Xiamen SET Electronics Co., Ltd.

TFMOV is a combination of varistors (MOV) and thermal protection component. Since varistor has the characteristics of aging or degrading; TFMOV can separate the varistor from the main circuitry by opening the thermal protection component when the varistor (MOV) degrades or fails. It is often used in which requires high reliability and weather withstanding, such as photovoltaic inverters, communication equipment, and power supplies in data centers, etc.

V_N

Nominal Varistor Voltage

Voltage, at specified d.c. current used as a reference point in the component characteristic.

8/20 μs

8/20 Current Impulse

Current impulse with a nominal virtual front time of 8 µs and a nominal time to half-value of 20 µs. 

— (IEC 61643-11)

1.2/50 μs

1.2/50 Voltage Impulse

Voltage impulse with a nominal virtual front time of 1.2 µs and a nominal time to half-value of 50 µs. 

— (IEC 61643-11) 

U_c

Maximum Continuous Operating Voltage

Maximum r.m.s. voltage, which may be continuously applied to the SPD's mode of protection.  

— (IEC 61643-11)

I_n

Nominal Discharge Current

Crest value of the current through the SPD having a current waveshape of 8/20.  

— (IEC 61643-11)

I_imp

Impulse Discharge Current for Class I Test

Crest value of a discharge current through the SPD with specified charge transfer Q and specified energy W/R in the specified time.

— (IEC 61643-11)

I_max

Maximum Discharge Current

Crest value of a current through the SPD having an 8/20 waveshape and magnitude according to the manufacturers specification. I_max is equal to or greater than I_n.  

— (IEC 61643-11)

V_C

Clamping Voltage

Peak voltage developed across the varistor terminations under standard atmospheric conditions, when passing an 8/20 class current pulse.  

C_V

Capacitance

Capacitance across the MOV measured at a specified frequency and voltage.   

Modes of protection

An intended current path, between terminals that contains protective components, e.g. line-to-line, line-to-earth, line-to-neutral, neutral-to-earth.

— (IEC 61643-11)

U_p

 Voltage Protection Level

Maximum voltage to be expected at the SPD terminals due to an impulse stress with defined voltage steepness and an impulse stress with a discharge current with given amplitude and wave shape. 

— (IEC 61643-11)

TCO

Thermal-Link

A non-resettable device incorporating a THERMAL ELEMENT which will open a circuit once only when exposed for a sufficient length of time to a temperature in excess of that for which it has been designed.  

ATCO

Alloy Thermal-Link

Alloy Type Thermal-Link, Alloy is the thermal element.

Through Hole

Solder Pin

● Telecom Equipment

● String Inverter in Photovoltaic System

● AC / DC Power Supply

● Uninterruptable Power Supply (UPS)

● Surge Protective Device (SPD)

● Electric Meter

● Power Distribution Unit (PDU)

View Product Structure, Principle, Application Video

SETsafe | SETfuse Quality Policy

Provide Industry-Leading Products

Raw-materials Supplier

Select critical raw materials: Must be from a manufacturer with quality management system (ISO9001, IATF16949) certification.

Annual or Quarterly Audits.

IQC (Incoming Quality Check)

AQL(MIL-STD-105E), Dimensions, Function, Visual Inspection, RoHS & REACH Test.

Document

Formulate corresponding incoming inspection specifications (01-QA-06-xxx) for each key material according to design data such as material technical indicators.

Testing Equipment and Tools

Projector, Tool Microscope, Digital caliper, Salt Spray Tester, Universal Material Testing Machine, Spectrum Analyzer, etc.

Manufacturing Process

Online Inspection and Testing (Function 100% Testing).

Document

Process Flow Chart.

Failure Mode and Effects Analysis (FMEA).

Quality Control Flow Chart (QCFC).

Standard Inspection Procedure (SIP).

Work Instruction (WI).

Online Testing and Inspection

Static three-parameter detection system.

Resistance test system (100% Testing).

100% Visual inspection.

etc.

IPQC (In Process Quality Control) Inspection

AQL(MIL-STD-105E), Dimensions Inspection, Function Test, Visual Inspection.

FQC ( Final Quality Control)

AQL(MIL-STD-105E), Dimensions Inspection, Function Test, Visual Inspection, RoHS & REACH Test.

Reliability Test

Test specification (01-TE-01-xxx).

Including 29 items of appearance requirements, electrical performance, mechanical performance, Soldering performance, environmental test and Material performance. e.g.

Voltage Protection Level Up Test.

Operating Duty Test.

High temperature and high humidity test

Tensile Test.

Solderability Test.

etc.

OQC (Outgoing Quality Control)

AQL(MIL-STD-105E), Packaging, Labeling, Quantity Inspection.

Agency

Agency (Safety Certificate) Annual, Quarterly Audits.

Management System

ISO9001, (TUV approved and issued certificate).

ISO14001, ISO45001, etc.

Click to view the certificate

Environmental

RoHS & REACH Compliant.

SETsafe | SETfuse

Usage

1. Frequency range is from 47 Hz to 63 Hz.

2. The voltage applied continuously to the TFMOV can not exceed its maximum continuous operating voltage Uc.

3. When atmosphere press is from 80 kPa to 106 kPa, the related altitude shall be from 2000 meters to - 500 meters.

4. Do not touch the product body or pins directly when power is on, to avoid electric shock.

5. Do not clean the TFMOV with strong polar solvent such as ketone, esters, benzene, halogenated hydrocarbon, to avoid damaging the enclosure.

6. It should have a reliable grounding when using these products.

Replacement

TFMOV is a non-repairable product. For safety sake, please use equivalent TFMOV for replacement.

Storage

Do not store TFMOV at high temperature, high humidity or corrosive gas environment. To avoid reducing the solderability of the pins, please use them up within 1 year after receiving the goods.

Installation Position

Do not install the TFMOV on a place that may often suffer severe continuous vibration.

Mechanical Stress

Do not take violent action such as knocking when assembling to avoid mechanical damage.

SETsafe | SETfuse

SET

Thermal Fuse & MOV (TFMOV) Catalog

View PDF

ABSTRACT

According to the working principle and failure mode of varistor, this paper will explain the disadvantage of only overcurrent protection against MOV’s failure. At the same time, the best protection mode –Thermal protection is promoted.

KEYWORD

Varistor, Failure Mode, Overcurrent Protection, Thermally Protected MOV.

Discussion on Thermal Protection against MOV’s Failure.pdf