Electric Power Trowels

Single-phase versions rated at roughly 1.5–2.2 kW run from a 230 V socket on a 16 A fuse and draw around 8–11 A under load. Three-phase machines of 3–4 kW call for a site distribution board with a 400 V 16 A 5-pin socket, and in exchange hold torque with the disc pressed down hard through hours of continuous work. Refurbishment work indoors is covered by 230 V; an industrial floor slab makes 400 V the sensible pick. Protect the circuit with a 30 mA residual current device, because the machine operates on damp concrete.

Conductor cross-section and run length decide this. A 230 V machine drawing about 10 A is served by a 3 × 1.5 mm² cable over runs up to 25 m, while 25–50 m calls for 3 × 2.5 mm². An undersized lead causes a voltage drop and overheats the windings, which with a loaded disc trips the thermal cut-out. Unroll cable drums fully. Three-phase 400 V supplies use 5-core cable and 16 A 5-pin connectors.

Generator operation works given headroom for the starting surge. An induction motor pulls 2–3 times its running current at start-up, so a 2.2 kW machine needs a generator of at least 5 kVA continuous output, and a 4 kW unit something in the 8–10 kVA class. Steady 50 Hz output and surge headroom matter more than the rating on the label, so pick the generator with room to spare. Keep it outside the building — run it indoors and you lose the whole point of an electric machine, which is finishing concrete without exhaust fumes in an enclosed space.

Electric machines with a 60–100 cm working diameter cover roughly 200 to 1500 m² per working day, depending on output, the number of passes and how fast the concrete sets. The 230 V version suits flats, basements and small warehouse units; the 400 V version fits industrial buildings with a distribution board on site. Past a few thousand square metres the limit is no longer power but the cable trailing behind the operator; at that scale petrol or ride-on machines finish faster.