מבחן לרישיון חשמלאי הנדסאי וחשמלאי מהנדס

When changing the current, if the measuring/protection device is not connected, its secondary windings should be shorted. This is done to prevent any induced voltage or current from affecting the device or causing any damage. Shorting the secondary windings ensures that the current flows through a low resistance path and avoids any unwanted effects.

The main circuit breaker and sub-circuit breaker are planned to be installed in a single-phase agreement. The question asks whether the installed sub-circuit breaker can serve as a main circuit breaker for the sub-panel, or if the installation of a load disconnect without protections is required. The correct answer states that a sub-circuit breaker cannot serve as a main circuit breaker because it is not designed to protect against excess current. Additionally, a load disconnect or current switch should be installed in addition to the sub-circuit breaker. However, a sub-circuit breaker can serve as a main circuit breaker for the sub-panel if there is an overcurrent protection installed at the top of the feed.

The correct answer is that the riser including the accumulation strips will include only isolated accumulation strips. This means that the accumulation strips will be separate and not connected to any other electrical components or circuits. This is required by electrical regulations to ensure safety and prevent any potential hazards or malfunctions.

The correct answer states that it is allowed to install the described manual isolation device, as long as it is accompanied by a sign that states "Caution - Danger to human life - Cutting off the supply is only allowed after receiving approval from a qualified medical authority." This means that the device can be installed in a medical facility of usage group-2, but it requires proper authorization before use.

The answer states that the cause of resonance in a receiving system is when the combined internal frequency of the receiving system and the load is close to a specific harmonic frequency. This means that when the internal frequency of the receiving system and the power supply network are close to a specific harmonic frequency, it can cause resonance in the system.