China
Africa
Explore chapters and articles related to this topic
Oil Film Thickness in Engine Bearings
Published in Wilfried J. Bartz, Engine Oils and Automotive Lubrication, 2019
The oil film capacitance was measured continuously as a function of crankshaft angle by a capacitive divider circuit (3) in the case of the 2.3I L-4 engine and by a transformer ratio arm bridge circuit for the 2.8I V-6 engine (12). A check was made (19) that both techniques gave the same capacitance by replacing the ratio-arm circuit by a capacitive divider circuit for the 2.81 V-6 engine. The ac voltages applied to the bearing capacitor had frequencies of 100 kHz and 20 kHz for the 2.3 litre and 2.8 litre engines, respectively. The output voltage was used to calculate a capacitance by use of a voltage/capacitance calibration relationship established by replacing the bearing by a series of fixed capacitors. Further details of the electrical circuits and the data acquisition systems are given elsewhere (3,4,12–14).
Monitoring and Diagnostics
Published in S.V. Kulkarni, S.A. Khaparde, Transformer Engineering, 2017
This test, which helps to determine the quality of the insulation between the windings and between the windings and the core/tank/ground, is conducted using a Schering bridge or transformer-ratio-arm bridge. The corresponding capacitance and tanδ values can also be determined. The measured power factor value is indicative of losses in the total insulation system including the bushings. With aging the power factor deteriorates; the measured power factor should be compared to previous test readings to ascertain its trend. When the power factor or tanδ value is higher than the limits specified in the standards, other conventional tests, such as moisture-in-oil analysis, can be conducted to confirm the insulation status. Additionally, advanced dielectric response tests as discussed in Sections 14.5 and 14.6 can also be performed.
Transformer Testing
Published in Leonard L. Grigsby, Electric Power Transformer Engineering, 2017
Shirish P. Mehta, William R. Henning
The measurement of insulation capacitance and dissipation factor (tan δ) is carried out using a capacitance bridge. A transformer ratio arm bridge or a Schearing bridge can be used for this purpose. In a two-winding transformer, there are three measurements of capacitance: (1) HV to ground, (2) LV to ground, and (3) HV to LV. These values of capacitance and their respective values of insulation dissipation factor (tan δ) are to be measured.
Achievable Accuracy in Industrial Measurement of Dissipation Factor of Power Capacitors
Published in NCSLI Measure, 2018
In order to investigate the achievable accuracy, a representative measurement setup has to be defined in order to identify possible contributions to measurement uncertainty. In this case we consider measurement of a power capacitor using a transformer ratio arm bridge with a compressed gas capacitor as reference and using a two-stage current transformer for the current from the test object.