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HOW DOES THE RESETTABLE FUSE WORK
HOW DOES THE RESETTABLE FUSE WORK
Figure 3 - PTC Curve For Fuzetec TM R esettable Fus e
10,000,000,000.0
Log (Resistance), ohms
PPTC resettable fuses are designed and
made of patented Polymeric PTC
(PPTC) material in thin chip form. It is
placed in series to protect a circuit. At
“normal operating condition” the device
remains at an extremely low resistance
and allows the electrical current to flow
through it without any restriction. When
overcurrent conditions occur, the
Polymeric PTC material heats up and its
resistance increase sharply. Such a sharp
resistance increase cuts off the current in
the circuit. Upon fault current being
removed, the resettable fuse cools and
its resistance drops to the original
extremely low value. The resettable fuse
is “reset” and allows the current through
the circuit again.
1,000,000,000.0
100,000,000.0
10,000,000.0
1,000,000.0
100,000.0
10,000.0
1,000.0
100.0
10.0
1.0
0.1
0
20
40
60
80
100
120
140
160
180
200
220
Temperature, C
TRIP CURRENT, HOLD CURRENT AND THERMAL DERATING
Hold & Trip Current and Thermal Derating Curve
300
Percentage of Hold and Trip
Current
Trip Current (IT) and Hold Current (IH) of
resettable fuse are rated at 23°C. Typically its
Trip Current is twice as much as its Hold
Current. The PPTC does not trip at or below
its rated Hold Current, and will trip at or above
its Trip Current value. However, due to PTC
effect both IT and IH reduce with ambient
temperature increase and vice versa. As shown
below, the currents are reduced nearly at 50%
at 85°C and increased to 150% at -40°C.
250
200
150
100
50
0
-40
-20
0
20
40
60
80
Ambient Temperature (C)
Hold Current
Trip Current
PPTC resettable fuses are designed for todays’ demanding electronic and electrical industries. Its resettable feature,
compact size, flexible construction, low thermal output and competitive cost out performed the traditional fuse,
Ceramic PTC, Bimetal fuse and Current control IC. They are ideal for all low voltage DC and AC application. PPTC
resettable fuse are offered in a variety constructions, which include: Radial Leaded, Axial Leaded, Surface Mount
and Custom Design.
Third party approvals (UL, C-UL and TÜV), of PPTC products ensure the long lasting safety and performance. From
product design and development, through manufacturing and quality control to delivery and shipment, we strictly
implement ISO 9001-2000 quality standards to assure products quality and consistency. With continuous
improvement, we are committed to provide top products and services to better satisfy our customer’s needs. We
strongly believe that excellent partnership with our customers is the best and only route to achieve success in
tomorrow’s competing business world.
WARNING!
- Operation beyond the specified maximum ratings or improper use may result in damage and possible electrical
arcing and/or flame.
- PPTC device are intended for occasional overcurrent protection. Application for repeated overcurrent condition
and/or prolonged trip are not anticipated.
- Avoid contact of PPTC device with chemical solvent. Prolonged contact will damage the device performace.
RFE International • Tel:(949) 833-1988 • Fax:(949) 833-1788 • E-Mail [email protected]
C5EA02
REV 2003.09.08