Insulating oil dielectric loss tester with improved temperature control
A technology of dielectric loss and insulating oil, which is applied in the direction of dielectric performance measurement, instruments, and measuring devices, can solve the problems of dielectric loss of insulating oil, easy deviation of temperature rise, and inability to control the measurement temperature stably, so as to ensure temperature balance Effect
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Embodiment 1
[0031] In the present invention, sensors are arranged at the lower ends of the two sets of circulating oil inlet and outlet pipes 402, and the Figure 8 In the temperature measuring circuit, the thermal resistance R t The platinum resistance sensor with stable performance, good repeatability and high precision is adopted, and the thermal resistance R t Two wires are drawn out from both ends, and R1, R2, R3, R4 are wiring resistors respectively, which constitute the R and N conversion circuit of the four-wire connection method, and the Rt The resistance change is converted into a voltage change. In order to realize the linear change from the resistance to the voltage in the R / V conversion circuit, as long as a constant current flows on the thermal resistance, that is:
[0032] V 0 =-IR t
[0033] Since the constant current I only flows through the two wires R1 and R3, basically no current flows through the two wires R2 and R4, so that the voltage drop on the thermal resistan...
Embodiment 2
[0040] Embodiment 2: the difference based on Embodiment 1 is;
[0041] The analog control system of this device adopts a digital PID controller, which can only calculate the control quantity according to the deviation value at the sampling time, and needs to be discretized. According to the calculation formula of the simulated PID control algorithm:
[0042]
[0043] This leads to the difference equation in discrete form:
[0044]
[0045] In the formula: K is the sampling number, T is the sampling period, u(k) is the output at the kth sampling time, e(k) is the input deviation at the kth sampling time, K p is the proportionality factor, T i is the integral time constant, T d is the differential time constant. Obviously, when the output u(k) is calculated according to the first formula above, the output value is related to all past states, and the computer needs to memorize all e(i) values from the initial state, which will take up a lot of memory and take a lot of...
Embodiment 3
[0049] Embodiment 3: the difference based on embodiment 1 and 2 is;
[0050] Inject an appropriate amount of insulating oil into the oil cup according to the standard GB5654-85, and use the above-mentioned constant temperature control system to control its temperature. Figure 9 The set values for the constant temperature are θ S = 50°C, 70°C, 90°C and 110°C, the temperature of the oil cup is controlled from room temperature, and the experimental data obtained by recording the temperature value every 30 seconds. Figure 10 The set value for the constant temperature is θ S =90°C, start heating the oil cup from different initial temperatures, and record the experimental data obtained from the temperature value every 30 seconds. It can be seen that the time from heating the oil cup to the constant temperature setting value is generally not more than 15 minutes, and the constant temperature deviation is less than ±0.5°C.
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