JPH04275079A - Starting method for synchronous motor - Google Patents

Abstract

PURPOSE:To suppress influence on a power system at the time of starting by appropriately reducing the starting current of a generator-motor which is started as a synchronous motor. CONSTITUTION:When a synchronous motor 6 is started, a current having phase reverse to that of a current flowing through parallel buses is fed from a starter 31 to an armature winding 33 while at the same time a parallel circuit breaker 2 is thrown in to feed a current having same phase as the bus current to an armature winding 32. Current flowing through the armature winding 33 is then reduced and it is subsequently increased in same phase direction as the bus current thus accelerating a synchronous motor 6. When the output current from the starter 31 is in-phase with the current flowing from the parallel circuit breaker 2 to the armature winding 32 and has substantially same magnitude, an AC circuit breaker 34 is closed while a starter load circuit breaker 27 is opened thus connecting the armature windings 32, 33 in parallel.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method of starting a synchronous motor.

0003

2. Description of the Related Art Conventionally, methods for starting a synchronous motor include full voltage starting, half voltage starting, synchronous starting, and static starter starting.

Full-voltage starting requires a large starting current, so it cannot be applied to large-capacity machines, and synchronous starting is the same as static starter starting in that it uses a variable frequency voltage, but it uses a different synchronous generator. The disadvantage is that it requires

Therefore, in the following explanation, half-voltage starting and static type starting device starting will be taken as examples.

FIG. 3 shows a single-line connection diagram when applying the half-voltage starting method, where 1 is the main transformer, 2 is the parallel breaker, 3 is the starting breaker, and 4 is the generator disconnector. , 5 is a motor disconnector, 6 is a generator motor, 7 is a field breaker,
8 is an excitation rectifier, 9 is an AC power supply, 10 is an electromagnetic contactor,
11 is a starting resistor, and 12 is a field winding.

[0007] In the above, the generator motor 6 is a synchronous machine and is operated as a generator or an electric motor. in this case,
The rotation direction of the generator motor 6 in each operating state is different.

When starting the generator motor 6 as a synchronous motor, first open the generator disconnect switch 4 connected to the generator motor bus and close the motor disconnect switch 5 to stop the phase rotation of the generator motor 6. Switch to electric motor direction.

Next, the electromagnetic contactor 10 is closed, the starting resistor 11 is connected to the field winding 12, and the secondary circuit of the generator motor 6 is constructed. Connect rectifier 8. However, at this point, the excitation rectifier 8 is not in operation, and no excitation current is passed through the field winding 12.

After the field circuit of the generator motor 6 is constructed,
Close the starting circuit breaker 3. In this case, since the power supply side of the starting breaker 3 is connected to the half-voltage tap of the secondary winding of the main transformer 1, the generator motor 6 receives a voltage equivalent to approximately 50% of its rated voltage. is applied via the disconnector 5, and the generator motor 6 is started.

When the generator motor 6 is accelerated, the excitation rectifier 8 is put into operation, the power from the AC power source 9 is rectified, and the field current is passed through the field winding 12.

Next, when the generator motor 6 reaches the synchronous speed, the starting breaker 3 is opened, and the bus voltage from all voltage taps of the secondary winding of the main transformer 1 to the parallel circuit breaker 2 and the power generation are When the phases of the bus voltages of the motor 6 match, the parallel circuit breaker 2 is closed. After closing the parallel breaker 2, the electromagnetic contactor 10 is opened, and the starting of the generator motor 6 is completed. The half-voltage starting method configured as described above has the disadvantage that the starting current of the generator motor 6 when the starting breaker 3 is closed is large, causing large fluctuations in the power system connected to the main transformer 1. be. In addition, the opportunity to open the starting breaker 3 and turn on the parallel circuit breaker 2 is only once in one start of the generator motor 6, and if the parallel connection fails, the generator motor 6 is turned on. After it is stopped, it must be started again. In this case, synchronous parallel connection cannot be performed unless the allowable phase difference shift is larger than usual, so there is a drawback that a shock is given to the generator motor 6 when the parallel connection occurs.

Next, a method for starting the static starter will be explained with reference to FIG. In addition, in FIG. 4, the same parts as in FIG. 3 are given the same reference numerals.

In FIG. 4, 21 is a main transformer, 22 is a starting device power breaker, 23 is a starting transformer, 24 is a forward converter, 25 is a DC reactor, 26 is an inverter, and 27 is a starting device load. The circuit breaker 28 is a starting circuit breaker. Note that, unlike the case in FIG. 3, the main transformer 21 is not provided with a half-voltage tap.

In the control circuit for the synchronous motor having such a configuration, when starting the generator motor 6, first the generator disconnector 4 is opened and the motor disconnector 5 is closed, thereby controlling the phase rotation of the generator motor 6. After switching to the direction of the motor, the field breaker 7 is closed and the excitation rectifier 8 is operated to convert the alternating current of the alternating current power source 9 into direct current, which is then supplied to the field winding 12 as a constant field current. .

[0016] Next, the starting disconnector 28, the starting device load breaker 27, and the starting device power breaker 22 are respectively closed to form a starting circuit and start the variable frequency starting.

In this case, the alternating current on the secondary side of the main transformer 21 is applied to the forward converter 24 via the starter power breaker 22 and the starting transformer 23, and is converted into direct current by its operation. The DC output of this forward converter 24 is applied to the inverse converter 26 via the DC reactor 25, and the inverse converter 26
is converted into a variable frequency voltage from zero frequency to the rated frequency by the regulation control of This variable frequency voltage is applied to the generator motor 6 via the starter load breaker 27 and the starter disconnector 28 to start and accelerate it.

After accelerating the generator motor 6 to a synchronous speed, the secondary bus voltage of the main transformer 21 and the bus voltage of the generator motor 6 are synchronized, and the parallel circuit breaker 2 is closed. after,
By opening the starter load breaker 27, the starter disconnector 28, and the starter power breaker 22 and stopping the operation of the forward converter 24 and reverse converter 26,
The start-up of is completed.

In such a static starter starting method, the starting current of the generator motor 6 is transmitted through the starter power supply breaker 22, the starting transformer 23, the forward converter 24, the DC reactor 25, the inverse converter 26, and the starter motor 6. The starting circuit including these devices requires 100% capacity of the starting current as it flows through the equipment load breaker 27 and starting disconnector 28.

[0020]

[Problem to be solved by the invention] As explained above,
In the conventional technology, when starting the generator motor as a synchronous motor, the starting current increases, causing large fluctuations in the power system. Further, due to this influence on the electric power system, there is a disadvantage that full-voltage starting methods and half-voltage starting methods cannot be adopted for large-capacity generator motors.

[0021] Furthermore, in the case of the half-voltage starting method, if the parallel generator-motor fails, it is necessary to start it again, resulting in poor responsiveness to the power grid and low reliability as a system. . Moreover, since a shock is applied to the generator-motor when they are paralleled, the generator-motor must have sufficient electrical and mechanical resistance.

On the other hand, in the case of starting with a static starter device, the capacity of the equipment installed in the starting circuit is large, which has the disadvantage that the equipment becomes large and the cost of installing the system becomes large. .

[Configuration of the invention]

[0024]

[Means for Solving the Problems] A method for starting a synchronous motor according to the present invention includes, when starting a synchronous motor, a current having a phase opposite to the current phase of a parallel bus bar flowing from a starting device to an armature winding b, and , turn on the parallel circuit breaker to flow a current in the same phase as the bus bar through the armature winding a of the synchronous motor, then reduce the value of the current flowing from the starter to the armature winding b, and further perform the instruction described above. The value of the current flowing from the device to the armature winding b is increased in the same direction as the current phase of the bus bar to accelerate the synchronous motor, and the output current of the starter device and the armature winding from the parallel breaker are increased. When the currents flowing through B are in the same phase and have approximately the same value, the AC breaker is closed and the starter load breaker is opened to connect the armature winding a and armature winding B in parallel. Features.

[0025]

[Operation] In the method of the present invention configured as described above, the armature windings a and b are divided into two circuits for each phase of the generator motor.
The output from a separately provided starting device is applied to one of the two. Next, the parallel circuit breaker is closed to guide the starting current from the power grid to the generator motor. In the early stages of starting, the output current from the starter is the same value as the starting current from the power grid and flows in the opposite direction, so the starting current from the power grid is canceled out.
It acts like an armature reaction.

Next, the output current from the starting device is increased in the positive direction, and the starting force of the generator motor is obtained while suppressing the starting current from the power system to start the generator motor. Even if the output current from the starter reaches zero, the generator motor is accelerated by increasing it further in the positive direction.

When the current values of both armature windings become approximately equal, the AC breaker is closed, the armature windings are connected in parallel, and the armature windings are connected in a normal operating state. , disconnect the starter from the generator motor and complete the start.

As a result, the starting current at the time of starting the synchronous motor is suppressed, so that fluctuations in the electric power system are reduced, and the withstand capacity of the synchronous motor and the capacity of the starting device can be reduced.

[0029]

Embodiment Next, an embodiment of the present invention will be described with reference to FIGS. 1 and 2. In FIG. 1, the same parts as in FIGS. 3 and 4 are given the same reference numerals, and explanations of the same parts will be omitted unless necessary.

In FIG. 1, reference numeral 31 is a starting device consisting of a forward converter 24, a DC reactor 25, an inverse converter 26, and their control device (not shown), and 32 and 33 are armatures of the generator motor 6. The winding 34 indicates an AC breaker.

The armature winding of the generator motor 6 normally has a winding divided into several windings for each phase, and is connected to a terminal outlet (not shown) of the stator of the generator motor 6. The windings for each phase are configured by connecting the respective windings in parallel. The above-mentioned armature windings 32 and 33 are not special windings, but are made by equally dividing the divided windings into two groups for each phase, and opening the terminals of the stator of the generator motor 6. This was extracted individually by the department.

In the synchronous motor control circuit configured as described above, when starting the generator motor 6, which is a synchronous machine, as a synchronous motor, first open the generator disconnector 4,
The motor disconnector 5 is closed to switch the phase rotation of the armature winding of the generator motor 6 in the direction of the motor.

Next, the electromagnetic contactor 10 is closed, and the starting resistor 11 is connected to the field winding 12. Subsequently, the field breaker 7 is closed, the excitation rectifier 8 is connected to the AC power supply 9, and preparations for starting the field circuit are made. At this time, since no operation command is given to the excitation rectifier 8, the rectification function of the AC power supply 9 does not operate.

Further, the starting disconnector 28, the starting device load breaker 27, and the starting device power breaker 22 are each closed, and the starting device 31 is connected to the generator motor 6.

When the starting device 31 starts operating in response to a starting command for the generator motor 6, power is supplied from the main transformer (not shown) via the motor disconnector 5, the starting device power breaker 22, and the starting transformer 23. The generated electric power is rectified by the forward converter 24 of the starting device 31, smoothed by the DC reactor 25, and becomes DC. Further, it is converted into an alternating current starting current by an inverter 26, and is converted into an alternating current starting current by a starting device load breaker 27.
is applied to the armature winding 33 of the generator motor 6 via the starting disconnector 28.

At the same time that the starter 31 starts operating, the parallel circuit breaker 2 is closed, and current from the power system is allowed to flow through the armature winding 32 of the generator motor 6.

The basic current waveform flowing through the armature winding 32 is as shown in the input current waveform 41 in FIG. On the other hand, the current flowing from the starter 31 to the armature winding 33 has a starting current waveform 42 at the initial stage of starting.

Since these currents 41 and 42 flow in opposite phases through the armature windings 32 and 33 of the same phase of the generator motor 6,
They act to cancel each other out, and their combined current is shown in Figure 4.
The result is a composite current waveform 49. In this state, the voltage induced in the field winding 12 is zero, so the generator motor 6 does not start.

Next, by adjusting and controlling the inverter 26, the starting current from the starting device 31 is changed to the starting current waveform 43.
When the value is increased to , a difference is generated between the input current waveform 41 and the current of the composite current waveform 50 flows as the starting current. This starting current causes current to flow through a damper winding (not shown) of the generator motor 6, generating driving force. Further, a voltage is induced in the field winding 12, and a current flows through the field winding 12, the electromagnetic contactor 10, and the starting resistor 11, and this current also provides the driving force for the generator motor 6. , the generator motor 6 is started.

Furthermore, when the output current waveform from the starting device 31 is increased in the order of starting current waveforms 44, 45, 46, and 47, the current waveform effective for starting the generator motor 6 becomes the composite current waveform 51, 52, 53. , 54.

Since this starting current adjustment is smoothly and steplessly controlled by the starting device 31, the current effective for starting the generator motor 6 increases slowly, and the generator motor 6 is also slowly accelerated. Note that in this acceleration state, the generator motor 6 is not started as a synchronous motor;
It is started as a wound induction motor with a secondary circuit consisting of a field winding 12, an electromagnetic contactor 10, and a starting resistor 11.

When the rotational speed of the generator motor 6 increases and the slip with respect to the synchronous speed becomes small to some extent, the excitation rectifier 8 starts operating. By this operation, the current from the AC power source 9 is rectified by the excitation rectifier 8, passes through the field breaker 7, and is applied to the field winding 12 as a field current.

At this time, since the generator motor 6 does not rotate in perfect synchronization, the secondary current due to the slip flows through the starting resistor 11, but the generator motor 6
When the rotational speed of the generator motor 6 is accelerated to the synchronous speed, this current value decreases and is synchronized by the field current flowing through the field winding 12, so that the generator motor 6 rotates as a synchronous motor.

When the rotational speed of the generator motor 6 approaches the synchronous speed, the current from the starter 31 is increased to a starting current waveform 48. This starting current waveform is in phase with the input current waveform 41 flowing through the armature winding 32, and the current values are also approximately the same. In this state, the AC breaker 34 is closed, and the armature winding 32 and the armature winding 33 are connected in parallel for each phase.

After closing the AC breaker 34, the starter load breaker 27, the starter disconnector 28, and the starter power breaker 22 are opened to disconnect the starter 31 from the generator motor 6 and disconnect the starter 31 from the generator motor 6. Stop the generator motor 6
Completes startup.

As a result, the armature windings 32 and 33 of each phase of the generator motor 6 are connected normally as a synchronous motor, and approximately 1/2 of the load current of each phase is shunted to each armature winding. , operation continues.

As described above, according to the present invention, by suppressing the starting current of the generator motor 6, smooth startup without shock to the generator motor is possible. In addition, since the parallel circuit breaker is turned on at the beginning of the generator motor's startup, if a problem such as three-phase misalignment occurs when the generator motor is turned on, it is only necessary to turn it on again at the beginning of startup. There is no need for

Furthermore, since the starting device controls a current that is half the armature current from the beginning to the end of starting the generator motor, a small capacity starting device is sufficient.

Note that in the above embodiment, the forward converter 24,
Starting device 3 consisting of a DC reactor 25 and an inverter 26
Although the present invention is not limited to this example, it is possible to control the output current of the starting device steplessly from the negative side to the positive side with respect to the input current waveform of the generator motor. For example, a cycloconverter that directly converts alternating current into another waveform of alternating current, or a power converter that has a switching device that reverses the polarity to control from the negative side to zero current and from zero current to the positive side. You may use a container. Alternatively, a starting device may be used in which a composite waveform is created by shifting the phase of the output current of the starting device with respect to the current phase of the input current.

In addition, in the case of starting a generator motor of small to medium capacity, the initial starting as an induction motor using an electromagnetic contactor and a starting resistor is omitted, and the starting device is operated by applying excitation from the initial stage of starting. , a parallel circuit breaker is installed to limit the starting current while synchronizing the generator motor with the power grid.
A method of accelerating while maintaining the starting torque may be adopted.

[0051]

[Effects of the Invention] As explained above, according to the present invention,
By reducing the starting current of the generator motor, which starts as a synchronous motor, to an appropriate value, it is possible to reduce fluctuations in the power system during startup, and also to reduce shocks to the generator motor, as in the half-voltage starting method. without giving
Generator motor electrical, which can start smoothly
Mechanical tolerance can be reduced.

[0052] When synchronously paralleling the generator motors, an excitation current is applied from the beginning of startup to synchronize, so there is no need for repeated restarts due to failure to close the parallel circuit breaker, etc., and it is possible to respond quickly to the demands of the power system. As a result, system reliability can be improved.

Furthermore, since the capacity of the starting device only needs to be controlled to 1/2 of the starting current of the generator motor, it is approximately half the capacity of a conventional starting device, simplifying equipment and reducing installation space. This makes it possible to reduce the construction cost of the system.

Furthermore, the present invention can be applied regardless of the capacity of the generator motor, and can be used as a method for starting any synchronous motor.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram showing an embodiment of the method of the present invention.

FIG. 2 is a basic waveform diagram of a starting current flowing through an armature winding of a generator motor in an embodiment of the method of the present invention.

FIG. 3 is a single-line connection diagram of a starting circuit for a synchronous motor to which a conventional half-voltage starting method is applied.

FIG. 4 is a single-line connection diagram of a starting circuit for a synchronous motor to which a conventional static starter starting method is applied.

[Explanation of symbols]

1......Main transformer 2...Parallel circuit breaker ３……Starting disconnector 4...Disconnector for generator 5...Disconnector for electric motor 6... Generator motor 7......Field breaker 8……Excitation rectifier 9……AC power supply 10……Magnetic contactor 11……Starting resistor 12……Field winding 21……Main transformer 22……Starting device power breaker 23……Starting transformer 24……Forward converter 25……DC reactor 26……Inverse converter 27……Starting device load breaker 28……Starting disconnector 31……Starting device 32, 33...armature winding 34……AC breaker 41……Input current waveform 42-48...Starting current waveform 49-55…Synthetic current waveform

Claims (1)

[Claims] 1. A starting circuit comprising a starting device power breaker, a starting transformer, a starting device, a starting device load breaker, and a starting disconnector, a parallel breaker, an AC breaker,
A main circuit comprising armature winding a and armature winding b of a synchronous motor connected in parallel for each phase, a field winding, a magnetic contactor, a starting resistor, a field breaker, and an excitation rectifier. and a field circuit equipped with an AC power source, when starting the synchronous motor, a current having a phase opposite to a current phase of a parallel bus bar from the starting device to the armature winding b is generated. At the same time, the parallel circuit breaker is turned on to flow a current in the same phase as the bus bar to the armature winding a of the synchronous motor, and then the value of the current flowing from the starter to the armature winding b is reduced. Further, the value of the current flowing from the starter to the armature winding b is increased in the same direction as the current phase of the bus bar to accelerate the synchronous motor, and the output current of the starter and the parallel circuit breaker are increased. When the current flowing through armature winding b is in the same phase and has approximately the same value, the AC breaker is closed and the starter load breaker is opened, and the armature winding a and armature winding b are connected in parallel. A method for starting a synchronous motor characterized by connecting.