Selection and Debugging of Basler CBS 212A Current Boosting System

Application and Selection Guide of Basler CBS 212A Current Boosting System in Generator Excitation Support

In industrial diesel generator sets, marine generators, and emergency power systems, starting large capacity motors or short circuit faults in the near area often cause a sudden drop in generator terminal voltage, resulting in insufficient excitation current, and in severe cases, even causing the unit to lose step or trip protection. To solve this problem, the Basler CBS 212A Current Boost System utilizes the power current transformer (CT) in the generator output circuit to directly extract energy, providing instantaneous and high-intensity magnetic field current support for the excitation system, ensuring smooth motor start-up and reliable fault clearance. This article is based on the official technical specifications of CBS 212A, systematically explaining its working principle, selection and matching, parameter tuning, and key points of on-site application, to help electrical engineers correctly configure the device in new or renovated projects and improve the dynamic stability of the power generation system.

Product positioning and core values of CBS 212A

CBS 212A is a passive excitation boosting device designed specifically for brushless generators (50/60Hz). When the voltage of the generator drops to the threshold where it cannot maintain the rated excitation current due to load impact, the device responds instantly and extracts energy from the high current CT at the output of the generator to provide the excitation system with a maximum forced excitation current of 20Adc for 10 seconds. This feature makes it particularly critical in the following scenarios:

Directly starting a large motor (such as a compressor, water pump, or crusher) with a starting current of 6-8 times the rated current results in a voltage drop of over 20%.

The short circuit fault in the vicinity of the generator outlet needs to be quickly cleared and the system stability maintained.

Replace expensive permanent magnet generators (PMGs) or auxiliary winding solutions to reduce equipment costs and installation complexity.

Compared with traditional PMG, CBS 212A does not require additional permanent magnet machines and rectifier bridges, but utilizes existing CT energy, with a more compact structure and higher reliability, especially suitable for renovation projects.

Working principle and connection method

As shown in Figure 1 (typical application wiring diagram), the input side of CBS 212A is connected to two power CTs (selected according to the current range) at the generator output terminal, and the output side is connected to the stator winding of the exciter or the auxiliary input terminal of the AVR. Its internal circuit includes:

CT input rectification and filtering: convert CT secondary current into DC voltage.

Voltage detection and comparator: Real time monitoring of generator terminal voltage (sampled through voltage transformer PT), triggering output when the voltage is lower than the preset "action point".

Controllable silicon/transistor switch: During operation, it guides CT energy to the excitation circuit while limiting the output voltage to the set value (60/120/220Vdc optional).

Exit logic: When the generator voltage returns to a certain hysteresis (5V or 10V) above the operating point, the boost will be automatically cut off to avoid overexcitation.

The device is fully self powered and does not require an external control power supply. Its response is instantaneous (in milliseconds), ensuring support in the early stages of voltage drops.

In depth interpretation of key electrical specifications

3.1 Output power and voltage selection

Output DC voltage: 60V, 120V, or 220Vdc can be selected through internal jumpers to adapt to the rated voltage of different excitation systems.

Output current capability: 20Adc (lasting for 10 seconds), sufficient to meet the strong excitation requirements of most small and medium-sized brushless generators (<1000kVA).

Output limiting: Based on the selected voltage level, it can also be fine tuned within the range of 50% to 100% through a potentiometer to match the optimal operating point of the exciter.

Selection tip: If the rated voltage of the generator excitation machine is 90V, the 120V gear should be selected and the amplitude limit should be adjusted to around 75% to avoid overexcitation.

3.2 Voltage detection and action threshold

Rated detection voltage: 120V or 240Vac (jumper selection, corresponding to PT secondary side).

Adjustment range of action points:

120V gear: 70-131Vac

240V gear: 140~262Vac

This range is far below the rated value, ensuring that it is only started when the voltage drops severely to avoid normal load fluctuations and misoperation.

Return coefficient (Dropout):

120V gear: action point+5Vac

240V gear: action point+10Vac

For example, if the operating point is set to 100Vac (120V system), the voltage needs to rise above 105Vac before exiting the boost, providing a certain hysteresis to prevent oscillation.

3.3 Selection Table for Matching Current Transformers (CT)

CBS 212A must be equipped with two dedicated power CTs, as shown in the table below (partially truncated):