Current transformers
Current transformers are a special application of transformers for an electrically isolated detection and measuring of alternating currents. They are made of a toroid with one winding at a high
number of turns. The conductor which is to be measured is lead through the hole and represents the primary winding. The current in the secondary winding is proportional to the current through the
conductor. This secondary current is measured via the voltage of a load resistor for further processing.
Technical specifications, materials and areas of application:
Generally, our CT's are suitable within 50Hz and 10kHz, some types up to 100kHz. Limitation of that is in some cases possible. Measurements outside this area
may work but have to be sufficiently tested by the customer. Maximum drive level rises with the frequency. However at higher frequencies unwanted effects (i. e. distortion) may occur. Since
ferrites are to operate well only at higher frequencies they don't work too good at 50Hz/60Hz mains frequency.
Materials
ferrite (X)
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lowest cost material
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small drive level at lower frequencies (~50Hz) only
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->current identification or short circuit identification
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better operation at higher frequencies (drive level, linearity)
ferrite (V)
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low cost
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low loss
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small drive level at lower frequencies (~50Hz) only
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->current identification or short circuit identification
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better operation at higher frequencies (drive level, linearity)
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applications with higher demand
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higher temperature possible
tape wound core (BB)
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highest saturation flux density
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limited area of frequency (50Hz, audio)
amorphous / nanocristalline tape wound cores
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high saturation flux density
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high linearity
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limited area of frequency (50Hz, audio)
Designs:
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open version
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case with feed-through-hole for primary winding
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case with integrated primary winding (limited primary current!)
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flat case with feed-through-hole for primary winding
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case with connecting wire to be put on heavier cable