Siemens & ABB VFD Capacitor Replacement Guide: SINAMICS, MICROMASTER & ACS Drives
Last Updated: February 2026 | Reading Time: 15 minutes
After Rockwell Automation, Siemens and ABB dominate the industrial VFD market worldwide. Between SINAMICS, MICROMASTER, and the ACS family of drives, these two manufacturers account for a substantial share of the installed base in manufacturing, water treatment, HVAC, and process industries. And every one of those drives relies on aluminum electrolytic DC bus capacitors that will eventually fail.
If you maintain Siemens or ABB drives, capacitor failure is not a matter of if — it's a matter of when. Drives installed 8-15 years ago are entering the failure window now. The good news: replacing DC bus capacitors is well-documented, and sourcing compatible replacements is straightforward once you know the specifications.
This guide covers the most common Siemens and ABB drive platforms, their capacitor configurations, fault codes that indicate capacitor degradation, and how to find the right replacements.
All VFDs follow the same basic power topology: AC input is rectified to DC, filtered by a capacitor bank, and inverted back to variable-frequency AC for the motor. The DC bus capacitor bank is the energy reservoir that makes the entire system work.
These capacitors endure:
- High ripple currents from the rectifier input and inverter switching (typically several amps RMS continuous)
- Elevated temperatures inside enclosed drive cabinets (often 40-55°C ambient)
- Voltage stress at 50-80% of their rated voltage
- Years of continuous operation — many drives run 24/7
Aluminum electrolytic capacitors contain a liquid or gel electrolyte that slowly evaporates through the end seal. Higher temperatures accelerate this process exponentially. The Arrhenius relationship predicts capacitor life halves for every 10°C increase in operating temperature above the rated base. A capacitor rated for 10,000 hours at 105°C may last 80,000+ hours at 65°C — but that's still only about 9 years of continuous operation.
As electrolyte evaporates, capacitance drops and ESR (equivalent series resistance) rises. The drive's DC bus becomes less stable, ripple voltage increases, and eventually the drive's protective systems begin to trip.
For a detailed explanation of ESR and its impact on capacitor performance, see our ESR guide.
The SINAMICS G120 is Siemens' current general-purpose drive platform, covering 0.37 kW to 250 kW. The drive uses a modular design with separate Control Units (CU) and Power Modules (PM).
DC Bus Specifications:
| Power Module | DC Bus Voltage | Typical Cap Bank | Capacitor Type |
|---|
| PM240 (230V) | 320 VDC nominal | 2-4 x 400V caps | Snap-in electrolytic |
| PM240 (480V) | 650 VDC nominal | 2-4 x 400V in series | Snap-in electrolytic |
| PM240-2 (480V) | 650 VDC nominal | Series/parallel bank | Snap-in electrolytic |
| PM250 (with regen) | 650 VDC nominal | Larger bank for regen energy | Snap-in or screw terminal |
Fault Code F30004 — DC Link Undervoltage
This is the most common capacitor-related fault on SINAMICS drives. When DC bus capacitors degrade, they can no longer maintain stable bus voltage during load transients or brief input voltage dips. The drive detects the undervoltage and trips.
Other capacitor-related SINAMICS faults:
| Fault Code | Description | Capacitor Connection |
|---|
| F30004 | DC link undervoltage | Capacitors can't maintain bus voltage |
| F30005 | DC link overvoltage | Degraded capacitors cause voltage spikes during deceleration |
| F30024 | Overtemperature power unit | High-ESR capacitors add thermal load |
| A30004 | Warning: DC link undervoltage | Early warning — capacitors still partially functional |
| F30011 | Power unit overcurrent | Bus instability causes current spikes |
How to verify it's the capacitors:
- Measure DC bus voltage with the drive powered but not running — should be approximately 1.35 x AC input voltage (e.g., 650V for 480V input)
- Monitor DC bus voltage ripple under load — ripple exceeding 5% of nominal indicates degraded capacitors
- Physically inspect capacitors for bulging tops, electrolyte leakage, or discoloration
- Measure capacitance and ESR if the capacitors can be safely isolated — capacitance below 80% of rated value or ESR above 2x nominal indicates end-of-life
The S120 is Siemens' high-performance drive system for servo and multi-axis applications. It uses a shared DC bus architecture with a separate Active Line Module (ALM) or Smart Line Module (SLM) providing the rectifier and DC bus.
The ALM/SLM contains the main DC bus capacitor bank. For the 480V versions, the bus operates at approximately 600-720 VDC. The capacitor bank typically consists of multiple 400V snap-in or screw-terminal capacitors in series pairs, with balancing resistors across each capacitor.
Key S120 capacitor considerations:
- Capacitors in the ALM/SLM are high-ripple-current types rated for 3,000-10,000 hours at 105°C
- Individual motor modules may have additional local capacitors
- Series-connected capacitors require voltage balancing — always replace complete pairs or the entire bank
- Siemens part numbers for replacement capacitor kits are available through their documentation portal
The MICROMASTER 440 series is discontinued but remains widely installed. These drives cover 0.12 kW to 250 kW and were workhorses in HVAC and general industrial applications.
Common MICROMASTER 440 DC bus capacitors (480V class):
| Drive Rating | Typical Cap Config | Common Values |
|---|
| 0.75-4 kW | 2 x 400V in series | 470 uF - 1,000 uF / 400V snap-in |
| 5.5-11 kW | 2 x 400V in series | 1,000 uF - 2,200 uF / 400V snap-in |
| 15-37 kW | 2 x 400V in series (paralleled) | 2,200 uF - 4,700 uF / 400V snap-in or screw terminal |
| 45-90 kW | Multiple series/parallel | 4,700 uF - 10,000 uF / 400V screw terminal |
Since the MICROMASTER 440 is discontinued, Siemens no longer supplies original replacement capacitors. However, aftermarket replacements are readily available if you match the specifications: capacitance, voltage, ESR, ripple current, dimensions, and terminal style.
The ACS580 is ABB's current general-purpose drive, covering 0.75 kW to 500 kW. It uses a standard 6-pulse diode rectifier front end with an aluminum electrolytic DC bus capacitor bank.
DC Bus Specifications:
| Frame Size | DC Bus Voltage | Typical Cap Configuration |
|---|
| R1-R3 (230V) | 320 VDC nominal | 2-3 x 400V snap-in |
| R1-R5 (480V) | 650 VDC nominal | 2 x 400V in series, possibly paralleled |
| R6-R9 (480V) | 650 VDC nominal | Multiple series/parallel screw terminal |
ABB Fault 2310 — DC Overvoltage
ABB drives use a different numbering scheme than Siemens. The primary capacitor-related faults on ACS580:
| Fault Code | Description | Capacitor Connection |
|---|
| 2310 | DC overvoltage | Degraded capacitors cause voltage spikes during braking |
| 2340 | DC undervoltage | Capacitors can't maintain bus voltage |
| 3220 | Earth fault | May indicate capacitor insulation breakdown |
| 7121 | Overcurrent | Bus instability from degraded capacitors |
| 3210 | Short circuit | Capacitor internal short (catastrophic failure) |
The ACS880 is ABB's industrial drive platform for demanding applications — cranes, extruders, winders, and process lines. Available in wall-mounted, cabinet, and multi-drive configurations from 0.55 kW to 6,000+ kW.
Key ACS880 capacitor details:
- Wall-mounted units (R1-R8) use snap-in and screw-terminal electrolytics similar to the ACS580
- Cabinet units (R11+) use large computer-grade screw-terminal capacitors, often 10,000 uF to 47,000 uF at 400V or 450V
- Multi-drive configurations share a common DC bus with dedicated capacitor modules
- ABB provides maintenance schedules recommending capacitor replacement at 5-7 year intervals for continuously operating drives
The ACS355 is ABB's compact drive for simpler applications. Now discontinued in favor of the ACS580, it remains widely installed.
Common ACS355 capacitor configurations (480V class):
| Drive Rating | Typical Capacitor | Notes |
|---|
| 0.75-2.2 kW | 2 x 270 uF-560 uF / 400V | Snap-in, compact package |
| 3-7.5 kW | 2 x 560 uF-1,200 uF / 400V | Snap-in, single series pair |
| 11-22 kW | 2 x 1,200 uF-2,200 uF / 400V | Snap-in or screw terminal |
WARNING: VFD DC bus capacitors store lethal energy. A 650V DC bus with 2,000 uF of capacitance stores over 400 joules — more than enough to be fatal.
Before working on any drive's capacitor bank:
- Disconnect all input power — Lock out/tag out per your facility's procedures
- Wait the required discharge time — Siemens and ABB drives have internal bleed resistors that discharge the bus. Minimum wait times:
- Small drives (< 15 kW): 5 minutes minimum
- Medium drives (15-75 kW): 10 minutes minimum
- Large drives (> 75 kW): 15 minutes minimum or per manufacturer specification
- Verify zero voltage — Use a properly rated voltmeter (CAT III 600V minimum) to measure across the DC bus terminals (DC+ to DC-). Voltage must be below 50V before touching any internal components.
- Measure to ground — Also verify zero voltage between DC+ and ground, and DC- and ground
- Apply safety grounds if working on cabinet drives with large capacitor banks
Never rely solely on the wait time. Always verify with a meter.
When sourcing replacement DC bus capacitors, these parameters must match or exceed the original:
| Parameter | Requirement | Why It Matters |
|---|
| Capacitance | Within +20%/-10% of original | Bus filtering and energy storage |
| Voltage rating | Equal or higher than original | Must withstand DC bus voltage + transients |
| Ripple current rating | Equal or higher at 105°C | Prevents overheating and premature failure |
| Physical dimensions | Must fit the mounting location | Height, diameter, terminal pitch |
| Terminal type | Must match (snap-in, screw, solder) | Mechanical and electrical connection |
| Parameter | Notes |
|---|
| ESR | Equal or lower than original — lower ESR means less heating |
| Temperature rating | 105°C strongly preferred over 85°C for VFD applications |
| Useful life | 5,000-10,000 hours at 105°C typical for quality replacements |
| Manufacturer reputation | Nichicon, Nippon Chemi-Con, Kemet, Cornell Dubilier are proven in VFD applications |
- Siemens and ABB use capacitors from major Japanese and American manufacturers. The original manufacturer part number is usually printed on the capacitor body.
- Common OEM suppliers: Nichicon (LG, GU, GW series), Nippon Chemi-Con (KMH, KMR series), EPCOS/TDK (B43xxx series — especially common in Siemens drives), Kemet (ALS30/ALS31 series)
- When the exact original part is discontinued, match the specifications and choose a current-production equivalent from the same or comparable manufacturer
- For discontinued MICROMASTER 440 and ACS355 drives, aftermarket capacitor kits are available from specialty distributors
Browse our selection of electrolytic capacitors for VFD-grade replacement parts, including snap-in and screw-terminal types.
Waiting for a fault code means unplanned downtime. Many facilities schedule preventive capacitor replacement based on operating hours and conditions:
| Operating Condition | Recommended Replacement Interval |
|---|
| Continuous operation, well-ventilated (< 40°C ambient) | 8-10 years |
| Continuous operation, enclosed cabinet (40-50°C ambient) | 5-7 years |
| Continuous operation, hot environment (> 50°C ambient) | 3-5 years |
| Intermittent operation, well-ventilated | 10-12 years |
ABB explicitly recommends capacitor replacement at 5-7 year intervals for continuously running drives. Siemens provides similar guidance through their drive maintenance documentation.
For a comprehensive look at derating strategies that extend capacitor life, see our derating guide.
Specap has been supplying capacitors for industrial drives since 1984. We stock snap-in and screw-terminal electrolytic capacitors from Nichicon, Nippon Chemi-Con, Cornell Dubilier, Kemet, and other major manufacturers in the voltage and capacitance ranges used by Siemens and ABB drives. We can cross-reference your existing capacitor part numbers and ship replacements quickly — because we understand that a drive down means production down.
Contact us for VFD capacitor availability, cross-references, or help identifying the right replacement for your Siemens or ABB drive.
