JPH07123781A - Brushless excitation controller for variable speed synchronous motor - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a highly accurate and compact brushless excitation control device of a variable speed synchronous motor for sudden load changes and speed control over a wide range. [Structure] Using an induction machine type AC exciter, the rotor winding 9
Is controlled as a function of the time change rate (di _s / dt) of the armature current i _s of the main machine 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless exciter adopting induction machine type excitation of a variable speed synchronous motor for driving a large capacity, sudden variable load.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a brushless exciter for a variable speed synchronous motor according to the prior art. In FIG.
The armature 6 of the variable speed synchronous motor (main machine) has a variable frequency
The variable voltage power source 20 changes the supply frequency of the power source 20 to excite it and drive it as an electric motor.

At this time, in the main machine field 18, as shown in FIG. 6, the stator winding 2 of the exciter machine 1 is provided with a variable voltage power source 21.
Is excited, and the alternating current induced in the rotor winding 9 of the rotating portion 19 is converted into direct current by the rotary rectifier 17 to be excited.

The exciter 1 is a so-called induction machine type exciter, and since the stator winding 2 and the rotor winding 9 are both AC windings that form a multi-phase rotating magnetic field, Since the frequency and voltage of the alternating current induced in the winding 9 changes depending on the rotation speed of the main machine, and the necessary exciting current of the main machine also needs to change depending on the load current of the main armature 6,
The gate control circuit 25 controls the voltage of the power source 21 through the signal converters 22 and 23 and the arithmetic unit 24 which determines the voltage of the power source 21 from the signals of the rotation frequency detector 5 and the main armature current detector 7. Excitation operation is performed by controlling the output voltage.

Since the field current of the main machine steady load (torque) must be kept constant, when the main machine rotation speed changes, the power supply for exciting the exciter stator winding 2 accordingly. The voltage of 21 is controlled to keep the main machine field current constant.

Of course, when the load (torque) changes, it is necessary to change the excitation of the main engine.
The voltage of the power supply 21 for exciting the stator winding 2 is controlled.

[0007]

The conventional brushless exciter for a variable speed synchronous motor shown in FIG. 6 has the following drawbacks when the load is changed rapidly, when the load suddenly changes, or when the speed is controlled over a wide range. is there.

(1) The induction of the exciter 1 from the stator side to the rotor side is induced by the change in the amount of magnetic flux due to the magnetic coupling through the iron core. Excitation due to overvoltage (forcing) in order to secure the necessary main-unit excitation current
It is necessary to increase the power supply capacity and exciter size.

(2) In a machine requiring a wide range of speed variation, electric power is converted from the stator side to the rotor side according to the principle described in (1) above, so the exciter 1 may be used depending on the number of revolutions of the main machine. In some cases, the frequency induced in the rotor winding 9 of the motor may become extremely low, and as a result, the induced electric power decreases. Therefore, the exciter 1 having a large physique is prepared from the design stage in consideration of such special conditions. You need to do it. As described above, in the conventional technique, the exciter 1 considering the special operating conditions is used.
Since it is necessary to prepare the power supply device and the power supply device, these excitation-related devices become large and economically expensive.

Therefore, according to the present invention, it is possible to perform a predetermined function in a small-sized device without enlarging these devices related to the excitation, and to reduce the time delay when the load suddenly changes.
It is an object of the present invention to provide an exciter capable of changing excitation rapidly.

[0011]

In order to achieve the above object, a synchronous motor (main engine) operated by a variable frequency power source.
In the brushless excitation control device of the present invention, the exciter machine is an induction machine type AC exciter machine, a stator winding of the exciter machine is connected to a power source of a variable frequency variable voltage, and a rotating magnetic field from the power source is generated. It has a main machine field winding that is excited via a rotary rectifier that converts from a rotor winding that obtains alternating current to direct current by induction, and the frequency of the alternating current induced in the rotor winding is the time of the main machine armature current. The gist is that the control circuit as a function of the rate of change is provided in the variable frequency variable voltage power supply.

Further, the present invention provides a control circuit for controlling the voltage of a variable frequency variable voltage power supply by the magnetic flux by the main machine armature current signal, and the sum of the rotation frequency signal and the frequency as a function of the time change rate of the main machine armature current. The main point is that

Further, the gist of the present invention is that the power supply of the variable frequency variable voltage is provided with a control circuit for obtaining a magnetic flux at a voltage and a frequency obtained based on the main machine drive voltage and the power supply frequency.

[0014]

The function of the main machine can be controlled by the high-speed response caused by the change in the frequency of the exciter, and it is possible to cope with a sudden change in the load and control with high accuracy. For this reason, the size of the body is not increased by the prompt excitation, and the tolerance for overexcitation is small, and the size can be reduced. Further, by setting the frequency, the operation can be performed irrespective of the number of revolutions and a wide range of operation control can be performed.

[0015]

FIG. 1 shows an embodiment of the configuration of a brushless exciter for a variable speed synchronous motor according to the present invention. In FIG. 1, the same parts as those in FIG. 6 are designated by the same reference numerals. In FIG. 1, a power supply 3 for exciting the stator winding 2 of the AC exciter 1 is a power supply that can output a variable frequency and a variable voltage, unlike the conventional power supply.

In order to control the output frequency and output voltage of the power source 3, the following detectors and control devices are constructed. First, in order to control the output frequency of the power supply 3 for excitation, a rotation frequency detector 5 of the main machine synchronous motor 4, a main machine armature 6, and a detector 7 for detecting current are provided. Among them, the current detector 7 is connected to a circuit 8 for differentiating the signal of the main motor armature current i _s, and further connected to the frequency setting device 10 for determining the frequency relationship shown in FIG. 2 by the output signal, the rotation frequency By the output signal of the adder circuit 12 which is connected to the detector 5 and adds the output signal f _r of the frequency signal converter 11 for converting the frequency f _s to the AC exciter frequency signal and the output signal f _2c of the setter 10, It controls the gate control circuit 13 and consequently controls the output frequency of the inverter 32 of the power supply 3. Here, the frequency setting device 10 inputs the main machine armature current to the differential signal (di _s / dt) as its input,
The set value signal f _2c based on the relationship shown in FIG. 2 is used as the output.

Further, the frequency signal converter 11 has a function of converting the signal of the rotation frequency f _{s into} the signal of the frequency fr corresponding to the number of poles of the exciter 1, and is _{expressed by} the equation (2) described later. The signal is converted.

In order to control the output voltage of the excitation power source 3, the signal i _{s of the} detector 7 which detects the current of the armature 6 is used.
As an input, a magnetic flux signal control device 14 for generating a signal level Φ _c related to the exciter magnetic flux with respect to a preset main machine armature current as shown in FIG. 3, and its output signal and the output signal of the adder circuit 12 are input. A gate control circuit 16 having a voltage control device 15 controlled as an input and controlled by this output signal controls the DC output voltage of the converter 31 of the power supply 3, and consequently the output AC voltage of the inverter 32. .

Here, the magnetic flux signal control device 14 has a function of generating a signal Φ _c related to the magnetic flux Φ of the exciter 1 having the relationship shown in FIG. 3 with respect to the main machine armature current i _s . Further, the voltage control device 15 includes the magnetic flux signal control device 14
Output signal Φ _e of the output signal of the addition circuit 12 (f _r
This is a control device having a calculation function of multiplication of + f _2c ).

When the stator winding of the exciter 1 is excited by the power source 3 controlled in this way, the rotating magnetic field thereof causes the rotor winding 9 to rotate.
The alternating current induced by is converted into direct current by the rotary rectifier 17, and the field winding 18 of the main engine 4 is excited.

Next, the operation of the configuration shown in FIG. 1 will be described. The output frequency of the power supply 3 for exciting, i.e. excitation frequency f ₁ of the exciter stator windings 2, induction frequency f ₂ of the exciter rotor windings 9, the relationship between the rotational frequency f _r in terms of the exciter number of poles It can be expressed by the following equation (1).

[0022]

[Number 1] _{f 1 = f 2 + f r} ...... (1) where the rotation frequency f _s of the main machine armature 6, the main motor number of poles P
_s, and the number of poles of the exciter and P _e, the rotation frequency f _r in terms of the exciter pole P _e can be expressed by the following equation (2).

[0023]

## EQU00002 ## _f.sub.r = _f.sub.s + ( _P.sub.e / _P.sub.s ) (2) The signal detected by the rotation frequency detector 5 in FIG. 1 corresponds to _f.sub.s , and the frequency signal converter 11 sets (2). since the conversion formula, the gate circuit input signal f ₁ which determines the output frequency of the power source 3, the sum of the output signal f _r of the output signal f _2c and the frequency signal converter 11 of the frequency setting device 10, the following ( 3)
It can be expressed by a formula.

[0024]

## _EQU3 ## f ₁ = f _2c + f _s × (P _e / P _s ) (3) Then, the following equation (4) is obtained from the above equations (1) to (3).

[0025]

## _EQU00004 ## f ₂ = f _2c (4) That is, the output signal f _2c of the frequency setting device 10 has a one-to-one correspondence with the rotor winding induction frequency f _{2 of the} exciter 1. Therefore, if the output signal of the frequency setting device 10 changes, the induction frequency of the rotor winding 9 of the exciter can also change.

[0026] constant load, i.e. when the constant primary machine armature current i _s, the temporal change rate of the armature current (di _s / dt)
Is zero, and f _{2c produces} a signal of f _2o as shown in FIG. That is, the rotor winding induction frequency f ₂ of the exciter machine 1 is constantly excited regardless of the rotation speed of the main machine. Also, power source 3
Voltage of the exciter stator winding 2, voltage v ₁ , exciter 1
The relationship of the induced voltage v ₂ of the rotor winding 9 of
It can be expressed by equation (6).

[0027]

[Formula 5] v ₂ = ke ₂ × f ₂ × Φ (5) v ₁ = ke ₁ × f ₁ × Φ = ke ₁ × (f ₂ + _fr ) × Φ (6) Take (5) , (6), ke ₁ and ke ₂ are constants determined by the exciter machine design, and Φ is the number of magnetic fluxes of the exciter 1 magnetic circuit.

In this way, the output voltage v ₁ of the power supply 3 is calculated according to the above equation (6) with respect to the magnetic flux Φ, the output signal of the magnetic flux signal controller 14, and the output signal of the adder circuit 12 for (f ₂ + _fr ). Is determined by controlling the output voltage of the converter 31 by the function of the voltage control device 15 controlled by the input signal.

In the circuit of the rotating portion 19, the main machine field current If is Rf, the resistance value of the main machine field winding 18, and k is a constant.
If f is taken into consideration, it can be expressed by the following equation (7) considering equation (6).

[0030]

(6) If = kf × v ₂ / Rf = (kf / Rf) × ke ₂ × f ₂ × Φ (7) That is, the main machine field current If changes depending on f ₂ and Φ.

Next, a control method during operation in which the load on the main engine changes rapidly will be described. When the main machine armature current i _s rapidly increases, (di _s / dt) becomes a positive value, and in the case shown in FIG. 2, f _2c > f _2o , and from the above description, the exciter 1
The induction frequency f ₂ of the rotor winding 9 is controlled to increase. At the same time, v ₁ is controlled so as to increase the magnetic flux Φ as shown in FIG.

Describing this with equation (7), both f ₂ and Φ will increase rapidly. Φ has a delay in the magnetic circuit, but f ₂ increases If rapidly without delay. Therefore, it is possible to realize a quick field current response as compared with the conventional technique which is based only on the change of the magnetic flux Φ.

On the contrary, when the main machine armature current i _s sharply decreases, the opposite action can also rapidly reduce the field current change. The operation of this embodiment has been described above for the steady load and the sudden load change.

The effect of the variable speed electric motor according to this embodiment will be described below. Especially when the load changes suddenly, the frequency of the exciter can be changed compared to the conventional technology, so the field current of the main machine can be controlled with a quick response corresponding to the load. With respect to a sudden increase in load during time, a small time delay can be provided, prompt response excitation can be provided, there is no need to increase the physique of the main engine, and there is no need to have a margin on the device such as overexcitation (forcing). Even the control device and the power supply device can sufficiently exhibit their functions.

Since the AC exciter can also be operated at a constant frequency f ₂ regardless of the number of revolutions during most steady loads, even if it is a drive machine for a load that requires a wide range of operation control, an exciter of a large size can be used. It is possible to configure without need.

As its ultimate effect, it is possible to provide a compact and highly controllable brushless synchronous motor. FIG. 4 is another embodiment according to the present invention. Here, the rotation frequency detector 5 of the above-described embodiment is not provided, and the detection of the main machine rotation frequency is obtained from the frequency (power supply frequency) signal of the main machine drive power supply voltage detector 29. This is because the target of the present embodiment is the synchronous machine, and therefore the rotation frequency and the power supply frequency are uniquely associated with each other by the following equation (8) under any operating condition.

[0037]

F _r = 2 × f _s / P _s (8) where f _{r is the} rotation frequency, f _{s is the} power supply frequency, and P _{s is the} number of main machine poles. The magnetic flux signal control device 26 in this embodiment is different from the above-described embodiment in that the main unit drive power supply voltage v _s
Output signal T _{s of the} divider 27 of the signal of frequency f _s and the signal of frequency f _s
Is further divided by the signal of the frequency setting device 10, and the output signal of another divider 28 is used as an input to generate a setting signal Φ _c having the relationship shown in FIG.

The main-machine generated torque T _s is given by the following equation, where the main-machine magnetic flux Φ _s , the armature current i _s , the phase difference θ, the main-machine terminal voltage v _s , the power factor angle φ, the rotational angular velocity ω, and the main-machine efficiency η. Expressed in a relationship. However, k _sa and k _sb are constants.

[0039]

(8) T _s = k _sa (Φ _s × i _s × cos θ) = k _sb (i _s × v _s × cos φ) × η / ω (9) Equation (9) and ω = 2πf _s Therefore, Φ _s becomes the following equation. Note that k _sc is a constant.

[0040]

Φ _s = k _sc (v _s × η × cos φ) / (f _s × cos θ) (10) Since Φ _s is approximately proportional to the exciting current If, (7)
From the equation, the magnetic flux Φ of the exciter 1 is given by the following equation. However, η,
The values related to φ and θ are collectively the function f (η, φ, θ)
Will be expressed as k _sd is a constant.

[0041]

[Equation 10] The combination of the arithmetic devices described above can realize the relationship of the expression (11). That is, in the divider 27, the elements related to the main machine voltage and the frequency are
From the relationship of equation (4), the induction frequency f of the exciter machine rotor winding 9 is
Elements related to ₂ can be calculated. Therefore, the magnetic flux signal control device 26 uses another element of the equation (11), that is, k _sd , f
It has a calculation function in consideration of set values related to (η, φ, θ), kf, Rf, ke ₂ . According to the embodiment of FIG. 4, the magnetic flux amount of the exciter 1 required for the main machine operating state can be set to control the power supply 3, that is, the exciter stator winding 2, the applied voltage, and the frequency.

Needless to say, the present invention is not limited to the embodiments described above, and the embodiments shown in FIG. 1 can be combined or modified in whole or in part without changing the scope of the invention.

[0043]

The effects of the present invention are summarized as follows. (1) It is possible to provide a brushless variable speed synchronous motor capable of performing field current control with a quick response as a drive machine for a load that changes rapidly.

(2) As a drive device for a load that requires a wide speed range, the AC exciter may be small, and the installation area of the electric motor as a whole can be small, and an inexpensive brushless variable speed synchronous electric motor can be provided.

(3) Not only the electric motor, but also the power supply equipment can have a smaller capacity than in the past, which brings great economic advantages to the user. (4) Since it is a brushless type with no sliding parts such as brushes,
Not only is maintenance and inspection easy, but it can be applied to a wide range of applications in any atmosphere.

[Brief description of drawings]

FIG. 1 is a block diagram of a brushless excitation control device according to an embodiment of the present invention.

FIG. 2 is a functional operation characteristic diagram of a frequency setting device according to an embodiment of the present invention.

FIG. 3 is a functional operation characteristic diagram of a magnetic flux signal controller according to an embodiment of the present invention.

FIG. 4 is a block diagram of a brushless excitation controller according to another embodiment of the present invention.

FIG. 5 is a functional operation characteristic diagram of a magnetic flux signal controller according to another embodiment of the present invention.

FIG. 6 is a block diagram of a brushless excitation control device according to a conventional technique.

[Explanation of symbols]

 1 Exciter 2 Stator Winding 3 Variable Frequency Variable Voltage Power Supply 4 Synchronous Motor (Main Machine) 5 Rotation Frequency Detector 7 Armature Current Detector 8 Differentiation Circuit 9 Rotor Winding 10 Frequency Setter 14 Magnetic Flux Signal Controller 15 Voltage Control device 27, 28 Divider 29 Drive power supply voltage detector

Claims (3)

[Claims] 1. A brushless excitation controller for a synchronous motor (main machine) operated by a variable frequency power source, wherein the exciter is an induction machine type AC exciter, and a variable frequency variable is provided in a stator winding of the exciter. A mains field winding that is connected to a voltage power supply and is excited via a rotary rectifier that converts from a rotor winding that obtains an alternating current by the induction of a rotating magnetic field from this power supply to a direct current; A brushless excitation control device for a variable speed synchronous motor, characterized in that a control circuit in which the frequency of the alternating current induced in is a function of the time change rate of the main machine armature current is provided in the variable frequency variable voltage power supply. 2. A voltage control circuit for a variable frequency variable voltage power supply is formed by the magnetic flux of the main machine armature current signal, and the sum of the rotation frequency signal and the frequency of a function of the time change rate of the main machine armature current. The brushless excitation control device for a variable speed synchronous motor according to claim 1. 3. A brushless excitation control device for a variable speed synchronous motor, wherein a control circuit for obtaining a magnetic flux at a voltage and a frequency obtained based on a main machine drive voltage and a power supply frequency is provided in a variable frequency variable voltage power supply. .