Sensorless condition monitoring implemented inside the AC drive itself reads the motor's own current and speed signals and uses FFT plus statistical indicators to flag unbalance, misalignment, and bearing wear before a failure [S2].
The approach targets conveyor systems, machine-tool feed drives, hydraulic pumps, and fans where adding external vibration hardware per motor becomes uneconomic at fleet scale [S1][S3].
What "drive-based" actually means
Drive-based condition monitoring is software running on the drive's own controller, not a separate condition monitoring system box, so the same current transducers and encoder feedback that close the torque loop are reused for diagnostics [S2].
Reference values are captured once during a known-good operating state, then repeated comparative measurements are taken in production at fixed intervals or on demand, with deviations generating a warning when adjustable thresholds are crossed [S2].
Baumüller ships this as a firmware module on the b maXX softdrivePLC and explicitly markets the no-sensor variant to retrofitters of textile machinery and similar multi-motor lines, where per-motor sensor cost dominates the bill of materials [S2].
Which motor faults can be inferred from the drive signals alone
Without external sensors, the drive can attribute a deviation to rotating-element categories such as unbalance, shaft misalignment, and rolling-bearing damage, because these faults modulate the stator current at characteristic frequencies that FFT can resolve [S2].
ifm's moneo platform extends the same idea with add-on sensors to cover soiling, drive-belt wear, operating-hours, and winding temperature on top of vibration, treating these as four to five measurable variables per motor [S1].
Higher winding and bearing temperatures are the classic early indicators and are detectable with contact sensors or IR cameras, which is why most published CM stacks still pair current-signal analysis with at least one temperature channel [S6].
Sensorless vs sensor-augmented drive monitoring
The sensorless path needs zero new wiring and zero new hardware on the motor, which is the main economic argument in machines with 10 or more drives such as textile lines, printing presses, and extruders [S2].
The sensor-augmented path adds freely positioned external vibration condition monitoring transducers to the same drive firmware, trading hardware cost for a more precise fault pattern and the ability to detect issues the current signal cannot see, such as lubrication loss on a coupled gearbox [S2].
Danfoss frames the integrated version as a CBM (condition-based maintenance) capability that turns the VFD into a data logger for the motor, and pairs it with edge analytics so the drive can issue local fault signals even when the plant network is down [S5].
How it compares to a dedicated vibration monitoring stack
On motor-bearing inner-race defects, a published bearing benchmark dataset showed that data-driven classifiers can reach high accuracy on vibration features, and most of the cited research relies on accelerometers rather than current alone [S7].
Feed-drive reviews in the ASME Journal of Manufacturing Science and Engineering position drive-based CM as the intermediate step between raw acquisition and full diagnostics, with vibration-only methods still the reference baseline for sensitivity on spindle and ballscrew faults [S3].
On cost, ifm's published use case claims about 6 hours of configuration labor, roughly $1,200 in lower integration cost, and $5,900 saved by preventing complete motor damage on a typical retrofitted cell, which is the order of magnitude where sensorless drive monitoring becomes a no-brainer [S1].
Selection criteria and where it fits, and where it does not
For fixed-speed utility loads such as fans, pumps, and simple conveyors driven by a VFD already on site, drive-based monitoring is the lowest-cost first step and replaces run-to-failure maintenance with alarm-driven service [S1][S8].
For high-speed spindles, machine-tool feed drives, and any asset where bearing-fault latency must be measured in days rather than weeks, a sensor-augmented stack with accelerometers mounted on the bearing housing remains the engineering baseline, and the drive's sensorless channel serves as a backup layer rather than the primary diagnostic [S3].
For hazardous areas or retrofit projects where adding sensors means new cable glands and re-certification, drive-internal monitoring is the path of least resistance because nothing mechanical is added inside the classified zone [S5].
What to verify before specifying
Confirm the drive firmware exposes the FFT or statistical indicators used for the comparison, because some platforms only log raw waveforms and the host PLC has to do the math, which is a different engineering scope [S2].
Confirm whether the reference capture is taken automatically or requires a manual baseline run, and how the system handles operating-point changes such as a new product SKU that changes the load curve, since threshold drift is the most common cause of false alarms in drive-based monitoring [S2][S5].
Confirm the fieldbus path for alarms: PROFINET, EtherNet/IP, or OPC UA over MQTT are the typical options on modern servo drive controllers, and the host SCADA must accept the drive as a power monitoring system-style data source for the alarm to be actionable [S5].
Limitations and failure modes
Current-based detection is weak at low speed and low load, where the signal-to-noise ratio on stator current collapses, so any drive-based CM spec must state the operating envelope (typically above 10–15% rated speed and torque) where the algorithm is valid [S2].
Shared couplings, gearboxes, and belt drives between the motor and the process load can shift fault frequencies and confuse the FFT unless the drive's model is told about the mechanical train, which is a configuration step many end users skip [S1][S8].
Reference-baseline drift is the dominant failure mode of sensorless drive monitoring: if the baseline was captured on a worn bearing, the system will treat that worn state as healthy and miss the next stage of degradation, so periodic re-baselining must be part of the maintenance plan [S2].
Standards, sourcing, and trackable signals
No single ISO or IEC standard governs drive-based condition monitoring as a product, but ISO 17359 sets the general condition monitoring and diagnostics framework that vendors align their terminology to, while ISO 13373 covers vibration condition monitoring on which the sensor-augmented variants build [S3].
NORD's published approach packages sensors, software architecture, and interfaces together as a service tier, which signals that more drive makers will move CM into the firmware rather than selling it as a separate hardware SKU over the next 12–24 months [S8].
Two signals worth watching: the spread of PROFINET profile extensions that expose drive-side FFT and statistical data to the PLC, and the number of motor makers offering CM as a no-cost firmware option rather than a paid license, both of which will set the floor for retrofit pricing in 2026 and 2027 [S2][S5][S8].
See also our earlier report, Aerial Work Platform Working Height Ranges for Construction Sites.