JPS6236108Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a device that measures temperature by using a resistance element whose resistance value changes depending on temperature, such as a rotor coil of a generator, as a temperature detection element. The present invention provides a device that can achieve high voltage resistance and is easy to adjust to cope with the object to be measured.

FIG. 1 is a circuit diagram showing an example of a conventional device of this type, and shows an example of measuring the temperature of a rotor coil in a generator. 1st
In the figure, R _t is the rotor coil, r is the shunt,
E _f is the field voltage source, SL1 and SL2 are the slide resistances,
SA is a servo amplifier, and BM is a balancing motor.
The circuit of FIG. 1 is configured as a Kelvin double bridge. That is, the servo amplifier SA amplifies the unbalanced voltage of the bridge, rotates the balancing motor BM in either the forward or reverse direction depending on the polarity, and moves the brushes of the slide resistors SL1 and SL2. Here, since the movement of these brushes is configured to counteract the bridge imbalance,
When the brush moves to the position where the bridge is balanced, it is automatically balanced and the balancing motor BM stops.
This position corresponds to the temperature of the rotor coil _Rt , and the temperature can be measured by providing a temperature scale corresponding to the slide resistors SL1 and SL2 and providing a marking and recording device on the brush. .

However, with such a configuration, since the object to be measured and the measurement circuit are electrically connected,
It is difficult to increase the voltage resistance of circuits. In addition, it is necessary to calculate the resistance of each bridge side and linearize the function characteristics of the bridge for each specification of the object to be measured, which takes time to manufacture. Furthermore, when measuring the rotor coil of a generator as shown in Figure 1, the high-voltage system and low-voltage system will coexist in the measurement circuit, resulting in indication errors due to leaks, etc. Cheap.

The present invention solves these shortcomings, and uses a resistance element whose resistance value changes depending on temperature,
A shunt and a DC power supply connected in series with the resistive element, a first amplifier that detects the voltage across the resistive element, a second amplifier that detects the voltage across the shunt, and a second amplifier that detects the voltage across the shunt. A pulse width modulation divider circuit that divides the output of the amplifier and the output of the second amplifier, a photocoupler that electrically isolates and transmits the output signal of this pulse width modulation divider circuit, and an output of this photocoupler. The present invention provides a temperature measuring device comprising an integrating circuit that integrates a signal and an indicator recorder that records the output signal of the integrating circuit.

FIG. 2 is a circuit diagram showing an embodiment of the present invention, in which the same parts as in FIG. 1 are given the same reference numerals. In Figure 2, PA and PB are amplifiers, PWM
is a pulse width modulation divider circuit, PC is a photocoupler,
INT is an integrator circuit. Note that a known instruction recording mechanism may be used, and is not shown in the drawings.

The amplifier PA detects the voltage across the rotor coil _Rt , which is a resistive element, and is composed of a voltage divider and a differential amplifier, and the amplifier PB detects the voltage across the shunt r. It is configured as a non-inverting amplifier. Here, rotor coil R _t
Since a current I is supplied from the field voltage source E _f which is a DC power source to the series circuit of the current shunt r and the current shunt r, the output of the amplifier PA represents the voltage V applied across the rotor coil R _t . , the output of the amplifier PB will represent a voltage depending on the supply current I occurring in the shunt r. The pulse width modulation division circuit PWM performs a division operation between the output of these amplifiers PA and the output of amplifier PB. FIG. 3 is a circuit diagram showing an example of such a pulse width modulation division circuit PWM, and FIG. 4 is a waveform diagram showing an example of the waveform of the main part of FIG. 3. In Figures 3 and 4, _E01 is the output voltage of amplifier PA, _E02 is the output voltage of amplifier PB, SW is an analog switch, Ra is a variable resistor for compensating the resistance value of rotor coil _Rt , R _b and Rc are fixed resistors, u ₁ is an operational amplifier, G ₁ and G ₂ are inverters, E ₀₃ is the output voltage of the operational amplifier u ₁ , and E ₀₄ is the output voltage of the inverter G ₂ . Here, if the resistance values of variable resistor Ra and fixed resistors R _b and Rc are respectively Ra~Rc, then
Since the sum of currents in one period in the circuit of Fig. 3 is zero, E ₀₁ /Ra+R _b (T ₁ +T ₂ )+E ₀₂ /RcT ₂ =0 ∴-E ₀₁ /E ₀₂・Rc/Ra+R _b =T ₂ /T
₁ + T ₂ is established, and a division operation corresponding to R _t =V/I is performed. Again in Figure 2,
Photocoupler PC is a pulse width modulation divider circuit PWM
The output signal is electrically isolated and transmitted. This photocoupler PC allows electrical isolation between the side to be measured and the side of the indicator/recorder. The integrating circuit INT converts the pulse width modulated division signal E ₀₄ sent from the photocoupler PC into direct current, and sends it to the servo amplifier SA that constitutes the indicator recorder.
FIG. 5 is a circuit diagram showing an example of such an integrating circuit INT, where Vs is a reference voltage, Vz is a voltage for zero point adjustment, R _d is a variable resistor for zero point adjustment, Rc is a variable resistor for span adjustment, and R _f ~ _Rh is a fixed resistance, _u2 is an operational amplifier, and Eo is an output voltage. Here, variable resistance R
_d , Rc, and the resistance values of fixed resistors _Rf to _Rh are respectively _Rd to _Rh , the output voltage Eo is Eo= _Rh +Rc/ _Rf・_T2 / _T1 + _T2・_E05p−
R _h +Rc/Rg・Vz (E _05p : pulse height of E ₀₅ ), and Eo= _Rh +Rc/R _f・(−E ₀₁ /E ₀₂・Rc/
Ra+R _b )・E _05P −R _h +Rc/Rg・Vz.

According to the device configured in this way, the object to be measured and the indicator recorder can be completely electrically isolated, so that the measurement circuit can have a high withstand voltage. Furthermore, various constant calculations that were necessary in the apparatus shown in FIG. 1 are no longer necessary, and the specifications of the object to be measured can be met by adjusting the zero point and gain of the integrating circuit INT. Furthermore, by separately arranging the voltage divider constituting the amplifier PA, it is possible to separate the high voltage system and the low voltage system, and it is also possible to prevent the occurrence of indication errors due to leakage or the like.

In addition, although the above embodiment describes an example in which the rotor coil of a generator is the object to be measured, the measurement is not limited to this, and it is possible to measure the coils of electric motors, coils of transformers, etc. in the same way. .

As explained above, according to the present invention, it is possible to realize a temperature measuring device whose measuring circuit has a high withstand voltage and which can be easily adjusted to cope with the object to be measured, and has great practical effects.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a conventional device; Figure 2 is a circuit diagram showing an example of a conventional device;
The figure is a circuit diagram showing one embodiment of the present invention, FIG. 3 is a circuit diagram showing an example of a pulse width modulation division circuit used in the present invention, and FIG. 4 is a waveform diagram of each part in FIG. 3.
FIG. 5 is a circuit diagram showing an example of an integrating circuit used in the present invention. R _t ... rotor coil, r ... shunt, E _f ...
Field voltage source, SL...Slide resistor, SA...Servo amplifier, BM...Balance motor, PA, PB...
Amplifier, PC...photocoupler, INT...integrator circuit.

Claims (1)

[Scope of utility model registration request] a resistive element whose resistance value changes depending on temperature; a shunt and a DC power supply connected in series with the resistive element; and a first resistor that detects the voltage across the resistive element.
a second amplifier that detects the voltage across the shunt, and a second amplifier that detects the voltage across the shunt;
A pulse width modulation divider circuit that performs division with the output of the amplifier, a photocoupler that electrically isolates and transmits the output signal of this pulse width modulation divider circuit, and an integration circuit that integrates the output signal of this photocoupler. and,
A temperature measuring device comprising an indicator recorder that indicates and records the output signal of this integrating circuit.