A Polymeric Positive Temperature Coefficient device (PPTC, commonly known as a resettable fuse, polyfuse or polyswitch) is a passive electronic component used to protect against overcurrent faults in electronic circuits.
I am making use of this little device to protect the DC outputs of my SMILODON range of DC Model Train Controllers from overcurrent faults.
A GREAT PRODUCT, many thanks to Raychem and Rick Astley in particular!
"PolySwitch® technology offers resettable protection strategy:
Auto Application Manager
Raychem Circuit Protection
Introduction:
Motor drives and controls are subjected to some of the harshest
operating environments, yet are depended upon for consistent, reliable operation.
Field failures are inevitable so choosing the right circuit protection strategy is important to help ensure product reliability and to minimize service costs to manufacturers and customers.
The PolySwitch Polymeric Positive Temperature Coefficient
(PPTC) resettable circuit protection devices from Raychem Circuit Protection help protect motor drive and control systems from some common failures, resulting in a more robust and reliable product.
These PPTC devices are available in leaded, axial, chip, disc and surface-mount configurations.
The small form factor of the PPTC helps conserve board space, while their resettable functionality allows for placement in inaccessible locations, in contrast to traditional fuses that require user accessibility for replacement.
Since PPTC devices are solidstate, they are also able to withstand mechanical shock and vibration, helping to provide reliable protection in a variety of applications.
Principle of operation:
PPTC devices are made from a conductive polymer blend of
specially formulated plastics and conductive particles.
At normal temperature, the conductive particles form low-resistance chains in the polymer.
However, if the temperature rises above the device’s switching
temperature, the crystallites in the polymer melt and become amorphous.
This increase in volume during the crystalline melting phase
causes separation of the conductive particles and results in
a non-linear increase in the resistance of the device.
The heating can take place from external sources or can be
generated internally by resistive heating from an overcurrent condition.
The increased resistance, reduces the amount of current that can flow under the fault condition, helping to protect the equipment in the circuit.
Fig. 1 presents the typical resistance versus temperature
characteristic of a PolySwitch device.
Note that the resistance value changes by several orders of magnitude at the trip point of approximately 120°C.
Once the power is removed and the fault is cleared, the temperature of the PolySwitch device drops below its trip temperature, allowing it to reset to its low resistance state which enables the circuit to operate normally.
The high resistance change and resettability characteristics of the
PolySwitch devices enable them to help protect electronic circuits from failure due to both over temperature and over current faults.
Power supply protection:
PolySwitch devices have long been used to help protect the DC outputs of power supplies from overload and short circuit failures.
With the development of the LVR family, a PolySwitch device can now be used on the AC mains side of the power input, adding the AC Line transformer and other line side devices to the protection envelope of the PolySwitch device family of products.
In addition, the AC Line transformer and other line side devices will help protect the power supply in cases where a neutral line is
inadvertently disconnected or when an AC line voltage is applied to a 24Vac input.
LVR devices are suitable for power systems with maximum
input currents of up to 400mA at either 120Vac or 240Vac."
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Solar, Battery and Inverter nice to know info -
LINK: https://www.aussiebatteries.com.au/
LINK: How do I read specifications of my Solar Panel
LINK: Sizing batteries, charge controllers, inverters, solar panels for your off grid solar energy system.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
What is the difference between inductive and resistive loads?
A load is any device that absorbs energy in a power system. Home appliances, and appliances generally fall into two broad groups of loads: resistive and inductive. Resistive loads are simply those in which the electricity produces heat and motion. Typical of such loads are incandescent lamps or electric radiators.
Inductive loads generally are those in which electricity flows through the coils. Normally are motors, such as fans or refrigerators, or transformers, which are found in most electronic devices, such as televisions, computers or fluorescent lamps.
No comments:
Post a Comment