Rated current across the temperature band
The 3RW4036-1BB15 delivers 45 A at 40 °C, derating to 42 A at 50 °C and 39 A at 60 °C. That 6 A drop from 40 °C to 60 °C means the thermal budget in a warm cabinet directly sets the motor full-load current you can start — if the enclosure ambient runs at 50 °C, you lose 3 A of headroom off the 40 °C nameplate. The derating temperature threshold is 40 °C, so any panel ambient above that forces a linear reduction in continuous motor current. For a 37 kW motor at 400 V drawing roughly 72 A FLC, this unit is undersized — you step up to the next frame. It fits 22 kW motors comfortably at 40 °C ambient.
Integrated bypass and thyristor stack
An integrated bypass contact system means the thyristors are shorted out once the motor reaches full speed. This eliminates SCR conduction losses during run — the heat load in the panel drops to just the bypass contactor's dissipation, not the full semiconductor drop. The thyristors themselves handle the start ramp only. Because the bypass is internal, you do not need an external contactor in parallel. That saves one DIN-rail slot and the wiring between the soft starter and the bypass contactor. The S2 frame (55 mm wide) fits standard 35 mm DIN rail with screw or snap-on mounting.
Control supply and protection features
Control supply voltage accepts 110-230 VDC, which covers common DC bus voltages in industrial panels. The wide range means you can power it from a standard 24 VDC supply only if you step up — 110 VDC is the minimum, so a 24 VDC-only panel needs a DC-DC converter or a separate 110 VDC rail. Motor overload protection is built in, along with intrinsic device protection and adjustable current limitation. The minimum load is 20 % of the rated current, so light-load applications like small pumps or fans need to stay above that threshold or the soft starter may not trigger correctly. The insulation voltage is 600 V, matching standard 400 VAC systems with margin.
Mounting clearances and cable lengths
The 3RW4036-1BB15 requires 60 mm clearance upwards, 40 mm downwards, and 30 mm at the sides. These are the minimum air gaps for heat dissipation from the thyristor stack and bypass contactor — crowding them raises internal temperature and accelerates derating. Maximum motor cable length is 300 m. For long cable runs from the panel to the motor, stay under this limit to avoid reflected wave voltage spikes that can stress the thyristors. The unit accepts stranded wire up to 25 mm² on the main circuit terminals and solid wire up to 2.5 mm² for control.