The sigma resistors cover a power range from 100W to 7kW average load and it is a popular economically type of brake resistors capable of solving many brake resistor jobs. The resistor components consist of fully welded wire wound ceramic resistors, which is a well-known and proven technology. The base material is cordierite, which is a type of ceramic with a very high resistance to temperature changes and the wire is coated with aluminum phosphate to protect the wire and conduct the heat developed in the wire onto the ceramic core. Aluminum-phosphate is stable up to 500°C. The resistor cages comply with IP20 (IP21 for UL versions)  giving electrical and thermal protection  The resistors having a nominal load from 100W - 7kW are particularly suitable for pulse load of 10 - 20 times or more compared to the nominal load because of the ceramic core material and an extra high weight of the wire.

SIGMA Ceramic brake resistors

This resistor family ZRF 55/ ... 08X is an updated version of
the original brake resistor family.
The power range is from 100W to 7kW continuously.

SIGMA, UL Listed version

SIGMA ZRF 55/... 0A8X is a
range of Ceramic Wire Wound
Brake Resistors mounted in IP21
/ Type 1X housings and equipped
with Thermostats for temperature warning.


SIGMA Resistors mounted in a
sheet metal housing and cooled with