JPH10136568A - Power supply facility - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly secure an input power supply to an inverter device when an AC power supply is lost and then recovered, by increasing the secondary side voltage of a transformer with an output voltage variable function by a specific value as compared with a rated voltage when the AC power supply is lost and then recovered, and returning it to a rated voltage after a specific amount of time passes. SOLUTION: An AC power supply 1 is connected to a transformer 5 with an output voltage variable function and is transformed to a specific voltage. On the other hand, a plurality of inverter devices 3a-3n are connected to a load system and motors 4a-4n are connected to each of them. In this case, when the power of the AC power supply 1 fails temporarily and then recovers, a control device 6 switches the tap of the transformer 5 with an output voltage variable function to increase the output voltage by a specific value as compared with a rated voltage, and switches a tape again after a specific amount of time passes and returns to the rated voltage, thus enabling the inverters 3a-3n to properly drive motors 4a-4n when the AC power supply 1 is lost and then recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply for supplying power to a load system in which a plurality of motors are driven by respective inverters.

[0002]

2. Description of the Related Art FIG. 3 shows a power supply system for supplying power to a load system in which a plurality of motors are driven by respective inverter devices. In FIG. 3, an AC voltage of an AC power supply 1 is transformed to a predetermined voltage by a transformer 2 and supplied to a load system to be supplied to an inverter device 3a.
To 3n. A plurality of inverters 3a to 3n are connected to the load system, and motors 4a to 4n as loads are respectively connected to the inverters 3a to 3n.
Is connected. That is, one inverter 3 has one
The drive of the motors 4 is controlled.

In such a power supply system, if the input power to the inverter device 3 is temporarily lost or reduced due to the influence of a lightning strike or the like while the motor 4 is operating at the rated speed, the inverter device 3 turns off the motor 4. It cannot be driven. For this reason, while the input power is lost or the voltage drops below the specified voltage, the inverter device 3 keeps the motor 4
Stop operation of.

Accordingly, during this time, the motor 4 is stopped or in a natural speed-down state. Thereafter, when the input power of the inverter device 3 is restored, the inverter device 3 resumes the operation, and drives the motor 4 which has been stopped or in the natural speed reduction state again.

[0005]

However, in order to drive the motor 4 again in a stopped or naturally lowering state, the inverter device 3 requires a larger amount of driving power than when the motor 4 is driven during rated operation. It is necessary to supply to the motor 4. Therefore, the current of transformer 2 that supplies AC power to inverter device 3 temporarily increases. That is, the input power supply of the inverter device 3 must supply a large amount of power until the motor 4 in the stopped or naturally lowering speed returns to the rated rotation speed again.

As a result, a voltage drop occurs in the secondary side voltage of the transformer 2, and the voltage of the input power supply to the inverter device 3 becomes lower than during the rated operation of the motor 4. FIG.
FIG. 3 is a characteristic diagram when a power failure occurs in the AC power supply 1 and the power is restored after that. If a power failure occurs in the AC power supply 1 at time t1, the voltage of the AC power supply 1 is lost and the voltage of the
The secondary voltage is also lost. Therefore, the power supply to the inverter device 3 is stopped, so that the inverter device 3 stops, and the rotation speed of the motor 4 decreases, and eventually stops.

If power is restored at time t2, the voltage of AC power supply 1 recovers, and the secondary voltage of transformer 2 also recovers. Therefore, the inverter device 3 starts the drive control of the motor 4 at a time t3 after a lapse of a predetermined standby time T from the recovery time t2 of the secondary voltage of the transformer 2. In this case, since each of the inverter devices 3a to 3n starts drive control at the same time, the secondary voltage of the transformer 2 causes a voltage drop. Then, when the voltage becomes equal to or lower than the predetermined value at time t4, the inverter device 3 determines that a power failure has occurred, stops the drive control of the motor, and stops. Note that the secondary voltage of the transformer 2 is recovered by the stop 3 of the inverter device 3.

As described above, although the input voltage from the AC power supply 1 to the transformer 2 has been restored to normal, the voltage of the input power supply to the inverter device 3 is reduced. There was a case where the malfunction of stopping the operation again occurred.

Therefore, it is conceivable to operate the inverter system by always increasing the voltage of the input power supply supplied to the inverter device 3 in advance. In general, many load devices other than the inverter device 3 are connected to the load system. In many cases, it is not preferable to increase the voltage of the input power supply in advance and operate the load devices other than the inverter device 3 at all times with an excessively high voltage.

After the input power of the inverter device 3 is restored, the operation of the plurality of inverter devices 3 may be restarted with a time delay so as to control the input power so that no load is applied to the input power source at the same time. Conceivable. That is, 1
After the third inverter device 3a drives the motor 4a, which is stopped or in the natural speed reduction state, to the rated speed again, the next inverter device 3b drives the motor 4b in the stopped or natural speed reduction state to the rated speed again. An operation method in which the same operation is repeated up to the inverter device 3n is also conceivable. However, in this operation method, since the plurality of inverter devices 3a to 3n are sequentially operated, the total number of motors 4
There is a problem that it takes too much time for a to 4n to return to the rated speed again.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a power supply capable of properly securing input power to an inverter device when AC power is lost and power is restored.

[0012]

According to a first aspect of the present invention, there is provided an output voltage variable function for inputting an AC power supply to a primary side, transforming the AC power to a predetermined voltage, and supplying a secondary side voltage as input power to the inverter device. And a control device for raising the secondary voltage of the transformer with an output voltage variable function by a predetermined value from the rated voltage and returning to the rated voltage after a lapse of the predetermined value when the AC power is lost and the power is restored. And

According to the first aspect of the present invention, when the AC power supply is lost and the power is restored, the control device raises the secondary voltage of the transformer with an output voltage variable function by a predetermined value from the rated voltage to increase the voltage of the input power supply. The voltage is prevented from dropping, and after each motor is started up to the rated operation by each inverter device, the voltage is returned to the rated voltage.

According to a second aspect of the present invention, in the first aspect of the present invention, when the AC power is lost and the power is restored, the control device sets the secondary voltage of the transformer with an output voltage variable function to 10% of the rated voltage.
Only to be higher.

In the invention of claim 2, in addition to the operation of the invention of claim 1, when the AC power supply is lost and the power is restored, the control device changes the secondary voltage of the transformer with an output voltage variable function to the rated voltage. The voltage of the input power supply is maintained at an appropriate voltage during the startup of each motor by the inverter device up to the rated operation by 10%.

[0016]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram showing an embodiment of the present invention.
In this embodiment, a transformer 5 with an output voltage variable function is provided in place of the transformer 2 of the conventional example shown in FIG. 3, and when the AC power supply 1 is lost and the power is restored, the transformer 5 with an output voltage variable function is provided. 2
A control device 6 is provided for raising the secondary voltage by a predetermined value from the rated voltage and returning the voltage to the rated voltage after a lapse of a predetermined time.

In FIG. 1, an AC voltage of an AC power supply 1 is input to a primary side of a transformer 5 having an output voltage variable function, is transformed to a predetermined voltage by the transformer 5 having an output voltage variable function, and is converted to a secondary side. Output that voltage. The transformer 5 with an output voltage variable function has a plurality of taps, and by switching these taps, it is possible to make the secondary voltage variable, and these taps are switched by a control device 6 described later. . The secondary voltage of the transformer 5 with an output voltage variable function is supplied to a load system and becomes input power to the inverter devices 3a to 3n.

The load system includes a plurality of inverter devices 3a.
To 3n, and motors 4a to 4n as loads are connected to the inverter devices 3a to 3n, respectively. That is, one inverter 4 drives and controls one motor 4. The inverter device 3
The input power supply is converted into a DC power supply in a forward direction, and the input power supply is converted back into a frequency power supply required by the motor 4, which is a load.

When the input power of the output voltage variable function transformer 5 is temporarily lost and the power is restored, the control device 6 switches the tap of the output voltage variable function transformer 5 to change the output voltage to a predetermined rated voltage. The value is increased by a value (about 10% of the rated voltage), and after a predetermined time has elapsed, the tap is switched again to return to the rated voltage.

For example, if the AC power supply 1 is lost due to a lightning strike or the like during the operation of the motor 4 at the rated speed, the secondary voltage of the transformer 5 with an output voltage variable function is also lost, and the inverter device 3 The input power to the is lost. in this case,
The inverter device 3 cannot drive the motor 4 because the input power is lost. Therefore, the inverter device 3 stops the operation of the motor 4 while the input power is lost.

Thereafter, when the AC power supply 1 recovers power and recovers, the secondary voltage of the transformer 5 with an output voltage variable function also recovers, and the input power supply of the inverter device 3 recovers. At this time, the control device 6 switches the tap of the transformer with output voltage variable function 5 to change the output voltage to a predetermined value of the rated voltage (10% of the rated voltage).
Degree). In this state, each of the inverter devices 3a to 3n restarts the operation of the motors 4a to 4n all at once and controls the drive to the rated operation. In this case, since the secondary voltage of the transformer 5 with the output voltage variable function is set high,
Even if the inverter devices 3a to 3n start drive control at the same time, the voltage does not drop to the voltage at which the inverters 3a to 3n stop.

When each of the motors 4a to 4n enters the rated operation state, there is no need to worry about a voltage drop. Therefore, the control device 6 switches the tap of the transformer 5 with an output voltage variable function to return the output voltage to the rated voltage.

As described above, in this embodiment, when the AC power from the AC power supply 1 is supplied to the plurality of inverter devices 3 via the transformer 5 with an output voltage variable function,
When the AC voltage of the AC power supply 1 is lost, the AC voltage supplied to the inverter device 3 from the transformer with output voltage variable function 5 is set high, and is restored after a predetermined time has elapsed.

FIG. 2 is a characteristic diagram in the case where a power failure occurs in the AC power supply 1 and thereafter the power is restored. Assume that a power failure occurs in the AC power supply 1 at time t1. Due to the loss of the AC power supply 1, the secondary side voltage of the transformer 5 with the output voltage variable function is also lost.
That is, since power supply to the inverter device 3 is stopped, the inverter device 3 is stopped, and the number of rotations of the motor 4 is naturally reduced, and eventually stopped.

If it is assumed that the AC power supply 1 is restored at time t2, the secondary voltage of the transformer 5 with the output voltage variable function is also restored. At this time, the control device 6 switches the tap of the transformer with output voltage variable function 5 to increase the output voltage by a predetermined value of the rated voltage (about 10% of the rated voltage).

Each of the inverter devices 3a to 3n simultaneously controls the drive of the motor 4 at a time t3 after a lapse of a predetermined standby time T from a recovery time t2 of the secondary voltage of the transformer 5 having a variable output voltage function. Start. Therefore, although the secondary voltage of the transformer 5 with the output voltage variable function generates a voltage drop,
Since the secondary voltage of the transformer 5 with the output voltage variable function is set high, even if the inverter devices 3a to 3n start drive control all at once, the inverters 3a to 3n may drop to a voltage at which they stop. There is no.

At time t4 when a predetermined time has elapsed from time t2, control device 6 switches the tap of transformer 5 with an output voltage variable function to return the output voltage to the rated voltage. That is, as the predetermined time in the control device 6, each of the inverter devices 3a to 3n is connected to each of the motors 4a to 4n.
A time longer than the time required to start up from the start to the rated operation is set.

As described above, in the embodiment of the present invention, when the input power of the inverter device 3 is lost and returned, the motor 4 returns the input power supplied to the inverter device 3 to the rated speed again. In the meantime, the output voltage variable function-equipped transformer 5 causes the voltage to rise above the rated voltage. This allows
By keeping the voltage of the input power supply of the inverter device 3 equal to or higher than the predetermined voltage, the inverter device can drive the motor 4 properly.

The reason for raising the voltage of the input power supply is as follows.
Since it is only a predetermined time until the motor 4 in the stopped or naturally lowering state returns to the rated speed again, when the load device is connected to the load system to which the inverter device 3 is connected, the load device is The operation time of the excessive voltage is shortened. Therefore, the life of the load device is not adversely affected.

Further, since the voltage of the input power supply of the inverter device 3 can be maintained at a predetermined voltage or higher, it is not necessary to sequentially operate the plurality of inverter devices 3a to 3n after the input power supply is restored. Since the operation can be started, the plurality of motors 4a to 4n can be returned to the rated speed again in a short time.

[0031]

As described above, according to the power supply system of the present invention, a motor in a stopped or naturally decelerating state can be properly driven by the inverter device, and a plurality of motors after the input voltage is restored are restored. The operation of the inverter device can be started all at once. Therefore, it is possible to return the plurality of motors to the rated speed again in a short time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing operation characteristics in the embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional example.

FIG. 4 is a characteristic diagram showing operation characteristics of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Transformer 3 Inverter device 4 Motor 5 Transformer with output voltage variable function 6 Control device

Claims (2)

[Claims] In a power supply system for supplying power to a load system in which a plurality of motors are driven by respective inverter devices, an AC power supply is input to a primary side and transformed to a predetermined voltage to convert the secondary power to a predetermined voltage. A transformer with an output voltage variable function for supplying a voltage as an input power to the inverter device, and a secondary voltage of the transformer with an output voltage variable function which is predetermined from a rated voltage when the AC power is lost and the power is restored. A power supply system having a control device for increasing the value by a predetermined value and returning to a rated voltage after a predetermined time has elapsed. 2. The control device according to claim 1, wherein when the AC power is lost and the power is restored, the secondary voltage of the transformer with an output voltage variable function is increased by 10% of a rated voltage. The power supply equipment according to claim 1.