Fundamentals
The operating principle of WHOCP(WH Overcurrent Protection Device) resettable fuse is based on the dynamic equilibrium of energy, with part of or all the head brought about by the current passing WHOCP component due to the relation with WHOCP sending forth into the ambience while the heat not sending out raising the temperature of WHOCP component. Temperature is rather Iow during normally working, while a dynamic equilibrium between the heat produced the that sent forth being reached. When WHPTC component being at Iow resistance state, WHPTC does not operate. And though the current passing WHPTC component increases and the ambient temperature rises, but if the heat produced and that sent forth reaching a equilibratory state, WHPTC will still not operate. When current and ambient temperature further raising, WHPTC will come to a rather high temperature. If right now current and ambient temperature continue to further rise, then the quantity of heat produced will be larger than that sent forth, thus causing the temperature of WHPTC component abruptly rising. In this stage, the least change of temperature will cause resistance value substantially increasing and WHPTC component will be in the high resistance protection state. The increase of impedance will limit current, which will dramatically fall within a very short time, thus protecting circuit unit from damage. So provided for the quantity of heat produced by the applied voltage is enough to match that sent forth by WHPTC component, the WHPTC component under changing state will always remain in the operating state (high resistance) Once the applied voltage disappears, WHPTC will automatically reset itself.
Application
Network Equipment, Customer Premise Equipment, MDF Module.Automotive Harness, Automotive Security, Small Motor, Automotive Electronics.
Satellite Receivers, Security Alarm System, Speaker, Industrial Process Controls.
Power Supply Devices, Ballast, Mini-motors, Fire Alarm System, Apparatus.
Installation
The WHPTC has no polarity and Iow resistance, so it is usually series connected with other devices toform a circuit. The power sources can be DC or AC .
Specification Definition
Specificagion |
Definition |
Ih |
Hold current-maximum current at which the device will not trip at 25℃ |
It |
Trip current-minimum current at which the device will always trip at 25℃ |
Vmaxi |
Maximum voltage device can withstand without damage at rated |
Imax |
Maximum fault current device can withstand without damage at rated |
Pdmax |
Power dissipated from device when in the tripped in 25℃ still air |
Rmin |
Minimum device resistance at 25℃ prior to tripping |
Rmax |
Maximum device resistance at 25℃ prior to tripping |
Methods of Selection
For helping you correctly using proper WHPTC resettable fuses please make your choice according to the following methods:
1. List out the average operating current value (I) and operating voltage (V.) on the device line.
2. Select the WFI series of resettable fuse according to I value, V value, types of product and the form of installation
3. If the ambient temperature inside the device being higher than 25℃, the PTC phenomenon of resettable fuses will increase as the temperature becoming higher, In this case, maintaining normal current offer will calculate as follows according to discount rate:
Ih=operating current (I) ÷ discount rate of ambient temperature and current value
4. Then make selection according to step two, and the Ih needed should larger than or equivalent
calculated in step three.
If a customer puts forward some special demand and there is no the relevant element on the performance and specification table, please contact us, we will carry out special development according to your demand, and will not impose any surcharge.
Discount rate of ambient temperature and current
WH Seties |
-20℃ |
0℃ |
25℃ |
30℃ |
40℃ |
50℃ |
60℃ |
70℃ |
85℃ |
WH 600 |
138% |
119% |
100% |
92% |
83% |
73% |
64% |
55% |
42% |
WH 250 |
132% |
117% |
100% |
91% |
85% |
77% |
68% |
61% |
48% |
WH 130 |
136% |
119% |
100% |
92% |
81% |
72% |
63% |
54% |
40% |
WH 60 |
136% |
119% |
100% |
90% |
81% |
72% |
63% |
54% |
40% |
WH 30 |
130% |
115% |
100% |
91% |
83% |
77% |
68% |
61% |
52% |
WH 16 |
132% |
120% |
100% |
96% |
88% |
80% |
71% |
61% |
47% |
WH 6 |
130% |
115% |
100% |
91% |
83% |
77% |
68% |
61% |
52% |
Model
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