JPH0870594A - Method for restarting after voltage drop or instantaneous power failure in inverter - Google Patents

Abstract

PURPOSE: To make possible smooth restarting by storing the direction of the rotation of a motor in operation, comparing a signal, input at the time of power restoration, with the stored rotational direction, and starting the motor in accordance with the stored rotational direction before switching the rotation to the input signal at the time of power restoration. CONSTITUTION: If pick-up mode is established at step (ST) 22, when power supply is restored after an instantaneous power failure, operation proceeds to ST 27 'Reverse rotation mode=1' in order to determine the direction of rotation to pick up according to input signal at the time of power on starting. If the direction of operation is forward and input signal is reverse, it is judged that reverse rotation mode=1. Then, if there is not forward rotation signal at ST 28. 'Pick up forward rotation' is selected at ST 29, and output is made in the direction of forward rotation. Thereafter, the motor is decelerated and stopped at ST 30, and is then accelerated in reverse at ST 31. This smoothly switches the direction of the rotation of the motor from forward to reverse. If there is a forward rotation signal at ST 28, operation proceeds to ST 32 'Pick up forward rotation', and output is made in the direction of forward rotation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting normally when power is restored due to voltage drop or momentary power failure during inverter operation.

[0002]

2. Description of the Related Art FIG. 1 is a diagram showing a conventional inverter circuit configuration, in which a commercial AC power source 1 converts a DC voltage including ripples through a converter unit 2,
The smoothing capacitor 3 produces a DC voltage that does not include ripples. 4 is an inverter unit for converting direct current into alternating current,
The output is applied to the electric motor 5 through the inverter unit 4.
A control unit 6 includes a drive circuit unit 7, an A / D converter 8, an interface circuit 9, a CPU unit 10, and a non-volatile memory element 1.
1 is comprised.

A frequency setting input voltage, which is an analog signal set by the frequency setting unit 12, is input to the A / D converter 8, converted into a digital signal, and input to the CPU section 10. On the other hand, when either the normal rotation switch 13 or the reverse rotation switch 14 is closed, the normal rotation or reverse rotation signal is input to the CPU section 10 through the interface circuit 9 which isolates an external signal. When the CPU section 10 performs all the arithmetic processing, the CPU section 10 reads the data from the non-volatile memory element 11 in which the arithmetic result and the data of various parameters are stored and performs the arithmetic processing. The signal calculated from the CPU unit 10 is input to the drive circuit unit 7, is further amplified, and drives the inverter unit 4.

FIG. 2 is an explanatory view of the normal rotation and reverse rotation of the inverter. When the normal rotation signal is input, the output frequency is output in the normal rotation direction according to the set acceleration time, and the inverter operates at the set frequency. After that, when the forward rotation signal is opened and the reverse rotation signal is closed, the motor decelerates and stops according to the set deceleration time.After a certain period of rest, the output frequency is output in the reverse rotation direction according to the set acceleration time, and runs at the set frequency. To do.

FIG. 3 is a diagram for explaining the operation of the inverter during a momentary power failure. The normal signal is input and the normal signal is operated in the normal direction at the set frequency, and then the normal signal is opened and the reverse signal is closed. It is a figure which shows the operation state at the time of a power failure, when an instantaneous power failure occurred during deceleration in deceleration time. When an instantaneous power failure occurs at time t1, the inverter stops and the output frequency becomes 0, but the electric motor continues to rotate in the forward direction due to inertia.
Next, when power is restored at time t2, the inverter tries to output a frequency synchronized with the rotation speed of the motor, but at time t2
Since the reverse rotation signal is input at, the frequency in the reverse rotation direction is output. For this reason, the inverter cannot be normally started, and in some cases, the overcurrent protection circuit of the inverter operates and stops.

[0006]

During operation of the electric motor, a voltage drop or an instantaneous power failure occurs immediately after the signal input of the inverter is switched, and the signal input is switched when the electric power is restored during deceleration of the electric motor. The present invention relates to a method of outputting a frequency in the direction of, thereby preventing the overcurrent protection circuit from operating and stopping in some cases, and smoothly switching the rotation direction of the electric motor.

[0007]

Data of the rotating direction of the electric motor is stored in a non-volatile memory element 11 during operation, and the signal input which is input at the time of power recovery and the above-mentioned non-volatile memory element 11 are stored.
The problem was solved by comparing and judging the data in the direction of rotation of the electric motor stored in the above, and switching the rotation to the input signal at the time of power recovery after starting according to the direction of rotation of the electric motor.

[0008]

The voltage drop or the instantaneous power failure occurs immediately after the signal input for determining the operating direction of the motor is switched,
If power is restored during deceleration of the motor, it can start normally.

[0009]

【Example】

[Table 1] Is a table showing the combination of the operating direction of the inverter and the input signal, and FIG. 4 is a diagram showing the relationship between the operating direction of the inverter and the input signal.

As shown in Table 1, the operating states are classified into three types, and the data are stored in the non-volatile memory element 11 at the address set as the reverse mode. Reverse mode = 0 is when the direction of the input signal coincides with the stop or driving, and reverse mode = 1 is when the driving direction is forward and the input signal is reverse direction, the reverse mode = 2 Shows the case where the driving direction is reverse and the input signal is forward.

FIG. 5 is a diagram for explaining the operation of the inverter of the present invention during a momentary power failure. After the forward rotation signal is input and the inverter operates at the forward rotation direction set frequency, the forward rotation signal opens and the motor decelerates for the set deceleration time. It is a figure which shows the operation state at the time of a middle and momentary power failure generate | occur | produced, and power is restored. When an instantaneous power failure occurs at time t1, the inverter stops and the frequency becomes 0. However, when power is restored at time t2, the power supply in FIG.
As shown in the flow chart for determining the reverse rotation, the power is turned on in step 21 in the nonvolatile memory element 11, and then the pick-up mode in step 22 is read.
In this case, if the pick-up mode is not set in step 22, it is judged that the operation method is the conventional one shown in FIG. 3, and the process proceeds to step 23 to see if there is a normal rotation signal. Forward rotation acceleration operation is performed. If there is no forward rotation signal in step 23, it is determined in step 25 that there is a reverse rotation signal, and the reverse rotation acceleration operation in step 26 is performed.

If the pick-up mode of step 22 is read and the pick-up mode is set, the rotation direction of pick-up is determined by the input signal when the power is turned on. Go to. If the driving direction is normal and the input signal is reverse as shown in Table 1, it is judged that the reverse mode is 1, and if there is no forward signal in step 28, normal rotation is picked up in step 29 and normal rotation is taken. Direction, and then in step 30, deceleration and stop are performed, and then in step 31, reverse rotation acceleration is performed, and the rotation direction of the electric motor smoothly switches from forward rotation to reverse rotation. If there is a normal rotation signal in step 28, the normal rotation pick-up is proceeded to in step 32 and output in the normal rotation direction.

If the reverse mode is not 1 in step 27, the process proceeds to reverse mode = 2 in step 33. When the driving direction is reverse rotation and the input signal is forward rotation as shown in Table 1, it is judged that the reverse rotation mode is 2. If there is no reverse rotation signal in step 34, the reverse rotation is picked up in step 35 and the reverse rotation direction is set. After that, the output is decelerated and stopped at step 36, and then forward rotation acceleration is performed at step 37, and the rotation direction of the electric motor is smoothly switched from reverse rotation to forward rotation. If there is a reverse rotation signal in step 34, the operation proceeds to reverse rotation pickup in step 38 and outputs in the reverse rotation direction.

If the reverse mode is not 2 in step 33, no output is made if there is no input signal when the power is turned on, but if the input signal is input after the power is turned on, the forward rotation or the reverse rotation is picked up. As a result, if there is a forward rotation signal in step 39, the operation proceeds to forward rotation pickup in step 32 and outputs in the forward rotation direction, and if there is no forward rotation signal in step 39, proceeds to reverse rotation pickup in step 38 and outputs in the reverse rotation direction. To do.

[0014]

By storing the above-mentioned program in the non-volatile memory element, it is possible to pick up by an output suitable for the rotating direction of the electric motor when the voltage drops or the momentary power failure is restored without increasing the number of parts. It becomes possible and restarts after a momentary power failure in any operating condition.

[Brief description of drawings]

 This will be described below.

FIG. 1 is a block diagram of an inverter circuit that has been conventionally implemented.

FIG. 2 is a diagram for explaining the forward / reverse operation of the inverter.

FIG. 3 is a diagram for explaining the operation of the inverter during a momentary power failure.

FIG. 4 is a diagram showing a relationship between an operating direction of the inverter and an input signal.

FIG. 5 is a diagram for explaining the operation of the inverter of the present invention during a momentary power failure.

FIG. 6 is a flowchart for determining whether the inverter is rotating normally or reversely after the power source is activated.

[Explanation of symbols]

 1 Commercial AC Power Supply 2 Converter Section 3 Smoothing Capacitor 4 Inverter Section 5 Motor 6 Control Section 7 Drive Circuit Section 8 A / D Converter 9 Interface Circuit 10 CPU Section 11 Nonvolatile Storage Element 12 Frequency Setting device 13 Forward rotation switch 14 Reverse rotation switch

Claims (1)

[Claims] 1. A converter for converting a commercial AC power source into a direct current.
An inverter section for controlling the pulse width of the DC output of the converter section and applying it to the AC motor, a control section for controlling the pulse width of the inverter section, and the control section for the AC motor. In the inverter having a CPU unit for controlling the rotation speed and the rotation direction, which starts synchronously with the rotation speed of the AC motor at the time of the voltage drop of the commercial AC power source or the momentary power failure, the voltage drop of the commercial AC power source or the momentary power failure occurs. The rotation direction of the AC motor is stored in a non-volatile storage element, and the rotation direction of the AC motor is not matched by comparing the rotation direction of the AC motor when the voltage drop or the instantaneous power failure is restored with the storage data of the non-volatile storage element. Time,
A method for restarting a voltage drop or an instantaneous blackout of an inverter for applying an inverter output to the AC motor in synchronism with the rotation direction and rotation speed of the AC motor after decelerating and stopping the AC motor.