Applying IEEE 493-2007, IEEE 3004.8-2016, and ISO 10816-3:2009 with the ATC Diversified Motor Director™

Electric motors rarely fail without warning. They fail after weeks or months of progressive mechanical stress, thermal degradation, and electrical imbalance that go undetected in most facilities.

Three major standards describe this reality from complementary angles:

• IEEE 493-2007 (Gold Book) — documents why motors fail based on field statistics
• IEEE 3004.8-2016 — defines how motors must be protected in industrial systems
• ISO 10816-3:2009 — defines how vibration must be measured, evaluated, alarmed, and tripped at the bearings where most failures begin

Together, these standards establish a complete philosophy:

Motor reliability depends on monitoring the mechanical, thermal, and electrical precursors to failure, not just reacting to faults.

The ATC Diversified Motor Director™ Advanced Motor Protection System provides a practical way to implement this full standards-based philosophy at the MCC, starter, or feeder level, where traditional protection has historically been insufficient.

What Actually Causes Motor Failures

IEEE 493 compiles decades of industrial failure data and consistently shows:

• Bearing failures are the largest contributor to motor outages
• Insulation failures are strongly tied to overheating and voltage stress
• Misalignment, imbalance, and looseness frequently precede failure
• Failures develop gradually, with measurable warning signs long before trip conditions occur

IEEE emphasizes that: Motors rarely fail without warning and the warning signs simply go unmonitored. This shifts the philosophy from: “Trip when a fault happens” to “Detect the conditions that cause faults.”

The Engineering Requirements for Motor Protection

IEEE 3004.8 translates reliability lessons into protection requirements. It requires protection to consider:

• Motor heating characteristics
• Starting stress and locked-rotor heating
• Voltage unbalance and phase loss
• Ground faults and overcurrent
• Power quality issues
• Motor importance to the facility

The standard strongly recommends the use of a multifunction motor protection relay (IEEE Device 11) like the ATC Diversified Motor Director™ Advanced Motor Protection System instead of relying on overload relays and breakers alone, especially for low-voltage (240VAC to 480VAC) MCC motors.

Why Bearings and Vibration Matter

IEEE 493 shows bearings are the dominant failure mode.

• Where do bearing problems show up first? At the bearing housing as increased vibration.

ISO 10816-3 is written specifically for: Industrial rotating machines above 15 kW, including electric motors, measured on the bearing housings in place. It defines:

• Where to measure
• What to measure
• What values mean
• How to set alarms and trips
• How to detect early changes (25% rule)

What ISO 10816 Requires Technicians to Do

ISO requires vibration to be measured:

• On bearing housings
• In two radial directions
• As RMS velocity (mm/s)
• Across 10–1000 Hz
• At normal load and temperature
• Using the highest reading

This removes subjectivity from vibration assessment.

ISO 10816 Severity Zones — Turning Vibration into Action

For typical MCC motors (Group 2, rigid support):

These are internationally accepted limits.

The Most Important Rule — The 25% Change

ISO Criterion II states: A change of 25% from the machine’s normal vibration is significant and must be investigated.

This aligns directly with IEEE 493’s finding that failures develop gradually.

Why Combining Electrical, Thermal, and Vibration Is Powerful

Most motor problems affect multiple domains simultaneously:

Seeing all three provides earlier and more accurate diagnosis than any single parameter.

How the ATC Motor Director Is Applied in the Field to Meet These Standards

Step 1 — Electrical Integration (IEEE 3004.8)

Motor Director is connected to all three motor phases and control circuits to monitor:

• Thermal loading
• Phase unbalance
• Overcurrent
• Undervoltage
• Phase loss
• Ground fault awareness

This fulfills the multifunction relay role IEEE 3004.8 recommends.

Step 2 — Thermal and Starting Protection

Motor Director tracks:

• Start duration
• Inrush magnitude
• Restart attempts
• Cumulative heating

This enforces thermal limit curves and locked-rotor protection.

Step 3 — Vibration Sensor Installation (ISO 10816)

A vibration sensor is mounted:

• On the bearing housing (drive end preferred)
• Radially
• Connected to Motor Director
• Configured for RMS velocity (mm/s)

This matches ISO measurement requirements exactly.

Step 4 — Threshold Setup Using ISO Zones

For a Group 2, rigid motor:

• Alarm ≈ 2.0–2.5 mm/s
• Additional 25% change alarm

Step 5 — Establish Baseline (IEEE 493 + ISO)

At normal operation, record:

• Vibration
• Current
• Voltage
• Power Factor
• Temperature

Future alarms are based on deviation from this baseline.

Step 6 — Continuous Monitoring and Trending (IEEE 493)

Motor Director trends all parameters to detect:

• Bearing wear
• Misalignment
• Looseness
• Cooling issues
• Electrical stress

Weeks or months before failure.

Step 7 — Alarm, Notification, and Trip Strategy

• Alarm when entering ISO Zone B trend
• Electrical/thermal alarms per IEEE

From Reactive Protection to Standards-Based Predictive Reliability

Practical Results Facilities Can Expect

Facilities using this approach typically experience:

• 50–80% reduction in unexpected motor failures
• Longer bearing and winding life
• Better root-cause diagnosis
• Lower maintenance costs
• Higher uptime

Because they stop reacting to faults and start detecting causes.

When installed and configured as described, the ATC Diversified Motor Director™ enables facilities to implement all three standards in a practical motor control installation.

Motor protection is no longer about stopping faults; it is about preventing failure using standards-based monitoring.

References

• IEEE 493-2007 — Reliability of Industrial Power Systems
• IEEE 3004.8-2016 — Motor Protection Practice
• ISO 10816-3:2009 — Vibration Severity Evaluation for Industrial Machines

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