Epstein frame

The Epstein frame is a standardized measuring method for determining iron losses in soft magnetic, grain-oriented and non-grain-oriented electrical steel sheets . In the DIN standard "DIN EN 60404-2: 2009-01: Magnetic materials - Part 2: Method for determining the magnetic properties of Electrical steel and sheet with the help of an Epstein frame ”, both the structure and the measuring method of the Epstein frame are described in more detail. The measuring device is named after the German physicist Joseph Epstein .

construction

The Epstein frame is constructed similarly 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 as standard, which are distributed over the 4 coils of the Epstein frame (175 turns per coil).

The measuring strips made of magnetically soft electrical steel should be between 280 mm and 320 mm long and 30 mm wide. They are placed in pairs opposite one another in the coils so that four legs of equal length and cross-section are created. The ends of the measuring strips must alternately overlap in the open corners of the Epstein frame. All legs must contain the same number of measuring strips, with all measuring strips weighing at least 240 g together.

Measurement method

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

{\ displaystyle H = {\ frac {N_ {1} \ cdot I} {l}}}

certainly. is the number of turns of the primary winding, I the measured current and l the effective magnetic length of the Epstrein frame, which is defined as 940 mm. The magnetic flux density results from ${\ displaystyle N_ {1}}$

{\ displaystyle B = {\ frac {1} {N_ {2} \ cdot A}} \ int {U {\ rm {{} dt}}}}

.

Here, the number of turns of the secondary winding, A the cross-sectional area of the sample and U is the measured voltage at the open secondary winding. The excitation voltage at the primary winding is now set in such a way that a sinusoidal voltage curve results in the secondary winding, so that the iron does not yet saturate. ${\ displaystyle N_ {2}}$

credentials

↑ Beuth Web Shop | DIN EN 60404-2: 2009-01 Magnetic materials - Part 2: Method for determining the magnetic properties of electrical steel and sheet with the aid of an Epstein frame (IEC 60404-2: 1996 + A1: 2008); German version EN 60404-2: 1998 + A1: 2008
↑ Epstein, J .: "The magnetic test of sheet iron"; Elektrotechnische Zeitschrift, vol. 1900, pp. 303-307

[1] Beuth Web Shop | DIN EN 60404-2: 2009-01 Magnetic materials - Part 2: Method for determining the magnetic properties of electrical steel and sheet with the aid of an Epstein frame (IEC 60404-2: 1996 + A1: 2008); German version EN 60404-2: 1998 + A1: 2008

[2] Epstein, J .: "The magnetic test of sheet iron"; Elektrotechnische Zeitschrift, vol. 1900, pp. 303-307