Technical Definitions

ELCUT Brand Technical Definitions

from the Elcut 2009 Catalog
Functioning Temperature

The temperature at which the thermal cutoff opens (fuses off) while passing 0.1 amp or less in a controlled oil bath at arise of 1°C per minute. The functioning temperature is not the Rated Functioning Temperature.

Rated Functioning Temperature (Tf)

Rating of the functioning temperature based on safety standards. Tolerance of Rated functioning temperature is +0, -10°C for IEC 60691. Tolerance for METI is ±7°C except some types. ELCUT thermal Cutoffs are rated to satisfy those requirements.

Holding Temperature (Th)

The highest temperature of the thermal cutoffs at which it does not open the circuit while passing rated current for 168 hours. (Applicable to UL, cUL and CCC).

Maximum Temperature Limit (Tm)

The highest temperature at which continuity does not occur for 10 minutes after the function of the thermal cutoff.

Rated Current (Ir)

The allowable maximum current, which the thermal cutoffs is able to carry.

Rated Voltage (Ur or Vr)

The allowable maximum voltage, which the thermal cutoff is able to be applied.

Maximum Use Temperature

Maximum allowable normal use temperature

SEFUSE® Brand Technical Definitions

From the SCHOTT 08/2018 Catalog
Rated Functioning Temperature (Tf)

Rated functioning temperature is the operating temperature of the thermal link, measured using the method specified in the safety standard.

As stated in the Electrical Appliance and Material Safety Law (PSE) of Japan (Appendix 3, Section 3), the thermal links should operate within ±7°C of the specified operating temperature. In cases where Tf is greater than 200°C, the thermal links should operate within ±10°C of the specified operating temperature.

In standards that comply with the IEC standard, it is indicated that the thermal links should operate within +0/-10°C of the specified temperature range.

Operating Temperature

Operating temperature and tolerance refers to the operating temperature range measured by the following conditions.

A thermal link test sample is placed in the condition where the temperature of a thermostatic oven is raised until 12°C below the rated functioning temperature of the test sample at optionally increasing speed.

Then the temperature of the thermostatic oven is raised at the rate of 0.5-1.0°C a minute.

At this time, the electric current flowing through the test sample for opening confirmation shall be less than 10mA.

Furthermore, the distance between a measuring point and a test sample shall be less than 20 mm.

Th (Holding Temperature)

Th is the maximum temperature measured on the thermal links when it continues to conduct a rated current without changing its state of conductivity for 168 hours.

Maximum Temperature Limit (Tm)

Maximum temperature limit is the maximum temperature for which conductivity does not occur again during the following test.

First, the samples are maintained at Tm for a period of 10 minutes. Then, the withstand voltage test is conducted for 2 minutes with twice the rated voltage. During the test, the thermal links must remain in the functioned state, i.e. open.

Hence, no current is allowed to pass through.

(Functioned state of the SF-type: not less than 0.2MΩ; SM-type: not less than 2MΩ (between body and lead) and not less than 0.2MΩ (between lead and lead).

Recommended Usage Temperature

Temperature of the thermal link that should not be exceeded on a regular basis.

Produt Design

Elcut Brand Fusible Alloy Design

ELCUT Thermal Links are available with axial or radial lead wires, both having the same basic design. The fusible thermal element is a fusible alloy that is welded across a pair of lead wires. The fusible alloy is coated with a special compound to ensure stable and reliable fusing off of the thermal element. The coated element is sealed in a special insulated container housing. The final product is a miniaturized, fusible alloy-type thermal unit with extremely simple construction.

When the cutoff temperature is reached, the thermal element melts and liquefies. This breaks or “cuts-off” the electrical current through the thermal fuse.

Animation of the Operation of the Elcut Brand Thermal Links.

Sefuse® SF Series Design

The SEFUSE brand, SF-R series thermal links are designed for high current applications. The thermal sensitive pellet in the SEFFUSE brand TCO liquefies when the temperature rises to the melting point of the thermal element. This, in turn, allows a spring action to permanently break the electrical circuit.


SEFUSE SF-R Series Thermal Link Design

Unique to the SCHOTT SEFUSE design, is the increased reliability of the leads that are supported by an epoxy-seal- end ceramic pipe. Design features of the SEFUSE brand include:

  • Simple construction for trouble-free operation.
  • High Current carrying capabilities
  • Miniature sizes permit unparalleled design possibilities in extremely small spaces.
  • Many styles and configurations available for maximum design flexibility.
Animation of the Operation of the SEFUSE SF-R Series Thermal Fuse


Before Operation

The SF-type contains a sliding contact, springs and a thermal pellet inside a metal case. When spring B is compressed, there is firm contact between lead A and the sliding contact. At normal temperatures, current flows from lead A to the sliding contact and then through the metal case to lead B.


After Operation

When the ambient temperature rises to the operating temperature of the SF-type, heat is transferred through the metal case and melts the thermal pellet. Springs A and B then stretch and the sliding contact moves away from lead A, thereby opening the electrical circuit.


Sefuse® Battery Protectors

SCHOTT SEFUSE® D6S battery fuses offer reliable overcurrent and overcharging protection for lithium-ion batteries.

The D6S series components are designed to protect lithium-ion batteries from potentially damaging and dangerous overcurrent and overcharging circumstances. The D6S battery protectors are thin surface mount devices suitable for products that require space-saving lithium-ion battery components. The D6S fuse will cut off the current in cases of overcurrent, and its self-heater element is able to externally cut off the current in case of overcharging. The D6S series are suitable for high currents and are compatible with up to 14 cells. They are RoHS compliant and are antimony and halogen free. Many variations are available with different current and package sizes.

CLICK HERE to view an animation video of how these battery protectors work.

Sefuse® D6S Battery Fuses