Thermal Cut-Offs Resistors (FKU/FRU)

Ultimate Protection Thermal Cutoffs for High Power Applications.

Fast-acting protection device for high-power applications combines thermal fuse element and resistor on a single substrate.

Direct offers FKU (Wirewound Resistor + Thermal Cut-offs) and FRU (Metal Oxide Film Resistor + Thermal Cut-offs) two Series, both are a new concept in thermal fuse technology and are designed to protect against over-heating in electrical products.

The two active components, a thermal cutoff is a fusible alloy and a resistor is a voltage divider, both are surrounded by a ceramic cement with special resin. Under normal operating temperatures the fusible alloy joins the two lead wires within the body of the cutoff and the power resistor acts as a normal function resistor. When the preset temperature of the cutoff is reached, the fusible alloy melts and with the aid of the special resin, complete cutoff is ensured.

By combining a thermal fuse element and resistor on a single substrate, Direct has created a fast-acting ultimate protection device for high power applications up to 10A/250V.

Resistance range of FKU Wirewound Type Thermal Cut-offs is 1Ω~100Ω and FRU Metal Oxide Film Type Thermal Cut-offs is 110Ω~10KΩ. Both standard precision tolerance is J(±5%).

Our custom solutions are designed to address your need for technical and economic success in a timely manner. Contact us with your specific needs.

Download complete PDF Thermal Cut-Offs Resistors (FKU/FRU).

Features :
  1. Miniature size
  2. Radial leaded form
  3. Accurate fusing temperature
  4. Various temperature settings
  5. Current Rating: Up to 10Amp
  6. Products with Pb-free Terminations and RoHS compliant
  7. Economical by combining both function of a thermal fuse and a pulse resistor
Applications :
  1. Motors - fans, copiers, washing machines, air conditioners, compressors.
  2. Electronics - TVs, tape recorders, stereos, video recorders, fluorescent lamps, transformers, surge suppressors, computers, telecommunication equipment.
  3. Appliances - electric blankets, space heaters, stoves, irons, hair dryers, cookers, toaster ovens, clothes dryers, toasters, mixers, microwave ovens, crock pots.
General Specifications (FKU, FRU)
Type Dimension (Unit: mm)
W ± 1 D ± 1 H ± 1.5 RM+2/-1 h D1 (R terminal) D2 (F terminal)
FKU/FRU-5M 13 9 25 5 4.5±1 0.8±0.1 2A:0.6 ±0.1
10A:1.0 ±0.1
FKU/FRU-7M 13 9 38 5
FKU/FRU-10M 16 12 35 7.5
Electrical Performance (FKU, FRU)
Fusing Temperature Protector Rated Power at 25°C (W) Resistance Range (Ω) Tolerance (%)
MARK Fusing
Standard Current(A) Standard Voltage(V) 5M 7M 10M FKU FRU FKU FRU
A 109+1/-3 10 250 1.2 1.4 2.0 1~100 110~10K J(±5)
B 129±4 1.6 2.0 2.5
C 152±4 1.6 2.0 2.5
D 188+3/-1 2.0 2.4 3.5
E 226+1/-3 2.0 2.4 3.5
F 95+3/-0 2 0.8 1.2  
G 110±4 1.2 1.4  
H 126±4 1.4 1.6  
N 130±4 1.6 2.0  
M 145±4 2.1 2.4  
Order Codes (FKU, FRU)
FRU - 5M A 5R K P
Part Number
FRU Metal Oxide type Thermal Cut-offs
FKU Wirewound type Thermal Cut-offs
Rated Power
Thermal Cut-offs
Resistance Value (Ω)
10R 10Ω
100R 100Ω
1K 1000Ω
Resistance Tolerance
J ±5%
K ±10%
P Bulk