605

Monitor DC bus voltage during alarm occurrence via DIAGNOSIS > SERVO > DC LINK VOLTAGE screen (specific diagnosis number varies by series: #300-#399 range). Normal voltage is 280-310VDC for 200V class, alarm typically triggers above 380-400VDC.

Check servo parameters 1620 (time constant for acceleration) and 1621 (time constant for deceleration) for all axes. Increase Parameter 1621 values by 20-30% to slow deceleration rate and reduce regenerative peak power.

Review rapid traverse override settings and program G00 moves. Reduce rapid feedrate (Parameter 1420) or feedrate override if deceleration distances are insufficient for the load inertia.

If alarm persists after deceleration adjustments, calculate total regenerative power requirements and install external regenerative resistor unit matched to PSM capacity. Consult amplifier specifications for maximum continuous and peak regenerative power ratings.

External resistor installation requires proper wiring to PSM terminals RB1/RB2 and setting Parameter 8905#0 (regenerative resistor selection bit) correctly per Connection Manual

Verify Parameter 8905 regenerative resistor settings: bit 0 selects internal/external resistor, bits 1-3 specify resistor capacity. Cross-reference with amplifier model's Maintenance Manual specification table to ensure correct configuration.

If external resistor is installed, measure resistance value with power OFF between RB1 and RB2 terminals on PSM. Typical values are 20-80Ω depending on capacity. Open circuit or significantly high resistance indicates failed resistor.

Disconnect all power and wait 5 minutes for DC bus capacitor discharge before measuring. Verify using insulated 1000V rated multimeter

Inspect PSM amplifier LEDs during alarm: DC link overvoltage typically shows specific LED pattern (consult model-specific Hardware Manual). Check for burnt smell or discoloration around regenerative resistor terminals indicating thermal damage.

Check wiring integrity of regenerative resistor connections and verify thermal protection switches (if equipped) have not opened. Reset any thermal protectors and verify resistor cooling fans (if present) are operational.

Analyze program for simultaneous multi-axis deceleration points. Use DIAGNOSIS > SERVO screens to monitor real-time current (diagnoses #200-#207 range) on all axes during alarm to identify regenerative peaks.

For spindle-related regeneration, check spindle parameters 3770-3773 (spindle deceleration time constants for each gear). Increase these values to extend spindle coast-down time, especially for high-inertia spindles or during orientation.

Modify program logic to stagger deceleration timing of axes where possible. Use G09 exact stop or introduce controlled dwell (G04) to prevent all axes from regenerating simultaneously.

Calculate total machine regenerative capacity requirements using formula in PSM specifications: sum of (motor inertia + load inertia) × (speed change)² for all axes. If total exceeds 150% of PSM rating, upgrade to higher-capacity PSM or add external resistor bank.