1SVR730885R3300, CM-MPS.21S: CM-MPS.21S relay: phase, voltage and neutral supervision
The ABB CM-MPS.21S is a multifunction three-phase monitoring relay for systems with neutral. ABB lists an 180–280 V AC line-to-neutral measuring range, two changeover outputs and monitoring for phase failure, phase sequence, over/undervoltage, phase unbalance and interrupted neutral. The trip delay can be selected from instantaneous to 30 seconds.
Key technical data
| Technical item | Verified value / selection note |
|---|---|
| Type | CM-MPS.21S |
| Order code | 1SVR730885R3300 |
| Supply / measuring voltage | 180–280 V AC line-to-neutral |
| Functions | Phase failure/sequence, over/undervoltage, unbalance and interrupted neutral |
| Output | 2 c/o (SPDT) contacts |
| Trip delay | Instantaneous or adjustable 0.1–30 s |
| Terminals | Screw terminals |
The table summarizes family or catalog values for identification and initial selection. Confirm the nameplate, environmental limits, standards, revision and options for the exact device before procurement or engineering approval.
Application and system selection
Use the relay when the application needs more than phase sequence alone, such as voltage-window supervision or neutral monitoring. Set thresholds and delay to match the load and control response; nuisance-trip immunity and equipment ride-through should be considered. Determine whether the output should alarm, inhibit starting or trip a contactor.
Configuration and compatibility
Check that the neutral-referenced voltage and line configuration match the relay. Compare screw terminals, output contact ratings, selectable delay and front-panel settings with the control design. Its functions differ from the simpler CM-PFS.S, so choose the exact model by the required measurements rather than the shared CM family name.
Related models and order-code references
The following designations are related catalog references, not automatic substitutes. Check each complete code, rating, connection, revision and application requirement before selecting a variant.
- 1SVR730884R3300 CM-MPS.41S
- CM-MPS.21P, 1SVR740885R3300
- CM-MPS.21S
- CM-MPS.41S
- CM-MPS.41S 1SVR730884R3300
- CM-MPS.43S, 1SVR730884R4300
Installation and commissioning
Install in the specified orientation and wire all monitored conductors according to the diagram. Confirm neutral integrity, phase order and the voltage threshold settings before putting the output into the protection chain. Test each configured fault condition, verify delay timing and record the final relay settings and contact logic.
Replacement and procurement information
For a quotation or replacement review, provide the complete designation 1SVR730885R3300, CM-MPS.21S, the order code where applicable, serial or hardware revision, quantity, operating environment, connected equipment and required delivery date. Include a legible nameplate image and relevant wiring, loop or switchgear drawing so the exact interface and configuration can be checked.
Ask the supplier to confirm accessories, revision compatibility and any approved successor in writing. Do not select solely from a family name or product photograph. Follow the current ABB installation and safety instructions for the exact unit.
