INDUSTRIAL DIAGNOSTIC SYSTEMS & SERVICES LLC

ESTABLISHED IN 1983

PROACTIVE predictive PARADIGM

IDSS PROGRAMS

PROJECTS

DIVERSIFIED TECHNOLOGIES

NEW EQUIPMENT SURVEYS

DATASTICK PDA BASED SPECTRUM ANALYZERS

CTC   VIBRATION ANALYSIS HARDWARE

FRONTPAGE

MOTOR CONDITION TESTING  SPECIFICATIONS

Following is a specification of on-site services performed by Industrial Diagnostic Systems & Services LLC. for the purpose of diagnosing the electrical health of motors.  A verbal summary of the finding shall be provided to the customer at the job site.  A detailed report shall be provided.  The report will take the form of either an electronic file or paper document, whichever is preferable to the customer.

Testing will focus on the six fault zones of an electric motor listed below.  Reporting will determine a ‘good’, ‘warning’, or ‘alarm’ status for each fault zone.  Complete analysis of a motor’s health requires testing be performed on a motor in both energized and de-energized states.   Some energized tests recommend >70% motor loading.

POWER QUALITY

Tests performed:

Total Harmonic Distortion - energized motor test

Crest Factor - energized motor test

Voltage Unbalance - energized motor test

Possible faults:

Incoming voltage and current distortion

Distortion in power caused by non-linear loads

Spikes caused by variable frequency drives

POWER CIRCUIT

Tests performed:

Resistive imbalance measured in microhms - de-energized motor test

Inductive imbalance measured in mH over rotation - de-energized motor test

Possible faults:

Loose or weak terminal connections for cables and in-line components such as

Overloads or disconnects

Corroded connections at motor connection box

Weak contact connections or pitted surfaces

Improper Materials or repairs

INSULATION

Tests performed:

Resistance to ground measured in Megohms (temperature compensated) –

De-energized motor test

Dielectric Absorption ration with plot - de-energized motor test

Polarization Index with plot - de-energized motor test

Possible faults.

Current leakage paths to ground

Old or embrittled insulation condition

Moisture contamination

Corrosive or solvent aerosols

Heat

STATOR

Impedance Unbalance - energized motor test

Infrared scan - energized motor test

Resistive imbalance measured in microhms - de-energized motor test

Inductive imbalance measured in mH over rotation - de-energized motor test

Possible faults.

Deteriorated or improper connections between coils

Turn to turn and phase to phase leakages

Stresses from mechanical vibration or unbalanced magnetic forces

Partial discharges in voids of high voltage motors

ROTOR

Tests Performed.

Three phase motor current signature analysis (>70% load recommended) – energized motor test

Inductive imbalance measured in mH over rotation - de-energized motor test

Possible faults.

Broken or cracked rotor bars

Manufacturing flaws such as porosity in cast aluminum rotors

High resistance connections between bars and the end rings

AIR GAP/ ECCENTRICITY

Tests performed.

Three phase motor current signature analysis (>70% load recommended) -energized motor test.

Inductive imbalance measured in mH over rotation - de-energized motor test

Possible faults.

Dynamic eccentricity due to rotor

Static eccentricity from misalignment or out of round stator

Mishandled or dropped motors

Warping caused by uneven heating

Itemized list of tests on a de-energized motor:

RESISTANCE TO GROUND

The test of measuring resistance between each phase and ground.  The measurement shall be made using an optional 500 or 1000 VDC.  The tester shall charge the circuit to a minimum of 500 VDC potential for a minimum of fifteen seconds prior to taking the resistance measurement.  The test shall perform a monitored voltage discharge of the circuit after making the measurement.  As an additional feature, the tester shall be capable of measuring and calculating a polarization index and dielectric absorption ratio with graphing available.

The measured value of resistance shall be recorded in megohms.

The test shall be capable of testing each phase separately to ground.

CAPACITANCE TO GROUND

The test of measuring the capacitance between each phase and the motor circuit ground connection.

The measured value of capacitance shall be recorded in picofarads.

DC RESISTANCE

The test measures the resistance between each of the circuit connections on an AC induction motor: phase 1 to 2, 1 to 3 and 2 to 3.  Test leads 1 and 2 shall be used to measure the resistance values of DC circuits in testers supplied with the option of DC testing.  As an additional test, the tester may provide special DC commutator test leads which will allow the technician to perform DC bar to bar testing.

The measured value of resistance shall be recorded in ohms.

AC INDUCTANCE

The test measures the inductance between each of the circuit connections: phase 1 to 2, 1 to 3 and 2 to 3. The measured value of inductance shall be recorded in millihenries.

ROTOR INFLUENCE CHECK

The purpose of the Rotor Influence Check is to chart the reflected inductance of the rotor that appears through the stator windings to be able to identify rotor faults.

The test performs a rotor diagnostic test by plotting sequential inductance measurements taken from indexing a rotor position in a motor while measuring the inductance from phase to phase.

DIELECTRIC ABSORPTION RATIO

The test will record and graph resistance to ground measurements over a one minute period.  These readings shall automatically be taken every five seconds.  A ratio between the readings at sixty seconds to the reading at thirty seconds will be calculated.

POLARIZATION INDEX

The test will record and graph resistance to ground measurements over a ten minute period.  These readings shall automatically be taken every five seconds.  A ratio comparing the reading at ten minutes to the reading at one minute will be calculated.

The measured value of resistance shall be recorded in megohms.

Itemized list of tests on an energized motor:

VOLTAGE MEASUREMENTS

The test will record and graph three phases of voltage simultaneously and display both line to line voltage and line to neutral voltage.  This will be recorded as engineering data as well as in a graphical format and will also include Crest Factor and Total Harmonic Distortion, average voltage and %Voltage Imbalance.  NEMA derating associated with voltage imbalance will be calculated and recorded.  All of this data will be trendable in a history chart and graphical format.

CURRENT MEASUREMENTS

The test will record and graph 3 phases of current simultaneously.  This will be recorded as engineering data as well as in graphical format and will also include Crest Factor and Total Harmonic Distortion, average current, %Full Load Amp and % Current Imbalance.  All of this data will be trendable in a history chart and graphical format.

POWER DATA

The test will record power information including KW, KVAR, KVA and Power Factor for each individual phase and total.  All of this data will be trendable in a history chart and graphical format.

EFFICIENCY CALCULATIONS

The test will record the Calculated Efficiency, including the power out (HP) and the power out (kW).  All of this data will be trendable in a history chart and graphical format.

IMPEDANCE SEQUENCE DATA

The test will record zero, positive and negative sequence data for both self and mutual impedance as well as the angle associated with each.  All of this data will be trendable in a history chart and graphical format.

IMPEDANCE IMBALANCE

The test will record the Impedance Imbalance.  All of this data will be trendable in a history chart and graphical format.

HARMONIC DATA

The test will record and display the harmonics up to the 50^th harmonic in a graphical format.

CURRENT SIGNATURE ANALYSIS

The test will record and graph 3 phases of current simultaneously in an FFT (spectral) format with the ability to use cursor functions to highlight and label multiple peaks, automatically calculate the speed, automatically identify eccentricity and assist in determining the magnitude of broken or cracked rotor bars.  This data will be trendable in a history chart and graphical format.

INRUSH / START-UP ANALYSIS

The test will record the inrush and startup current for all three phases.  It will be stored in a graphical format and compared to the baseline on the same graph.  The various times available for recording the inrush / start-up will be 15 seconds, 30 seconds, 45seconds and 60 seconds.

LIBRARY

VARIABLE FREQUENCY DRIVES:

SOLUTIONS TO CRITICAL FREQUENCIES

MOTOR & POWER TESTING