238-1002

Check axis acceleration parameters

Access MOD function, select Machine Parameters, navigate to MP1020-MP1029 (axis acceleration values). Verify acceleration/deceleration rates are not excessive for the regenerative capacity.

Typical deceleration should not exceed 80% of maximum rated values for continuous operation

Inspect regenerative resistor circuit

Check regenerative resistor for proper connection and resistance value. Measure resistance across regenerative resistor terminals - should match nameplate specification typically 47-68 ohms.

Ensure power is OFF and capacitors discharged before measuring resistance

Monitor DC-link voltage during operation

Use TNC diagnostic screen (CTRL+DIAG) to monitor real-time DC-link voltage during programmed moves. Normal operation should be 540-580VDC, alarm triggers typically above 750VDC.

Record voltage peaks during different feed rates to identify problematic motion profiles

Measure incoming mains voltage

Use calibrated multimeter to measure L1-L2-L3 voltages at power supply input terminals. Verify voltage is within ±10% of rated voltage (typically 400VAC or 480VAC three-phase).

Use proper PPE and lockout procedures when measuring live voltages

Verify power supply voltage selection

Check voltage selection jumpers or DIP switches on power supply module. Ensure configuration matches actual mains voltage. Consult power supply label for jumper positions.

Document jumper positions before making changes for easy restoration if needed

Check power supply specifications

Verify power supply part number matches machine electrical drawings. Cross-reference with HEIDENHAIN documentation to ensure correct voltage rating and capacity.

Power supply model number typically indicates voltage rating in the part number

Test DC-link capacitor condition

With power OFF and capacitors safely discharged, measure capacitance and ESR of DC-link capacitors using appropriate test equipment. Compare to nameplate values.

DC-link capacitors store lethal voltage - follow proper discharge procedures and wait minimum 10 minutes after power removal

Verify voltage monitoring circuit

Check voltage divider resistors in monitoring circuit for proper values and connections. Measure actual DC-link voltage with external meter and compare to TNC displayed value.

Voltage monitoring typically uses precision resistor dividers - even small resistance changes affect accuracy

Inspect for physical damage

Visually inspect DC-link capacitors for bulging, leakage, or discoloration. Check PCB traces and connections for signs of overheating or corrosion.

Capacitor tops should be flat - any bulging indicates internal pressure from electrolyte breakdown

Test chopper transistor operation

Using oscilloscope, monitor chopper switching signals during regenerative conditions. Verify proper PWM operation and switching frequency typically 4-16kHz.

Chopper should activate when DC-link voltage exceeds approximately 650VDC threshold

Check chopper control signals

Verify control signals from TNC to chopper circuit are present and correct amplitude. Check for proper isolation and signal integrity.

Use isolated probes when measuring signals referenced to high voltage DC-link

Measure regenerative resistor current

During regenerative events, measure current through regenerative resistor using current probe. Should see pulsed current when chopper is active.

No current flow during regenerative events indicates chopper circuit failure

Perform motor insulation resistance test

Disconnect motor cables and test insulation resistance from each motor phase to ground using 500V megohmmeter. Minimum acceptable resistance typically 1 megohm.

Ensure motor and drive are completely disconnected before applying test voltage

Check motor cable integrity

Inspect motor cables for damage, moisture ingress, or contamination. Test cable insulation resistance and continuity. Pay attention to cable routing through cable chains.

Cable chain movement can cause gradual insulation wear - check cables at chain connection points

Verify proper grounding

Check motor frame ground connections and verify low resistance path to electrical panel ground. Measure ground resistance - should be less than 1 ohm.

Poor grounding can cause common-mode currents that affect power supply regulation