On $V_{ce}$ Method: In Situ Temperature Estimation and Aging Detection of High-Current IGBT Modules Used in Magnet Power Supplies for Particle Accelerators

Magnet power supplies used in particle accelerators are a specialized application of power electronics that require long lifetime operation with no unscheduled interruptions and high output current precision. In this paper, the $V_{ce}$ method with sensing current is considered for the estimation of the junction temperature and the aging detection of high-current insulated gate bipolar transistor (IGBT) modules used in this specialized application. First, sensitivity analysis of the sensing current and the gate– emitter voltage are documented to quantify their impact on the precision of the $V_{ce}$ method for high-current modules independently of the application of interest. Two measuring circuits offering ease of calibration and reduced number of components are proposed but their applicability is not limited to this application. Their performance is tested on a 1.6 kA IGBT module that exhibits the highest current ratings documented for the $V_{ce}$ method with sensing current. The test is carried out at a switching frequency of 6.5 kHz using an experimental set-up that emulates a phase leg of the considered power supply. The $V_{ce}$ method with sensing current is evaluated for the aging detection of high-current IGBT modules in general and its effectiveness for the specialized application is verified experimentally.