Disadvantages of eddy current dynamometer
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Very susceptible to magnetic permeability changes. Small changes in permeability have a pronounced effect on the eddy currents, especially in ferromagnetic materials. This makes testing of welds and other ferromagnetic materials difficult but, with modern digital flaw detectors and probe design, not impossible.
Only effective on conductive materials. The material must be able to support a flow of electrical current. This makes testing of fibre reinforced plastics unfeasible.
Will not detect defects parallel to surface. The flow of eddy currents is always parallel to the surface. If a planar defect does not cross or interfere with the current then the defect will not be detected.
Not suitable for large areas and/or complex geometries. Large area scanning can be accomplished, but needs the aid of some type of area scanning device, usually supported by a computer, both of which are not inexpensive. The more complex the geometry becomes, the more difficult it is to differentiate defect signals from geometry effect signals.
Signal interpretation required. Due to the many factors which affect eddy currents, careful interpretation of signals is needed to distinguish between relevant and non-relevant indications.
No permanent record (unless automated). Normally the only permanent record will be a paper print out or computer file when using automated systems.
Only effective on conductive materials. The material must be able to support a flow of electrical current. This makes testing of fibre reinforced plastics unfeasible.
Will not detect defects parallel to surface. The flow of eddy currents is always parallel to the surface. If a planar defect does not cross or interfere with the current then the defect will not be detected.
Not suitable for large areas and/or complex geometries. Large area scanning can be accomplished, but needs the aid of some type of area scanning device, usually supported by a computer, both of which are not inexpensive. The more complex the geometry becomes, the more difficult it is to differentiate defect signals from geometry effect signals.
Signal interpretation required. Due to the many factors which affect eddy currents, careful interpretation of signals is needed to distinguish between relevant and non-relevant indications.
No permanent record (unless automated). Normally the only permanent record will be a paper print out or computer file when using automated systems.
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Answer:
Disadvantages of Eddy Current Dynamometer
It cannot produce torque at zero speed.
Comparatively smaller in size, which reduces its strength and reliability.
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