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Real production delay: “We arranged a complete ACB test for our 4,000-amp main breaker over a weekend in a shut down. Unfortunately, we ran out of time to inspect the ETU comm interface cable and the mechanical fixture to install the energy storage type of mechanism was lost. The test was delayed two weeks and cost $15,000 in lost production time.” The data center maintenance manager. Testing an Air Circuit Breaker (ACB) is not simply checking that the device has continuity; it also involves validating that the spring mechanism operates correctly, checking the settings of the Electronic Trip Unit (ETU), measuring contact resistance and confirm insulation integrity at extreme current […]

Real production problem: The production manager of a medium voltage switchgear manufacturer reported that they were experiencing inconsistent trip times on their MCCB long time calibration bench with regards to the morning and the afternoon. Upon investigation into the cause of this phenomenon, it was discovered that there was a temperature change of 12°C within the room that housed the calibration bench and the calibration bench itself did not have temperature compensation built into it. As a result, the production manager has been having to recalibrate the calibration bench every 2 hours. A machine used to calibrate MCCB is not just a “pass/fail tester”. It also functions as a highly […]

Real safety incident: “A factory’s 100A MCCB failed to trip when a short circuit occurred. The downstream panel exploded and injured an electrician as a result of the breaker not having been tested in eight years; the thermal mechanism was stuck in place from the long term usage of it.” – Maintenance manager, industrial plant A circuit breaker test consists of multiple individual test actions that range from a basic “click” test performed on the internal push button of the circuit breaker, to a full primary current injection verification of trip times and calibration. Circuit breaker testing ensures that your Miniature Circuit Breakers (MCBs), Molded Case Circuit Breakers (MCCBs), and […]

Real field failure: “A new hotel had 500 wall switches installed. Three months later, twelve of those switches were malfunctioning because their contacts had welded together. The supplier had performed only a basic continuity test, not a full endurance test of the product.” – Project manager, a contractor specializing in commercial electrical installations. Besides just seeing if a switch’s contacts work or not, the switch test must also verify mechanical endurance, electrical life, contact resistance, insulation integrity, and temperature rise when energized for products such as industrial/highly used switches (e.g., wall switches, isolators, auxiliary contacts, pressure switches). This Guide talks about what the five main types of testing switches are, […]

Real production headache: The manually soldered silver contacts on our MCCB terminals have a failure rate of 0.8% due to intermittent high resistance, with occasional contact loss from the MCCB terminals during the dielectric test. We required an inspectable and repeatable process. — Manufacturing Executive, a switchgear manufacturer in Southeast Asian Region. A machine called a MCCB contact welding machine doesn’t just operate like a generic spot welder. It is specifically designed as an automated system for the purpose of joining silver-based alloy contacts (either stationary or moving) to copper terminals or braids in Molded Case Circuit Breakers (MCCBs) that generally range from 100A – 1600A frame sizes. Since purpose-built […]

Real quality challenge: According to the Quality Manager at a panel building LLC the following was concluded after testing 500 MCCBs: “We passed all of them through routine tests. However, regarding thermal trip intermittent failures we had 12 reject in the field after being installed.” The reason why the thermal trip fail rates were missed at the test bench; delta/variation were not tested since the test was conducted only at 25 degrees Celsius. An MCCB test bench isn’t a basic go/no-go station but rather one that has additional responsibilities. The test bench’s responsibility is to properly test molded case circuit breakers (rating ranges of 10A – 1600A; interrupting capacity up […]