Storage chokes are used for energy storage in SMPS's. They are usually made of iron or metal powder cores with one winding. Since the inductance decreases with increasing load current the
operating point of the load current is typically selected at 60..75 % of the no-load inductance.
All iron powder cores are susceptible to thermal aging. This means an increasing core loss when exposed to elevated temperatures for extended periods of time. The cores we use have a very little and defined thermal aging.
Core losses are an issue in these applications and have to be considered when designing a choke. Yet, each choke has to be tested in its determined application by the customer to ensure thermal stability. As for single choke thermal aging of iron powder cores is an issue here, too. Core loss depends on current ripple, switching frequency and core material. Especially when reversing current direction the use of metal powder cores is recommended.
- D: standard material
- M: low cost material with slightly higher core loss
- K: low cost material with higher core loss
- F: low cost material with high core loss (frequencies below 50kHz)
- L: material for use at high temperature
- MS: low loss material (current reverse)
- MP: lowest loss material (current reverse)
- HF: low loss material with best L = f(IDC) (current reverse)