Selection and Debugging of Basler CBS 212A Current Boosting System

CT model variable ratio applicable to generator 3-phase short-circuit current (300% rated) system voltage level

BE25925001 1:8 125～250A ≤600V

BE25926001 1:17 250～500A ≤600V

BE25927001 1:34 500～1000A ≤600V

... (up to 8000A)

BE34704001~BE34709001 Same Left Same Left ≤ 15kV (medium voltage)

Important note:

Two CTs are necessary, installed on the two phases (or two phases of the three phases) of the generator output to synthesize the required energy.

The CT marked with "†" has a pre wound primary winding (without a conductor through window), and when in use, the generator lead wire needs to be directly connected to the primary terminal of the CT, rather than through the core.

The "3-phase short-circuit current" in the table refers to the line current flowing through the generator during a three-phase short circuit at the end (usually around 300% of the rated current), not the long-term operating current. When selecting, it is necessary to estimate based on the rated current and short-circuit factor of the generator.

Calculation example: If the rated current of the generator is 400A and the short-circuit current is calculated as 1200A at three times, then BE25928001 (with a transformation ratio of 1:69, covering 1000-2000A) should be selected.

3.4 Environmental and Mechanical Specifications

Working temperature: -40 ° C to+60 ° C (suitable for outdoor cabinets)

Shock/Vibration: 15G shock resistant, suitable for marine and vehicular environments

Weight and size: 15 pounds (6.8kg), with a size of 343 × 230 × 121mm, using a sturdy metal shell, can be wall mounted or installed inside a cabinet.

Key points for on-site installation and wiring

4.1 CT installation and polarity

Two CTs should be installed on the output side of the generator (near the generator end) to ensure that the true short-circuit current is measured.

The polarity (P1/P2) of CT must be consistent, otherwise the phase difference of the secondary output will affect the boosting effect and even cause device failure. When connecting to the CT secondary terminal of CBS 212A, it should be strictly connected according to the instructions marked (usually K1, K2).

Open circuit is strictly prohibited on the secondary side of CT, and short circuit protection is required before connecting to CBS.

4.2 Voltage detection wiring

The voltage detection terminal is connected to the secondary side (120V or 240V) of the generator terminal PT, and it should be noted that the phase should be in phase with the CT to ensure that the voltage and current phases are consistent (used for internal power direction discrimination? The actual CBS is amplitude detection, only voltage amplitude is required, but for safety reasons, it is recommended to be in phase).

The detection voltage should be within the rated range. If it exceeds 240V, an external step-down PT is required.

4.3 Output Connection

The output DC terminal (+/-) is connected to the stator winding of the exciter (usually in parallel or series with the excitation output of the AVR, depending on the system design). The common connection method is parallel connection: CBS output and AVR output are isolated by diodes and jointly supplied to the excitation machine. When CBS operates, its voltage is higher than AVR output, and it naturally undertakes the excitation task; AVR is cut off due to reverse bias.

If using a series connection method (cutting off AVR when CBS intervenes), it is necessary to add switching contactors, which is more complex, and parallel connection is generally recommended.

4.4 Grounding and Shielding

The device casing must be grounded, and the CT signal line uses shielded twisted pair cables. The shielding layer is grounded at one end to prevent interference and false triggering.

Parameter tuning and debugging steps

5.1 Setting output voltage

Open the front panel of the device, find the output jumper (J1), and select the 60, 120, or 220V range according to the rated voltage of the exciter.

Turn the "Output Limit" potentiometer clockwise to the maximum (100%) and wait for further adjustments.

5.2 Setting the operating point voltage

Measure the PT secondary voltage (such as 120V) at the rated no-load voltage of the generator.

Adjust the "Operation Point" potentiometer to achieve an action value of approximately 70% to 80% of the rated voltage. For example, for a 120V system, set the operating point to 85V (corresponding to the expected drop below 85V when starting the large motor before starting).

An adjustable ratio autotransformer can be used to simulate voltage drop, observe the action indicator light (if any) or measure whether the output voltage is established.

5.3 Verification of Boosting Effect

Actually start a large motor and use a waveform recorder to record the generator voltage, excitation current, and CBS output current.

Check if the CBS output quickly rises to the set limit when the voltage drops below the operating point.

After the motor is successfully started, the voltage is restored, and it is confirmed that CBS exits when the hysteresis value (about 5V) is above.

5.4 Fine tuning output limit

If the excitation current is too large or too small during the start-up process, the "Output Limit" can be adjusted to reduce or increase the output DC voltage, so that the generator terminal voltage during start-up is not lower than the allowable minimum value (such as 85% rated).