MT-6920 Motor Rotor Test System

The Microtest MT-6920 Motor Rotor Test System is a multi-channel test platform designed for comprehensive electrical verification of motor armatures and rotors with commutator connections. Available in 24-channel and 48-channel configurations, the system measures bar-to-bar resistance, performs surge comparison testing, verifies hipot withstand, and measures inductance across all commutator segments in an automated sequence that catches manufacturing defects before rotor assembly.

Test Parameters

Test	Purpose	Detection Capability
Bar-to-Bar Resistance	Winding continuity across commutator segments	Open coils, high-resistance connections, wrong wire gauge
Surge Comparison	Turn-to-turn insulation integrity	Shorted turns, layer-to-layer shorts
Hipot Withstand	Winding-to-shaft insulation	Dielectric breakdown, contamination
Inductance	Winding symmetry per slot	Missing turns, wrong connections
Insulation Resistance	Winding-to-core isolation	Moisture, surface tracking, damaged insulation
Growler Test	Electromagnetic fault detection	Shorted coils, grounded windings

Specifications

Feature	Specification
Test Channels	24 or 48 (model dependent)
Bar-to-Bar Resistance	4-wire measurement, micro-ohm resolution
Surge Voltage	Programmable impulse with waveform capture
Hipot	AC/DC withstand, programmable voltage
Inductance	Multi-frequency per commutator segment pair
Switching	High-speed electronic multiplexing
Indexing	Automatic commutator segment indexing
Cycle Time	Complete rotor test in seconds
Interface	Handler, USB/RS232, barcode reader
Display	Graphical bar-to-bar profile + waveform overlay

Bar-to-Bar Resistance Profiling

The bar-to-bar resistance test measures DC resistance between every adjacent pair of commutator segments, generating a complete resistance profile around the rotor circumference. A healthy rotor shows uniform resistance across all segment pairs. Deviations in the profile indicate manufacturing defects: a high reading between two segments points to an open or high-resistance connection, while a low reading suggests a shorted turn or bypassed coil. The graphical display shows the complete bar-to-bar profile, making pattern recognition immediate for operators.

The 4-wire Kelvin measurement technique with micro-ohm resolution ensures that contact resistance at the commutator probe interface does not mask genuine winding resistance variations. Automatic commutator segment indexing positions the measurement probes at each segment pair without manual rotation, enabling complete rotor profiling in seconds.

Surge Comparison for Rotor Windings

Surge comparison testing applies a controlled impulse voltage to each coil group through the commutator segments and compares the resulting damped oscillation waveform against a reference pattern. This test detects turn-to-turn insulation defects that bar-to-bar resistance measurements cannot reliably identify — a single shorted turn may change the DC resistance by a fraction of a percent (below measurement noise) while producing a clear waveform shift in the surge test. The waveform overlay display shows test and reference waveforms simultaneously for immediate visual comparison.

Production Applications

Commutator motor manufacturers producing universal motors for power tools, vacuum cleaners, and kitchen appliances deploy the MT-6920 for 100% armature testing before rotor assembly. The complete test cycle — bar-to-bar resistance, surge, hipot, and inductance — executes in seconds per rotor, matching the throughput requirements of high-volume motor production lines.

Automotive motor production for seat motors, window lift motors, wiper motors, and HVAC blower motors requires consistent rotor quality to meet automotive reliability standards. The MT-6920 provides the statistical process control data needed for automotive quality management systems, logging measurement values and pass/fail results for every rotor tested.

Dynamic balance correlation combines electrical test data with mechanical balance measurements to build a complete quality profile for each rotor. Rotors that pass electrical testing but exhibit balance issues, or vice versa, can be flagged for engineering review to identify systematic manufacturing process deviations.

Handler interfaces support integration with automated rotor handling systems, enabling fully automatic test-and-sort operations without operator intervention. Barcode-triggered test program selection enables mixed-model production where different rotor variants run on the same test station.

Watch the MT-6920 Motor Rotor Test System on YouTube

GSAS Micro Systems provides MT-6920 motor rotor test systems with fixture design, commutator probe configuration, test sequence programming, and production line integration for Indian motor manufacturers serving automotive, industrial, and consumer markets.