Motor Stator Testing in EV Manufacturing: Microtest MT-6910 Series

A motor stator is the stationary assembly that generates the rotating magnetic field, the part that makes the motor work. In a BLDC motor for an electric vehicle, the stator contains three-phase windings wound on a laminated core, with precise turn counts, insulation barriers, and connection points that must all be correct for the motor to deliver its rated torque, efficiency, and lifetime.

Every electrical fault in a stator, a shorted turn, a miswired phase, an insulation weakness, a high-resistance joint, produces a motor that either fails immediately or fails prematurely in the field. For EV motors where the stator operates at high voltage, high current, and elevated temperature for hundreds of thousands of kilometres, the quality standard is unforgiving.

Stator testing is the production process step that verifies every electrical parameter before the stator proceeds to rotor insertion and final motor assembly, while rework is still practical.

The Microtest MT-6910 Series

The Microtest MT-6910 Motor Stator Test System is a dedicated multi-channel platform that integrates all the electrical tests a stator requires into a single automated test cycle. Three models address different channel requirements:

Model	Channels	Typical Application
MT-6910	8 channels	Small motors, single-phase, basic 3-phase
MT-6913	13 channels	Standard 3-phase BLDC and induction motors
MT-6917	17 channels	Complex multi-phase motors, redundant winding designs

The channel count determines how many winding terminals and connection points the system can test simultaneously. More channels enable testing of more complex stator configurations without fixture reconfiguration.

Integrated Test Capabilities

A complete stator test sequence includes multiple distinct electrical tests, each targeting a different defect class:

AC/DC Hipot. Dielectric withstand testing verifies insulation between windings and between windings and the stator core. AC hipot stresses the insulation with alternating voltage, while DC hipot tests with sustained voltage. Both are required for comprehensive insulation verification.

Insulation Resistance (IR). Measures the DC resistance of the insulation at a specified test voltage. Complements hipot testing by quantifying insulation quality, a stator that passes hipot but has low insulation resistance may degrade over time in humid or high-temperature environments.

Impulse Winding Test. Detects shorted turns and layer shorts within individual windings, the defect class that hipot testing misses. The system applies a high-voltage impulse to each winding and compares the resulting waveform against a known-good reference.

DCR (DC Resistance). Measures the winding resistance of each phase. DCR imbalance between phases indicates turn count errors, wire gauge errors, or high-resistance connections. In a 3-phase motor, DCR balance directly affects torque smoothness and efficiency.

Inductance. Measures the inductance of each winding. Inductance imbalance correlates with winding geometry errors. Combined with DCR, inductance measurement provides two independent checks on winding consistency.

3-Phase Current Balance. Applies a controlled current and measures the current distribution across three phases. Imbalance indicates winding asymmetry that will cause torque ripple, vibration, and efficiency loss in the assembled motor.

Phase Rotation. Verifies that the phase sequence is correct. A stator with reversed phase rotation produces a motor that runs backward, an assembly defect that must be caught before the stator is mated with the rotor.

Welding Resistance. Measures the resistance of welded connections between winding terminals and bus bars. High-resistance welds create localised heating under load, leading to connection failure. This test catches incomplete or cold welds that visual inspection may miss.

Why Integrated Testing Matters

Each of these tests can be performed with separate instruments, a hipot tester, an impulse winding tester, an LCR meter, a milliohm meter. But in a production environment, separate instruments mean separate fixtures, separate operator steps, separate data systems, and cumulative test cycle time that limits throughput.

The MT-6910 integrates all tests into a single fixture connection and a single automated test cycle. The operator loads the stator into the fixture, initiates the test, and the system executes the full test sequence, hipot, IR, impulse, DCR, inductance, current balance, phase rotation, welding resistance, in seconds. Pass/fail results are immediate, and all data is linked to the stator’s serial number for traceability.

Rotor Testing: MT-6920

The companion MT-6920 Motor Rotor Test System extends the platform to rotor and armature testing with 24 or 48 channels. For motors with commutators, the MT-6920 performs bar-to-bar resistance, surge comparison, hipot, and inductance testing across all commutator segments. Together, the MT-6910 and MT-6920 cover the complete electrical verification of both stator and rotor before final motor assembly.

Applications Across Motor Types

The MT-6910 series serves motor manufacturers across multiple sectors:

Electric vehicles. Traction motor stators for cars, buses, trucks, and two-wheelers. EV motor quality directly affects vehicle range, performance, and warranty cost.

Home appliances. Washing machine, air conditioner compressor, and fan motor stators. High-volume production with tight cost margins demands fast, reliable testing.

Industrial automation. Servo motor, stepper motor, and spindle motor stators for CNC machines, robots, and automation equipment.

E-bikes. Hub motor and mid-drive motor stators for the fast-growing Indian electric two-wheeler market.

Medical devices. Motor stators for medical pumps, ventilators, and imaging equipment where reliability is safety-critical.

Availability in India

GSAS is Microtest’s authorized engineering partner in India, providing the MT-6910 stator test series and MT-6920 rotor test system with local installation, fixture design support, training, and calibration. Our team serves motor manufacturers and automotive suppliers across Bengaluru, Hyderabad, Chennai, Pune, Mumbai, Delhi NCR, and Visakhapatnam.

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