JPH0350517B2 - - Google Patents

Description

[Detailed description of the invention] [Object of the invention] "Industrial application field" This invention maintains water supply pressure constant using a variable speed electric motor whose speed is controlled by an inverter and a pump driven by the variable speed electric motor. This invention relates to a variable speed water supply device that supplies water in accordance with water supply demand.

``Prior art'' In general, inverters that vary the speed of induction motors or periodic motors are equipped with a control system to protect the inverter when a sudden change in the system puts a load on the inverter and causes it to become uncontrollable (called an inverter trip). It is designed to output a signal indicating a failure (called an inverter trip signal).

Variable speed equipment equipped with an electric motor whose speed is controlled by an inverter, such as a variable speed water supply equipment that changes the rotation speed of the pump in order to maintain a constant water supply pressure, stops the equipment in response to an inverter trip signal. It was common to do so.

"Problems to be Solved by the Invention" When considering the causes of inverter trips, they can be broadly classified into the following two types.

A coincidence caused by adverse system conditions.

A fatal problem that has an obvious cause in the system itself, and if left untreated will lead to damage to the equipment.

In the case of an inverter trip due to an accidental cause, if the inverter is reset, it is unlikely that the inverter will trip again.

If the inverter trips due to a fatal cause, the inverter will immediately trip again even if the engine is restarted.

In equipment such as water supply equipment where stopping would lead to dehydration, when an inverter trip is due to an accidental cause, it is desirable to immediately reset the inverter, but conventionally the inverter has been stopped.

The first invention of the present application determines, when an inverter trip occurs in a variable speed motor that is controlled and driven by an inverter, whether the cause is a fatal cause such as a failure of the device driven by the variable speed motor or non-conformity of the entire system. An object of the present invention is to provide a control device for a variable speed electric motor that can output signals that can be used.

The second invention of the present application is that in a variable speed water supply system equipped with a pump driven by a variable speed electric motor operated by inverter control, restarting the water supply system may lead to destruction of the water supply system in the event of an inverter trip. To provide a variable speed water supply device capable of determining whether the water supply device should be stopped or whether the water supply device may be restarted because it is due to an accidental factor.

[Structure of the invention]

"Means for Solving Problems" The first invention of the present application includes an inverter that changes the power frequency, an electric motor supplied with variable frequency power from the inverter, and an inverter that outputs a start/stop signal reset signal frequency command to the inverter. , is equipped with a control device that inputs the inverter trip signal, and when the inverter trips, if a predetermined period of time has passed since the previous inverter trip, it automatically resets the inverter and restores the previous inverter trip. This variable speed electric motor is characterized in that it is equipped with a control device that stops the device if the motor fails within a predetermined period of time.

The second invention of the present application includes a pump that is operated at variable speed by an electric motor supplied with variable frequency power from an inverter that changes the power supply frequency, and inputs a water supply information signal on the pump discharge side to a control device by the pump, thereby controlling the water supply pressure. This is a variable speed water supply system that performs constant control, and when the inverter trips, the control device automatically resets the inverter if a predetermined period of time has elapsed since the previous trip. This is a variable speed water supply system that will shut down the system if it fails within a set period of time.

Embodiment FIG. 1 is a block diagram of an embodiment of the present invention.
Power is supplied from a power source 1 to an inverter 3 via a switch 2. A frequency command signal S _f is input from the control device 4 to the inverter 3, and power at the frequency of the frequency command signal S _f is output from the inverter 3 to generate an induction motor or a synchronous motor (hereinafter, a type of motor that can be controlled by an inverter). It is designed to energize a motor (simply referred to as an electric motor). The electric motor 5 drives the working machine 6 as a prime mover.

The inverter 3 sends an inverter trip signal when the motor 5 becomes uncontrollable by the inverter 3.
The inverter 3 is designed to output the inverter trip signal S _i and input the inverter trip signal S _i to the control device 4.

The control device 4 is equipped with a timing device that counts the time since the last input of the inverter trip signal S _i , and when the inverter trip signal S _i is input, the control device 4 counts the time since the last input of the inverter trip signal S _i . The elapsed time T _x from time T _i to time T _i+1 when the current inverter trip signal S _i is input is measured. The control device 4 predetermines a time T _p that is sufficiently short compared to the long time considered from the probability that an overload may occur accidentally on the work implement 6 in view of the system of the work implement 6 driven by the electric motor 5. , compare a predetermined time T _p with the elapsed time T _x of the inverter trip signal generation, and if the time T _x exceeds the time T _p , output a reset signal S _r to the inverter 3;
The inverter 3 is restored and the motor 5 continues to operate, and if the time T _x is within the time T _p , a cut signal S _c is immediately sent to the switch 2 to cut off the power.

FIG. 2 is a flowchart showing the operation of the control device of FIG. 1. Step 1 when the system starts
Then, the control device 4 determines whether or not the inverter trip signal S _i is being input. If the inverter trip signal S _i is not being input, the operation continues, and the inverter trip signal S _i is input to the control device. 4
If it is entered, proceed to step 2.

In step 2, the predetermined time T _p set in the control device 4 and the elapsed time from when the previous inverter trip signal S _i was issued to when the current inverter trip signal S _{i +1} is issued are determined.
T _x is compared and if T _p <T _x , proceed to step 3A.

In step 3A, the control device 4 outputs a reset signal S _r
is sent to the inverter 3, and the electric motor 5 is restarted.

If T _p ≧T _x in step 2, proceed to step 3B.

In step 3B, the disconnection signal S _c of the switch 2 is issued, and at the same time, an alarm signal S _a is output.

In addition, when the inverter trip signal _{S r} is output between step 1 and step 2 in the flowchart of FIG. In step 3A of FIG. 2, the switch 2 may be turned on at the same time as the inverter reset signal S _r , and in step 3B, the disconnection signal S _c of the switch 2 may not be output again.

FIG. 3 shows another example of the operation of the control device 4 shown in FIG. 1. Steps 1, 2, and 3B are the same as in FIG. 2, and in step 3A, the reset signal is
_Sr , an alarm output _S'a indicating that the inverter has tripped and been reset is output.

FIG. 4 is a flow sheet of an embodiment of the variable speed water supply device. A pump 7 as a working machine is driven by an induction motor 5, and has a water tank 8.
The water sucked in through the suction pipe 9 is pressurized by the pump 7 and discharged into the discharge pipe 11. The discharge pressure of the pump is detected by a pressure sensor 12 provided in the discharge pipe 11, and the discharge pressure signal S _w is sent to the control device 4 of the pump. The pump control device 4 uses the detected value of the discharge pressure detected by the pressure sensor 12.
Using the relationship between S _w and the rotational speed of the pump 7, a frequency command signal S _f with a constant terminal pressure is output to the inverter 3, and the inverter 3 converts the frequency of the commercial power supply 1 input via the switch 2 to generate a frequency command signal
Power with a frequency corresponding to S _f is output, the speed of the electric motor 5 is changed, and the rotational speed of the pump 7 is changed to perform constant terminal pressure control. Alternatively, for example, when piping resistance is low, constant discharge pressure control is performed. Alternatively, the discharge piping 11 is equipped with a flow meter, and the water supply terminal pressure is controlled to be constant using the flow meter signal and the detected value S _w of the pressure sensor.

Now, for example, if the water supply amount increases beyond the maximum water supply amount, and the terminal pressure of the pump 7 is constant, the pressure sensor 1
Since the motor 5 rotates at high speed while a high discharge pressure signal is being output from the motor 5, a discharge pressure signal S _wMAX or higher is input to the control device 4 to control the terminal pressure constant control. If the frequency command signal S _f exceeds the signal S _fMAX equal to the frequency corresponding to the maximum rotational speed of the pump 7, then the frequency command signal S f exceeds the signal S _fMAX
Even if the control device 4 is equipped to issue an alarm together with S _fMAX , if this part of the control device 4 is out of order, the motor 5 will be overloaded and an inverter trip will occur.

Therefore, since such an abnormal increase in water supply demand is generally temporary and quickly resolved, the control device 4 sends a reset signal to the inverter 3 when an inverter trip occurs. Send S _r to restart the electric motor 5. And normally, an inverter trip will not occur if it remains as it is. It is possible that the same condition will occur after a sufficiently long elapsed time T _x .
Therefore, a sufficiently short time _Tp , for example, 30 minutes, is predetermined for the elapsed time _Tx , which is long enough to be regarded as an accident.
Such time T _p is determined from, for example, the temperature rise limit of the electric motor 5, pump 7, etc. so that there is no problem in continuously operating the pump device during the time T _p .

A control device 4 that controls and drives the electric motor 5 shown in FIG.
The inverter 3 performs water supply pressure constant control that controls the discharge pressure of the pump 7 according to the amount of water supplied so that the water supply pressure remains constant. is designed to perform the same function, so even if the pump 7 is stopped due to temporary overload, operation will continue.

As the demand changes permanently such that the amount of water supplied always exceeds the maximum amount of water supplied, the elapsed time _T The pump 7 is often not restarted as the time Tp is shorter than the time _Tp . From this, trends in water supply demand can be indirectly determined.

In addition, if a serious failure occurs in the pump device, the elapsed time T _x of the subsequent inverter trip will be T _p > T _x
Therefore, switch 2 is opened and the variable speed water supply device is stopped.

〔Effect of the invention〕

The first invention is provided with a motor control circuit that inputs the inverter trip signal to the control device and compares the elapsed time from the previous inverter trip signal to the current inverter trip signal with a predetermined constant time. It is possible to half-indicate whether an inverter trip has occurred due to an accidental combination of conditions in a working machine system driven by an electric motor or whether the inverter trip has occurred due to a failure of the system, and maintenance management can be performed appropriately.

In the second invention, since the control device of the first invention is attached to the control device of a variable speed water supply device that supplies water by controlling the terminal pressure to be constant, when the pump device stops due to an inverter trip, the stoppage is caused by accident. If the problem is due to an increase in the amount of water supplied, the pump equipment will continue to operate, so there will be no water outage.

If the demand for water supply increases on average compared to the initial plan for water supply equipment, or if a defective part of the water supply equipment occurs, it can be determined and appropriate measures can be taken.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an embodiment of the present invention, FIGS. 2 and 3 are flowcharts each showing the operation of FIG. 1, and FIG. 4 is a flowsheet of an embodiment of a variable speed water supply device. 1...Power source, 2...Switch, 3...Inverter, 4...Control device, 5...Induction motor, 6...
Work equipment, 7... pump, 8... water tank, 9... suction pipe, 11... discharge piping, 12... pressure sensor.

Claims (1)

[Claims] 1. An inverter that changes the power frequency, an electric motor supplied with variable frequency power from the inverter, an inverter start/stop signal, a reset signal,
It is equipped with a control device that outputs frequency commands to the inverter and inputs inverter trip signals, and automatically resets the inverter if a predetermined period of time has passed since the previous inverter trip when the inverter trips. A variable speed electric motor characterized in that the variable speed electric motor is equipped with a control device that stops the electric motor if an inverter trip occurs within a predetermined period of time since the previous inverter trip. 2. A variable speed pump that is equipped with a pump that is operated at variable speeds by an electric motor that is supplied with variable frequency power from an inverter that changes the power supply frequency, and that the pump inputs a water supply information signal on the pump discharge side to a control device to control the water supply pressure at a constant level. In the water supply device, the control device automatically resets the inverter if a predetermined period of time has elapsed since the previous trip when the inverter trips;
A variable speed water supply device characterized by comprising a control device that stops the pump device if the pump device fails within a predetermined period of time since the previous trip.