Low Power, High Isolation Voltage Transformer Testing: Energy Storage, Charging Systems and EV

Abstract:
The usage of small form factor high voltage isolation transformers has grown exponentially over the past few years. These transformers are used in a wide range of applications but primarily in isolated driver circuits for GaN, SiC and IGBT systems in EV charging, EV onboard systems and energy storage systems. Due to the presence of high voltage (400-1200Vdc) battery packs ensuring the long-term isolation capabilities of these transformers is critical. Although the design of the magnetic can ensure that the isolation requirements are met in principle, the design cannot ensure that certain defects, due to variations in materials or manufacturing processes, will not lead to failures through time. As a result, it is critical that a reliable test is applied to the component to evaluate the integrity of the insulation. This paper details two important isolation tests including the well-known hi-pot test and the more critical but often misunderstood partial discharge test. The different isolation parameters measured will be presented and the effectiveness of the two methods compared.