3-Phase Monitor
The Model 257 3-Phase Monitor provides essential protection for industrial systems. It detects critical conditions such as phase loss, low voltage, and phase reversal, safeguarding equipment from damage. With both automatic and manual reset options, it offers operational flexibility. The unit is compatible with Wye or Delta systems and operates across a wide range of nominal AC voltages including 120VAC, 208/240VAC, and 480VAC. Its robust design ensures reliability, backed by a five-year unconditional warranty. Output contacts are rated for 10 amps at 240VAC resistive, supporting diverse applications. The monitor features a 50ms drop out response time and a repeat accuracy of ± 0.1% of set point, ensuring precise operation. Its mechanical relay life is rated for 10 million operations, contributing to long-term system integrity. This device is a dependable component for maintaining consistent power quality.
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Specifications
| Function | Detects phase loss, low voltage, phase reversal |
|---|---|
| Reset Type | Automatic or manual |
| Warranty | Five year unconditional warranty |
| Config: Model (Auto Reset) | B257B, 257B, A257B, EX257B, B257B-400, 257B-400, EX257B-415V |
| Config: Model (Manual Reset) | B257BM, 257BM, A257BM, EX257BM, B257BM-400, 257BM-400, EX257BM-415V |
| Config: Nominal AC Voltage | 120VAC, 208/240VAC, 480VAC, 380VAC, 415VAC |
| Config: Case Color | Gray, Red, Yellow |
| Config: Adjustment Range | 85-120VAC, 160-240VAC, 380-480VAC, 300-400VAC, 340-440VAC |
| Config: Frequency | 50Hz, 60Hz, 400Hz |
| Config: Power Consumption | 1.4W, 2.4W, 3.7W, 3.0W, 3.3W |
| Transient Protection | 2500VAC for 10ms |
| Repeat Accuracy | ± 0.1% of set point (fixed conditions) |
| Response Time | 50ms drop out |
| Dead Band | Approximately 2% |
| Output Contacts | SPDT 10 amps at 240VAC resistive |
| Expected Relay Life (Mechanical) | 10 million operations |
| Expected Relay Life (Electrical) | 100,000 operations at rated load |
| Operating Temperature | -20° to +131° F |
| Humidity Tolerance | 0-97% w/o condensation |
| Enclosure Material | ABS plastic cover |
| Mounting | 8-pin socket (sold separately) |
| Agency Approvals | UL Recognized and CSA Certified |
| UL Condition of Acceptability 1 | The 380V and 480V versions must be used with a UL Recognized 600VAC socket |
| UL Condition of Acceptability 2 | For use in a Pollution Degree 2 environment |
| UL Condition of Acceptability 3 | To be installed on the load side of branch circuit protection rated 10A |
| Neutral Connection | Not required |
| System Compatibility | Wye or Delta systems |
| Indicators | "TRIP" and "NORM" condition indicators |
| Dimension Tolerance | ± 0.06 |
