Double layer (plasma): Difference between revisions

Revision as of 07:39, 3 February 2014

An Epstein frame or Epstein square is a standardised measurement device for measuring the magnetic properties of soft magnetic materials, especially used for testing of electrical steels.

In Europe, the measurement configuration and conditions are defined by a standard: IEC 60404-2:1996 Magnetic materials - Part 2: Methods of measurement of the magnetic properties of electrical steel sheet and strip by means of an Epstein frame.^[1] BS EN 60404-2:1998+A1^[2] contains an updated version of IEC 60404-2.

An Epstein frame comprises a primary and a secondary winding. The sample under test should be prepared as a set of a number of strips (always a multiple of four) cut from electrical steel sheet or ribbon. Each layer of the sample is double-lapped in corners and weighted down with a force of 1 NTemplate:Clarify (see photo).

The power losses are measured by means of a wattmeter method in which the primary current and secondary voltage are used. During the measurement, the Epstein frame behaves as an unloaded transformer.

Power loss, P_c, is calculated as:

$P_{c}={\frac {N_{1}}{N_{2}}}\cdot P_{m}-{\frac {\left(1,111\cdot |{\bar {U_{2}}}|\right)^{2}}{R_{i}}}$

where:
$N_{1}~$ is the number of turns of primary winding
$N_{2}~$ is the number of turns of secondary winding
$P_{m}~$ is the reading of the wattmeter in watts
$R_{i}~$ is the total resistance of the instruments in the secondary circuit in ohms and
$|{\bar {U_{2}}}|$ is the average secondary voltage in volts.

Specific power loss, P_s, is calculated as:

$P_{s}={\frac {P_{c}\cdot 4\cdot l}{m\cdot l_{m}}}$

where:
$l~$ is the length of the sample in metres
$l_{m}~$ is the average magnetic path length = 0.94 (constant value)
$m~$ is the mass of the sample in kilograms

If all conditions are as defined in the standard, the standard deviation of the reproducibility of the values is not greater than 1.5% up to 1.5 TTemplate:Clarify for non-oriented electrical steel and up to 1.7 T for grain-oriented electrical steel.

References

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[1] IEC 60404-2

[2] BS EN 60404-2:1998+A1

[1]

[2]

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+[[File:Epstein frame.jpg|thumb|right|Epstein frame]]
+An '''Epstein frame''' or '''Epstein square''' is a standardised measurement device for measuring the [[magnetic properties]] of soft magnetic materials, especially used for testing of [[electrical steel]]s.
+In [[Europe]], the measurement configuration and conditions are defined by a standard: ''IEC 60404-2:1996 Magnetic materials - Part 2: Methods of measurement of the magnetic properties of electrical steel sheet and strip by means of an Epstein frame''.<ref>[http://webstore.iec.ch/webstore/webstore.nsf/mysearchajax?Openform&key=60404-2&sorting=&start=1&onglet=1 IEC 60404-2]</ref> ''BS EN 60404-2:1998+A1''<ref>[http://shop.bsigroup.com/en/SearchResults/?q=60404-2%26&no=0&d=&c=10&f=&t=d BS EN 60404-2:1998+A1]</ref> contains an updated version of IEC 60404-2.
+An Epstein frame comprises a [[primary winding|primary]] and a [[secondary winding]]. The sample under test should be prepared as a set of a number of strips (always a multiple of four) cut from electrical steel sheet or ribbon. Each layer of the sample is double-lapped in corners and weighted down with a force of 1&nbsp;N{{Clarify|reason=explain abbreviation|date=October 2013}} (see photo).
+The power losses are measured by means of a [[wattmeter]] method in which the primary current and secondary voltage are used. During the measurement, the Epstein frame behaves as an unloaded [[transformer]].
+Power loss, ''P<sub>c</sub>'', is calculated as:
+<math>P_c = \frac {N_1}{N_2} \cdot P_m -  \frac {\left( 1,111 \cdot |\bar{U_2}| \right)^2}{R_i} </math>
+where:<br>
+<math>N_1~</math> is the number of turns of primary winding<br>
+<math>N_2~</math> is the number of turns of secondary winding<br>
+<math>P_m~</math> is the reading of the wattmeter in [[watt]]s<br>
+<math>R_i~</math> is the total resistance of the instruments in the secondary circuit in [[ohm]]s and<br>
+<math>|\bar{U_2}|</math> is the average secondary voltage in [[volt]]s.
+Specific power loss, P<sub>s</sub>, is calculated as:
+<math>P_s = \frac {P_c \cdot 4 \cdot l}{m \cdot l_m}</math>
+where:<br>
+<math>l~</math> is the length of the sample in metres<br>
+<math>l_m~</math> is the average magnetic path length = 0.94 (constant value)<br>
+<math>m~</math> is the mass of the sample in kilograms
+If all conditions are as defined in the standard, the [[standard deviation]] of the reproducibility of the values is not greater than 1.5% up to 1.5&nbsp;T{{Clarify|reason=explain abbreviation|date=October 2013}} for [[non-oriented electrical steel]] and up to 1.7&nbsp;T for [[grain-oriented electrical steel]].
+== See also ==
+* [[Soken tester]]
+==References==
+{{reflist}}
+[[Category:Magnetism]]

Double layer (plasma): Difference between revisions

Revision as of 07:39, 3 February 2014

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