Philips Ingenia 2.7T/2.8T (271/281): gradient trips only in DWI
What happened
Gradient chain trips into protection only during DWI, and both the upper and lower gradient power supplies drop into fault and then recover.
What was checked
- As reported in the case, run DWI and confirm whether the lower PSU flashes a fault and recovers.
- Check the gradient amplifier protection and whether the trip lines up with the DWI load on both supplies.
Cause
The engineers found failed input capacitors (reported in the case as 6000 µF, 350 V) after the rectifier bridge in the gradient PSU — under the heavy DWI gradient current the weakened DC bus tripped the protection. This was one case, and the outcome was reported as probable.
The cause is probable and was not fully confirmed.
What was done
Replacement of the two input capacitor cans (6000 µF / 350 V, as reported) after the bridge in the affected supply. Reported in this single case as the probable fix, not as a general rule.
Safety
Gradient power supplies keep a lethal charge on the DC-link capacitors long after shutdown — de-energise, allow the manufacturer's discharge time, verify zero voltage with a meter, and leave the high-voltage section to authorised personnel.
Lesson: A trip that appears only in one demanding sequence usually means the power chain sags under peak load, so test the supply under that load before condemning the gradient coil.
Covered in the course: MRI Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.