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Check input voltage at power supply

Measure AC input voltage at the power supply terminals. Verify voltage is within ±10% of rated voltage (typically 400V/480V 3-phase).

Use proper PPE and lockout procedures when measuring high voltage

Monitor voltage stability

Use oscilloscope or power quality analyzer to check for voltage dips, spikes, or phase imbalances during machine operation.

Check voltage during spindle acceleration and axis rapid moves when power demand peaks

Verify facility power quality

Check building electrical system for loose connections, overloaded circuits, or transformer issues affecting the CNC power supply.

Coordinate with facility maintenance to check upstream electrical components

Power down and inspect capacitors

After proper lockout, visually inspect DC-link capacitors in the power supply for bulging, leakage, or discoloration indicating failure.

Capacitors retain dangerous voltage even when powered off - use proper discharge procedures

Measure capacitor ESR and capacitance

Use capacitor analyzer to test ESR (Equivalent Series Resistance) and capacitance values against manufacturer specifications.

ESR values above 0.1 ohms typically indicate capacitor degradation requiring replacement

Check capacitor mounting and connections

Inspect capacitor mounting brackets and electrical connections for looseness or corrosion that could cause intermittent voltage drops.

Torque connections to manufacturer specifications - typically 8-12 Nm for power connections

Review axis acceleration parameters

Check machine parameters MP1020-MP1029 for axis acceleration/deceleration values and reduce if excessive for the application.

Gradual deceleration reduces regenerative energy spikes

Verify regenerative resistor operation

Check regenerative (brake) resistors for proper resistance values and thermal condition. Measure resistance when cool.

Regenerative resistors operate at high temperatures during normal use

Monitor DC-link voltage during operation

Use TNC diagnostic screens to monitor DC-link voltage during rapid moves and spindle operations to identify voltage spikes.

Access voltage monitoring through MOD function and select drive diagnostics

Check power supply diagnostic LEDs

Examine status LEDs on the power supply unit for fault indications. Refer to power supply manual for LED code interpretation.

Document LED patterns and timing for technical support diagnosis

Measure switching frequency and ripple

Use oscilloscope to check switching frequency (typically 16-20kHz) and DC output ripple voltage on power supply outputs.

Use differential probes when measuring switching circuits to avoid ground loops

Verify cooling and thermal protection

Check power supply cooling fans, heat sinks, and air filters. Clean if necessary and verify thermal protection circuits are not activating.

Power supply efficiency drops significantly when overheated, causing voltage regulation issues