Rudolf offer a comprehensive range of Current Transformers for measuring and protective applications. Two types are available: • Encapsulated type and • Tape Wound Ring type.

The advantages derived from the utilization of current transformers are:
Economy, since they allow the use of wires with smaller cross-sections in the connection to the measuring panels.

Standardization of the relays and measuring instruments (rated 5 or 1 A).

Safety, because of the galvanic insulation that exists between the primary and secondary windings.

Construction
The high grade silicon steel core is annealled, varnished then insulated with polycarbonate core caps. The secondary winding is toroidally wound by high precision semi-automatic machinery.

For Ring type CTs, the PEW coated windings are then covered with elephantite paper, varnished and double - lapped with PVC tapes.

For Encapsulated type CTs, the windings are enclosed in a impact and heat resistant split cap which is ultrasonically welded.

Performance
Designed to meet the highest standards in accordance to IEC 44 (previously BS 7626/93, 3938/73 and IEC 185), Rudolf CTs have performance as follows:

Overloads : As in IEC 44
Temperature : Ambient Range - 40°C to +70°C
Dielectric Strength : 2,500V r.m.s. for 1 min.
Frequency : 50/60Hz
Voltage : Primary rated at 660V AC

Application
Current transformers convert an alternating current, usually high, into a proportional lower one.

Depending on their use, transformers are classified as:
Measurement Transformers For measuring of current, power, power factor or energy connected to measuring instruments. They are characterized by their accuracy and for saturating at moderate overcurrents (normally, at less than 5 times the nominal current). Thus the effects of these possible overcurrents on the measuring instruments is minimized.

Protection Transformers These are generally connected to protective relays, in which the proportionality between the primary and secondary currents has to be kept, even in overloaded conditions (normally, more than 5 times the nominal current). Thus, quick operation of the relays is guaranteed.

Burden Requirements
The Burden imposed on a Current Transformer consist mainly of the following:
a) The impedance of pilot wire between CT & Relay/ Instruments
b) The impedance of the relays or instruments
c) The sum of (a) & (b) constitute the external burden required.