JPH05227646A - Motor protection equipment - Google Patents

Abstract

PURPOSE:To provide a motor protection equipment capable of calculating with simple arithmetic means the integrated amount of the accumulated heat in a three-phase AC motor in an overcurrental state and the amount of heat radiat ed in the three-phase AC motor during instantaneous interruption of a control power supply. CONSTITUTION:Amount of heat accumulated in a three-phase AC motor is calculated by IM<2>XT1 (where, IM is rated current ratio of motor, and T1 is sampling interval); there is means of calculating integrated amount of accumulated heat by integrating the accumulated heat; and there is means of calculating the amount of heat radiated for three-phase AC motor during instantaneous stop of a control power source by using TSXTD (where, TS: instantaneous time, TD: motor radiation constant). Therefore, the integrated amount of accumulated heat of three-phase AC motor can be accurately calculated by simple computing methods using step P6 and step P4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor protection device for protecting an electric motor from overheating and burning due to overload.

[0002]

2. Description of the Related Art In order to protect an electric motor from overheating and burnout,
Power supply monitoring means for detecting a power failure and power recovery of the control power supply of the protection device, timer means for measuring a power failure time from the power failure of the control power source to power recovery, and a temperature rise value calculated from an intrinsic constant of the motor and a motor current. Calculating means, a storage means capable of storing a temperature calculation result calculated by the calculating means during a power failure of the control power supply, and a power failure time measured by the timer means when power recovery is detected by the power supply monitoring means, and An electric motor protection device comprising means for calculating the heat radiation temperature of the electric motor from the temperature calculation result stored in the storage means is disclosed in JP-A-3-2281.
No. 9 is known.

[0003]

In the conventional motor protection device, the means for calculating the accumulated heat storage amount of the motor and the means for calculating the heat radiation amount of the motor during a power failure of the control power supply are complicated. An object of the present invention is to calculate the accumulated heat storage amount of the electric motor and the heat radiation amount of the electric motor by a simple calculation means.

[0004]

A motor protection device of the present invention is a current transformer for an instrument for determining an overcurrent state of a three-phase AC motor, a control power source connected to a three-phase line via a transformer,
An instantaneous blackout detection circuit for detecting an instantaneous blackout and power recovery of the control power supply,
An instantaneous blackout time detection circuit for measuring the instantaneous blackout time of the control power supply,
Based on the output of the current transformer for measuring instrument, the heat storage amount of the three-phase AC motor is I _M ² × T ₁ (where I _M : motor rated current ratio, T ₁ :
(Sampling interval time), means for calculating the accumulated heat amount by accumulating the accumulated heat amount obtained by the calculating means, an internal memory for storing the accumulated heat amount, the instantaneous interruption of the control power source, and A non-volatile memory for storing the integrated heat storage amount, and a heat release amount T _S × T _D from the integrated heat storage amount at the momentary power failure of the control power source stored in the nonvolatile memory when the control power source is restored. (However,
T _S : momentary power failure time T _D : means for storing in the internal memory by subtracting the motor heat dissipation time constant, and determining whether the accumulated heat accumulation amount stored in the internal memory is equal to or greater than the allowable accumulated heat accumulation amount And an overcurrent relay circuit that trips the three-phase AC motor when the determining unit determines that the accumulated heat storage amount is equal to or larger than the allowable accumulated heat storage amount.

[0005]

The heat storage amount of 1 of the three-phase AC motor is calculated by I _M ² × T, and the heat storage amount is integrated.

[0006]

1 is a block circuit diagram of a motor protection device of the present invention, and FIG. 2 is a flow chart showing the operation of a microcomputer of the present invention. In FIG.
The three-phase AC motor 1 is electrically connected to the three-phase line 2. The current transformer 3 for an instrument is electromagnetically engaged with the three-phase line 2 to detect an overcurrent flowing through the three-phase line 2. Current transformer for instrument 3
Is the analog input terminal of the microcomputer 4.
Entered in a. The microcomputer 4 has a built-in memory 9 in which a program is stored, and according to the program, the heat storage integrated amount of the three-phase AC motor 1 is calculated by the overcurrent detected by the instrument current transformer 3, and the calculated heat storage integrated amount is calculated. Are stored in the internal memory 12 of the microcomputer 4. The overcurrent relay 5 is electrically connected to the port output P of the microcomputer 4, and the internal memory 12
When the accumulated heat storage amount of exceeds the preset value, the three-phase AC motor 1 is tripped. The transformer 6 is electrically connected to the three-phase wire 2, and its output is input to the control power supply 8. The output of the control power supply 8 is input to the power supply terminal of the microcomputer 4. The instantaneous blackout detection circuit 7 is connected to the output terminal of the transformer 6 and detects when the control power supply 8 has an instantaneous blackout. The instantaneous blackout time detection circuit 10 is composed of, for example, an RC timer or the like, and inputs from the port output P of the microcomputer 4. Since it is composed of RC timer etc., the instantaneous power failure time detection circuit 10 has a control power source 8
Even after the momentary stoppage, the time during the momentary stoppage is measured.
The instantaneous blackout time measured by the instantaneous blackout time detection circuit 10 is input to the analog input a of the microcomputer 4. E ² PROM
The non-volatile memory 11 consisting of is attached to the port input / output terminal P of the microcomputer 4 and stores the accumulated heat storage amount of the internal memory 12 at the moment when the control power supply 8 is instantaneously stopped.

Next, the operation of the embodiment shown in FIG. 1 will be described. When the three-phase AC motor 1 is in an overcurrent state, the instrument current transformer 3 connected to the three-phase line 2 causes the three-phase AC motor 1 to move.
Of the three-phase AC motor 1 is integrated by the memory 9 that stores the program stored in the microcomputer 4, and when the integrated heat storage amount exceeds a preset value, Port output P
The overcurrent relay 5 operates via the, and trips the three-phase AC motor 1. Next, when the control power supply 8 is momentarily stopped due to the overcurrent of the three-phase AC motor 1, the instantaneous power failure detection circuit 7 detects the instantaneous power failure of the control power supply 8 and simultaneously interrupts the microcomputer 4 via the port input P. , Internal memory 12
The accumulated heat storage amount of the three-phase AC motor 1 stored in the above is written into the nonvolatile memory 11 composed of E ² PROM via the port output P. In addition, the momentary blackout time detection circuit 11 is operated via the port output P to measure the time during which the control power supply 8 has a momentary blackout. After that, when the control power supply 8 is restored and rises, the microcomputer 4 also rises, and at the same time, the instantaneous blackout time detection circuit 11 is stopped. When the control power supply 8 starts up and the three-phase AC motor 1 becomes overcurrent again, the accumulated heat storage amount written in the non-volatile memory 11 is momentarily stopped by the momentary power failure time detection circuit 11 via the port input / output P. The time is read by the microcomputer 4 via the analog input a. The memory 9 in which the program is stored calculates the amount of heat released by the three-phase AC motor 1 during the momentary power failure of the control power supply 8, and subtracts the amount of heat released from the accumulated heat storage amount in the non-volatile memory 11 at the time of instantaneous power failure. Then, the integrated heat storage amount immediately after the control power source 8 starts up is set. Upon completion of the calculation, the data in the non-volatile memory 11 and the instantaneous blackout time detection circuit 10 are cleared.

FIG. 2 shows a flow chart of the microcomputer 4. In step P ₁ , an initial set is performed,
At step P ₂ , the instantaneous blackout time (Ts) is read from the instantaneous blackout time detection circuit 10. In step P ₃ , the accumulated heat storage amount S ₁ when the control power supply 8 is instantaneously stopped is read from the non-volatile memory 11 composed of E ² PROM. The heat dissipation of the three-phase AC motor 1 is approximately T _S × T
_D (where T _D: Motor radiating time constant of) so can be expressed as, then the amount of heat released in the three-phase AC motor 1 in the instantaneous power failure time from the thermal storage integration amount S ₁ of a momentary power failure in step P ₄ T _S × T _D is subtracted and stored in the internal memory 12. Next, in step P ₅ , it is determined whether or not the three-phase AC motor 1 is in the overcurrent state. If the three-phase AC motor 1 is in the overcurrent state, the output of the current transformer 3 for the meter causes the sampling interval time T _{1 to} increase. Calculate the heat storage amount of the three-phase AC motor 1 of I _M ² × T ₁ (where I _M : motor rated current rate). Further, the heat storage amount I _M ² × T ₁ is integrated with the heat storage integrated amount S ₁ stored in the internal memory 12,
The new integrated heat storage amount S ₁ is stored in the internal memory 12 (step P ₆ ). Next, the magnitude relationship between the accumulated heat storage amount S ₁ stored in the internal memory 12 and the preset allowable accumulated heat storage amount (S _M ) is determined (step P ₇ ), and the accumulated heat storage amount S ₁ is determined as the allowable accumulated heat storage amount. If it is determined that the amount is smaller than the amount (S _M ), it is determined based on the signal input from the instantaneous blackout detection circuit 7 whether or not the control power source 8 is an instantaneous blackout (step P ₁₀ ). Control power supply 8
If is not an instantaneous blackout, return to Step P ₅ . Then, in step P ₅ , if the three-phase AC motor 1 is overcurrent again,
The heat storage amount I _M ² × T ₁ of the three-phase AC motor 1 at a predetermined sampling interval time is calculated from the output of the instrument current transformer 3. The heat storage amount I _M ² × T ₁ is integrated with the heat storage integrated amount stored in the internal memory 12, and is stored in the internal memory 12 as a new heat storage integrated amount S ₁ . When it is determined that the integrated heat storage amount S ₁ stored in the internal memory is larger than the allowable integrated heat storage amount (S _M ) (step 7), the overcurrent relay circuit 5 is operated from the port output P (step P ₈ ), with tripping the three-phase AC motor 1, or instantaneous power failure or not of the control power supply 8 in the next step P ₁₀ it is determined. When it is determined that the control power supply 8 is in the momentary power failure, the timing of the momentary power failure time detection circuit 10 is started (step P ₁₁ ), and at the same time, the accumulated heat storage amount S ₁ of the internal memory 12 is written in the nonvolatile memory 11. . The writing time of the accumulated heat storage amount S ₁ is about 10 msec. Then enter an infinite loop and stop the step (step P ₁₃ ). The operation of each circuit is stopped after the control power supply 8 is momentarily stopped, but since the momentary power failure time detection circuit 10 is composed of an RC timer or the like, the instantaneous power failure time detection circuit is also provided during the momentary power failure of the control power supply 8. 10 performs the timekeeping operation, and step 1 is performed by the sequence of the microcomputer 4.
Return to. When it is determined in step P ₅ that the three-phase AC motor 1 is not in the overcurrent state, the accumulated heat storage amount S _{1 in the} internal memory 12
Is cleared (step P ₉ ), and as the next step, it is determined whether the control power supply 8 has an instantaneous power failure (step 1
0).

[0009]

As described above, according to the present invention, after a momentary power failure occurs in the control power supply 8 due to the overcurrent state of the three-phase AC motor 1, the control power supply 8 is restored again and the three-phase AC motor 1 is operated. Momentary blackout time detection circuit even when the
In the motor protection device that calculates the heat radiation amount T _S T _D of the three-phase AC motor 1 during a momentary power failure based on the momentary power failure time T _S measured in 10, the integrated heat storage amount S ₁ is calculated by I _M ² × T ₁ . Therefore, the accumulated heat storage amount S ₁ of the three-phase AC motor 1 is accurately calculated by a simple calculation method.

[Brief description of drawings]

FIG. 1 is a motor protection device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the microcomputer according to the embodiment of the present invention.

[Explanation of symbols]

 1 Three-phase AC motor 2 Three-phase wire 3 Current transformer for instrument 4 Microcomputer 5 Overcurrent relay circuit 6 Transformer 7 Instantaneous power failure circuit 8 Control power supply 9 Memory storing program 10 Instantaneous power failure time detection circuit 11 Nonvolatile memory 12 Internal memory

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[Procedure amendment]

[Submission date] June 15, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

As described above, according to the present invention, after a momentary power failure occurs in the control power supply 8 due to the overcurrent state of the three-phase AC motor 1, the control power supply 8 is restored again and the three-phase AC motor 1 is operated. Momentary blackout time detection circuit even when the
The electric motor protection system for calculating a heat radiation amount T _S × T _D of the three-phase AC motor 1 in the instantaneous power failure by timed instantaneous blackout time T _S 10, calculates the heat storage integration amount S ₁ by I _M ² × T ₁ Since it is decided to do so, the accumulated heat storage amount S ₁ of the three-phase AC motor 1 is accurately calculated by a simple calculation method.

Claims (1)

[Claims] 1. A current transformer for an instrument for determining an overcurrent state of a three-phase AC motor, a control power source connected to a three-phase line via a transformer, and an instantaneous voltage for detecting an instantaneous power failure and a power recovery of the control power source. stop detection circuit, the instantaneous blackout time detection circuit for measuring the instantaneous power failure time of the control power supply, the per sampling interval time of the three-phase AC motor by the output of the current transformer heat storage amount I _M ² × T ₁ (where I
_M : motor rated current rate, T ₁ : sampling interval time), means for calculating the accumulated heat amount obtained by the calculating means, and means for calculating the accumulated heat amount, internal memory for storing the accumulated heat amount A non-volatile memory that stores the integrated heat storage amount at the same time as the instantaneous blackout of the control power supply, an instantaneous blackout time from the integrated heat storage amount during the instantaneous blackout of the control power supply stored in the nonvolatile memory when the control power is restored. Heat dissipation at T _S × T _D (however, T _S : instantaneous blackout time, T
_D : motor heat dissipation time constant) means for storing in the internal memory, means for determining whether or not the integrated heat storage amount stored in the internal memory is equal to or greater than the allowable integrated heat storage amount, the determining means An electric motor protection device comprising: an overcurrent relay circuit that trips a three-phase AC motor when it is determined that the accumulated heat storage amount is equal to or greater than the allowable accumulated heat storage amount.