JPS6241597Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a starting device for starting a synchronous motor at reduced voltage, and in particular to tap switching control of a starting compensator.

Conventionally, in this type of starting device, tap switching of a starting compensator for performing reduced voltage starting has been performed using a timer. That is, by calculating in advance the time required to reach the set rotational speed for switching the reduced voltage tap, and setting the calculated time in a timer, the switching control of the reduced voltage tap of the starting compensator is performed after the start of the synchronous motor. was.

However, since the tap switching control of conventional starting compensators is performed by a timer as described above, for example, if there is a change in load torque or fluctuation in power supply voltage, the rotation speed at the time of tap switching becomes the set rotation speed. As a result, an excessive current flows or a large torque is generated during switching, resulting in a disadvantage that reliable and accurate tap switching cannot be performed. Especially in the case of a salient pole type synchronous machine,
Because the magnetic poles (and spiders) around the outside of the rotor protrude and the damper windings are not evenly wound around the entire rotor, during normal operation, unlike induction machines and other cylindrical synchronous machines, The problem is that frequency control without pulsation cannot be performed, and smooth startup cannot be achieved due to the influence of the fluctuating frequency, which is the pulsating frequency, at the time of startup.

This invention was made to eliminate the drawbacks of the conventional ones as described above.The rotation speed is determined from the fluctuating frequency that pulsates during starting based on the rotor salient pole machine structure of the armature input, and the rotation speed is set. When the value is reached, the starting compensator's reduced voltage tap is switched,
Furthermore, the present invention provides a starter device that can forcibly switch the voltage reducing tap if the voltage reducing tap is not switched even after a predetermined period of time has elapsed.

Below, an embodiment of the present invention will be explained based on the drawings. Fig. 1 shows the pulsating fluctuation state of the armature input (primary input) at the time of starting a salient pole type synchronous motor (hereinafter referred to as the synchronous motor). , the above armature input has a fluctuating frequency F = 2sf (where s is slip and f is the power supply frequency) that occurs based on the salient pole machine structure around the rotor where magnetic poles (and spiders) are provided with protrusions. When the synchronous motor starts, the slip S changes from 1 to 0. For example, when the power supply frequency f is 60 Hz, the armature input fluctuation frequency F changes from the start to the end of the start. It will change from 120Hz to 0Hz depending on S. Therefore, by detecting this fluctuation frequency F, the rotation speed of the synchronous motor can be detected, and when the rotation speed reaches the set value, a control signal for switching the voltage reduction tap is output to the starting compensator. The synchronous motor can be started at a reduced voltage.

That is, in the configuration shown in FIG. 2, the input line of the synchronous motor 1 is connected to the potential current transformer CT and the potential transformer PT.
A power detector 2 detects the armature input of the synchronous motor 1 through these CT and PT, and a frequency detector 3 connected to the power detector 2 detects the salient pole of the armature input. The structure is configured such that a fluctuating frequency F ₁ occurring in the structure is detected. Then, the rotation speed is calculated by the calculation unit 4 from the detected fluctuation frequency of the armature input, and the controller 5 connected to the calculation unit 4 calculates the rotation speed when the rotation speed reaches the set rotation speed. A voltage reduction tap switching signal is output to the starting compensator 6 which starts the synchronous motor at reduced voltage. Figure 3 shows the relationship between the armature current I ₁ at reduced voltage starting, the synchronous motor generated torque T ₁ , and the load reaction torque T ₂ against the slip S corresponding to the rotation speed.
is subjected to two-stage voltage reduction tap control, and then full voltage is applied. In this case, two set rotational speeds are set in the controller 5 of FIG. 2.

In addition, in the above embodiment, the fluctuating frequency generated in the salient pole structure of the armature input is detected, the rotational speed is calculated based on this fluctuating frequency, and when the rotational speed reaches a set value, the voltage reduction tap is switched. However, if a start jam occurs before the set rotation speed is reached during a reduced-voltage start and the next tap change cannot be performed, a conventional timer is used as a backup to ensure the tap change. In this case, for example, a timer may be built into the controller 5.

As described above, according to the present invention, the fluctuating frequency generated in the salient pole structure of the armature input is detected, the rotational speed is determined from this fluctuating frequency, and when the rotational speed reaches the set rotational speed, the voltage reduction tap is switched. Furthermore, if the voltage reducing tap is not changed even after a predetermined period of time has elapsed, the tap is forcibly changed. Accurate reduced voltage tap switching can be performed regardless of fluctuations.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the fluctuating frequency of armature input, Fig. 2 is a block diagram showing the starting device for a synchronous motor according to the present invention, and Fig. 3 is a diagram showing the relationship between torque and armature current with respect to slip during reduced voltage starting. It is an explanatory diagram showing a relationship. 1...Synchronous motor, 2...Power detector, 3...
Frequency detector, 4... Arithmetic unit, 5... Controller, 6
...Starting compensator.

Claims (1)

[Scope of utility model registration request] In a starting device that starts a salient pole type synchronous motor at reduced voltage by performing tap switching of a starting compensator, there is a detector that detects the fluctuating frequency based on the salient pole machine structure of the armature input, and a detector that detects the fluctuating frequency based on the salient pole machine structure of the armature input. A calculator that calculates the number, a controller that outputs a reduced voltage tap switching signal to the starting compensator when the rotational speed reaches the set value, and a controller that sets the time until the set rotational speed is reached at the time of reduced voltage starting. When the set time of this timer is reached and the switching of the voltage reduction tap is not performed based on the output of the controller, a signal to switch the voltage reduction tap is forcibly sent to the starting compensator. A starting device for a synchronous motor, characterized in that it has a configuration that gives.