JPS6122479Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an excitation device for a synchronous motor having a field voltage control circuit.

[Conventional technology]

In addition to various torques, GD ² , slip field current, etc., the ability of synchronous pull-in at the time of starting a synchronous motor is greatly influenced by the phase difference angle between the rotating magnetic field generated by the armature and the magnetic poles at the moment when DC excitation is applied. . For this reason, appropriate phase input that provides DC excitation at the optimal phase difference angle is necessary for synchronous pull-in.

FIG. 1 shows an excitation device for a synchronous motor in which a suitable phase input circuit is incorporated into a synchronous motor having a field voltage control circuit.

In the figure, 1 is a synchronous motor, 2 is a field winding of the synchronous motor, and 3 is a control circuit that controls the field voltage to adjust the operating state of the synchronous motor 1, and a feedback circuit that detects the field voltage. The feedback voltage taken out to the circuit 4 is set by the reference voltage setting resistor 5.
The field voltage is controlled by comparing the output of the thyristor rectifier 8 via the voltage control unit 6 and the phase control amplifier 7 based on a comparison signal between the two and a reference voltage set at .

9 is an appropriate phase input circuit. After closing the discharge resistor contactor 10 and making the field winding 2 a closed circuit through the discharge resistor 11, the switch 12 is turned on to start the synchronous motor 1 as an induction motor. At this time, the frequency of the induced voltage generated in the field winding 2 is
The terminal voltage of the discharge resistor 11 is shaped by a waveform shaping circuit 13, detected by an appropriate phase detection circuit 14, and compared with a preset appropriate phase frequency. Further, when DC excitation is applied to the field winding 2, the polarity must be such that the DC excitation is applied in the same direction as the induced current in the field winding 2, as shown in FIG. With such polarity, as shown in FIG. 3, the polarity of the rotor and stator is in the attracting direction, making synchronous retraction easier. Therefore, the proper phase detection circuit 14 detects not only the proper phase frequency of the induced voltage in the field winding 2 but also the polarity at the same time. When both of these conditions are satisfied, the appropriate phase detection circuit 14 outputs an appropriate phase input signal, and this signal turns on the thyristor rectifier 8 via the phase control amplifier 7, and the field winding DC excitation is applied to 2, and the synchronous motor is pulled in synchronously.

[Problem that the invention attempts to solve]

However, the induced voltage generated in the field winding 2 at the time of starting is taken out as the feedback voltage of the feedback circuit 4 of the control circuit 3 described above, so that the appropriate phase input circuit 9 outputs an appropriate voltage for the operation of the control circuit 3. The thyristor rectifier 8 may not be turned on even by the phase turn-on signal, and synchronous pull-in may not be possible. That is, as shown in FIG. 4, when the synchronous motor 1 is started, the induced voltage generated in the field winding 2 by the rotating magnetic field is detected by the voltage detection means 15.
For example, the voltage is divided by a voltage dividing resistor 16 via a diode bridge circuit and taken out as a feedback voltage _V1 , and this feedback voltage _V1 becomes the reference voltage _E3 set in the reference voltage setting resistor 5 as described above. I am faced with. Therefore, the reference field voltage E ₃ set in the reference voltage setting resistor 5
is lower than the feedback voltage _V1 , the matched signal is transmitted to the voltage control amplifier 17 and current control amplifier 1 constituting the voltage control unit 6.
8, the output voltage of the thyristor rectifier 8 is controlled to decrease via the phase control amplifier 7. Therefore, even if the thyristor rectifier 8 is turned on in such a state, its output voltage
Since _E2 cannot overcome the induced voltage generated in the field winding 2, the thyristor rectifier 8
is not turned on, the timing of the appropriate phase is shifted, synchronous pull-in is not performed smoothly, and there are drawbacks such as a hunting phenomenon of the synchronous motor.

The object of this invention is to overcome the above-mentioned drawbacks and to provide an excitation device for a synchronous motor that can input the appropriate phase without causing the hunting phenomenon even when the set field voltage is low.

[Means for solving problems]

The present invention comprises a field voltage control circuit that feeds back the voltage of the field winding, compares it with a set value, and applies the difference voltage to a phase control amplifier via a voltage control unit to control the field voltage by its output; It is equipped with an appropriate phase switching circuit that detects the appropriate phase and polarity of the induced voltage generated in the field winding at the time of starting, and outputs a signal for direct current excitation of the field winding, and the output of the appropriate phase switching circuit is controlled in phase. In a synchronous motor in which the field DC excitation means is turned on by applying it to an amplifier, means is provided in the field voltage control circuit to limit the feedback voltage of the field voltage control circuit to a value smaller than the set value at the time of starting. This is an excitation device for a synchronous motor, characterized in that it is provided with a synchronous motor.

[Effect]

When the induced voltage generated in the field winding 2 of the synchronous motor 1 is larger than the set reference field voltage _E3 at the time of starting, the induced voltage detected from the feedback circuit 4 is transmitted through the limit circuit 20. Due to the Zener action, the excitation DC current to the field winding 2 is controlled by limiting it to a value lower than the reference field voltage _E3 .

〔Example〕

This invention will be explained below based on an embodiment shown in FIG. It should be noted that each component of this invention that is the same as the component described above will be described with the same reference numerals.

In this embodiment as well, one synchronous motor, two
It is equipped with a field winding of a synchronous motor, a control circuit for controlling the field voltage (3), and an appropriate phase input circuit (9). As described above, the proper phase closing circuit 9 detects the proper phase and polarity of the induced voltage generated in the field winding 2 when the synchronous motor 1 is started, and outputs a proper phase closing signal. The control circuit 3 detects the induced voltage using a voltage detection means 15 and a voltage dividing resistor 16 so that the induced voltage generated in the field winding 2 due to the rotating magnetic field reaches a preset field voltage value, so that synchronous pull-in is performed. A feedback circuit ₄ is installed between the voltage dividing resistor 16 and the voltage control unit 6, and a changeover switch 19 (when its normally open contact 19a is turned on, its normally closed contact 19b is limit circuit 2 which is switched by
0, a reference voltage setting resistor 5, a voltage control unit 6, a phase control amplifier 7, and a thyristor rectifier 8. The above limit circuit 20 connects the feedback voltage _V1 to the reference voltage setting resistor 5.
It is set to a value smaller than the reference voltage _E3 set in .

Next, the operation of the above embodiment will be explained.

When starting synchronous motor 1, selector switch 1
9 to limit the feedback voltage _V1 . The synchronous motor 1 is first started as an induction motor, and at this time the induced voltage generated in the field winding 2 due to the rotating magnetic field is detected via the voltage detection means 15 and divided by the voltage dividing resistor 16. This feedback voltage V ₁ is made by a limit circuit 20 to a value V ₂ smaller than the reference field voltage E ₃ .
Therefore, the matched signal acts in the direction of increasing the output voltage E ₂ of the thyristor rectifier circuit 8 via the voltage control amplifier 17, the current control amplifier 18, and the phase control amplifier 7. Therefore, when the proper phase and polarity are detected from the induced voltage generated in the field winding 2 and the proper phase closing signal is output from the proper phase closing circuit 9, the thyristor rectifier 8 is turned on and the field winding 2 is turned on. DC excitation is applied to. In this way, synchronous pull-in is performed.

After turning on the appropriate phase, change the changeover switch 19 so that it does not go through the limit circuit 20.
The field voltage is automatically controlled during operation of the synchronous motor by a matching signal between the feedback voltage V ₁ and the reference field voltage E ₃ .

[Effect of idea]

This idea is structured as above,
Even if the set field voltage is low, hunting does not occur and appropriate phase input can be performed at any field voltage (field current).

[Brief explanation of the drawing]

Figure 1 is a single connection diagram of a synchronous motor excitation device with a voltage control circuit and a suitable phase input circuit installed in parallel, Figure 2 is a diagram showing the direction of field current at the appropriate phase, and Figure 3 is at synchronous pull-in. FIG. 4 is a circuit diagram of a conventional excitation device for a synchronous motor, and FIG. 5 is a circuit diagram showing an embodiment of this invention. 2... Field winding, 3... Control circuit, 8... Thyristor rectifier, 9... Appropriate phase input circuit, 20...
...Limit circuit.

Claims (1)

[Scope of utility model registration request] A field voltage control circuit feeds back the field winding voltage, compares it with a set value, and applies the difference voltage to a phase control amplifier via a voltage control unit to control the field voltage using its output. and an appropriate phase input circuit that detects the appropriate phase and polarity of the induced voltage generated in the magnetic winding and outputs a signal for direct current excitation of the field winding, and applies the output of this appropriate phase input circuit to a phase control amplifier. In a synchronous motor in which the field DC excitation means is turned on by
An excitation device for a synchronous motor, characterized in that the field voltage control circuit is provided with means for limiting the feedback voltage of the field voltage control circuit to a value smaller than the set value at the time of starting.