Littelfuse plants for PolySwitch devices are ISO/TS 16949:2009 and ISO 9001:2008 certified.įuses and PPTCs are both overcurrent protection devices, though each offer their own unique operating characteristics and benefits. The 600R, TRF600, TR600, TS600 and TSM600 series is designed to be used in applications that need to meet the requirements of GR–1089-CORE and UL60950/ EN60950/IEC60950. The 250R, 250S, TRF250, TSL250, TS250, TCF250 and TSV250 series can be used to help telecom networking equipment meet the protection requirements specified in ITU K.20 and K.21. The Telecom resettable PPTC Series is designed to protect against short-duration high-voltage fault currents (power cross or power induction surge) typically found in telecommunications and networking applications. New Littelfuse Lo Rho resettable PPTCs offers ultra-low normal operating resistance while maintaining the same performance of other Littelfuse PPTC products and are available in Surface Mount Low Rho SMD Seriesand Surface Mount Lo Rho Series. VLR, VLP, VTP, MXP, MGP, SRP, LR4, RSD. USBR, 16R, 30R, 60R, 72R, 250R, 600R, RGEF, RUEF, RXEF, RHEF, RKEF, AGRF, AHRF, AHEF.īattery strap resettable PPTCs provide reliable, non-cycling protection against overcharging and short circuits events for rechargeable battery cells where resettable protection is desired. Radial leaded resettable PPTCs are designed to provide overcurrent protection for applications where space is not a concern and resettable protection is preferred. Package size varies from 0402 to 3425, while hold current ranges from 50mA to 7.0A. Surface mount resettable PPTC devices provide overcurrent protection for applications where space is at a premium and resettable protection is desired. Designed to limit unsafe currents while allowing constant safe current levels, resistance will "reset" automatically when the fault is removed and temperature returns to a safe levels. PPTCs increase resistance as temperature increases due to increased flow. Ideal for situations where frequent overcurrent conditions occur or constant uptime is required, resettable PPTCs are typically used in consumer electronics, power line, telecom, I/O port, process control and medical equipment protection applications. It should be optimum so as the remain the circuit closed for load currents below the permitted safe range and able to interrupt the circuit if the current exceeds.Littelfuse PolySwitch and POLY-FUSE devices are Polymeric Positive Temperature Coefficient (PPTC) devices which offer a resettable overcurrent protection alternative, thereby reducing warranty, service and repair costs. Hence the rating of a selected fuse should not be under or over. So, the maximum capacity of the wiring and the components can be utilized without causing any damages. To avoid this the rated value of the fuse current needs to be just below the permitted safe operating value. Then the wiring or other devices get damaged or burned and the current flow through the circuit continues until it becomes electrically open at some other part of the wiring (a weak point that melts first). Such a fuse remains the circuit close and allows the current to flow beyond the limit permitted to the wiring or other components. What happens if the fuse has a rating higher than the permitted rating of the wiring? Then the fuse will not blow out even the current rises above the permitted value. A fuse of a lower rating doesn’t cause any damages as no overcurrent occurs, but it results in unwanted power interruptions and causes the inconvenience of replacing or resetting the fuse very often. If the rating of the fuse is too low then it will frequently blow out even for a current value which is actually safer for the circuit. So, in order to operate the fuse properly but without unwanted interruptions the fuse should be selected appropriate to the circuit ratings.
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