Plant maintenance
Capacitor reforming for spare VFD and servo drives
If a spare drive has been sitting in stores, the DC-bus capacitors may need a controlled forming process before the drive is put back on the machine.
About this service
Star Automations is a multi-brand servo motor repair company with 25+ years of work on industrial machines. Capacitor reforming is a supporting service for the spare VFD and servo drives that sit beside those motors. You can read about our core motor work on the servo motor repair page.
Aluminium electrolytic capacitors on the DC bus can lose forming if a drive stays unused for a long time. Putting full voltage straight onto a long-stored spare can stress those capacitors and, in some cases, the drive fails just when you need it. Reforming applies a controlled, rising DC voltage so the capacitors can recover before the unit is returned to service.
Puducherry operations are ISO certified. We can discuss bench work at our facilities in Puducherry, Chennai, Bengaluru, Hyderabad and Delhi, or work on a store of spares at your plant when that is the better route.
Why it matters
Spare drives are often bought for breakdown cover and then left on a shelf. Many drive makers advise a forming step after a long storage period, commonly when a unit has been idle for around a year or more. The right interval depends on the maker, the model and how it was stored, so we do not treat one figure as a rule for every drive. Tell us the model and how long it has been stored, and we will say whether reforming is the sensible next step.
This service is for spare and stored units. If a drive has already failed in service, you may need VFD repair or servo drive repair instead of, or as well as, this work.
Who it is for
- Factories and MRO teams that keep spare VFDs or servo drives for packaging, process, HVAC and machine lines.
- CNC shops and machine builders with spare axes or spare spindle drives in stores.
- Maintenance planners who want a dated service record on each stored drive, and a reminder to review it if the unit stays idle.
- Bulk lists are welcome. If you hold a cupboard of spares, send the list in one enquiry.
How the work runs
- 1. Send the details. Send a nameplate photo of each drive, how long it has been stored, and whether the units will come to our bench or stay at your plant.
- 2. We confirm. We confirm whether reforming is appropriate for those units and how the work will be arranged.
- 3. Inspection. We inspect the drive visually, including terminals, cooling paths and obvious storage damage.
- 4. Forming. We apply a controlled DC forming process to the DC-bus capacitors and keep a record of the process.
- 5. Return with report. We return the drive with a short service report and a label showing the date of the work. If the unit will remain in storage, the report can note a suggested date to review it again.
What to send us
A clear nameplate photo, the approximate storage period, the quantity, the plant city, and whether you want a one-time job or a yearly review of the spare stock. A simple spreadsheet is enough for a larger list. If inspection shows a fault that reforming will not address, we will say so and, where it fits, point you to drive repair.
Frequently asked questions
What is capacitor reforming on a VFD or servo drive?
Capacitor reforming is a controlled DC forming process on the DC-bus electrolytic capacitors of a drive that has been stored for a long time, so the capacitors can recover before the drive is returned to service.
When should a spare drive be reformed?
When a spare has been unused for a long period, often around a year or more, many drive makers advise forming before full voltage is applied. Send the model and the storage period and we will advise on your units.
Can you reform drives at our plant?
Yes, when a store of spares is better handled on site. Tell us the city, the quantity and how the drives are stored, and we will say whether a visit or a bench shipment is the better route.
Is this the same as repairing a failed drive?
No. Reforming is for stored spares that have not yet been put back into service, or that have been idle. A drive that has already failed in service is a repair job. We will tell you which path fits after we see the nameplate and the symptom.
Will you replace the capacitors as well?
Only when inspection or the condition of the unit points to replacement rather than forming. In that case we will say so, and you can also look at our VFD and servo PM kits for cooling fans and DC-link capacitors.
Do you publish a price for reforming?
No. Prices are not listed on this page. Send the models and quantities and we will come back with the next step.
Brand names identify the equipment and parts we work on. Star Automations is an independent multi-brand repair and maintenance company and is not an OEM service centre.