These types are suitable for non-linear components that can generate leakages with a high amount of direct current or AC residual currents at various frequencies. They can be found in frequency converters with a three-phase current supply just like in medical or laboratory equipment, charging stations, photovoltaic systems and construction site distribution boards. Only type B RCDs can detect smooth DC residual currents, which occur due to an insulation failure in a frequency converter's DC section. Type A or type F RCDs are able to do this only partly.
ABB has developed an AC/DC-fault current sensitive RCD named F200 Type B – currently the only two-pole device on the market that stands out due to its compactness. Before introducing the F200 type B RCCB to the market, the devices had to pass several field tests at the Corporate Research Center, Motor and Drives, in Ladenburg. Under real-world application conditions – using speed-controlled drives and frequency converters – ABB has tested the RCD with motors and generators during normal operation. In addition, tests were conducted on the immunity to unwanted trips during high surge currents, as created during faster switching operations.
The test setup consisted of two ABB asynchronous motors with 22 kW and 1 kW output, which were connected to one another through a shaft, which served as an oscillating weight. Loads in motor and generator modes were simulated through accelerations and slowdowns. A machinery drive ACS850 acted as the motor inverter. The inverter was connected to the intermediate circuit of an additional type ACSM1-204 machinery drive, which constituted the energy recovery system. The ACSM1 was equipped with an active filter, which creates high leakage current when switching from motor to generator operation. To secure the line that fed the three-phase motor inverter, the Test Engineers installed an ABB F200 RCCB type B. Furthermore, they ran tests using short and long motor cables with and without shielding in order to test the response at various fault frequencies.
To test the limits in the worst case scenario, a motor was switched on between motor and generator operation within 100 ms to produce high peak currents. Due to its 3 kA peak current resistance with a simultaneous short delay of 10 ms, the RCD was not tripping under these operating conditions either. "The field test proves that the F200 type B delivers the best trade off between its resistance to high temporary leakage currents and the required safety level . This ensures the accuracy and the reliability of the device and thus, of the entire installation", says Tobias Zahn, Product Marketing Specialist (RCDs) at ABB Stotz-Kontakt.