320-004A

Check Line Voltage at Main Disconnect

Using a true RMS multimeter, measure all three phases (L1, L2, L3) at the main electrical disconnect. Verify voltage is within ±10% of nameplate rating (typically 400V/480V systems).

Monitor voltage for at least 10 minutes during machine operation to catch intermittent drops.

Verify TNC Power Supply Input Voltage

Access the electrical cabinet and measure voltage at the TNC power supply input terminals. Check MP 7210 SUPPLY VOLTAGE parameter in MOD function to compare measured vs. displayed values.

Ensure proper PPE and lockout procedures before accessing electrical panels.

Inspect Power Quality with Oscilloscope

Connect oscilloscope to monitor AC input for voltage spikes, sags, or harmonic distortion. Look for voltage variations exceeding the TNC's tolerance specifications.

Capture waveforms during alarm occurrence to identify specific power quality issues.

Monitor Internal DC Voltages

Access Service menu and check MP 7200-7209 voltage monitoring parameters. Verify +5V, +15V, -15V, and +24V rails are within specification (typically ±5%).

Use the TNC's built-in voltage monitoring rather than external meters for most accurate readings.

Perform Power Supply Load Test

Run a complete axis movement sequence while monitoring supply voltages. Check for voltage drops during high-current operations like rapid traverse or spindle acceleration.

Ensure machine is properly secured and emergency stops are functional before testing.

Check Power Supply Cooling and Ventilation

Inspect power supply cooling fans, heat sinks, and air filters. Clean any debris and verify proper airflow. Overheating can cause intermittent AC Fail detection.

Use thermal imaging camera to identify hot spots in the power supply section.

Inspect Main AC Input Terminals

Power down system and inspect all AC input connections at the main disconnect, contactors, and TNC power supply input. Look for signs of arcing, corrosion, or loose hardware.

Follow proper lockout/tagout procedures and verify zero energy state before inspection.

Perform Torque Check on All AC Connections

Using appropriate torque wrench, verify all AC input terminals are tightened to manufacturer specifications. Typically 25-35 ft-lbs for main terminals.

Apply dielectric grease to connections in humid environments to prevent future corrosion.

Thermographic Inspection Under Load

With system running, use thermal imaging to identify hot connections. Temperature differences >10°C between phases indicate poor connections.

Schedule thermographic inspections during peak load conditions for best results.

Verify Circuit Breaker Sizing and Condition

Check that main circuit breaker amperage rating matches machine requirements per electrical schematic. Test breaker operation and inspect for signs of overheating or wear.

Breakers should be sized 125% of continuous load rating per NEC requirements.

Inspect Surge Protection Devices

Check status indicators on surge protective devices (SPDs) in the electrical panel. Replace any devices showing fault conditions or exceeded service life.

Failed surge protectors may create ground faults or allow damaging transients to reach the TNC.

Review Electrical Load Distribution

Analyze total electrical load including spindle, servo drives, and auxiliary equipment. Verify adequate capacity and proper load balancing across all three phases.

Use power quality analyzer to measure true power consumption including harmonics and power factor.