JPS60210193A - Operation system of variable frequency power source - Google Patents

Abstract

PURPOSE:To safely operate continuously a facility by switching from a variable frequency power source to a commercial power source if the change rate of a control output signal is displaced out of the prescribed range. CONSTITUTION:A motor 3 is driven by a variable frequency power source 2B, and a fan 4 is rotated. A variation command for the output air flow rate Q of a fan is applied as a control signal 6 to a controller 5b, and a control output signal 7B integrated by an integrator 5C is applied by a controller 5B to a variable frequency power source system 2. The change rate of the signal 7B is detected by a change rate detector 2A, if normal, the power source 2B is controlled to the frequency corresponding to a control output signal 7B, and if not normal, switches 9, 10 are opened, a switch 11 is closed, the variable frequency power source is switched to a commercial power source, and the operation is continued.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a variable frequency power supply (hereinafter abbreviated as VF power supply).
The present invention relates to a method of operating a variable frequency power supply that supplies power to an electric motor and uses the electric motor to drive a rotating body such as a fan pump.

[Prior art]

A conventional device for this purpose is shown in FIG. 1
1 is commercial! Ryo, 2B is variable frequency VFt Ryo, 3
HttEila, let rotating body, 5Al-1 control device,
6 is a control signal, 7A is a control output signal of control device 5A, 8
9 is a coupler for mechanically coupling the electric motor 3 and the rotating body 4, and 9 is a switch.

'Ffc, Figure 2 is an explanatory time chart diagram of Figure 1, and tl is a disconnection at the control output signal 7A (should be the connection terminal n,
t2 is the timing stop point when the system blade becomes stable after the wire breakage occurs t1.

F is the output frequency of the VF electric power supply 2B, n is the 30 rotation speed of the electric motor, and Q is the output air volume of the rotating body 4.

The operation shown in FIG. 1 will be briefly explained below.

Switch 9 from commercial power supply 1? Via VF Hiroshi! When the illumination voltage is applied to 2B, the output frequency F of the VF power supply 2B
There is a relationship between Equation 11 and the rotational speed n of the electric motor 3.

However, p: number of poles of tb machine 3 Therefore, the rotating body 4 will be explained as a fan.

The output air volume 111 of the fan 4 changes approximately in proportion to the rotation speed n. If the VF power supply 2B' is applied to a boiler in a power generation plant, there will be a change in the output air volume Q generation request in response to a request from the power system or a change in the fuel supply situation, and this change signal will be used for control. It is used as signal 6. This control signal 6 is a control output signal 7A suitable for control by the control device 5A.
(For example, VF is converted into a current signal of 4 to 20 mA.
7 as the rotational speed n of the electric motor 3 shown in equation (1) changes by following the value of the output frequency FY request.
Change the output air volume Q' of Ann 4.

Since the conventional VFl source is configured as described above, if a disconnection of the signal line occurs between the control device 5A and the VFt control device 2B at time t□ as shown in Fig. 2, the control signal 6 becomes normal. Despite this, the control blade signal 7A changes to zero and the output frequency Fa of the VF power supply 2B? It will be changed as shown in Figure 2.

Therefore, when the output frequency F changes, the rotation speed n of the electric motor 81130 and the output air volume Q of the fan 4 change as shown in equation (1). That is, there is a drawback that the output of the rotating body 4 changes drastically when it should not change, which can lead to accidents such as plant shutdown.

[Summary of the invention]

This invention has been made to eliminate the drawbacks of the prior art as mentioned above. The control signal 6 is integrated within the control device, and its output signal is VFI! A rate-of-change detector for verifying the rate of change of the integrated input signal is provided in the VFt source, and when the rate-of-change detector detects an abnormality, power is supplied to the blind motor 3. Illumination YVFll source 3
It is an object of the present invention to provide a variable frequency illumination operation method that can safely and continuously operate a Niji VF illumination system when switching from commercial to commercial mode. An example diagram will be explained. In FIG. 3, the same parts as in FIG. 1 are designated by the same reference numerals. In FIG. Control device,
7B is an output signal of the control device 5B, and 10 and 11 are switches.

Moreover, FIG. 4 is a time chart diagram for explaining FIG. 3. In the figure, t3 is the time when switches 9 and 10 are completed opening,
t, at the time when the ia switch 11 has been closed.

t5 indicates a point in time when the electric motor 3 reaches a rotational speed corresponding to the frequency of the commercial power source 1, and t6 indicates a point in time when the output air volume Q of the rotating body (fan) stabilizes at the usual value.

FIG. 5 shows a configuration diagram of the rate of change abnormality detector, and FIG. 6 is an explanatory diagram illustrating the operation of item 7.

In the figure, IIN is the input signal, G1+G2 is the select switch, PGRU pulse generator, HLD
, HLD2 is a hold circuit, DTR is a differential voltage detector,
COM is a size judger.

The operation shown in FIG. 3 will be briefly explained below.

1. Assuming that switches 9 and 10 are ON and switch 11 is OFF, VF power υ2Bk1 is generated from commercial power supply 1 as in Fig. 1.
A voltage is applied n, and the electric motor m3 is driven by its output n, 7
7-4 is rotated. A change command for the output air volume Q of the fan 4 is given to the control device 5B as a control signal 6, and the control device 5B integrates the control output signal 7B' in the integrating circuit 5C and gives it to the kVF power supply system 2. The rate of change detector 2A forming the VF illumination stem 2 verifies the rate of change of the control output signal 7B, and if it is normal, the output of the VFt source 2B is set to the frequency corresponding to the control output signal 7B. Follow the frequency F, and if there is an abnormality, turn off the switch 9.10.
F, continue to turn on the switch 11. As can be understood from Section 8, the operation of the rate of change detector described above is such that the pulse generator PGR generates pulses at one-foot intervals.
The selector switches G 1 t G 2 mutually respond to this pulse and send the instantaneous values of the input signal AE N to the hold circuits HLD 1 and HLD 2, respectively.

If the input signal N changes as in the sixth case, the hold circuit HLD1.21! Also, the instantaneous values of the input signal N at each pulse point are outputted as shown in the diagram. The output difference of the hold circuit BLD12 is detected by the difference voltage detector DTR, and when the difference voltage becomes one step or more (12+α
It is assumed that there is an abnormal change in the input signal III at the point in time), and an output signal is sent. Note that α is the pulse generator PGR
corresponds to the pulse interval of

Therefore, as shown in FIG. 4, at time t1, the control device 5B and VF
ii Even if a signal wire breakage occurs in the source system 2,
Is the rate of change detector 2A immediately abnormal? Detection and switch 9.1
Open 0 (1, time point), close switch 11 (t, time point)
do. When the switches 9 and 10 are opened, the motor turns 30 times n, and the number of revolutions decreases somewhat due to the voltage-free state, but the number of revolutions increases again with the subsequent closing operation of the switch 11. At this point, the rotation speed corresponds to the frequency of the commercial power source 1. In addition, in the case where the one-rotating body 4 is a fan, in addition to the control based on the rotation speed n, there is also a mechanical inlet vane (or fan vane control (not shown)) to control the blade air volume Q.The output depends on the rotation speed nK. During air volume Q control, the inlet vane is operated at a point close to fully open in order to reduce output loss.As mentioned above, the rotational speed n increases to a value 1 corresponding to the frequency of commercial If you set the output air volume QU artificial vane to 11 when controlling the air volume using the rotation speed n, the change will be great.

It will be a hailstorm. Therefore, the inlet vane is operated in the direction of decreasing the blade air volume Q under conditions such as operation of the change rate detector 2A, opening of the switches 9 and 1o, and closing of the switch 11.

Therefore, the cutting air volume Q of the fourth blade decreases by one degree when the switch 9, 1 degree is opened, and increases when the switch 11 is closed. In the normal case, the response of the artificial vane is as the rotational speed n increases.

Therefore, while the rotational speed n is increasing, the deba wind tq increases slightly due to the decreasing effect of the artificial vane.

After the rotation speed n reaches the rotation speed due to the commercial power supply 1 (at time t
, thereafter, the output air volume Q decreases due to the action of the inlet vane and returns to its original value at time t6.

Although the cutting air volume Q changes as shown in FIG. 1, the small change is kept within the tolerance of the system, and even if an abnormality occurs in the control output signal 7B, operation can be continued safely.

The above was explained using the example of power generation plant 7772.

It is clear that the present invention may be applied to other rotating bodies such as pumps and other plants.

Further, although the example has been explained in terms of a disconnection, other abnormalities such as a short circuit may be used, and the control output signal 7B may become abnormal due to an abnormality in the control device 5B rather than an abnormality in the signal transmission line.

〔Effect of the invention〕

As described above, according to the present invention, the control signal 'I:r: is integrated in the control device and then the control output signal is
! source system system 2. Two rate-of-change detectors monitor whether the integrated control output signal is within a predetermined rate of change, and when the rate-of-change detector is activated, the illumination applied to the motor is switched from the VF illumination to the commercial power supply. Since I configured the circuit to switch to the equipment? It has the effect of allowing you to drive continuously and safely.

[Brief explanation of drawings]

Figure 1 is a system diagram of a motor speed control system using conventional variable frequency illumination, and Figure 2 is an explanatory time chart 1 of Figure 1.
．． FIG. 3 is a system diagram of a motor speed control system using variable frequency illumination of the present invention, FIG. 4 is a time chart for explaining FIG. 3, and FIG. 5 is a configuration diagram of a rate of change detector. FIG. 6 is an explanatory diagram of FIG. 1... Commercial power supply, 2... Variable frequency VF power supply system, 2A... Rate of change detector, 2B... Variable frequency illumination. 3... Electric motor, 4... Rotating body, 5A, 5B... Control device. 5C...Integrator circuit, 6...Control signal, 7B...Control output signal, 8...Coupler, 9,10.11...Switch. Patent applicant: Mitsubishi Electric Corporation

Claims (1)

[Claims] An NFC motor connected to a variable frequency power supply, and a control signal given to the variable frequency illumination for controlling the rotational speed sound of a rotating body coupled to the motor. In the operating system of the variable frequency power source having a control device and a control device which generates a control signal for instructing an increase/decrease in the output of the rotating body, the control signal is integrated by an integrating circuit provided in the control device. The integrated output signal is transmitted as a control output signal to a rate of change detector in the variable frequency power supply system. The integrated circuit is characterized in that when the control output signal of the integrated signal n7 falls outside the required change rate range t', a rate of change detector is activated to switch the power supply to the motor from the variable frequency illumination to the commercial power supply. Operation method of variable frequency power supply.