JPH0649074Y2 - Motor overload detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an overload detection device for an electric motor, which detects load condition data of the electric motor by a heat generation temperature value and detects an overload condition.

[Conventional technology]

FIG. 4 is a block diagram showing a conventional electric motor overload detection device.

In the figure, (1) is an electric motor, and (2) is the electric motor (1).
(R) is a resistor for detecting armature current. (3) is an overload state detection calculation means for detecting the overload state while converting the load state data of the electric motor (1) into a heating temperature value, and generating voltage across the resistor (R). Isolation amplifier (3-1) for detection and A / D converter (3-2) for converting detection voltage into digital quantity
And a load detection circuit for converting the digital detection voltage into a heat generation temperature value of the electric motor, comparing the converted value with a heat generation temperature set value, and outputting a signal for stopping the drive power supply device (2) based on the comparison result. (3-3) and a D / A converter (3-4) for converting the calculated value into an analog signal.
The load state data of the electric motor (1) described here is
It shows a load increase state with respect to a constant load of the electric motor (1). Furthermore, in more detail, since the motor input current flowing in the winding (not shown) of the motor (1) changes depending on the load state, heat generation of the winding generated by the motor input current flowing in the winding. The load state data of the electric motor (1) can be obtained by measuring the amount, that is, the heat generation temperature value of the electric motor (1) in voltage conversion. Therefore, it is considered that the heat generation temperature is equivalent to the load state data.

Reference numeral (4) is a correction amount calculation means for inputting a heat generation temperature value when the driving power source is stopped, outputting load state data when the power source is turned on again after a lapse of a predetermined time, and making the corrected load state data. It has a time constant equal to the thermal time constant, and when a heat generation temperature value is input from the overload state detection arithmetic circuit (3), the heat generation temperature value that changes according to the time constant characteristic is sequentially output, and when the power is turned on again. The load state calculation circuit (4-1) that outputs the heat generation temperature value output at that time, and the calculation circuit (4-
A / D converter (4-2) that digitally converts the output from 1) and reads digital data when the power is turned on
It is composed of Incidentally, (3-3a) shows load state data, and (4-2a) shows load state correction data.

Next, the operation of the conventional electric motor overload detection device having the above configuration will be described with reference to the operation flowchart of FIG.

When detecting the overload of the electric motor (1) when the drive power supply (2) is turned on, the insulation amplifier (3-1) changes the voltage V _I generated across the resistor (R) in proportion to the armature current. It is detected and sent to the A / D converter (3-2). A / D converter (3
At -2), the detection voltage V _I is converted into a digital value A _VI at every sampling period (see FIG. 5-1, 5-1). The digital value A _VI converts the current load state data ML of the motor into a heat generation temperature value in the load calculation circuit (3-3) (FIG.
2). Further, the load state ML is compared with the heat generation set temperature value (overload state data) MOL (see FIG. 5-5), and when the set temperature value is exceeded, an electric motor overload alarm is generated and the drive power supply device ( 2) Emergency stop (see Fig. 5-4).

However, before the power supply of the drive power supply device (2) is stopped by the overload detection signal from the load calculation circuit (3-3), the load condition data ML at that time is stored in the D / A converter (3-
After being converted into an analog quantity AG _ML by 4), it is input to a load state calculation circuit (4-1) having a time constant circuit equal to the thermal time constant of the electric motor (1). The load state calculation circuit (4-1) outputs load state data AG _ML in accordance with the card characteristics whose time-output value relationship is determined by the time constant. A / D converter (4-2) that received a closing signal when the driving power supply (2) was turned on again while sending the load state data AG _ML accompanying the stop time of the driving power supply (2) Is the load status data corrected during the stop time at power-on AG _ML Xe
^{-T / T} (t: stop time, T: time constant approximating the motor thermal time constant) is digitally converted, and then the load calculation circuit uses the load state circuit ML as the load state data ML when the motor is restarted. It is set as data. Note that the above-mentioned stop time is a time from when the drive power supply device (2) is stopped to when the drive power supply device (2) is turned on again, which is actually a period, and is not particularly determined by measurement. .

[Problems to be solved by the invention]

Since the conventional motor overload detection device is configured as described above, the stop time of the drive power supply device is not particularly measured, and therefore the heat generation temperature value detected when the drive power supply device is stopped is calculated at which time the load state is calculated. There is a difference between the actual heat generation temperature value with the lapse of time and the heat generation temperature value detected when the driving power supply device is stopped, depending on whether or not the temperature is input to the circuit. Therefore, the load status data read from the A / D converter in the correction amount calculation means cannot be the load status data obtained by the load status calculation circuit when the power is turned on again. There is a problem that different values of data are set in the load calculation circuit as the correction initial data due to the difference in stop time. Furthermore, when monitoring the load state of the motors with different thermal time constants, the load state calculation circuit Has a problem in that it is necessary to provide a different time constant circuit for each motor, and the device itself can be large-scale.

This invention was made in order to solve the above problems, and when the drive power was stopped and the power was turned on again after a certain period of time, the load condition of the motor at that time was set to the characteristics of the motor. An object of the present invention is to obtain an overload detection device for an electric motor that can be corrected accordingly.

[Means for solving problems]

In the motor overload detection device according to the present invention, when the correction amount calculation means 4 stores the data memory (4-7) for storing the heat generation temperature value detected when the motor is stopped and the thermal time constant peculiar to each motor. A constant holding memory (7-8), a time measuring circuit (4-3) for measuring a stop time from when the electric motor is stopped to when the electric motor is restarted, the stored heat generation temperature value, and the stored electric motor. A correction circuit (4-10) for calculating a heat generation temperature value of the electric motor (1) when the electric motor drive is restarted based on the thermal time constant and the measured stop time.

[Action]

The correction circuit according to the present invention is based on the heat generation temperature value stored in the data memory, the thermal time constant of the motor stored in the time constant holding memory, and the stop time from the time when the motor is stopped until the drive is restarted, which is measured by the time measurement circuit. By calculating the heat generation temperature value of the electric motor when the electric motor is restarted and using it as the load state data, the load state of the electric motor can always be monitored accurately and the electric motor can be reliably protected from the overload state.

〔Example〕

An embodiment of this invention will be described with reference to FIG.
In the figure, the same reference numerals as those in FIG. 4 denote the same or corresponding parts, and detailed description thereof will be omitted. Correction amount calculation means (4) in the present invention
In (4-3), a time measuring circuit that measures the elapsed time from when the power is turned off to when the power is turned on again, (4-4) is a device that reads the output of the time measuring circuit (4-3) when the power is turned on, and (4 -5) is the stop time data read when the power is turned on, (4-6) is the load state data of the electric motor (1) when the power is stopped, and (4-7) is the load state data when the power is stopped (4-6 ) Writing data memory (non-volatile or battery-backed RAM), (4-8)
Is a time constant holding memory in which the thermal time constant of each electric motor is written, (4-9) is time constant data, (4-10) is stop time data (4-5), load state data (4-6). , A correction circuit that receives the time constant data (4-9) and processes the motor load state when the power is turned on.

FIG. 2 shows the flow of the motor load correction method when the power supply is stopped and the power is turned on, and FIG. 3 shows the method for measuring the drive device power supply stop time and the motor load correction method.

Next, the operation of this embodiment having the above configuration will be described.
The method of detecting the load state data of the electric motor when the power is turned on is the same as the conventional method. When the power is turned off (See Fig. 2 (2-
1)), the load state data ML of the electric motor is written in the data memory (4-7) (E ² PROM or battery-backed RAM) before the driving power source is turned off (Fig. 2 (2-2)). ). At the same time, the time measuring circuit (4-3) operates (Fig. 2 (2-3)). There are many possible methods for measuring the downtime. For example a constant voltage V ₀ is added to the third time integration and the drive power source stop as shown in FIG circuit (time constant T), when the power is turned on (FIG. 2 (2-4)) voltage V ₀
To obtain the stop time t = TlogV ₀ / V ₀ , or a counter may measure the stop time with a backed up power supply as shown in. The stop time data t (FIG. 2 (2-5)) read by the device (4-4) connected to the time measuring circuit (4-3) at the time of power-on is stored in each memory (4-7), ( 4-8) The motor load state data ML when the power supply is stopped and the motor thermal time constant data T _M
Based on the above, the motor load value ML 'is corrected by the correction circuit (4-10).
= ML × e ^{−t / TM,} and is used as the motor overload detection data when the power is on (Fig. 2 (2-6)).

Therefore, the load state data correction method of the present embodiment accurately measures the power supply stop time from the time of power supply stop to the time of power re-supply, and further, this power supply stop time, the load state data detected at the time of power supply stop, and Since the load state data when the power is turned on is calculated from the thermal time constant of the corresponding motor, the difference from the load state data correction in the conventional technique becomes clear as follows.

That is, since the conventional load state data correction method inputs the load state data detected at the time of power supply stop to the load state calculation circuit without considering the actual power supply stop time, a certain amount of time has passed from the input load state data. A difference appears between the true load state data and the corrected load state data is not always accurate when the power is turned on again.

[Effect of device]

As described above, according to the present invention, the data memory that stores and holds the load state data of the electric motor when the driving power supply is stopped, the time constant holding memory that stores the thermal time constant of each electric motor, It is equipped with a circuit that measures the elapsed time and outputs the measured data.When the power is turned on again, the load state data, time constant and elapsed time are used as calculation data to calculate and output the load state data when the power is turned on again. Even after the power is cut off for a predetermined time, the load condition of the motor is correctly corrected, and the load condition is measured according to the characteristics of each motor, so there is an effect that the motor can be driven safely without being overloaded. .

[Brief description of drawings]

FIG. 1 is a block diagram showing an electric motor overload detection device according to an embodiment of the present invention, FIG. 2 is a flow chart showing the operation of this embodiment, and FIG. 3 is a drive power supply stop time detection and electric motor load correction method. FIG. 4 is a block diagram showing a conventional electric motor overload detection device, and FIG. 5 is a flow chart showing a conventional electric motor overload detection method at power-on. In the figure, (1) is an electric motor, (2) is a drive power supply device,
(3) is an overload state detection calculation means, (3-3) is a load calculation circuit, (3-3a) is load state data, (4) is a correction amount calculation means, (4-2a) is load correction data, (4-3) is a time measuring circuit, (4-7) is a data memory, (4-8)
Is a time constant holding memory, and (4-10) is a correction circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. An overload state in which when the heat generation temperature value detected by the electric motor (1) exceeds a heat generation temperature set value, it is determined that the electric motor (1) is overloaded and the driving of the electric motor (1) is stopped. A detection calculation means (3) and a correction amount calculation means (4) for correcting the heat generation temperature value when the electric motor drive is stopped and setting it as the initial heat generation temperature value when the electric motor drive is restarted when the drive of the electric motor (1) is restarted. In the overload detection device for an electric motor comprising: a data memory (4-7), wherein the correction amount calculation means (4) stores a heat generation temperature value detected when the electric motor is stopped due to the stop of the drive power supply device for the electric motor. And a time constant holding memory (4-8) that stores a thermal time constant peculiar to each electric motor.
A time measuring circuit (4-3) for measuring a stop time from when the electric motor is stopped to when the electric motor is restarted by turning on the driving power supply device, the stored heat generation temperature value, the thermal time constant of the electric motor, And a correction circuit (4-10) for calculating the heat generation temperature value of the electric motor (1) when the electric motor is restarted based on the measured stop time from when the electric motor is stopped to when the electric motor is restarted. An electric motor overload detection device.