MV motor monitoring
Continuous stator monitoring from the MCC. No outage required.
Medium-voltage motors run the largest assets in the plant. Their failures are the most expensive, their outages the longest, their PD tests the most disruptive. SAM4 reads the current at the switchgear and watches the stator and rotor every second of every day.
Most MV motors are checked once a year. Failures don’t wait that long.
MV motors operate at 1–13.8 kV and drive critical process equipment. Stator insulation degradation accounts for 28–40% of failures, far higher than on low voltage motors. The standard diagnostic is an annual offline partial discharge (PD) test during a planned shutdown. Between tests, insulation condition is invisible.
of MV motor failures originate in stator winding insulation, driven by thermal aging, partial discharge, and contamination. (IEEE/EPRI reliability data)
typical replacement lead time for an MV motor. Large synchronous machines can exceed 12 months. Early detection is the only path to planned intervention.
between standard offline PD tests, the industry-accepted interval. Faults that develop between tests progress unmonitored until the next shutdown.
Continuous electrical monitoring from the MCC
SAM4 measures motor phase currents and voltages at the motor control centre or switchgear using Rogowski coils, the preferred sensor for MV applications because they provide wide bandwidth, no saturation risk, and accurate harmonic analysis.
Mechanical and electrical faults modulate the air gap magnetic field, which modulates the stator current. SAM4 analyses the frequency spectrum of this current signal to identify fault-specific signatures: rotor bar sidebands, bearing defect frequencies, load pattern changes, and impedance shifts consistent with insulation degradation.
The physics is identical for LV and MV motors. The differences are practical: MV motors have larger air gaps (reducing some mechanical fault coupling), higher rotor inertia (dampening torque pulsation signatures), and insulation failure mechanisms that shift toward partial discharge above 6 kV.
No sensors on the motor
All measurement happens at the MCC or switchgear. No terminal modifications, no cable routing to the motor, no arc flash exposure at the machine. This matters on MV motors where access constraints and hazardous zones make motor-mounted sensors expensive to install and maintain.
Continuous, not periodic
ESA runs continuously during motor operation. Unlike annual PD testing, it captures developing faults between shutdowns. Unlike periodic vibration routes, it provides weeks of trending data rather than monthly snapshots.
Screening, not replacing
ESA detects changes in the motor’s electrical signature consistent with developing faults. It does not replace dedicated PD testing for insulation diagnosis or vibration analysis for bearing condition. It fills the gap between those measurements.
Representative SAM4 dashboard view. The cabinet read produces fault classifications with evidence levels and recommended actions. On MV motors, the same workflow runs against the switchgear-side electrical signature, with Rogowski coils providing the wide-bandwidth read.
Signal flagged
Expert review
Fault classified
Action recommended
What SAM4 detects on this asset, and where it doesn't fit
One table. Each fault class appears once with its signal path, the strength of field evidence on this asset class, and the recommended use of SAM4. MV motors are mission-critical assets where vibration-based PdM and oil analysis are the established standard for bearing and mechanical fault diagnosis. SAM4 monitors the electrical envelope: stator winding, rotor bar, supply quality, and insulation trending continuously between annual PD tests. Mechanical PdM remains primary for bearings, lubrication, and driven-asset alignment.
| Fault class | Signal path | Field evidence on this asset | Use SAM4 as |
|---|---|---|---|
| Phase loss and voltage imbalance | Direct / electrical. Resolved at the switchgear from current and voltage symmetry. | Pathway established across motor-driven assets. | Primary monitoring |
| Stator winding faults | Direct / electrical. Inter-turn shorts and phase imbalance produce characteristic current signatures. | Pathway established across induction-motor cohorts. Continuous trending fills the gap between annual PD tests. | Primary monitoring |
| Power quality on the supply side | Direct / electrical. Voltage sags, swells, harmonic distortion, and supply-side disturbances. | Pathway established across motor-driven assets. | Primary monitoring |
| Rotor bar degradation | Indirect electromagnetic. Sidebands at characteristic slip frequencies in the current spectrum. | Pathway established across induction-motor cohorts. MV-specific cohort building. | Conditional |
| Eccentricity (static and dynamic) | Indirect electromagnetic. Rotor slot harmonics shift with air-gap variation. | Pathway established across induction-motor cohorts. MV-specific cohort building. | Conditional |
| Insulation trending | Direct / electrical. Phase-to-phase impedance and leakage signatures. | Pathway established as a precursor signal between offline PD tests. | Conditional |
| VFD-induced harmonics and switching faults | Direct / electrical. Drive-side disturbances visible in the supply current. | Pathway established. ABB ACS600 and ACS800 medium-voltage VFDs require dedicated engineering assessment. | Conditional |
| Bearing degradation | Outside the ESA envelope on MV motors. Bearing severity sits in the PdM domain. | Use vibration analysis. PdM is the established standard on MV-class bearings. | Use other methods |
| Mechanical unbalance | Outside the ESA envelope on MV motors. Mechanical balance sits in the PdM domain. | Use vibration analysis. | Use other methods |
| Misalignment with the driven asset | Outside the ESA envelope on MV motors. Driven-asset alignment is a PdM and laser-alignment task. | Use vibration phase analysis and laser alignment. | Use other methods |
| Insulation absolute value | Outside continuous monitoring scope. Absolute-value testing requires offline measurement. | Use offline partial-discharge testing or motor circuit analysis. | Use other methods |
| Stator core hot spots and thermal faults | Outside the ESA envelope. Thermal phenomena not coupled to current signature. | Use thermal imaging or motor-mounted RTDs. | Use other methods |
| Lubrication and bearing grease condition | Outside the ESA envelope. Chemical and physical state not in the electrical signature. | Use oil and grease analysis on a sampling cadence. | Use other methods |
ESA alongside vibration and PD testing: not instead of them
MV motors with high failure consequences already have vibration monitoring and periodic PD testing. ESA adds a continuous electrical monitoring layer that fills the gaps between those measurements. For fleet motors that lack individual monitoring, ESA provides the first layer of coverage at a fraction of the per-motor cost.
ESA from MCC
- Continuous rotor bar condition
- Load anomaly detection
- Electrical supply monitoring
- Basic insulation screening (trending)
- Energy efficiency tracking
- No motor-mounted sensors
What overlaps
- Bearing trending (rolling element only)
- Mechanical unbalance indication
- General health trending
PD testing + vibration
- Quantitative PD measurement (picocoulombs)
- PD source location within specific coils
- Sleeve bearing monitoring (proximity probes)
- High-frequency bearing defect detection
- Shaft position and orbit analysis
- Standards-based severity assessment (ISO 20816, IEEE 1434)
Recommended monitoring by scenario
Critical >2 MW compressor drive
Critical >2 MW compressor drive
Full stack: vibration (proximity probes), online PD, temperature, oil analysis, shaft voltage monitoring. ESA adds load profiling and a second opinion on rotor condition. Does not replace any of the above.
Fleet of 20 pump motors (200–500 kW)
Fleet of 20 pump motors (200–500 kW)
ESA across the full fleet from the MCC. Continuous vibration on the 3–5 most critical. Annual offline PD on all. This is where ESA’s economics are strongest: fleet-wide coverage where per-motor investment is not justified.
VFD-driven mill motor
VFD-driven mill motor
Shaft grounding (mandatory), vibration for fluting detection, online PD if >1 MW. ESA adds load profiling and rotor assessment, but VFD harmonics limit detection quality. Requires VFD-aware signal processing.
MCC installation. No motor access required.
1. Access the MCC or switchgear
SAM4 installs at the motor control centre, the same panel your electricians already access. No hazardous zone entry, no motor terminal modifications. MV arc flash safety requirements apply: qualified personnel, energised work permit, or installation during planned outage.
2. Install Rogowski coils on motor supply cables
Rogowski coils clip onto individual motor phase cables. No saturation risk, wide bandwidth for accurate harmonic analysis. Split-core design allows retrofit without disconnecting cables. Works with DOL, soft starters, and MV VFDs.
3. Connect and commission
The SAM4 gateway connects via cellular (4G/LTE), no dependency on your IT/OT network. Monitoring starts immediately. Baseline establishment requires several days of normal operation. Per-motor commissioning sets thresholds for the specific motor and drive configuration.
Other asset types SAM4 monitors
Pumps
Centrifugal pumps in water, chemicals, oil & gas, and process industries.
Compressors
Reciprocating, screw, and centrifugal compressors across process industries.
LV motors
Low voltage motors across all industrial applications.
Fans & blowers
Ventilation fans, cooling fans, process blowers, and aerators.
See SAM4 on MV motors
A 30-minute demo shows SAM4 running on MV motors, with real electrical signatures, real fault data, and an honest view of where ESA adds value alongside your existing monitoring stack.
How this page is validated
MV-specific evidence base building. The induction-motor physics is shared with the LV-driven fleet baseline, so pathway claims inherit from that body of evidence. Per-fault recall on MV motors will be published when the MV-specific sample reaches the threshold set in our reporting rules. Until then, this page reports pathways and scope.
How the MV evidence base grows
- Each alert SAM4 raises on an MV motor is followed up against customer-confirmed outcomes
- Cases are scored independently: detected, missed, or false alert
- Pathways resolved on the LV-driven fleet inform initial scoping and severity bands
- Field evidence on this asset moves from a clear signal path to case-by-case proof to a published metric as the evidence base grows
What evidence is available today
- Pathway analysis grounded in three-phase induction motor physics, identical to LV
- Fleet-level review of comparable-cohort performance available on request, see the LV motors page for the published baseline
- MV-specific case detail and review criteria available to qualified technical evaluators under engineering review
- Published research on ESA for MV applications referenced in the validation report