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Synthetic resin insulated, indoor bar type/ cable current transformers
for 0.72 kV, 1.2 kV Highest voltage for equipment
types ASM-0, ASM-1, ASM-0-I, ASM-0-II, ASM-1-I, ASM-1-II





Type marking

The letters and numerals applied in type markings have the following meanings:

A – current transformer
S – applicable on busbars / cables
M – synthetic resin insulated
0, 1 – highest voltage for equipment 0.72 kV or 1.2 kV
I, II – variants of current transformers applicable on cables



General description

The current transformers types ASM are manufactured of single core, synthetic resin insulated design for rated currents from 200 to 3000 A for use on busbars or on cables. The current transformers comply with the specifications of MSZ EN 60044-1 and EN 60044-1 standards respectively. At the thermal and dynamic tests the phase distance is 130 mm. The current transformers, manufactured in serial production, can be applied indoor under moderate climate conditions. On request these types can be produced in finish suitable for tropical use too.
The opening shaped on the body of the instrument is suitable to accomodate copper or aluminium busbars. The cable current transformer types are intended to be applied on medium voltage (e.g. 12 kV, 24 kV, 36 kV) cables. In this case the main insulation is provided by the cable itself. From these current transformers more than one can be applied on the cable, depending on the number of the requested measuring or protective circuits. The ends of the secondary winding, wound of copper wire, are connected to threaded blocks set in the synthetic resin body. The secondary terminals are covered by a plastic cover and can be sealed.

Packing, delivery

The current transformer is delivered in a finish suitable for use under normal climatic conditions, packed in corrugated paper box, but upon agreement the packing can be made according to requirement.


In case of a long-term storage, it is practical, to keep the current transformer indoor, in a covered, well ventilated room (storage temperature: –5 °C, +40 °C).

Installation, putting into operation, operation

Before installation the current transformer should be checked in order to discover on the surface, or on the terminals any possible damages occurred during the transportation or the storage. In case of any damages further investigation is necessary.
The current transformer can be mounted in any position. It can be fastened to the busbar by pivoted screws. A counterbore of 2–3 mm depth has to be prepared in the busbar for the screws. The screws must be tightened carefully to avoid rupture of the synthetic resin body. The nut on the screw prevents loosening.
Before connection, any contamination, occurred during the transportation and storage on the terminals has to be removed. The proper connection can be achieved paying attention to the markings on the primary (P1, P2) and on the secondary (S1, S2) side of the instrument.
The operation is possible keeping the prescriptions of the relevant security-, labour- and property-protection directives. Any faults and breakdowns emerging in the customer’s sphere of interest due to breaching, disobeying the afore-mentioned, exempt the manufacturer from the warranty and guarantee liabilities.


The maintenance consists of works to be done according to the general rules for indoor instruments and discontinuing of the accidental irregularities. These are:

– periodical inspection of the contamination and cleaning, depending on the degree of impurity,
– inspection of the surfaces,
– tightening of the bolts of the secondary connections,
– tightening of the fastening screws.

State verification

The secondary windings of the current transformers in class 0.5 are manufactured in finish suitable for verification. The verification will be made only on special request, in this case it will be accomplished and documented by an official seal or an affixed verification stamp, by the State Office for Measurement.

Data to be submitted with the order

– type (e.g. ASM-0),
– rated insulation level (e.g. 0.72/3/– kV),
– rated primary and secondary currents (e.g. 600/5 A),
– accuracy class, output and instrument security factor or accuracy limit factor of the secondary winding. (e.g. class 0.5, 15 VA, Fs10 or 15 VA 10P5),
– quantity,
– requested term of delivery.

Other or special requirements:

– application on busbar or on cable (bar type or cable current transformer),
– climatic zone of use other than normal,
– language of the rating plate,
– packing,
– number of pieces and sort of the documentation to be attached.

Warranty period, guarantee

warranty period is 12 months and otherwise it can also be established upon the mutual agreement of the parties respectively.
All right reserved for subsequent alteration without prior notice.

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