Epstein frame

The Epstein provides a standardized method for the measurement of iron losses in soft magnetic grain oriented and non-oriented electrical steel sheets dar. In the DIN standard "DIN EN 60404-2:2009-01: Magnetic materials - Part 2: Methods of measurement of magnetic properties of electric strip and sheet by means of an Epstein frame " describes both the design and the measurement method of the Epstein frame closer.

Construction

The Epstein frame is similar to a transformer. It consists of a uniformly distributed outer primary winding ( also called magnetization winding ) which surrounds the inner secondary winding (measuring winding). Both windings have 700 turns by default, which are distributed over the 4 coils of the Epstein frame (175 turns per coil).

The gauges of soft magnetic steel sheet should be between 280 mm and 320 mm long and 30 mm wide. They are in pairs opposite placed in the coil, so that four equal-length legs emerge with the same cross section. The ends of the gauges have to alternately overlap in the open corners of the Epstein frame. All legs must contain the same number of gauges, all gauges together must weigh at least 240 g.

Measurement methods

By measuring the current in the primary winding and the voltage in the secondary winding, the magnetic field strength and the magnetic flux density in the samples can be determined. The magnetic field strength is with

Determined. is the number of turns of primary coil, I is the measured current and L is the effective magnetic length of the Epstreinrahmens, which is fixed by definition at 940 mm. The magnetic flux density is given by

The number of turns of the secondary winding, A is the cross sectional area of ​​the sample, and U is the measured voltage at the open secondary winding. The excitation voltage across the primary winding is now adjusted so that in the secondary winding results in a sinusoidal voltage waveform, the iron that is not yet gets into saturation.

Credentials

• Metrology