provide the pattern generators 43 and 51 with a circuit that generates a signal that changes sinusoidally for each pulse of the pulse generator 34. This can be easily configured by storing values that change sinusoidally in a readout memory and reading out the address by advancing it every pulse. As shown in b and d, the first inverter 27 of group H is connected to arm WH (5
YH is conducting and the second inverter 2 of the L group
At 9, arms UL and YL are electrically connected. Therefore, between t1 and T2, there is no R-phase current flowing out from the H group, and the current 1R-L flowing out from the L group becomes the motor current 1R. Note that the amplitude of each current is determined by the output of the speed control circuit 35. Next, consider the time from T2 to T3. In this section, the current of H group is Isin(ωt-60ωt=60-, so ωt=
120i waveform, the current of L group is Isi
n(ωt+60 from ωt=60 to ωt=120 is controlled by the waveform of Arm ULI of inverter 29
:． YL is conducting. Therefore, the R-phase current 1R-H flowing out from the H group becomes e, the R-phase current 1R-L flowing out from the L group becomes f, and the motor current R becomes a composite value of both. This composite value is Isin(ωt-60.

)+Sin(ωt+60.Next, consider the time from T3 to T4.

In this section, the current of H group is Isin(ω of 0t
From t=120, it is controlled by a waveform of ωt=1800, and the current of L group is ωt=1 of Sin(ωt-120).
200, it is controlled with a waveform of ωt=180i. As shown in b and d, arms UH and ZH of the inverter 27 of the H group are electrically connected, and the inverter 27 of the L group
9 is arm VL (5ZL is conducting. At this time, the R phase current IB, -H flowing out from the H group flows as shown in e, but there is no current flowing out from the L group, and the motor current 1R is g. As shown, it is equal to IR-H.In summary, considering the waveform g of the motor current IR from t1 to T4, it can be seen that it is a perfect sine wave current for half a cycle.

In the period from T4 to T7, the same circuit operation is performed to cause a sine wave current to flow into the motor armature. Also in the S phase and T phase, a positive arc wave current flows through the motor according to this control method, and this current is synchronized in phase with the reverse induced voltage of the motor. Therefore, this synchronous motor is driven by a complete three-phase alternating current, and the acceleration torque is ripple-free and controlled in proportion to the speed deviation determined by the speed control circuit 35. Become. When the speed deviation signal is suppressed to the maximum value, the motor current is controlled to the maximum current, and the motor is started with the maximum torque. The motor started smoothly in this way,
When a particular speed level is reached, speed relay 18M is energized and operation is placed in a natural commutation mode with normal motor voltage.

At this time, the H group and L group are operated completely in parallel,
Divide the motor current into two and bear the burden. FIG. 5 is a diagram illustrating the operation mode after completion of startup. In Fig. 5, a is the motor reverse induced voltage, ER, es, et are R phase, respectively.
The S phase and T phase are shown, b shows the ignition arm name of the first inverter device 27 of the H group, and c shows the L
The ignition arm name of the second inverter device 30 of the group is shown, and d shows the R-phase current R of the electric motor 21.

γ shown in Fig. a is a margin angle for commutating current from arm ZH to arm XH, and performs a generally well-known inverter operation. In the H group and the L group, the first and second inverters 27 and 30 commutate simultaneously, and the first and second rectifiers 26 and 29 are phase-controlled based on the same command, so that the DC current of both groups 1d-H and Id-L are almost equal, and the current flowing through the motor is equally divided and borne by both groups. The operating point of the speed relay 18M is often set to a value at which the motor reverse induced voltage is established, for example, 10% of the rated speed, but it is preferable to set it in consideration of the resonance point with the mechanical system.

Currently, 6500KW, 20 is used for hot strip mill.
Kiwami, rated speed 80rp? Considering the motor, the frequency on the motor side at the rated speed is 13.3Hz.

Commutation at the reverse induced voltage of the motor is performed six times in one cycle, so in the conventional control method as shown in Figure 1 and the general control method explained in Figure 5, the 6th harmonic of the motor frequency is It is well known that torque pulsation occurs. In such a large-capacity machine, the resonance frequency of the mechanical system may reach 10Hz.
In this case, the motor frequency is 10HZ/6-1.66HZ
It is undesirable to operate the motor in commutation mode due to reverse induced voltage. The operating point of the speed relay 18M is 1.6
If you set it above 6Hz, you can accelerate without worrying about mechanical resonance. As described above, according to the present invention, it is possible to obtain a control device for a commutatorless motor that has quick response and has little torque ripple at low speeds.

Further, according to the present invention, it is also possible to reduce harmonics of the power supply side alternating current. That is, in the conventional system shown in FIG. 1, the rectifier is a three-phase full-wave rectifier circuit, so fifth- and seventh-order harmonics flow into the AC power supply, but according to the present invention, an input transformer is connected to the power supply side. By setting the voltage phase of the secondary winding of the H group and the secondary winding of the L group by 30 orders, it is possible to eliminate the 5th and 7th harmonic currents. It can be operated without any adverse effects on the vehicle.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an overview of the system of a conventional non-commutated motor, Fig. 2 is a waveform diagram showing the progression of DC current during conventional intermittent starting, and Fig. 3 shows the configuration of an embodiment of the present invention. FIG. 4 is a waveform diagram showing the course of current in each part during startup of the present invention, and FIG. 5 is a waveform diagram showing the operation after completion of startup of the present invention.

Claims (1)

[Claims] 1. A rotational position detector connected to the non-commutated motor and generating a rotational position signal indicating its rotational position; and a rotational position detector connected to the non-commutated motor and generating a speed signal indicating its rotational speed. Consisting of a speed generator, a speed control circuit that generates a difference signal between the speed signal and a predetermined speed reference signal, and a plurality of electric valves with control poles that convert the amount of AC electricity from the AC power source into the amount of DC electricity. a first and a second rectifier, each configured to convert the DC output of the first and second rectifier into an alternating current quantity of electricity, and whose output ends are commonly connected to each other so that the armature of the commutatorless motor and a pre-stored current pattern of direct current to be outputted by the first and second rectifying devices, respectively, according to the rotational position signal, and the first and second inverters each comprising a plurality of electric valves with control poles connected to the first and second current pattern circuits that read out signals, first and second multipliers that respectively calculate the product of each of the current pattern signals and the difference signal, and an output signal of each of the multipliers or the speed. points for the first and second rectifiers that respectively control the firing of the electric valves with control poles of the first and second rectifiers based on the difference signal between the difference signal of the control circuit and the current signal of the AC power supply; an arc circuit, first and second inverter ignition circuits that respectively control electric valves with control poles of the first and second inverters according to the rotational position signal; When the signal is less than a predetermined value, the first and second rectifier ignition circuits are supplied with the first and second rectifier ignition circuits based on the difference signal between the output signal of each multiplier and the current signal of the AC power source. 2 rectifiers to each other 9
It operates to perform firing control with a phase difference of 0°, and when the speed signal is greater than a predetermined value, the first and second rectifier firing circuits receive the difference signal between the speed control circuit and the above. Based on the difference signal from the current signal of the AC power supply, the first and second
A control device for a commutatorless motor, comprising a speed relay that operates to control the ignition of a rectifier. 2. The non-commutator motor according to claim 1, characterized in that a transformer is provided on the AC power source side, and the phases of two sets of rectifier circuits are shifted by 30 degrees to reduce harmonics flowing to the AC power source. control method.