JP3849131B2 - Inverter device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to protection related to a withstand voltage of an inverter drive device that operates a synchronous motor.
[0002]
[Prior art]
In a synchronous motor, since the motor has a permanent magnet, an induced voltage is generated at the terminal of the armature winding of the motor itself by rotation. For this reason, when the synchronous motor rotates at high speed, the induced voltage may exceed the withstand voltage of the inverter device, resulting in destruction of the inverter device.
Conventionally, in an inverter drive of a synchronous motor, insulation coordination of the synchronous motor has been attempted so as not to destroy the inverter device by an induced voltage of a permanent magnet of the synchronous motor.
Alternatively, as disclosed in Japanese Patent Laid-Open No. 6-178567, by using a method of decelerating the synchronous motor by short-circuiting the output terminal of the synchronous motor and applying a dynamic brake by the induced voltage of the synchronous motor. The inverter device was protected.
[0003]
This is shown in the connection diagram of FIG. That is, a three-phase AC voltage of U, V, and W phases supplied from the inverter device 1 through a DC power source 10 (generally generated from a commercial AC power source and received through a rectifier circuit and a smoothing circuit). When the three-phase AC voltage of the U, V, and W phases supplied from the inverter device 1 is cut off from the state of being applied to the armature terminal of the synchronous motor 2 and the line short-circuit switch 3 is turned on, the synchronous motor 2 Becomes a generator and is subjected to dynamic braking in the direction opposite to the direction of rotation of the motor, so that the induced voltage at the armature terminal of the synchronous motor 2 is lowered to avoid breakdown.
[0004]
[Problems to be solved by the invention]
However, in these conventional methods, when the synchronous motor is rotating at a speed higher than expected in applications where there is a possibility of being rotated by external force (disturbance) applied from the outside such as wind, such as a fan, etc. If there is an induced voltage exceeding the dielectric strength of the inverter device, there is a risk that the inverter device may be destroyed by the induced voltage before the synchronous motor decelerates, and therefore the inverter device of the synchronous motor There is a problem in that the use of driving at is limited.
[0005]
In addition, some reverse salient pole type synchronous motors can suppress the terminal voltage by passing a field weakening current. In such a synchronous motor, the terminal voltage is suppressed by voltage control during operation. However, when the inverter device becomes uncontrollable due to a power failure or the like, the terminal voltage increases. There is also a problem that it leads to destruction of the inverter device. In order to solve the above problems, the present invention automatically breaks the connection of the inverter device and the synchronous motor when the terminal voltage of the synchronous motor rises excessively regardless of the operation state of the inverter device. An object of the present invention is to provide an inverter device that prevents the above-described problem.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 of the present invention provides an inverter device receiving power from a DC power source and a method for protecting an inverter device having a synchronous motor driven by the inverter device. A terminal is connected to an input terminal of the synchronous motor via an electromagnetic switch having a B contact, and the operating voltage of the excitation coil for the B contact for operating the B contact is determined by the electromagnetic switch. The inverter device protection method is characterized in that it operates below a withstand voltage of the voltage applied to the output terminal and connects the exciting coil terminal of the electromagnetic switch to the input terminal of the electric motor.
[0007]
Therefore, according to the present invention, in a synchronous motor driven by an inverter, when a voltage is applied to its own exciting coil between the output terminal of the inverter device and the input terminal of the synchronous motor, the motor is cut off. The withstand voltage of the voltage applied to the output terminal of the inverter device when the exciting coil has a B contact that is in a conductive state when no voltage is applied to the exciting coil and the operating voltage of its own exciting coil for operating its own contact Since the electromagnetic switch that operates below is provided and the excitation current of the electromagnetic switch is introduced from the input terminal of the synchronous motor, the terminal voltage of the synchronous motor is excessive regardless of the operating state of the inverter device. When the voltage rises, the inverter device and the synchronous motor can be automatically disconnected to prevent insulation breakdown of the inverter device due to overvoltage. It exhibits the special effect.
[0008]
The invention according to claim 2 of the present invention is a method for protecting an inverter device according to claim 1, wherein a reverse salient pole type synchronous motor is applied to the synchronous motor. By applying the synchronous motor, protection of the inverter device is ensured, and a remarkable effect that contributes to improvement of the reliability of the equipment can be exhibited.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are the same or equivalent members.
FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention.
An electromagnetic switch 4 is inserted and connected between the lines connecting the output terminals U, V, W of the inverter device 1 and the input terminals 2a, 2b, 2c of the synchronous motor 2.
[0010]
The contact of this electromagnetic switch 4 is composed of each phase B contact 4Ub, 4Vb, 4wb. When the excitation voltage of the electromagnetic switch excitation coil 4c is energized and excited, each phase B contact 4Ub, 4Vb, 4wb is If the excitation coil 4c is not excited without being applied with an excitation voltage, the conduction (short-circuit / on) state is established.
The exciting coil 4c of the electromagnetic switch 4 is connected to the input terminal of the synchronous motor 2, and the operating voltage of the exciting coil 4c of the electromagnetic switch 4 is before the insulation breakdown of the inverter device, that is, withstand resistance. It is set to a certain voltage that does not exceed the voltage.
[0011]
FIG. 2 is a transition diagram illustrating the operation of the electromagnetic switch B contact in this embodiment over time.
Fig. 2 (a) shows the speed change of the synchronous motor, Fig. 2 (b) shows the transition of the field weakening current, Fig. 2 (c) shows the change of the output terminal voltage of the inverter device, and Fig. 2 (b) shows the synchronization. It is a change figure of an electric motor (input) terminal voltage.
[0012]
In this embodiment, a case where an inverted salient-pole synchronous motor is inverter-driven will be described.
When the operation of the synchronous motor 2 is started by the inverter device 1 (time t0), the synchronous motor 2 gradually increases in speed (time t0 → t2).
In response to this, the output voltage of the inverter device 1, that is, the terminal voltage of the inverter device 1 rises (time t0 → t1).
Then, as shown in FIG. 2, when the terminal voltage of the inverter device 1 reaches a certain level (e2) (time point t1), a field weakening current (-id) is caused to flow through the synchronous motor 2, thereby causing the synchronous motor 2 to flow. The (input) terminal voltage is limited to a constant (e1). This utilizes the characteristics of a reverse salient pole type synchronous motor.
[0013]
During operation in this state, when the inverter device 1 fails due to a power failure (time point t3) and enters the base block state, the output (terminal voltage) of the inverter device 1 is cut off, so the field weakening current is zero (- id = 0), and the (input) terminal voltage of the synchronous motor 2 suddenly increases (e1 → e5).
When this terminal voltage (e5) exceeds the operating voltage (e3) of the exciting coil 4c of the electromagnetic switch 4, the B contact of the electromagnetic switch 4 is opened (OFF / circuit cut off), and the inverter device 1 is connected to the synchronous motor 2. Released from the connection circuit.
[0014]
Therefore, since the (output) terminal voltage of the inverter device 1 becomes zero at this time (t3), it is possible to prevent a voltage higher than the withstand voltage (e4) from being applied to the (output) terminal of the inverter device 1. It becomes possible to protect the inverter apparatus 1 from the overvoltage which generate | occur | produces in 2 (input) terminal voltage.
Thereafter (after time t3), when the speed of the synchronous motor 2 becomes slow and the (input) terminal voltage of the synchronous motor 2 falls below the operating voltage (e3) of the exciting coil 4c of the electromagnetic switch 4 (after time t4), The B contact of the electromagnetic switch 4 becomes conductive again (ON / short circuit), and the drive circuit from the output terminal of the inverter device 1 to the input terminal of the synchronous motor 2 is connected.
The power supply for the operating voltage (e3) of the exciting coil 4c of the electromagnetic switch 4 may be taken from any two phases of the input terminals of the synchronous motor 2.
[0015]
In this way, the present invention provides an inverter device having an inverter device that receives power from a DC power supply and a synchronous motor driven by the inverter device, wherein the output terminal of the inverter device is connected via an electromagnetic switch having a B contact. The electromagnetic switch is connected to the input terminal of the synchronous motor, and the electromagnetic switch operates below the withstand voltage of the voltage applied to the output terminal of the inverter device. This is a protection method for the inverter device that connects the exciting coil terminal to the input terminal of the motor. Therefore, based on a simple measure, it is completely and reliable from the dielectric breakdown when driving the synchronous motor of an expensive inverter device in the event of an unexpected power failure. Avoidance is possible.
[0016]
【The invention's effect】
As described above, according to the present invention, in a synchronous motor driven by an inverter, when a voltage is applied to its excitation coil between the output terminal of the inverter device and the input terminal of the synchronous motor, When the voltage is not applied to the self-exciting coil, the operating voltage of the self-exciting coil for operating the self-contact is applied to the output terminal of the inverter device. Since it has an electromagnetic switch that operates below the withstand voltage of the applied voltage and the excitation current of the electromagnetic switch is introduced from the input terminal of the synchronous motor, the synchronous motor When the terminal voltage rises excessively, the inverter device and the synchronous motor are automatically disconnected to prevent the inverter device from being broken due to overvoltage. It has a remarkable effect that can be.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention. FIG. 2 is a transition diagram illustrating the operation of an electromagnetic switch B contact in one embodiment of the present invention over time.
(a) Speed change diagram of synchronous motor
(b) Transition diagram of field weakening current
(c) is the change of the output terminal voltage of the inverter device
(d) is a diagram of the change in voltage of the synchronous motor (input) terminal [Fig. 3] Connection diagram of the inverter device driven by the synchronous motor using the dynamic brake means of the prior art
DESCRIPTION OF SYMBOLS 1 Inverter apparatus 2 Synchronous motor 3 Line short circuit switch 4 Electromagnetic switch 4c Excitation coil
4Ub, 4Vb, 4wb B contact for each phase 10 DC power supply

Claims (1)

When the excitation coil (4c) is energized between the phases connecting the output terminals (U, V, W) of the inverter device and the input terminals (2a, 2b, 2c) of the synchronous motor, When the contact is cut off and the excitation coil (4c) is not excited, the electromagnetic switch (4) of the B contact that becomes conductive is inserted and connected, and the terminal voltage of the synchronous motor rises excessively. In the inverter device that automatically disconnects the synchronous motor from the inverter device,
The exciting coil (4c) of the electromagnetic switch (4) is connected to any two phases of the input terminals of the synchronous motor (2), and the operating voltage of the exciting coil (4c) of the electromagnetic switch (4) is Set to a certain voltage that does not exceed the withstand voltage before the dielectric breakdown of the inverter device, the exciting current of the exciting coil (4c) is taken from the synchronous motor,
The synchronous motor is a reverse salient pole type synchronous motor, and when the terminal voltage of the inverter device reaches a certain level, the terminal voltage of the synchronous motor is limited to a constant value by flowing a field weakening current through the synchronous motor. When the inverter device fails during current operation and the field weakening current becomes zero, and the terminal voltage of the synchronous motor exceeds the operating voltage (e3) of the electromagnetic switch (4),
An inverter device characterized in that the electromagnetic switch (4) is cut off by introducing an exciting current of the exciting coil (4c) from the input terminal of the synchronous motor.

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