150-C3NBR — SMC-3 Soft Starter, 3A, 200–480V AC, with Bypass

The 150-C3NBR is a 3A soft starter from the SMC-3 series, built for small three-phase induction motors up to about 0.75 kW at 480V. It controls motor voltage during starting to reduce inrush current and mechanical shock — the two things that shorten motor and driven equipment life in frequent-start applications.

This particular variant includes an internal bypass contactor. Once the motor reaches full speed, the bypass closes and shunts current around the SCRs, eliminating the continuous power loss and heat generation that non-bypass soft starters produce at full speed. For applications that run motors continuously after starting, the bypass makes a real difference to panel temperatures and long-term reliability.

Specifications

Parameter	Value
Part Number	150-C3NBR
Series	SMC-3
Rated Current	3 A
Input Voltage	200–480V AC, Three-Phase
Control Voltage	100–240V AC (separate control supply)
Max Motor (at 480V)	~0.75 kW / 1 HP
Starting Mode	Voltage ramp (soft start)
Internal Bypass	Yes
Soft Stop	Yes (programmable)
Start Ramp Time	1–30 seconds (adjustable)
Initial Torque Setting	Adjustable (torque control potentiometer)
Fault Output	1 × relay, Form A
Enclosure	IP20 / Open Type
Operating Temperature	−10°C to 40°C (derate above 40°C)
Standards	IEC 60947-4-2, UL 508, CE

How Soft Starting Works — and When It Matters

A standard across-the-line starter applies full voltage the instant the contactor closes. For a 3A motor that might seem harmless, but inrush current still reaches 6–8× rated current for several cycles, and the shaft torque spike transmits directly into the driven load — belts, couplings, gearboxes, and pump impellers all take that hit every start.

The SMC-3 ramps voltage from an adjustable initial level up to full voltage over a set time (1–30 seconds). The motor accelerates smoothly rather than lurching. Inrush current is reduced, belt and coupling wear drops noticeably in frequent-start applications, and liquid hammer in piping systems is largely eliminated on pump loads.

The soft stop function is equally useful for centrifugal pumps — it ramps down voltage over a set time rather than cutting power abruptly, which prevents pressure surges and water hammer in the discharge line.

FAQ

Q: What is the difference between the 150-C3NBR and a version without the "R" suffix?

The "R" suffix indicates an internal bypass relay/contactor is included. Non-R variants run current through the SCRs continuously at full speed, which generates more heat. The bypass version is preferred for continuously-running loads.

Q: Can I use this soft starter for a star-delta motor?

The SMC-3 is designed for in-line (series) connection with standard three-phase motors. Star-delta motors can be connected in their delta configuration with a soft starter in-line, but the specific wiring arrangement must be confirmed against the motor's terminal configuration.

Q: Does the soft starter protect against motor overload?

No. The SMC-3 does not include electronic overload protection. A separate overload relay must be added to the circuit for motor overcurrent protection.

Q: How is the ramp time adjusted?

Ramp time and initial torque are set via potentiometers on the front face of the unit — no programming software needed. Adjust, run a test start, observe the acceleration, and fine-tune until the ramp matches the load requirements.

Q: Can this unit handle frequent starts — say, 10–15 per hour?

At 3A with the internal bypass, thermal loading is manageable for moderate start frequencies. Exact limits depend on motor size, ramp time setting, and ambient temperature. Check the product's thermal duty cycle rating if the application requires more than 10 starts per hour.

150-C3NBR New In Box SMC-3 3A Smart Motor Controller 150C3NBR