Video: CAB

Video transcript

What the CAB measures on a circuit breaker, how its main contact, coil and voltage channels are connected, and what the coil current curve tells you. Timing is one of the most important tests on a circuit breaker. Contacts in one pole must operate together, and so must the three poles. Coil currents show the state of the coils and the mechanism. The CAB does all of this in a handheld unit, for breakers with one break per phase. Three main contact inputs, one per phase, with a time resolution down to 0.05 ms and sampling up to 20 kHz.

A color touch screen readable in full sunlight, and an internal battery for up to 8 hours, in 1.4 to 1.6 kg. are two versions. One has coil control built in, so it can operate the breaker itself. The other takes coil control from an external module and adds the online first trip test read from the current transformer secondaries with the installation and service. top, the three measuring sockets, the DC current clamp,

the DC voltage input, and the main contact inputs. Then the touch screen with its soft keys, the keypad for breaker and test data, ready to prepare the test, and start and stop. Coil supply and coil control outputs are on the top edge. instrument ships with the PC software, a USB memory stick and cable, a touch pin, and a plastic case. The recommended set adds the main contact cable set, the coil control and coil supply cables, and test probes.

The current clamp, voltage sense cables, and longer sets are options. the first cable, the breaker is disconnected from its circuit on both sides, as national safety rules require, and it is properly earthed to protective earth. Then the instrument is cabled, and only then the breaker. timing, the main contact cable goes into MC inputs. Its common lead goes to earth, then one lead per phase, red to phase A, yellow to phase B, blue to phase C, each on the terminal across the open contact from the earthed one.

To operate the breaker, the coil supply input takes the station battery, and the coil control cable goes to the close and trip switches and to the coils. The DC voltage input reads the battery during the operation, and the clamp around the coil wire records the coil current. On a dead tank breaker, the connection is the same. The common lead goes to earth, and each phase lead goes to the bushing on the other side of the contact, phase by phase. The CAB runs every operation, open, close,

trip free, recluse, close open, and open close open. Multiple operations start after a set delay or when a contact position is sensed, and the recording can be triggered by the coil control channel, the DC clamp, or the DC voltage channel. Synchronism is judged against the rated frequency. When opening, the poles must not drift apart by more than one-sixth of a cycle, 3.33 milliseconds at 50 hertz. When closing, one-quarter of a cycle, 5 milliseconds at 50 hertz.

The coil current tells a story. The coil is energized, and the plunger starts to move. When it hits the buffer, the current dips, then rises to a level set by the coil resistance. The auxiliary contact opens, and the current drops to zero. Higher currents or longer times at each point point to friction, burn insulation, or a weak drive. Results appear as numbers and graphs on the screen,

and up to four records can be overlaid to compare operations on site. The memory holds more than 30,000 results, and they go to a USB stick or to the PC. The PC software downloads the tests over Bluetooth or USB. Cursors and zoom measure any point and interval, several records overlay for comparison, units convert automatically, and the results are edited, printed, and exported. suits low, medium, and high voltage breakers with one break per phase, from maintenance contractors to industrial plants.

Timing, synchronism, bounce, coil currents, auxiliary contacts, and the control circuit wiring. Circuit breaker testing from Amperis.