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A Motor control center or MCC is a group of combination motor starters, branch feeder devices, and lighting panelboards, each mounted in an individual isolated compartment with its own cover. It is a free-standing structure, consisting of a common busbar arrangement to distribute power to each compartment and a network of wireways to accommodate outgoing … Read more
It is vital to maintain good ground in a system. In order to ensure that, ground resistance measurements and tests are conducted on existing earth electrodes at periodic intervals after their installation. This ensures the resistance in the ground is at an acceptable level and is maintained. Here are the different methods of ground/ earth … Read more
The fall of potential method or 3-point method is the most commonly used method to measure ground resistance. It is used to determine the earth resistance of an existing grounding system. The fall of potential method requires only a minimum amount of calculation and is best suited for small installations. It can be used for … Read more
One of the key elements affecting ground resistance is soil resistivity. Soil resistivity measurements are conducted before setting up an earthing system, in order to ensure an effective earthing. Good soil models are the basis of all grounding designs and they are developed from accurate soil resistivity testing. The ground/earth resistance measurements are conducted to … Read more
Grounding transformers are used to obtain a neutral when an existing delta-connected or ungrounded systems are to be grounded. These transformers provide a path for the flow of fault currents during unbalanced ground faults. They can be found in transformer substations where neutral might not be available as the transformer windings are delta connected. Types … Read more
Time-delay fuses can provide overload and short circuit protection while overcoming momentary current spikes. They are used for the protection of motors and transformers. The time-delay characteristics of these fuses typically allow them to be sized closer to the running rated full load current of the loads. Time-delay fuses are also known as slow-blown fuses … Read more
The AC contactors differ from the DC contactors in their construction, arc extinction, and usage in a circuit. In this article, let us discuss the major differences between AC contactors and DC contactors. Contactors are electrically controlled switching devices. They are used to switch electric motors, lights, reactors, capacitors, heating loads, EV charging systems, UPS, … Read more
A resonant grounded system can significantly reduce the ground fault currents. This grounding system basically consists of a tuned reactor connected between the neutral and the ground that resonates with the line-to-ground capacitance of the system so that the magnitude of the ground current is reduced. This reactor is knowns as a ground-fault neutralizer or … Read more
In a reactance grounded system, the neutral is connected to the ground through an inductance (inductive reactance). The magnitude of the ground fault current can be limited to a value close to the three-phase short circuit current of the system (since it is a function of the phase to neutral voltage and the neutral impedance). … Read more
IEC 60529 has classified the degree of protection offered by an enclosure against solid particles and liquid. This classification is known as the ingress protection code/ IP code/ IP rating/ index of protection. To ensure the correct protection of the internal components and to suit the environment where the enclosure is installed, these codes are … Read more
