238-1021

Check AC input voltage at power supply

Measure AC voltage at L1, L2, L3 terminals on the power supply unit. Verify voltage is within ±10% of rated voltage (typically 400V/480V 3-phase).

Use proper PPE and lockout procedures when measuring high voltage

Verify DC-link voltage in TNC diagnostics

Navigate to MOD > Service > TNC diagnostics > Power supply monitoring. Check DC-link voltage reading against specification (typically 565V DC for 400V AC input).

Compare readings with machine documentation - some systems use 24V or 48V DC-link

Inspect power supply LED indicators

Check status LEDs on power supply module. Red LED typically indicates DC-link undervoltage fault. Consult power supply manual for specific LED patterns.

Test with reduced load

Disconnect non-essential loads and attempt restart. If alarm clears, power supply may be undersized or failing under full load conditions.

Check capacitor visual condition

Inspect DC-link capacitors for bulging tops, electrolyte leakage, or discoloration. These are signs of capacitor failure.

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

Measure capacitor ESR if equipped

Use ESR meter to check equivalent series resistance of DC-link capacitors. High ESR indicates degraded capacitors that cannot maintain voltage under load.

Monitor voltage ripple

Use oscilloscope to measure DC-link voltage ripple. Excessive ripple (>5% typically) indicates capacitor degradation.

Ripple measurement should be done under normal operating load conditions

Check capacitor age and operating hours

Review machine service records and check TNC operating hours in MOD > Service > Machine data. Capacitors typically need replacement every 5-7 years or 40,000-60,000 hours.

Check brake resistor continuity

Measure resistance of brake resistor(s) connected to power supply. Open circuit indicates failed resistor that cannot dissipate regenerative energy.

Ensure power is off and resistors are cool before testing - they operate at high temperatures

Verify brake chopper operation

Check brake chopper status in TNC diagnostics under MOD > Service > TNC diagnostics > Drive status. Verify chopper activates during deceleration.

Review program for excessive rapid moves

Examine NC program for rapid acceleration/deceleration cycles that generate excessive regenerative energy. Check feed rates and acceleration parameters in machine parameters.

Monitor during typical cycle

Observe DC-link voltage during normal machining cycle to identify when voltage drops occur relative to machine movements.

Voltage drops during rapid deceleration indicate brake system issues

Perform insulation resistance test

Use megohmmeter to test insulation resistance between motor phases and ground. Minimum 1 megohm typically required.

Disconnect drive connections before insulation testing to prevent damage

Check for ground fault indicators

Look for ground fault LEDs or messages in TNC alarm log. Navigate to MOD > Service > Error messages to review fault history.

Inspect cable routing and condition

Examine motor and feedback cables for damage, especially in cable tracks. Look for pinched, cut, or oil-contaminated cables.

Test with cables disconnected

Disconnect motor cables and attempt power-up. If alarm clears, fault is in external wiring or motor. If alarm persists, fault is in drive electronics.

Verify power supply parameters

Check machine parameters for correct AC input voltage setting. Navigate to MOD > Machine parameters and verify MP7300-MP7399 power supply settings match actual installation.

Compare with backup parameters

If available, compare current machine parameters with known good backup or factory settings using TNC parameter comparison function.

Check UVR threshold settings

Verify undervoltage release threshold parameters are set correctly for the installed power supply type and voltage rating.

UVR thresholds are typically 85-90% of nominal DC-link voltage

Reset to default if necessary

If parameters appear corrupted, restore from backup or reset power supply parameters to factory defaults and reconfigure for specific installation.