The errors of conventional standard current transformers inevitably depend on the burden. A magnetic flux in the core produces the e.m.f. which sustains the secondary current in the burden. This disadvantage has now been eliminated by the development of the two new current comparators, types 4761 and 4764. An indicator winding measures the magnetic flux in the core, while an amplifier - by regulating the current in a compensating winding makes sure that the flux in the core is approximately zero. DESIGN The housing of both comparators is made of a insulating material. All terminals and controls are mounted on the top panel. The holes for the wires of the bushing transformer are on the lateral face of the unit. Type 4761 is portable. Type 4764 is equipped with castors. CURRENT RANGES Secondary: Primary: 1-5A 5 ... 500 A* 500 ... 5000 A** * in 94 steps at the terminals. **in 62 steps, produced by one and two respectively. The range of type 4764 can be extended up to 10 000 A by means of the auxiliary transformer, type 4766 ( Higher values on request). K1: K2: K3: A: B: C: D: Outside (hollow) annular core Inside annular core Auxiliary core Secondary winding Compensation winding Indicator winding Primary winding

TRANSFORMATION RATIONS OF 4764 SWITCH POSITIONS PRIMARY CURRENT IN AMPERE TERMINAL CONNECTIONS EXTERNAL WINDINGS Since the electrical behavior of the comparator is equal to that of a normal current transformer i.e. it can also be used inverted it works for primary currents < 5 A.

TECHNICAL DATA TYPE 4761 Standards: Ratio error in a range of 1 ... 200 % IN: 0.001 % Phase angle: 0.05 min Primary I N: 1 _ 2 _ 5 _ 10 _ 20 _ 50 100 _ 200 _ 500 _ 1000A The ranges 500 ... 1000 A are produced by 2 or 1 turns. Secondary: 1-5A Output: max. 5 VA Power supply: 115/230 V, 50/60Hz,20VA Overload protection: Built-in overload protection with “Overload” warning and fuses in the power plug. Dimensions: x17.7in) 435 x 260 x 450mm (17.1 x 10.2 Hole diameter for cable: 55 mm Ratio error in a range of 1 ... 200 % IN: 0.001 % Phase angle: 0.05 min Connections: connected Primary I N: 5 ... 500...