| 摘要 |
The present invention relates to a downhole wireline tool for performing an operation in a well at a depth of up to 15 km downhole, the tool being powered by direct current at a predetermined voltage in a first end by a power supply unit which is configured to provide a specific steady-state voltage selected from a plurality of predetermined voltages, comprising an electrical motor being powered by alternating current, a frequency converter arranged between the first end and the motor, and a voltage peak reduction unit adapted to reduce the steady-state voltage of the selected power supplied to the frequency converter from the power supply, the voltage peak reduction unit comprising a capacitor, wherein the capacitor is a high temperature capacitor having a dielectric comprising a material capable of resisting a temperature above 150°C. Furthermore, the present invention relates to a downhole tool string and to a method of protecting a frequency converter from peaks of voltage in power supplied to the frequency converter in a downhole tool according to the present invention. |
