Cornell Dubilier Capacitors: AC Motor & Power Applications Complete Guide

Few capacitor brands carry the engineering credibility that Cornell Dubilier does in power electronics. Founded in 1909 — originally as the Dubilier Condenser Corporation — Cornell Dubilier (CDE) is one of the oldest capacitor manufacturers in the United States and holds a genuine claim to inventing the mica capacitor. Today, the company operates under Knowles Corporation following an acquisition, but the CDE brand, product numbering, and engineering team remain intact. CDE is the largest power capacitor manufacturer in North America, and their catalog spans aluminum electrolytic, metallized polypropylene and polyester film, mica, AC motor run, DC link, and supercapacitor technologies.

If you’re speccing capacitors for a motor drive, solar inverter, EV charger, UPS, or any application that demands long life under continuous ripple and temperature stress, Cornell Dubilier should be on your short list. This guide covers their key product families from a working engineer’s perspective, with the selection tables, part number context, and design tool references you need to make the BOM call efficiently.

Cornell Dubilier’s Market Position and Engineering Philosophy

CDE’s differentiator is not breadth — it’s depth in demanding applications. Their AS9100 registered facility in Liberty, SC handles military and aerospace custom capacitor design. Their engineering team publishes some of the most detailed application guides available for film and aluminum electrolytic capacitors. They are, by their own description, a company focused on power electronics — renewable energy, EVs, motor drives, inverters, aerospace, telecom, medical, and UPS systems. They don’t try to be the lowest-cost MLCC supplier. They try to make the capacitor that doesn’t fail when conditions get difficult.

Cornell Dubilier’s standard test philosophy reflects this. Several of their series are tested to THB (Temperature, Humidity, Bias) conditions that exceed industry minimums — a detail that matters when you’re designing equipment meant to run unattended outdoors for a decade.

Cornell Dubilier Film Capacitors: DC Link and Power Series

CDE’s DC link and power film capacitor portfolio is arguably the most important part of their current product catalog for power electronics engineers. These are metallized polypropylene (MKP) parts engineered specifically for the DC bus of inverters — where high ripple currents, continuous operation, and temperature stress combine to kill less robust designs.

## Type 947C and 947D: DC Link Polypropylene for Inverter Applications

The 947 series is CDE’s workhorse DC link film capacitor family. Both 947C and 947D use advanced metallized polypropylene film technology designed for long life and high reliability in inverter DC link applications.

The 947C covers general-purpose DC link applications in solar, wind, and fuel cell inverters. It offers high voltage and current ratings that allow it to replace complex series-parallel combinations of aluminum electrolytic capacitors — a common design pattern where engineers stack multiple smaller aluminums to handle DC link ripple current that a single part can’t manage. Using a single 947C where six aluminum electrolytics were previously required simplifies the BOM, reduces board area, and improves reliability through parts count reduction.

The 947D extends this concept to high-energy-density DC link applications with voltage ratings from 900V DC to 1,300V DC and operating temperature range from −45°C to +85°C. High capacitance combined with very high ripple current capability makes the 947D appropriate for the most demanding inverter DC link positions — particularly in industrial drives and high-power renewable energy converters where both bus voltage and ripple current requirements push aluminum electrolytic technology to its limits.

Series	Dielectric	Voltage Range	Key Feature	Primary Application
947C	Metallized PP	370–2,000V DC	High I, film DC link	Solar, wind, fuel cell inverters
947D	Metallized PP	900–1,300V DC	High energy density, very high I	Industrial drives, high-power inverters
944L	Metallized PP	450–1,200V DC	ESL 10–15 nH, 90A RMS	SiC/GaN fast-switching inverters
940C	Metallized PP	Up to 2,000V DC	High dV/dt, pulse rated	Snubber networks, pulse applications

## Type 944L: Low-Inductance DC Link for SiC and GaN Inverters

Launched in March 2023, the 944L is CDE’s direct answer to the fast-switching demands of SiC MOSFET and GaN-based inverters in EV charging and green energy systems. The series uses large-diameter, non-inductive windings with low-inductance internal bus connections, achieving ESL values from 10 to 15 nanohenries. Ripple current ratings reach up to 90 Arms at 55°C ambient.

This matters because silicon carbide inverters operate at switching frequencies typically 5–10× higher than legacy IGBT designs. At those frequencies, capacitor ESL becomes a primary design constraint — parasitic inductance causes voltage overshoot at switch-off, which either forces conservative voltage margin or directly stresses the switching devices. The 944L’s 10–15 nH ESL is specifically engineered to keep that overshoot manageable in level 3 EV charger and grid-tie inverter designs.

Rugged UL94V-0 flame-retardant plastic case with solid resin fill, male or female terminal options, and robust mounting flanges complete the mechanical specification for high-vibration inverter enclosures.

## Type 940C: Pulse, Snubber, and High dV/dt Applications

The 940C is CDE’s purpose-built polypropylene film capacitor for snubber networks and pulse applications. Its high dV/dt capability makes it appropriate wherever a capacitor absorbs the energy of rapidly switching voltage transients — across IGBT modules in motor drives, across diodes in rectifier stages, or in pulse-forming networks for specialized equipment.

For snubber design, the 940C’s metallized polypropylene construction provides the low dissipation factor and self-healing behavior that snubber duty demands. A snubber capacitor that fails short-circuit under a transient surge takes the switching device with it. The self-healing property of metallized polypropylene — where a local breakdown event vaporizes the metallization around the fault site and the capacitor survives — is not optional in this application; it’s the failure mode that saves the rest of the circuit.

Cornell Dubilier Harsh Environment DC Link Series: BLH and BLS

CDE developed the BLH and BLS series specifically because standard film capacitors were failing prematurely in outdoor and transportation applications where humidity, vibration, and thermal cycling combine. These are the series to specify when a competitor’s THB-rated film capacitor isn’t surviving your field return analysis.

## Type BLH: DC Link Film for Harsh Environments (AEC-Q200)

BLH is CDE’s board-mount DC link film capacitor series engineered to exceed industry humidity standards. Standard competitive THB film capacitors are tested to 1,000 hours at 85°C/85% relative humidity with rated voltage applied. The BLH series has been validated to 1,500 hours under the same conditions — 50% greater THB test life.

The series is qualified to automotive-grade AEC-Q200 electrical and mechanical testing standards. Solvent-resistant plastic case with epoxy encapsulation, UL Recognized construction, and tin-plated copper RoHS-compliant terminations make it appropriate for solar, wind, UPS, EV charger, and other inverter applications in environments with wide-ranging temperature and humidity exposure.

Capacitance ranges from 1.0 to 170 µF at 450–1,200V DC with high RMS ripple current ratings up to 36 Arms. These are PCB-mount (board-mount) parts — a practical distinction from the larger can-style DC link capacitors that require mechanical mounting.

## Type BLS: DC Link for Extreme Environments (125°C, AEC-Q200)

Where BLH pushes the humidity envelope, BLS pushes the temperature ceiling. BLS series DC link capacitors operate to +125°C and have been tested at 2,000 hours at 85°C/85% relative humidity with rated voltage applied — 100% greater than competitive THB test life. Like BLH, BLS carries AEC-Q200 qualification.

The +125°C operating temperature is the key differentiator for EV powertrain applications. Traction inverters, DC-DC converters, and on-board chargers in electric vehicles frequently see underhood ambient temperatures that exceed the standard +85°C upper limit of conventional film capacitors. BLS exists specifically for those positions.

Series	Max Temp	THB Test Life	AEC-Q200	Mount Style	Voltage Range
BLH	85°C	1,500 h at 85/85 + Vr	Yes	Board mount	450–1,200V DC
BLS	125°C	2,000 h at 85/85 + Vr	Yes	Board mount	450–1,200V DC

Cornell Dubilier AC Film Capacitors: Motor Run Applications

CDE has decades of heritage in AC motor run capacitors — the permanently energized film capacitors that provide the phase shift required to make single-phase induction motors run continuously in HVAC compressors, pump motors, and fan systems. These are not the same as DC link capacitors, and specifying DC-rated film capacitors in motor run positions is a failure mode waiting to happen.

## Motor Run Capacitor Technology: Why It’s Different

AC motor run capacitors must handle continuous AC voltage — typically 370V AC or 440V AC — without degradation over many years of continuous operation. The primary failure mechanisms are corona discharge at elevated AC voltages and dielectric aging under continuous AC stress. UL810 approval for fail-open (not fail-short) behavior is the key safety requirement: a motor run capacitor that fails shorted will overheat the motor winding and potentially cause a fire; fail-open means the motor simply loses the run capacitor and stalls safely.

CDE’s motor run line uses metallized polypropylene film in both the SF and MPF series, providing the low dissipation factor and self-healing characteristics that AC continuous duty requires. Both series are UL810 approved.

## SF and MPF Series: CDE’s Core Motor Run Products

The SF series covers AC-rated metallized polypropylene capacitors for motor run applications including refrigeration and air conditioning. They provide starting torque support, power factor correction, and continuous AC voltage handling with self-healing fault protection. Standard 4-tine, ¼” quick connect lug terminals simplify assembly in HVAC equipment.

The MPF series uses oil-filled metallized polypropylene construction in metal cases with 4-prong quick disconnect terminals. Oil impregnation reduces corona discharge at higher voltages and extends dielectric life under continuous AC stress. MPF parts offer high capacitance and voltage capabilities in a compact, lightweight package with internal protection for fail-safe operation.

Series	Dielectric	Construction	Voltage Rating	Applications
SF	Metallized PP	Dry film	370/440V AC	Motor run, HVAC, refrigeration
MPF	Metallized PP	Oil-filled metal case	370/440V AC	Motor run, high-reliability HVAC
SCD	Metallized PP/PET	Dry film	250–600V AC	General AC filter, line bypass
ALH	Metallized PP	THB-rated	AC rated	Harsh environment AC filtering

The ALH series extends the harsh-environment design philosophy to AC filter applications. Cornell Dubilier describes the ALH as offering 50% greater life than competitive 85/85 THB-rated film capacitors for AC-rated filter duty — the same margin improvement seen in the BLH/BLS DC link series, applied to AC circuit positions.

Cornell Dubilier Aluminum Electrolytic Capacitors: From PCB to Screw Terminal

CDE built their early reputation on high-reliability aluminum electrolytic capacitors for computer-grade and military applications. Today’s aluminum electrolytic lineup covers everything from SMT chip capacitors to large screw-terminal cans for industrial power supplies.

## Screw-Terminal and Snap-In Series for Power Electronics

The Type 3186 is CDE’s value screw-terminal aluminum electrolytic for high-capacitance DC link and power supply applications — described as the “best value 85°C high capacitance screw terminal type.” For industrial power supply designs where cost-per-microfarad matters and the operating environment is controlled, the 3186 is the pragmatic choice.

CDE’s snap-in aluminum electrolytic series extends to voltage ratings up to 450V DC — higher than much of the competitive snap-in market — which is relevant for designs on 277V single-phase or 480V three-phase mains where the DC bus voltage after rectification approaches or exceeds standard 400V ratings.

## MLPS: Military-Grade Flatpack Aluminum Electrolytic

The MLPS Flatpack is genuinely unique in the aluminum electrolytic market — a low-profile flat configuration rated to 10,000 hours at +105°C with a welded seal that resists dry-out typical of conventional electrolytics. Voltage ratings reach 450V DC with capacitance values from 120 to 51,000 µF.

The 0.6-inch height profile combined with high capacitance density makes MLPS practical for applications with strict Z-height constraints — avionics power supplies, shipboard electronics, and military-grade power conditioning where board space runs in three dimensions. The high-vibration (HV) option adds resistance to 20g vibration loading. High-reliability burn-in is available (48 hours at Vr, 105°C) for the most demanding procurement requirements.

## HZA Series: Hybrid Polymer Aluminum Electrolytic

The HZA series represents CDE’s entry into hybrid polymer aluminum electrolytic technology — combining liquid electrolyte for stable long-term capacitance with a polymer layer for dramatically lower ESR at high frequencies. Applications are power conversion circuits with high ripple current requirements where standard wet electrolytics run into ESR-limited ripple current budgets.

Cornell Dubilier Mica Capacitors: RF and Military Heritage

CDE is the only U.S. manufacturer of high-quality mica capacitors, and this heritage product category remains relevant for RF, military, aerospace, and precision electronics applications where ceramic MLCCs introduce unacceptable parasitics or aging concerns.

Silver mica capacitors offer extremely stable capacitance over temperature, zero aging (unlike Class 2 MLCCs), and very high Q at radio frequencies. For RF matching networks, precision timing circuits in military equipment, and any application requiring a stable, high-Q capacitor up to several hundred picofarads, CDE’s mica line has no equivalent in other technologies.

Cornell Dubilier Supercapacitors: EDC/EDS Coin Cell and DSM Modules

CDE offers supercapacitor (EDLC) products in both coin cell and module formats. The EDC and EDS series coin cell supercapacitors from 0.047 to 1.5 Farad replace or extend battery life in on-board memory backup applications. With quick response and recharge times, these devices offer higher power than batteries and greater energy than typical aluminum electrolytics without degradation over millions of charge-discharge cycles.

The DSM standard supercapacitor modules are designed for energy storage and power applications requiring greater energy potential and power output than single-cell parts provide. Three-cell DSM devices deliver higher voltage and more usable energy than PCB-mounted coin cells in systems where size allows for module-format parts.

Cornell Dubilier Capacitor Selection by Application

Application	Recommended CDE Series	Key Selection Criterion
Standard solar/wind inverter DC link	947C / 947D	High ripple current PP film, replaces Al banks
SiC/GaN fast-switching inverter	944L	ESL 10–15 nH, 90A RMS capability
IGBT snubber network	940C	High dV/dt, self-healing PP, pulse rated
Harsh environment inverter (humidity)	BLH	1,500h THB, AEC-Q200, PCB mount
EV powertrain, +125°C ambient	BLS	2,000h THB at 125°C, AEC-Q200
HVAC compressor motor run	SF / MPF	UL810 fail-open, 370/440V AC rated
AC filter, harsh environment	ALH	50% greater THB life vs. standard film
Industrial power supply DC link	3186 screw terminal	High capacitance, 85°C best-value
Military/avionics DC power supply	MLPS Flatpack	10,000h at 105°C, low-profile, welded seal
High-freq ripple power conversion	HZA hybrid polymer	Low ESR, high-frequency ripple handling
RF, military timing circuits	Mica	High Q, zero aging, precise temperature stability
Memory backup energy storage	EDC/EDS coin cell	EDLC, millions of cycles, no aging

Cornell Dubilier Design Tools and Application Resources

CDE provides engineering tools and technical documentation that go significantly deeper than most component manufacturers’ standard datasheets.

Flatpack Lifetime Calculator at cde.com/fpap — CDE’s online capacitor thermal and life calculation tool for the MLPS Flatpack series. Engineers enter operating voltage, temperature, duty cycle, and ambient conditions to calculate estimated useful life. The calculator explicitly notes that lifetime predictions beyond 200,000 hours (23 years) have not been validated — useful context for understanding the model’s range of applicability.

Application Guides at cde.com/tech-center/application-guides — CDE publishes full handbooks for each core capacitor technology: aluminum electrolytic, AC film, DC film, mica, and supercapacitors. These are genuinely detailed engineering references, not marketing brochures. The AC Capacitor Application Guide, for example, covers construction, failure modes, corona discharge in AC film capacitors, motor run vs. motor start vs. filter applications, and selection methodology in depth. Download and save them before you need them.

Useful Resources for Cornell Dubilier Capacitors

Official CDE Product and Technical Resources

• Cornell Dubilier Product Catalog Page — Complete capacitor product family navigation including film, aluminum electrolytic, mica, and supercapacitors
• CDE Application Guides — In-depth engineering handbooks for each capacitor technology
• CDE 947C Datasheet — DC link polypropylene film, technical specs and life prediction curves
• CDE 947D Datasheet — High energy density DC link, 900–1,300V DC specifications
• CDE 940C Datasheet — Pulse and snubber polypropylene, high dV/dt ratings
• CDE BLH Product Page — Harsh environment DC link, 1,500h THB, AEC-Q200
• CDE 944L Announcement — Low inductance DC link for SiC/GaN inverters
• CDE Motor Run Capacitor Catalog — AC motor run SF/MPF and related series
• CDE AC Capacitor Application Guide — Full handbook for AC film capacitor selection and application
• Flatpack Lifetime Calculator — Online life calculation tool for MLPS Flatpack series

Distributor Resources

• DigiKey Cornell Dubilier Supplier Center — Full CDE catalog with training modules, datasheets, and 944L/BLH series highlights
• TTI Cornell Dubilier — Authorized distributor with expanded HZA hybrid polymer, MYH Y2, and MLSH hermetic series listings
• CDE Custom Catalog Generator — Build a downloadable PDF of only the CDE series relevant to your project

5 Frequently Asked Questions About Cornell Dubilier Capacitors

Q1: What is the difference between CDE’s BLH and BLS series, and when do I need each?

BLH and BLS are both board-mount DC link film capacitors engineered for harsh environments and both carry AEC-Q200 qualification. The distinction is maximum operating temperature and THB test life. BLH operates to +85°C and is validated to 1,500 hours at 85°C/85% relative humidity with rated voltage applied — 50% more than the typical competitive THB test standard of 1,000 hours. BLS operates to +125°C and is validated to 2,000 hours under the same THB conditions — 100% more than competitive standards. Choose BLH for outdoor stationary applications (solar, wind, EV charging infrastructure) where 85°C is an adequate thermal ceiling but humidity and vibration reliability is the primary concern. Choose BLS for EV traction inverters, underhood DC-DC converters, or any application where the capacitor sees continuous temperatures above 85°C in addition to the humidity and vibration challenges. For standard commercial inverter designs in controlled environments, standard CDE film capacitors (947C/947D) provide excellent service life without the cost premium of the B-series harsh environment line.

Q2: Can I use a CDE 947C DC link film capacitor to replace multiple aluminum electrolytic capacitors?

Yes, and CDE specifically designed the 947C series for this application. Engineers frequently build DC link buses with multiple parallel aluminum electrolytic capacitors in order to meet the ripple current budget that a single part cannot handle. Film capacitors inherently handle higher ripple current density than aluminum electrolytics of comparable bulk capacitance, and their failure mode (gradual capacitance loss) is more benign than the wet electrolyte dry-out and seal failure modes of aluminum electrolytics. The 947C’s high voltage and current ratings are explicitly sized to replace series-parallel aluminum electrolytic banks in solar, wind, and fuel cell inverter DC link positions. Replacing six aluminum electrolytics with one or two 947C units also reduces connection resistance, simplifies the busbar layout, and removes the need to balance current sharing between parallel parts. Before doing this substitution, calculate the RMS ripple current at the DC link and verify the 947C’s rated ripple current covers it with appropriate derating margin.

Q3: When should I specify CDE’s 944L low-inductance series versus standard 947C for an inverter DC link?

The 944L becomes relevant when your inverter uses SiC or GaN switching devices operating at frequencies above approximately 20–50 kHz. At those frequencies, the capacitor’s ESL creates significant voltage overshoot at switch turn-off — the dV/dt of the switching event pumps energy into the parasitic inductance of the DC link, and when that energy releases, it appears as a voltage spike across the switching devices. Standard film capacitors (947C and similar) have ESL in the range of 20–100 nH depending on construction. The 944L’s 10–15 nH ESL reduces that overshoot proportionally, which either improves reliability margins on your switching devices or allows you to operate closer to their rated voltage without the overshoot risk. If you’re designing with legacy IGBT switching at 4–16 kHz, standard 947C is appropriate and the cost premium of 944L is not justified. If you’re designing a 200 kHz SiC-based LLC converter for a level 3 EV charger, the 944L’s low ESL is a real performance advantage.

Q4: What makes CDE’s MLPS Flatpack different from standard snap-in aluminum electrolytics for military applications?

The MLPS Flatpack addresses several failure mechanisms that conventional cylindrical snap-in and screw-terminal aluminum electrolytics struggle with in military and avionics applications. The welded seal construction resists the electrolyte dry-out that limits conventional electrolytic life — standard electrolytics rely on rubber or plastic gasket seals that allow slow vapor diffusion, which eventually depletes the liquid electrolyte. MLPS’s welded seal eliminates this mechanism, which is why it achieves 10,000 hours at +105°C rated voltage — a life spec that substantially exceeds standard 85°C or 105°C can-type aluminum electrolytics. The flat form factor is also practical: military and airborne power supply boards often have strict height limits driven by chassis depth constraints, and a 0.6-inch profile capacitor with 51,000 µF at 7.5V is a package configuration that simply doesn’t exist in conventional cylindrical form. The high-vibration option (20g rated) addresses the shock and vibration requirements of airborne and ground-mobile military equipment that would damage or dislodge standard axial-lead or snap-in capacitors.

Q5: How do I select between CDE motor run capacitor series (SF vs MPF) for an HVAC application?

Both SF and MPF series are metallized polypropylene film capacitors with UL810 approval for fail-open behavior in motor run service. The MPF uses oil-filled metal case construction while the SF uses a dry film construction. Oil impregnation in the MPF reduces internal corona discharge — the partial ionization of air within the capacitor body at elevated AC voltages that gradually degrades the dielectric. For continuous 370V or 440V AC duty in outdoor HVAC compressors and fan motors where the capacitor operates continuously for years, MPF’s oil-filled construction generally provides more conservative degradation under corona stress. The SF is appropriate for standard indoor HVAC applications and situations where the lighter weight and lower profile of dry film construction is preferred. For new HVAC equipment design, verify the specific UL810 capacitance tolerance and overvoltage surge requirements for the motor frame being used — motor run capacitor selection is typically specified by the motor manufacturer, and deviating from the specified µF value and voltage rating affects motor starting torque and running current directly.

Working with Cornell Dubilier in Your Next Power Electronics Design

CDE’s catalog depth rewards engineers who take the time to understand the product family hierarchy rather than defaulting to the first distributor result. The 947C/947D film capacitors regularly win designs where multiple aluminum electrolytic capacitors previously occupied the DC link — the reliability and board area benefits are straightforward. The BLH and BLS series are the correct answer when an application demands real humidity and temperature qualification, not just a datasheet claim. And for motor run applications, CDE’s AC film heritage means their SF and MPF series carry real-world validation from decades of HVAC field experience.

Download CDE’s application guides from their tech center before starting your next design involving any of their technologies. Their aluminum electrolytic and AC film guides in particular provide reliability models, failure mode analysis, and application-specific guidance that most other manufacturers don’t publish at equivalent depth.