Post by 9th on Aug 3, 2008 2:34:43 GMT 8
Polymeric Positive Temperature Coefficient (PPTC) Device.
Or "Resettable Fuse",
Primarily used as short-circuit and overcharge protection for Electronics Devices or Rechargeable Battery.
PPTC device can provide both overcurrent and overtemperature protection in one package.
Most common PPTC:
"Surface mounted Device (SMD)"
"Strap type" or "Axial Leaded",
Commonly seen inside the shrink wrap of Two-way Radio Rechargeable Battery.
"Radial Leaded" PPTC with higher current specs.
PPTC also used for transformer overvoltage protection
Ex: Tx rated with 120V accidentally plug to 220V
PPTC works as "Resettable Fuse":
If overload or shorted, the PPTC will begin to heat.
Polymer will expand, internal "materials" react.
(PPTC physically expands)
The expansion makes the resistance of the PPTC to increase sharply.
"Cut-Off" occur.
When fault or power are removed, the PPTC device will cool.
And PPTC returns to a low resistance level, "normal mode"
Cooling usually takes a few seconds, 3~5seconds.
Example for AEG, a 20A PPTC:
*image courtesy: "sorry forgot the owner"
Note:
*The black wire is not connected to PPTC.
*Recommended high temperature shrink wrap. The PPTC heat and expand, may tends to break the wrap.
Or "Resettable Fuse",
Primarily used as short-circuit and overcharge protection for Electronics Devices or Rechargeable Battery.
PPTC device can provide both overcurrent and overtemperature protection in one package.
Most common PPTC:
"Surface mounted Device (SMD)"
"Strap type" or "Axial Leaded",
Commonly seen inside the shrink wrap of Two-way Radio Rechargeable Battery.
"Radial Leaded" PPTC with higher current specs.
PPTC also used for transformer overvoltage protection
Ex: Tx rated with 120V accidentally plug to 220V
PPTC works as "Resettable Fuse":
If overload or shorted, the PPTC will begin to heat.
Polymer will expand, internal "materials" react.
(PPTC physically expands)
The expansion makes the resistance of the PPTC to increase sharply.
"Cut-Off" occur.
When fault or power are removed, the PPTC device will cool.
And PPTC returns to a low resistance level, "normal mode"
Cooling usually takes a few seconds, 3~5seconds.
Example for AEG, a 20A PPTC:
*image courtesy: "sorry forgot the owner"
Note:
*The black wire is not connected to PPTC.
*Recommended high temperature shrink wrap. The PPTC heat and expand, may tends to break the wrap.
