ABB CM-MPS.21S 1SVR730885R3300 Voltage Monitoring Relay

ABB CM-MPS.21S 1SVR730885R3300 — Stop the Clock on Your Downtime

A tripped phase monitoring relay at 2 AM. A production line dead. Every minute costs real money — in lost output, idle labor, and customer penalties. The ABB CM-MPS.21S (part number 1SVR730885R3300) is one of those components that nobody thinks about until it fails, and when it does, the entire 3-phase motor circuit it protects goes dark. We stock it. We ship it fast. That’s the only thing that matters right now.

Our Xiamen warehouse holds verified, original ABB CM-MPS.21S units ready for same-day dispatch via DHL Express or FedEx International Priority. From order confirmation to your panel room — typically 2–4 business days to most of Asia, Europe, and the Americas.

URGENT REQUIREMENT? Contact: [email protected] | WhatsApp: +86 18359268345

Quick Technical Datasheet

Troubleshooting & Replacement Tips

Before you pull the old relay, run through this checklist. Swapping hardware without diagnosing root cause means the replacement fails in the same way within weeks.

Step 1 — Confirm the relay is actually the fault. Check the output relay contact (terminals 15/16 or 15/18 depending on wiring) with a multimeter in continuity mode. If the relay coil is energized but the contact is open, the relay has failed internally. If the coil is de-energized, the relay has correctly tripped on a real fault — do not replace it yet.

Step 2 — Measure all three phase voltages at the relay input terminals (L1, L2, L3). Use a true-RMS meter. Common findings:

• One phase reading zero or <50% of nominal — phase loss upstream. Check fuses, MCB, and contactor contacts before replacing the relay.
• All three phases present but asymmetry LED lit — voltage imbalance exceeds the set threshold. Measure L-L voltages. If imbalance >3%, investigate upstream transformer tap settings or unbalanced single-phase loads on the feeder.
• Phase sequence LED lit — two phases are swapped. Swap L1 and L2 at the relay input terminals (not at the motor) to correct sequence without rewiring the motor.

Step 3 — Threshold and timer settings on the replacement unit. The CM-MPS.21S has three front-panel potentiometers: overvoltage trip point, undervoltage trip point, and asymmetry threshold. Before removing the failed relay, photograph the potentiometer positions. Set the replacement to identical positions before energizing. Mismatched thresholds cause nuisance trips or missed faults on the first power-up.

Step 4 — Power-up sequence. Apply 3-phase supply to the relay input terminals first, before closing the motor contactor. The relay requires approximately 0.5 s to measure and validate all three phases. If the output relay closes within that window, the supply is healthy. Only then close the motor contactor. Energizing the motor simultaneously with the relay can cause a false phase-loss detection during the relay’s initialization window.

Common fault codes / LED indications on CM-MPS.21S:

• Green LED steady ON — supply healthy, output relay energized, motor circuit enabled.
• Green LED OFF, red LED ON — relay tripped. Check which fault LED is active (OV, UV, PL, PS, or ASY).
• All LEDs OFF — no supply to relay. Check control power fuse and wiring to terminals A1/A2 (if separate control supply) or L1/L2/L3.
• Relay chattering (rapid on/off) — supply voltage oscillating near the trip threshold. Widen the hysteresis by adjusting the threshold potentiometer slightly, or investigate the upstream voltage instability.

Firmware / hardware note: The CM-MPS.21S is a hardwired analog relay — there is no firmware to update, no address switches, and no bus configuration. Replacement is purely mechanical and electrical. Confirm the replacement unit’s voltage range matches your system (200–240 V L-N variant vs. other voltage variants in the CM-MPS family).

Reliability in Harsh Conditions

The CM-MPS.21S is not a lab instrument. It is built to survive the environments where motors actually run.

Temperature extremes: Rated from −25 °C to +55 °C ambient. In practice, panel internal temperatures in tropical climates or near heat-generating equipment can push 50 °C continuously. The relay’s sealed relay coil and conformal-coated PCB maintain calibration accuracy across this range without drift in trip thresholds.

Vibration and mechanical shock: DIN rail mounting with positive locking prevents relay walk-out under continuous vibration from nearby compressors, pumps, or diesel generators. The relay has been tested to IEC 60068-2-6 vibration profiles representative of industrial machinery environments.

Humidity and condensation: IP40 front panel protection keeps fingers and tool tips out of live terminals. For installations in high-humidity environments — coastal facilities, food processing wash-down areas, or outdoor enclosures — the relay should be housed in an IP54 or IP65 enclosure. The relay itself tolerates up to 95% relative humidity non-condensing.

Electrical noise immunity: Industrial environments are full of switching transients from VFDs, contactors, and welding equipment. The CM-MPS.21S meets IEC 61000-4 series EMC immunity requirements, including 4 kV surge immunity and 2 kV fast transient burst immunity. True RMS measurement also means the relay is not fooled by harmonic distortion from VFD inputs or non-linear loads — it measures actual voltage, not a distorted average.

Long service life: The output relay is rated for 100,000 mechanical operations and 30,000 electrical operations at full load. In typical motor protection applications where the relay trips only on genuine faults, service life exceeds 10 years in most installations.

Global Express Logistics

Our dispatch hub is in Xiamen, China — one of the most connected export ports in Asia, with direct DHL and FedEx gateway access. Here is exactly what happens after you place your order:

• Order confirmed before 14:00 CST — unit picked, inspected, and packed same day. Carrier collection same evening.
• Order confirmed after 14:00 CST — dispatched next business morning.
• DHL Express Worldwide — 2–3 business days to Southeast Asia, Japan, South Korea, Australia. 3–5 business days to Europe and the Middle East. 4–6 business days to North and South America.
• FedEx International Priority — available as an alternative carrier on request. Same transit time benchmarks.
• Tracking provided — AWB number sent by email within 2 hours of carrier pickup. Real-time tracking link included.
• Commercial invoice and packing list — prepared for customs clearance. HS code 8536.49 (relays for <1000V) declared. We handle export documentation; you handle import duties at destination.
• Emergency same-day dispatch — for critical breakdowns, contact us via WhatsApp before 12:00 CST for priority handling.

We have shipped ABB CM-series relays to panel builders, EPCs, and maintenance teams across Germany, the Netherlands, Singapore, Malaysia, Saudi Arabia, Australia, Brazil, and the United States. The process is routine for us. For you, it means your line is back up faster.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com

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