Spotlight on Circuit Protection

Aug 1, 2008 12:00 PM

Surge-Protection Device Modules

Raycap's Strikesorb 40-mm and 80-mm surge-protection device (SPD) modules are now certified by Underwriters Laboratories (UL) for meeting the UL 1449 3^rd Edition Safety Standard. Featuring a flat-slope resistance characteristic, the Strikesorb SPD modules received a nominal discharge current test rating of 20 kA, the highest possible, without the use of internal fuses. The Strikesorb SPD modules have been designated as Type-4 devices deemed suitable by UL for use in Type-2 applications.

The 40-mm Strikesorb module is rated at 140 kA, and the 80-mm Strikesorb module is rated at 200 kA. The modules have an operating voltage range of 120 V to 600 V. The Strikesorb module is comprised of a single distribution-grade metal oxide varistor (MOV) disc that provides uniform distribution of the surge current over the total area of the MOV protection element. The Strikesorb's monolithic design provides a straight electrical path to its large single disc of distribution-grade varistor material, unlike other SPD systems that employ arrays of commercial-grade MOV components with 90-degree-angled lead wires to each varistor. The absence of lead wires and internal disconnect mechanisms give the Strikesorb extremely low let-through voltage. The Strikesorb module also can be directly connected on the power bus bars inside the cabinet of the equipment after the main circuit breaker.
Raycap
Liberty Lake, Wash.
www.raycapinc.com

ESD TVS Diodes

OnChip Devices' ESD2200 is a family of miniature transient voltage suppressor (TVS) diodes with very high protection levels from electrostatic discharge (ESD). The ESD2200 safely dissipates ESD strikes of ±30-kV contact discharge. It is offered in two, three, four and five channels and has superior electrical performance.

The input capacitance of the ESD2200 is under 20 pF. This diode capacitance also provides some EMI filtering when used in combination with a pc-board trace or series resistor. Packaged in miniature SOT23, SOT143 and SC70 (SMD), the OnChip ESD2200 is available immediately. Pricing ranges from $0.06 each to $0.15 each.
OnChip Devices
Santa Clara, Calif.
www.onchip.com

SMD Fuse

Schurter has added several current ratings to its UMT 250 series, for a total of 22 ratings from 80 mA to 10 A. The series is designed to provide overcurrent and short-circuit protection in both primary and secondary circuits.

The UMT 250 can be mounted on both sides of the pc board. Its low profile increases production rates when mounted with pick-and-place assembly machines. An ideal substitute for axial and radial leaded through-hole fuses where bending leads can cause assembly delays, the UMT 250 is packaged in plastic bags of 100 pieces or in 2000-piece taped reels for automated assembly. Pricing starts at $0.60 each in quantities of 100.
Schurter
Santa Rosa, Calif.
www.schurterinc.com/new_fuses

Fuse Selective Coordination Panel

The Ferraz Shawmut Fused Selective Coordination Panel is a UL 67-listed panel board that uses class CC ultrasafe fuse holders with easy-to-see blown-fuse indicators. The compact size and removable backpan allow for easier installation.

Features of the panel include a bonded ground bar and a neutral bar with set-screw terminations. Main-lugs-only terminations include an optional molded case switch. Branch circuit breakers provide circuit isolation, and the panel comes with a 100-A, 200-A or 300-A copper main bus. The panels accommodate 12 to 42 circuits.
Ferraz Shawmut
Newburyport, Mass.
http://us.ferrazshawmut.com

Inrush Current Limiter

With a high-temperature construction that allows safe operation at high continuous currents, Ametherm's MegaSurge Series inrush current limiter withstands up to 50 A of continuous current and 960 J of input energy. The device is offered in sizes ranging from 12 mm to 35 mm with resistance values from 1 Ω to 220 Ω. Steady-state current values are available from 2 A to 50 A. Target applications include ac motors and motor drives, X-ray equipment, power supplies, universal power supplies and welding equipment.
Ametherm
Carson City, Nev.
www.ametherm.com

Surge-Suppressor Guide

Circuit Components has developed a surge-suppressor selection guide to help customers narrow their search of surge suppressors for their application needs. The guide is a graphics page depicting the category and the location within the electrical network of the equipment to be protected. Clicking on the user's specific equipment location and category will display a list of available surge-suppressor solutions. It serves as a general guide, and final selection depends on specific requirements.
Circuit Components
Tempe, Ariz.
www.surgecontrol.com

Radial Leaded Fuses

The RoHS-compliant Cooper Bussmann SR-5, SS-5 and new SR-5H Series of radial leaded fuses provides cost-effective primary circuit protection without sacrificing performance in space-constrained power-supply applications. The IEC designs have approvals through 6.3 A, and UL designs through 10 A. For applications requiring fuse replacement, a radial fuse holder is available.

The SR-5H Series and more SR-5 low-amp ratings (now 40 mA to 6.3 A) expand an already diverse offering of radial fuses that include fast-acting and time-delay versions. The SR-5H Series also provides protection up to 300 Vac with an interrupting rating of 100 A. The round SR-5 radial fuses offer equivalent product performance to typical 5-mm glass fuses with a 60% footprint reduction. The rectangular SS-5 fuses offer an additional 33% reduction to the SR-5 footprint.
Cooper Bussmann
Ellisville, Mo.
www.cooperbussmann.com

Tantalum Capacitors

AVX's TAW Series of fused tantalum capacitors features an internal fuse to protect against short circuits and damaging high dc leakage currents. Each tantalum capacitor in this series will remove itself from the circuit and into fail-safe mode when the internal fuse exceeds the current limit.

The lead-free, RoHS-compliant TAW tantalum capacitor series provides capacitance values up to 10 MΩ and low ESR for high-reliability applications. Manufactured using thin-film technology, the TAW Series is priced starting at $0.65 each in quantities of 10,000.
AVX
Myrtle Beach, S.C.
www.avx.com

PPTC Thermistors

From Littelfuse, the 0603L series Polyfuse PPTC (polymer positive temperature coefficient thermistor) is a micro form-factor resettable overcurrent protection device. The 0603L PPTC series is available in four hold current/maximum voltage ranges: 0.10 A/15 Vdc, 0.20 A/9 Vdc, 0.25 A/9 Vdc and 0.35 A/6 Vdc. The 0603-sized device has a maximum fault current rating of 40 A and is certified by both TUV and UL.
Littelfuse
Des Plaines, Ill.
www.littelfuse.com

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