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6 | RCD Type F
Type F features at a glance:
Type F RCDs offer the same range of protection and functionality
as an RCD Type A APR; this means that they detect sinusoidal
AC currents as well as pulsating DC currents. In addition to this,
they are also tested according to IEC/EN 62423 which foresees
the application of a simulated multi-frequency residual current with
appropriate coefficient associated to the each level of frequency
up to 1kHz.
The intervention characteristic has a short-time delayed which
prevents unwanted tripping in case pulsed leakage currents of up
to ten milliseconds occur at activation of filters.
The RCDs Type F have a surge current withstand capacity of
more than 3kA and can accept superimposed smooth DC
residual currents of up to 10mA without affecting their standard
functionality.
Type F - Protection of lines including loads
with single phase inverters
Nowadays single phase inverters are present in many household and industrial
loads, such as washing machines, hoovers, dishwashers, ventilation, pumps etc….
Inverter technology is a “plus” in domestic equipment, since it helps to reach better
performance reducing power consumption and improving energy efficency.
10 mA
Working principle
A single phase frequency converter, also named inverter, is a
commonly used electric drive which regulates the speed of an
electric motor, operating on supply voltage and frequency.
During normal operation, the current generated by a single phase
inverter in the downstream section is the result of the overlapping
of mixed frequency components which varies from 10Hz (motor
frequency), to 50Hz (rated frequency) and 1000Hz (switching
frequency).
RCDs type F have been specifically designed for single phase
inverters applications in order to meet the requirement to
assure adequate protection level in case of an earth fault with
such harmonic content, offering at the same time an increased
resistance to nuisance tripping.
On the other side only RCD type B remain the only devices which
are suitable to detect smooth DC components in the residual
current caused by insulation faults in the DC section of a three
phase frequency converter.
Typical residual current waves that can occur in a circuit that supplies a single phase inverter:
Variable frequency
Detected only by Type F RCDs
(or Type B)
Alternate current
(can be detected
by Type AC RCDs)
Pulsating current with DC
components (can be detected
by Type A RCDs)