EPCOS B43570-S4338-Q3 Retrofit Capacitor for Legacy Systems

EPCOS B43570-S4338-Q3 Retrofit-Compatible Capacitor for Legacy Industrial Systems

The EPCOS B43570-S4338-Q3 is a high-reliability aluminum electrolytic capacitor from the B43570 series, engineered for demanding DC link, filter, and energy storage applications in industrial power electronics. As legacy variable frequency drives (VFDs), servo amplifiers, and inverter control cabinets age beyond their original design life, the B43570-S4338-Q3 has become a critical retrofit and replacement component for maintenance engineers seeking to extend system uptime without full platform migration.

Manufactured by EPCOS (a TDK Group company) in Germany, this capacitor is widely specified in original equipment from Siemens SINAMICS, ABB ACS series, Emerson Control Techniques, Danfoss VLT, and Schneider Electric Altivar drive platforms. Its screw-terminal mounting, standardized can dimensions, and broad voltage/capacitance ratings make it a direct retrofit candidate for aging DC bus assemblies where original capacitor banks have degraded or failed.

Upgrade Compatibility Table

Retrofit Planning for Existing Automation Systems

When planning a capacitor retrofit in an aging industrial control cabinet, the B43570-S4338-Q3 is rarely replaced in isolation. A thorough retrofit assessment must account for the full DC bus architecture and the surrounding power conversion chain. In Siemens SINAMICS G120 and S120 drive systems, for example, the DC link capacitor bank works in conjunction with the SINAMICS Power Module PM240 and the Control Unit CU240E-2. Degraded capacitance in the DC bus directly affects the ride-through capability of the drive during momentary supply dips, making timely replacement essential for process continuity.

In ABB ACS550 and ACS800 series drives, the DC link capacitor assembly is paired with the IGBT inverter bridge and the brake chopper module. When replacing the B43570-S4338-Q3 in these platforms, engineers should simultaneously inspect the ABB RINT-5611C rectifier interface board and the RDCU-02C control board for signs of electrolyte contamination or thermal stress, as capacitor failure often accelerates degradation of adjacent PCB components.

For Emerson Control Techniques Unidrive SP and Mentor MP platforms, the DC bus capacitor bank is mounted on a dedicated capacitor clamp assembly within the drive chassis. Retrofit planning should include verification of the Unidrive SP power board and the SM-Applications Plus option module to ensure that program logic and fieldbus configuration (PROFIBUS-DP or DeviceNet) remain intact after the power section is de-energized and reassembled.

In Danfoss VLT AutomationDrive FC302 installations, the B43570-S4338-Q3 or equivalent DC link capacitor is part of a bank that supports the VLT Brake Resistor MCE 101 and the VLT Advanced Cascade Controller MCO 102. Before capacitor replacement, engineers must discharge the DC bus fully using a calibrated discharge resistor and confirm residual voltage with a CAT III multimeter — a step that is frequently underestimated in field retrofit procedures.

Where the control cabinet also houses a Siemens SITOP PSU8600 power supply module or an ABB CP-E 24/10.0 DIN rail PSU, the 24 VDC logic supply must remain live during capacitor swap-out to preserve PLC program retention and HMI screen configuration. Coordinating with the site automation team to maintain the Siemens S7-300 CPU 315-2 DP or S7-400 CPU 414-3 PN/DP in a safe hold state — rather than a full cold restart — significantly reduces commissioning time after the retrofit is complete.

Signal isolation between the drive and the upstream Pepperl+Fuchs KFD2-STC4-Ex1 signal conditioner or Phoenix Contact MINI MCR-SL-UI-UI isolator should be verified post-replacement, particularly in hazardous area installations where intrinsic safety barriers are in the signal path. Any interruption to the 4–20 mA speed reference or the digital enable signal during capacitor replacement must be managed through the site’s management of change (MOC) procedure.

Downtime Control During System Migration

Minimizing unplanned downtime is the primary driver for proactive capacitor replacement programs in industrial facilities. The B43570-S4338-Q3 exhibits predictable end-of-life characteristics — rising ESR (equivalent series resistance), reduced capacitance, and increased leakage current — that can be trended using a portable LCR meter during scheduled maintenance windows. Establishing a baseline measurement at commissioning and re-measuring at 2–3 year intervals allows maintenance teams to schedule replacement before catastrophic failure occurs.

For critical production lines where the drive cannot be taken offline during peak production, a hot-standby drive strategy is recommended: a pre-configured spare drive with a freshly installed B43570-S4338-Q3 capacitor bank is kept on the shelf, allowing a complete drive swap in under 30 minutes. The original drive is then returned to the workshop for capacitor replacement and re-testing before being rotated back into the spare pool.

Where a full drive swap is not feasible, the capacitor replacement procedure should be sequenced as follows: (1) initiate a controlled process stop and confirm drive inhibit via the STO (Safe Torque Off) input; (2) isolate and lock out the incoming supply; (3) wait for DC bus discharge to below 50 VDC (minimum 5 minutes, confirm with meter); (4) remove the capacitor clamp and extract the B43570-S4338-Q3; (5) install the replacement, torque terminals to specification, and reassemble; (6) restore supply and perform a no-load run to verify DC bus voltage and drive output waveform before reconnecting the load.

Original PLC program logic stored in the Siemens S7 CPU or ABB AC500 PM595 is unaffected by DC bus capacitor replacement, provided the control supply remains energized throughout. HMI screens on Siemens SIMATIC TP700 Comfort or Weintek MT8071iE panels will continue to display normally. The only parameters that may require re-entry are drive-internal settings stored in volatile RAM — always upload drive parameters to a PC tool (Siemens STARTER, ABB Drive Composer, or Emerson UniSoft) before beginning any power section work.

Retrofit Support FAQ

Q1: Is the EPCOS B43570-S4338-Q3 a direct replacement for the original capacitor in my drive?
In most cases, yes — provided the voltage rating, capacitance value, can dimensions, and terminal configuration match the original specification. Always cross-reference the original part number on the capacitor label or the drive’s BOM before ordering. Our technical team can assist with cross-reference confirmation if you provide the drive model and original capacitor markings.

Q2: What pre-shipment testing is performed on the B43570-S4338-Q3?
Each unit is tested for capacitance (within ±20% of rated value), ESR, and leakage current before dispatch. Units that do not meet EPCOS datasheet limits are rejected. A test record is available upon request for quality-critical applications.

Q3: How do I confirm the correct torque for the screw terminals during installation?
The recommended terminal torque for B43570 series screw-terminal capacitors is specified in the EPCOS datasheet (typically 1.2–1.5 Nm for M5 terminals). Over-torquing can damage the terminal seal and cause electrolyte leakage; under-torquing increases contact resistance and generates heat. Always use a calibrated torque screwdriver.

Q4: What is the warranty coverage and what does it include?
All B43570-S4338-Q3 units supplied by NINERMAS carry a 12-month warranty from the date of shipment. The warranty covers manufacturing defects and premature failure under normal operating conditions. It does not cover damage caused by incorrect installation, over-voltage, reverse polarity, or operation outside the rated temperature range. Warranty claims are processed within 5 business days of receiving the returned unit.