Good understanding of power loss in a high frequency synchronous buck converter is important for design optimization of both power MOSFET and circuit itself. Most of the MOSFET power losses are relatively easy to quantify. The exception is the power loss associated with Cdv/dt induced turn on of the low-side MOSFET (synchronous rectifier). This paper characterizes the Cdv/dt induced power loss in two ways. First, detailed device characterization, in-circuit testing, and modeling are used for a comparative loss calculation. This method requires specialized test equipment and is rather complicated and time consuming. A simple method is then introduced to very accurately quantify the Cdv/dt loss. With this method, the impacts of the Cdv/dt power loss on synchronous buck converters at different operation conditions can be readily assessed. The impacts of Cdv/dt induced turn on different applications are addressed.

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-Good understanding of power loss in a high frequency synchronous buck converter is important for design optimization of both power MOSFET and circuit itself. Most of the MOSFET power losses are relatively easy to quantify. The exception is the power loss associated with Cdv/dt induced turn on of the low-side MOSFET (synchronous rectifier). This paper characterizes the Cdv/dt induced power loss in two ways. First, detailed device characterization, in-circuit testing, and modeling are used for a comparative loss calculation. This method requires specialized test equipment and is rather complicated and time consuming. A simple method is then introduced to very accurately quantify the Cdv/dt loss. With this method, the impacts of the Cdv/dt power loss on synchronous buck converters at different operation conditions can be readily assessed. The impacts of Cdv/dt induced turn on different applications are addressed.

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The winding system of high voltage machines is usually composed of pre-formed coils. To facilitate the winding fitting process stator slots are usually wide opened. These wide opened slots are known to cause disturbances of the magnetic field distribution. Thus losses are increased and machine's efficiency is reduced. A common way to counteract this drawback is given by placing magnetic slot wedges in the slots. During operation the wedges are exposed to high magnetic and mechanical forces. As a consequence wedges can get loose and finally fall out into the air-gap. State-of-the-art missing slot wedge detection techniques deal with the drawback that the machine must be disassembled, what is usually very time consuming. In this paper a method is investigated which provides the possibility of detecting missing magnetic slot wedges based only on measurement of electrical quantities and without machine disassembling. The method is based on exploitation of machine reaction on transient voltage excitation. The resulting current response contains information on machine's magnetic state. This information is composed of several machine asymmetries including the fault (missing wedge) induced asymmetry. A specific signal processing chain provides a distinct separation of all asymmetry components and delivers a high sensitive fault indicator. Measurements for several fault cases are presented and discussed. A sensitivity analysis shows the high accuracy of the method and the ability to detect even partially missing slot wedges.

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