Product Overview
When motor starting stresses equipment and causes unplanned downtime, the Allen-Bradley 150-F251NBRD SMC Flex Smart Motor Controller provides a controlled, reliable solution. Rated at 251 A and 100–200 hp at 460V AC, this soft starter reduces inrush current, extends mechanical component life, and protects motors with integrated overload detection. Its 24V AC/DC control circuit integrates easily into existing automation systems.
The 150-F251NBRD includes a built-in display for status indication, supports trip classes 10, 15, 20, and 30, and offers optional SMB smart motor braking. With a rugged open-type enclosure and heatsink hockey puck thyristor design, it suits demanding industrial environments.
Technical Specifications
The Allen-Bradley 150-F251NBRD is engineered for high-performance motor control. Key parameters include:
| Parameter |
Value |
| Controller Rating |
251 A, 100–200 hp @ 460V AC |
| Control Voltage |
24V AC/DC |
| Rated Operational Voltage |
200–480V AC (-15%, +10%) per UL/CSA/NEMA |
| Line Connected Motor Power Max |
75 kW @ 230V AC, 50Hz, 3-phase |
| Delta Connected Motor Power Max |
400 hp @ 575V AC, 60Hz, 3-phase |
| Overload Current (Line Connected) |
84 A |
| Overload Current (Delta Connected) |
145 A |
| Trip Classes |
10, 15, 20, 30 |
| Integrated Motor Overload Protection |
Yes |
| Operating Frequency |
50/60 Hz |
| Operating Temperature |
-5 to 50 °C (23 to 122 °F) |
| Enclosure |
Open type |
| Dimensions (W x D x H) |
225 x 253.8 x 560 mm |
| Weight |
30.4 kg |
Designed for Production Reliability
Many motor failures stem from electrical and mechanical stress during starting. The Allen-Bradley 150-F251NBRD addresses these failure modes with controlled acceleration and adjustable braking. The DV/DT protection uses an RC snubber network to limit voltage spikes, while metal oxide varistors manage transient surges. With a repetitive peak inverse voltage rating of 1400V and a rated impulse voltage of 6000V per IEC, the power circuit tolerates harsh electrical environments.
Industry Applications
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Conveyors: Soft starting prevents belt slip and reduces mechanical shock to gearboxes and pulleys.
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Pumps: Controlled ramp-up eliminates water hammer and reduces pipe stress during start and stop cycles.
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Fans and Blowers: Limiting starting torque protects fan blades and shafts, extending service life.
For high-inertia loads that require quick stops, the optional SMB smart motor braking provides braking current adjustable from 0 to 400% of motor full-load current, without additional contactors or brake resistors.
Installation and Setup
Install the Allen-Bradley 150-F251NBRD in a clean, ventilated location. Maintain clearance for airflow around the heatsink. Verify the control voltage is 24V AC/DC before energizing. Power terminal connections use two M10 x 1.5 mm holes per power pole; check the NEMA/CENELEC terminal markings for correct wiring. Configure trip class to match the motor load characteristics, and set PTC input thresholds according to motor thermal ratings.
Maintenance and Reliability
The modular heatsink hockey puck thyristor design simplifies heat dissipation and service. Regularly clean dust from heatsink fins and verify cooling fan operation. Monitor the status display for alarm conditions. The controller operates in temperatures from -5 to 50°C and withstands 5–95% noncondensing humidity. With a pollution degree of 2 rating, it suits typical industrial control panels.
Selection Guide
Before ordering, confirm your motor's full-load current and calculate line or delta connection requirements. Choose the trip class based on starting duration and load inertia. If your process needs fast stopping, select the SMB braking option. PLC Source PRO supplies the Allen-Bradley 150-F251NBRD SMC Flex Smart Motor Controller and supports spare part procurement for your automation needs.