The Siemens 3UF1868-3GA00 is a three-phase current transformer purpose-built for motor overload protection in SIMOCODE pro systems. It mounts directly onto the load side of a contactor via screw fastening, converting primary motor currents up to 820 A into a 1 A secondary signal for the SIMOCODE pro current measuring module.

What is this current transformer designed to protect?

The 3UF1868-3GA00 is part of the SIMOCODE pro motor management ecosystem. It senses the three-phase motor current and outputs a proportional 1 A secondary signal to a SIMOCODE pro current measuring module (e.g. 3UF7100-1AA00-0). The SIMOCODE system uses this signal for: overload protection (inverse-time and definite-time), phase failure/unbalance detection, stall protection, and current-dependent motor diagnostics. The 820 A primary rating covers medium to large LV motors — typical applications include pumps, fans, compressors, and conveyor drives in industrial plants where the motor is controlled by a contactor and protected by SIMOCODE.

How does contactor mounting work in practice?

The CT is designed with an aperture through which the contactor's load-side power conductors pass. The transformer body screws directly onto the contactor — no separate mounting bracket or DIN rail needed. This integrated mounting simplifies the motor starter assembly: contactor + CT + SIMOCODE module form a compact, pre-wired unit. The primary conductors pass through the CT windows; the 1 A secondary connects to the SIMOCODE current measuring module via screw terminals on the CT. For applications where contactor mounting is not suitable, the CT can also be installed as a stand-alone unit using the same screw fastening points — the 230 × 195 × 170 mm footprint and 8.92 kg weight require a solid mounting surface.

820 A primary / 1 A secondary — what does this ratio mean for my application?

The 820 A primary rating is the maximum continuous current the CT can measure. The actual operating range starts from 205 A (25% of rated primary), below which accuracy degrades. The 1 A secondary is the standard SIMOCODE pro interface — the current measuring module expects a /1 A input. The rated burden of 0.1 VA is very low, meaning the CT's secondary wiring to the SIMOCODE module must be kept short to avoid adding significant impedance. Accuracy is ±3% across the 205–820 A range — sufficient for motor overload protection (where the trip class and thermal model tolerance dominate) but not intended for precision metering applications. For billing-grade energy measurement, use dedicated metering CTs with Class 0.5 or better accuracy.