Many electrical   installations  now contain products which incorporate power electronics,  such  as inverters  for PV installations,   speed control  in  HVAC, some running machines,   UPS, medical   equipment  etc. This  type of equipment can produce, in addition to standard  50Hz earth leakage currents, pure DC and high frequency AC leakage currents which would not be detected by a standard  AC or A type RCD. 'B' type RCDs  in addition  to normal  AC, can detect high frequency AC and  pure DC earth leakage curents

A comparison  of the AC-DC sensitive residual current ciruit-breaker

Many standards,  regulations  and directives  demand the provision of a Type B AC-DC  sensitive residual current circuit-breaker  (RCCB).

Wherever  three-phase  electronic  equipment  is connected  to mains without  electrical  isolation, AC-DC  sensitive  residual current circuit-breakers must be employed.  There are, however,  also cases in the 240 V mains network where they are applicable,  e.g. photovoltaic (solar energy)  installations with inverters lacking a transformer.

Pumping   stations,   air conditioning  and ventilation  facilities, escalators, welding equipment, medical-technical equipment,  UPS and photovoltaic  installations,  agricultural and work premises with potential fire hazard, lecture rooms with experimentation facilities, exhibitors mobile displays. These are a few examples where - because mainly pulsed equipment is employed for the power control in such installations  (e.g. frequency converters)  - the use of residual current circuit-breakers is imperative.

To select the correct  RCCB for each individual  application, we offer you three different tripping  characteristics within the area of AC-DC  sensitive  RCCBs.

In many electrical  installations,  such as e.g. in construction site power distributors,  fire protection  plays a secondary  role. Here it is often the case that only fault  protection  and high availability  of plant are demanded.   Due to the lower response  sensitivity  at higher frequencies,   there are few equipment-related    unwanted  tripping  incidents.  The devices  in the SK model  range conform  to VOE Standard  0664-100  E.

The B+ model  range  is based  on the new VDE Standard  0664-110. Compared to residual current circuit breakers of the SK model  range, these devices will trip when residual currents up to max.20 kHz occur within an upper response limit of 420 mA and offer a higher  preventative fire protection.