Mersen (Ferraz Shawmut) Protistor High-Speed Fuse X300078

Description

This Mersen (formerly Ferraz Shawmut) Protistor fuse, model X300078, is an essential component for protecting power semiconductor devices. It is an extremely fast-acting (aR class) fuse designed to safeguard sensitive electronics such as diodes, thyristors, and IGBTs from the damaging effects of short-circuit events. With a rating of 630A and 700V AC, it is suitable for high-power industrial applications like variable speed drives, inverters, and rectifiers.

Specifications

• Manufacturer: Mersen (Ferraz Shawmut)
• Product Line: Protistor
• Model Number: X300078
• Voltage Rating: 660-700V AC
• Current Rating: 630A
• Characteristic: aR (Extremely Fast-Acting for Semiconductor Protection)
• Body Style: Square Body
• Indicator: Visual Trip Indicator (Red Dot)

Label Info

• Brand: FERRAZ
• Series: PROTISTOR
• Type: X300078
• Rating: 660-700V AC 630A
• Specification: 6.6 URD 33 TTF 0630
• Standard: VDE 0636/23classe aR
• Resistance: 0.188 mOhm (at 35 deg C)

Application

This high-speed fuse is ideally used in power conversion equipment to protect against catastrophic failures due to short circuits. Common applications include AC/DC drives, UPS systems, soft starters, and power supplies.

Country of Origin

This product was manufactured in France.

CO2 Impact

By choosing this reused industrial part, you are helping to avoid the production of a new one, which saves approximately 48 kg of CO2. This saving is equivalent to the emissions from driving a car for 240 kilometers.

Availability

This is an obsolete item but is available from our stock. Limited quantities are available. Order now from PLC2Day for expert support and fast delivery.

FAQ

What does the 'aR' characteristic mean?

The 'aR' class denotes an extremely fast-acting fuse designed for short-circuit protection of semiconductor devices like diodes, thyristors, and IGBTs. It does not provide overload protection.

No, this is not recommended. A 'gG' fuse provides both overload and short-circuit protection (full range), while an 'aR' fuse only provides short-circuit protection (partial range). Using an 'aR' fuse where a 'gG' is required would leave the circuit unprotected against overloads.

The red dot is a visual trip indicator. When the fuse blows, a small pin is released which makes the red dot pop out. This allows for quick identification of a faulty fuse in a panel. It can also be used to actuate a microswitch for remote signaling.

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Last Update: Friday, March 13, 2026