STANDARD TEST

The MCE Standard Test is a 2 to 3 minute test which provides a comprehensive view of overall motor and circuit condition. High frequency AC and low voltage DC signals are transmitted through the circuit to collect the parameters utilized for diagnosis. Results are trended, compared to caution and alarm levels, and annotated in red or yellow to alert the user of potential problems.

Initially, lead checks are conducted to ensure accurate readings, preventing rust, dirt or other corrosive contact surfaces from adversely influencing test results. The parameters collected are discussed below.

• Resistance-to-Ground parameters are obtained with either 500 VDC or 1000 VDC in a standard unit. Potentials as low as 100 VDC and as large as 5000VDC are available with our new 5 kV Module. All readings are temperature corrected and standardized to ensure precise trending of insulation condition.

• Capacitance-to-Ground This parameter capitalizes on the natural capacitance of the motor and circuit to trend dirt and moisture build-up on the insulation. It is utilized in combination of with the resistance-to-ground measurements to determine overall insulation condition.

• Phase Resistance Extremely accurate phase-to-phase resistance values on the micro-ohm level are recorded to determine the quality of connections in the circuit and motor itself. An imbalance figure is then calculated for ease of interpretation and trending. Stator faults, both turn-to-turn and phase-to-phase, may be detected using these parameters.

• Phase Inductance Once again, phase-to-phase inductance parameters are collected and an imbalance calculated to help determine rotor, stator and air gap health. Higher or escalating imbalances indicate the presence of an anomaly. Additionally, these parameters can be beneficial in identifying faulty capacitors within the circuit.

POLARIZATION INDEX (PI) AND DIELECTRIC ABSORPTION RATIO (DAR)

Utilizing detailed graphing and complete automation, the PI and DAR are used as advanced methods of evaluating insulation and can be highly effective at detecting the presence of contamination. Caution and alarm levels are set in accordance with IEEE specifications. The tests voltages selected are the same as those available for the Standard Test insulation-to-ground readings. The DAR applies a steady potential to the circuit for one minute, graphing results every 5 seconds and calculating a ratio of the reading at 60 seconds to that of 30 seconds. The Polarization Index (PI) is conducted in identical fashion, with the ratio calculated using the reading at 10 minutes compared to the one recorded at 1 minute.

ROTOR INFLUENCE CHECK (RIC)

The RIC is a test that examines the relationship between the rotor and stator fields. The rotor is incrementally rotated through one pole face, recording phase inductance at each position. The generated patterns are combined with standard test results to confirm the presence of rotor, stator and air gap problems. The collected parameters are sensitive enough to detect excessive porosity in cast rotors, cracked or broken rotor bars, or other defective conditions.