Free guide to the integration of high frequency components

Component size is particularly important in the design of high frequency systems. Ideal for battery charging circuits and switch mode power supplies, the HF transformers from REO can be made smaller in the same way as higher frequency satellite TV transmission allows for smaller domestic receiver dishes. Transformers which operate above 50Hz mains frequencies tend to be much smaller since undesirable characteristics such as eddy current losses and leakage inductance increase proportionally to the dimensions of the device. Therefore a small transformer will have lower eddy current losses and leakage inductance.

With a power range from 1-90kW in the frequency spectrum of up to 100kHz, REO also manufactures high frequency components, power transformers and chokes on toroidal basis or pot core basis.

Steve Hughes, REO UK managing director, comments: “REO’s use of amorphous, nanocrystalline and ferrite core materials ensures high efficiency design with reduced costs and increased product life. Size reduction prolongs service life and enables cost savings, as well as modular design with insulation between primary and secondary windings for test voltages up to 6kV, and insulation for partial discharge less than ten percent."

Skin effect is the tendency for HF current to run only at the surface of a conductor and explains why TV aerials are made from hollow tubes rather than solid rods. REO HF transformers use litz wires that are designed to reduce this skin effect.Operating over a temperature range from -40 to +85 degrees centigrade, the HF transformers feature ingress protection up to IP65, and encapsulation and insulation class B, F and H.

The magnetic field created by the flow of current at the centre generates a current that opposes the main flow. In HF wires the copper cross section is divided onto many small individual conductors, ensuring that the diameter of each conductor is less than the skin depth. This means that the entire cross section for the current flow is available. Offering high dielectric strength, HF wire suppresses the skin effect, minimises eddy current losses, and prevents hot spots.

Available with various options, such as example vacuum seal, REO HF transformers provide the highest compatibility and low heating as well as a minimal noise generation. Models with an aluminium profile feature improved heat dissipation and can be water-cooled by means of a cold plate. All Components are tested under real conditions at REO’s in-house laboratory to quality standards DIN EN60310 and DIN EN60076-6, as well as DIN EN61558. Long-term tests and ‘burn in’ are performed for encapsulated transformer models. Depending on the application REO offers different winding types including stranded wire winding, wire winding and copper strip.

REO power transformers are available in plastic housings for industrial use (HF transformers for less demanding applications), mounted onto a plate with pins or in aluminium profile case.