This work attempts to find values of thermal resistances for the heating simulation of an induction motor by measurement on this motor. This article works with the assumption of a special case in that it is not possible to bring up an external load torque on the shaft. Nevertheless it should be possible to measure temperatures according to the insulation class of the motor. These claims can be met by the reversing duty of the induction motor with different periods and duty factors. The very useful measurements of rotor temperatures were realised by a measurement transmission with silver...
It is very difficult to measure accurately the temperature of steel sheet using a radiation pyrometer when surface emissivity changes drastically. In order to solve this problem we propose a new radiation pyrometer using the information of reflectance.
The new method of measurement of true temperature and emissivity is considered. The method is based on use of redundancy of the information of Plank's radiation and changes of properties of substance finding the reflection in change of emissivity factor from temperature. The simultaneous application of relative spectroreflectometry allows to reduce quantity of used spectral components and to determine emissivity's meanings, including surfaces, which are not following Lambert law. It is shown, that the method allows to build a thermodynamic temperature scale without using of black body.
The TAM 2277-204 injection calorimeter by Thermometric is used nowadays for the determination of enthalpies of liquid mixtures. A good calibration of the device permits to obtain accurate thermal measures and advance in the knowledge of the energetic processes that are developed in the calorimeter. We identify the system with transfer functions of two poles; the parameters of the TF are determined through a non-linear least-square fit based on Marquardt´s method. Within the identification process we observe that the first time-constant and the sensitivity depend on ρ c p f ( ρ is the...
Photothermal radiometry has been proved being a versatile tool for the non-contact and non-destructive material inspection in near-surface zones. Although these near-surface areas represent only a few percent of the workpiece’s volume, they influence significantly its quality, functional behaviour, reliability and life time. In particular, they determine decisively the mechanical properties of precisely manufactured and/or surface finished parts. In photothermics, the propagation and penetration depths of optically excited thermal waves, the thermal response at the surfaces on optical...
Irreversible resistance changes of Thomas type 1 ohm resistors according to temporary temperature change is about 0.03 ppm/y in average by reported results of PTB, IEN and NIST, but the behavior did not occur in NML 1 ohm resistors under the same condition. By qualitative analysis based on thermal stress and strain, it is considered that a major element of the behavior is thermal stress by different thermal expansions of coils and mandrels.
In the field of calibration of temperature measurement devices, the comparison method is usually used. To improve the uncertainty of the method, a number of specific conditions should be taken into account, such as temperature stability and the homogenous field inside the working area of the heating device. It is more difficult to realise those demands at higher temperatures in excess of 1000°C. We discuss the commercial heating furnace, carry out the reconstruction of the heating element and improve regulation, attaching importance to the location of the sensors. The isothermal 600-mm-long...
For the thermometric sensor calibration by the method of comparison in the range of 300°C to 1300°C a uniform temperature field should be maintained in a metal insert for each temperature level selected. The insert containing measurement pockets is located in a tubular electric furnace. The functionality of calibrating system pertaining to the time of measurement requires appropriate dynamic properties of electrothermal system. To get a suitable static temperature field in the measurement insert some real electrothermal systems of similar class were investigated and the results have been...
The accurate measurement of temperature is very important to achieve high quality products in materials processing such as arc welding and thermal cutting. The IR(infrared) radiation thermometer has been applied to these processing, because it requires no physical contact with an object. Generally, the radiation thermometry leads to noticeable error in measuring temperature of molten pool under the welding where the emissivity is unknown. In the present paper, the molten pool temperature measurement by UV(ultra violet) thermal radiation has been discussed. In the experiment, stainless steel...
This paper presents a new method for observing the rotor temperature of high-power squirrel cage induction machines in measurable variables. The method is based on the fact that the rotor resistance depends on the actual rotor temperature. The main problem is to separate the changes in the rotor resistance due to temperature and skin effect. By comparing the input impedance with a known circle diagram measured in the start-up phase, it is possible to calculate changes in the rotor temperature. Further analyses also make it possible to obtain the absolute rotor temperature at any time.