FCMOV - Current Protective Overvoltage Protector: PPTC + MOV vs. TMOV

In an era of thinner, lighter devices with digital/AV convergence, higher data rates, and larger capacities, protection components must simultaneously deliver high AC withstand capability, compact size, and reusable, eco-friendly performance aligned with energy-saving and carbon-reduction goals. FUZETEC’s first-of-its-kind FCMOV (current-protective hybrid overvoltage protection technology) integrates a Resettable Fuse (PPTC) and a Metal Oxide Varistor (MOV) into a single device. It provides combined overvoltage/overcurrent protection and thermal risk mitigation, effectively addressing the traditional MOV pain point of thermal runaway—shorts and catastrophic failure—under surge or sustained abnormal voltage, while significantly lowering maintenance and replacement costs.

Background & Direction of Innovation

High AC withstand, small footprint, and reusability as the mainstream
Driven by miniaturization and high-reliability requirements, protection components must tolerate higher stress in smaller packages and offer reset capability to reduce maintenance cost.

Trends: thinner/lighter, digital/AV, and high-speed/high-capacity

Future product design is moving toward thinner and lighter builds, digitalization, rich media, and fast/high-capacity data transfer. FUZETEC has invested in developing the innovative FCMOV current-protective hybrid overvoltage technology, pioneering the combination of PPTC (Polymeric Positive Temperature Coefficient) overcurrent protection with MOV overvoltage protection. This approach prevents MOV burn-out caused by surge voltage/current and enables reusability.

ESG and Total Cost: sustainability, energy saving, carbon reduction, and total cost of ownership

By combining PPTC resettable fuse with an MOV, FCMOV balances Reliability and Total Cost. Its reusability supports sustainability goals (energy saving and carbon reduction), making it a core strategy for next-generation protection.

 

Illustration: FCMOV current-protective hybrid overvoltage protector (PPTC + MOV

Risks and Safety Requirements for MOVs under Transient/Sustained Overvoltage

Transient overvoltage vs. power-frequency sustained abnormal overvoltage

Beyond short transients, MOVs can be exposed to sustained abnormal line voltage. Under prolonged overvoltage/overcurrent conditions (as characterized in UL 1449 safety testing), an MOV can enter thermal runaway, leading to overheating, smoke, and potential fire—posing risks to life and creating exposure to major liability and litigation.

Thermal-runaway failure mode and system-level risk

In low-voltage systems, the ability of an MOV to withstand power-frequency overvoltage is critical to electrical safety. If the MOV cannot tolerate it, short-circuit and breakdown are likely, causing overheating and possible ignition.

Compliance perspective: withstand capability in UL 1449

Products compliant with UL 1449 must provide adequate protection to avoid these failure modes—specifically, sufficient withstand capability under power-frequency overvoltage.

Fuzetec Solution — FCMOV Current-Protective Hybrid Overvoltage Protector

Device architecture: PPTC (resettable fuse) + MOV (varistor)

FCMOV combines a PPTC resettable fuse with an MOV. The hybrid topology provides both overcurrent and overvoltage protection. Under sustained overcurrent/overvoltage, the device trips to a high-resistance state, protecting the MOV and drastically reducing the risk of catastrophic failure.

How FCMOV Works

During transient overvoltage

PPTC: Remains in a low-resistance state, allowing current to pass.
MOV: Drops its dynamic resistance, clamps the surge, absorbs transient energy, and dissipates it as heat to limit the overvoltage peak.

During sustained/abnormal overvoltage

PPTC: Transitions to high resistance (trips), current-limits the MOV and simultaneously shares the voltage across the series path.
MOV: Shifts from full load to partial operation; its temperature falls to non-catastrophic levels, preventing thermal runaway/thermal cycling.

FCMOV Innovative Features (Key Takeaways)

Package & spec highlights

1.    Industry-first hybrid overvoltage protector integrating MOV + PPTC (FCMOV).
2.    Protects MOVs against surge voltage/current from ~0.001 to >10 s, exceeding typical industry benchmarks.
3.    Enables MOV reusability: the PPTC’s reset action protects the MOV so it can withstand multiple events, extending lifetime and reducing maintenance.
4.    Radial leaded format using standard MOV disk diameters: 10, 14, and 20 mm.
5.    Reduces total protection part count and saves PCB space —supports miniaturization.
6.    Cuts design-in time and cost for PPTC-MOV pairing and coordination.
7.    Compliant with UL 1449 4CA safety test requirements.
8.    15 invention patents filed; 13 granted (core technologies).

FCMOV vs. conventional MOV and TMOV

Protection speed & energy handling

•    FCMOV: MOV provides fast surge clamping; under sustained abnormal conditions, the PPTC current-limits and shares voltage—a dual-mechanism defense.

•    TMOV (Thermally Protected Varistor / thermally coupled-fuse varistor): Uses an internal thermal fuse for one-time protection.

Failure mode & safety margin

•    FCMOV: Under long-duration stress, the PPTC actively increases resistance, lowering MOV thermal load and mitigating thermal runaway.

•    MOV: Under sustained overvoltage, thermal accumulation may occur; typically requires external fusing and circuit measures to share the load.

Serviceability & Total Cost

•    FCMOV: Reusable, reducing downtime and replacement frequency.

•    TMOV: After operation, typically requires replacement (one-time action), leading to higher maintenance cost.

Conclusion

FCMOV unifies the strengths of a PPTC resettable fuse and an MOV: fast surge clamping, active current-limiting and voltage-sharing under sustained abnormal conditions, reusability, compact footprint, and lower BOM/layout cost. Backed by UL 1449 4CA testing and a robust patent portfolio, FCMOV is a next-generation overvoltage/overcurrent protection solution that balances safety, reliability, and Total Cost across appliances, industrial controls, and automotive power electronics.

Learn more: See theFCMOV Product Series.