JP2594439B2 - Winding temperature detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a winding temperature detecting device for an electromagnet used for attracting and transporting a steel material and the like and an electromagnet used for magnetic force sorting.

[Prior Art] In general, this type of electromagnet is provided with a winding on a magnetic material, generates a magnetic force only when energized, and attracts steel or the like. However, when energized, the temperature of the winding rises due to Joule heat, and even if the current exceeds the allowable time, it may even burn. Therefore, during operation of the electromagnet, the temperature of the winding must always be ascertained and used within a range that does not reach the maximum allowable temperature.

By the way, there are two methods that have been used in the past to determine the temperature of the winding: a method of detecting the winding current and the winding voltage to obtain the temperature rise value indirectly, and the provision of a temperature sensor inside the electromagnet to directly control the temperature. There is a method of measuring.

The method of indirectly calculating the temperature rise value is based on the fact that the following relational expression holds between the temperature rise and the winding resistance.

[Problems to be Solved by the Invention] However, the above equation is a relational equation that is satisfied only when the winding current and the winding voltage are each in a steady state. Therefore, when the winding current gradually increases after the excitation voltage is applied due to the winding inductance, when the power supply voltage fluctuates, or when the current change is delayed by the winding inductor, the above equation is used. The obtained winding temperature value is far from the actual winding temperature. In other words, the success or failure of the result depends on whether or not the current winding temperature value obtained by the calculation is in a steady state such as the winding current. Such a method of indirectly calculating the winding temperature has a serious problem that the reliability of the value is lacking.

On the other hand, in the method of directly calculating the winding temperature, it is almost impossible to add it to the existing electromagnet because the temperature sensor must be directly attached to the winding. Has the disadvantage that it is easily damaged. Another disadvantage is that external wiring is required to attach the temperature sensor. Further, when the electromagnet has a molded structure, there is a problem that even if the temperature sensor itself fails, the electromagnet cannot be repaired without disassembling the electromagnet.

Therefore, an object of the present invention is to solve the above problems and drawbacks,
An object of the present invention is to provide a highly reliable electromagnet winding temperature detecting device which can be easily attached to an existing electromagnet without using a temperature sensor and is not affected by the inductance of the winding or the state of the winding.

[Means for Solving the Problems] According to the present invention, an abnormal change at the time of turning on the power of at least one of the voltage and the current supplied to the winding is detected. A winding temperature detecting device having a control unit for indicating the previous winding temperature is obtained.

[Embodiment] Hereinafter, before describing an embodiment of the present invention, an apparatus for detecting a winding temperature of an electromagnet to which the present embodiment is applied will be described with reference to the drawings.

This type of winding temperature detecting device has a first detector that detects a current value flowing through the winding 1 of the electromagnet, and a second detector that detects a voltage value at both ends of the winding 1. The first detector comprises, for example, as shown in FIG. 1, a shunt 2 connected in series to a winding 1 and a current amplifier 3 for converting the output of the shunt 2 into an appropriate voltage signal. . The second detector is
For example, as shown in FIG. 1, it is composed of a voltage divider 4 connected in parallel to the winding 1 and a voltage amplifier 5 for converting the output of the voltage divider 4 into an appropriate voltage signal. According to the above configuration, the current amplifier 3 can output a voltage signal proportional to the current time, that is, the current winding current of the electromagnet, and the voltage amplifier 5 can output a voltage signal proportional to the current winding voltage.

Both output signals from the amplifiers 3 and 5 are guided to a calculator 6 having a division circuit. The arithmetic unit 6 calculates the current winding resistance of the electromagnet by dividing the output of the voltage amplifier 5 by the output of the current amplifier 3. The output of the arithmetic unit 6 is guided to a temperature converter 7 and converted into a current winding temperature value of the electromagnet using the relation of the above equation. The converted current winding temperature value of the electromagnet is led to the display circuit 10 and converted into a visually comprehensible signal.

Next, an electromagnet winding temperature detecting device according to an embodiment of the present invention will be described with reference to FIG.

The winding temperature detecting device according to the present embodiment supplies a control signal to the holding circuit 8 for holding the winding temperature value for a predetermined time in order to control the current winding temperature value output. And a control circuit 9.

More specifically, the control circuit 9 detects whether or not the state of the electromagnet is in a steady state. If the state is not in the steady state, the control circuit 9 does not display the current winding temperature value on the display circuit 10, The display circuit 10 displays the temperature value. For this purpose, a holding circuit 8 composed of a memory, a register and the like is provided between the converter 7 and the display circuit 10. These holding circuits 8
The control circuit 9 functions as a control unit for controlling the winding temperature value as described above.

As shown in FIG. 1, the control circuit 9 shown in FIG.
Having a current lower limit detector 91 and a current stability detector 92 coupled to a current amplifier 3 forming part of the second detector, and coupled to a voltage amplifier 5 forming part of a second detector. A voltage lower limit detector 93 and a voltage stability detector 94 are provided. Further, the control circuit 9 has a timing pulse generating circuit 96 coupled to the holding circuit 8, the current stability detector 92 and the voltage stability detector 94. The current lower limit detector 91 is configured to output a binary digital signal "1" when the first detector output level is equal to or lower than a predetermined level, and to output a binary digital signal "0" when the first detector output level is higher than the predetermined level. . The voltage lower limit detector 93 is also configured to output a similar binary digital signal with respect to the second detector output level.

The current stability detector 92 and the voltage stability detector 94 operate with a trigger coming from the timing pulse generation circuit 96 at fixed time intervals, and sample the output levels of the first and second detectors. The sampled data is stored, for example, for one time, and a difference from the next sampled data is obtained. The difference between the two sampling data is compared with a predetermined allowable value. If the difference exceeds this allowable value, that is, if the operation result is inappropriate, a binary digital signal “1” is output and the allowable value is not exceeded. In such a case, it is configured to output a binary digital signal "0".

The predetermined level in the winding current value and the like is selected as the level of the current value and the like supplied in the steady state of the electromagnet, while the allowable value set for the difference between the two sampling data is
It is determined in consideration of the allowable level of the fluctuation of the power supply itself.

With the above-described configuration, it is possible to detect an inappropriate state for the calculation of the transition period that is fluctuating, such as when the operation switch of the electromagnet is turned on, and when an inappropriate state occurs in these calculations, the control circuit 9 performs the calculation. The holding circuit 8 holds the winding temperature value before the occurrence of the inappropriate state.

In the embodiment shown in FIG.
If an unsuitable state is detected in any one of the above, the control circuit 9 causes the holding circuit 8 to hold the winding temperature value before the occurrence of the unsuitable state. For this purpose, the control circuit 9 has a logical sum circuit 95 for calculating the logical sum of the outputs of the detectors 91 to 94.

The OR circuit 95 is configured such that any one of the detectors 91 to 94 is 2
When the binary digital signal “1” is output, ie, when the detector 91
When it is determined that the operation result is inappropriate in any one of ~ 94,
The logic “1” is sent to the holding circuit 8. When logic "1" is given from the OR circuit 95, the holding circuit 8 holds the previous value without updating the previous value even if a timing signal is given from the timing pulse generation circuit 96. As a result, the display circuit 10 displays the winding resistance value before the occurrence of a state unsuitable for calculation.

On the other hand, the OR circuit 95 may be replaced with another logic circuit to change the condition for determining the operation result.

[Effects] As described above, according to the present invention, a highly reliable electromagnet winding temperature detecting device which can be easily attached to an existing electromagnet and is not affected by inductance current fluctuation and voltage fluctuation of the winding. Can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an electromagnet winding temperature detecting device according to an embodiment of the present invention. In the figure, 1: winding of electromagnet, 2: current divider, 3: current amplifier, 4: voltage divider, 5: voltage amplifier, 6: arithmetic unit, 7: temperature converter, 8: holding circuit, 9: control Circuit, 91: current lower limit detector, 92: current stability detector, 93: voltage lower limit detector, 94: voltage stability detector, 95: AND circuit, 96: timing pulse generator circuit, 10: display circuit.

Claims (1)

(57) [Claims] 1. An apparatus for detecting a temperature of a winding from a voltage and a current supplied to the winding, wherein at least one of a voltage and a current supplied to the winding is temporarily changed from a steady state. Means for detecting an abnormal state, a control unit for instructing the winding temperature before the detection time when the abnormal state due to the temporary transition is detected in the detecting means, Means for displaying the winding temperature before the time point.