Molded Case Circuit Breakers or MCCB circuit breakers are black plastic–cased automatic switches. They are designed to primarily protect insulating materials from overheating. Molded case circuit breakers (MCCB) are by far the most commonly used breakers in residential, commercial, and industrial facilities. When an MCCB has opened (or “tripped”) to protect the circuit, it can […]
The term “power factor” (PF) is an expression of the relationship between the peak voltage and the peak current. Stated differently, the power factor is an expression of how far out of phase the voltage and current are to each other. What is power factor? Figure 1 shows both voltage and current peaks occurring at
A control panel is used to house instruments used for measurement, monitoring, protection, detection, control, and management of processes. For operational convenience, these panels are located in a control room as well as a field known as a local control panel. Types of Electrical Control Panels Industrial Panels VCB Panel (HT Section): A Vacuum Circuit
1. A transformer will work on (i) a.c. only (ii) d.c. only (iii) a.c. as well as d.c (iv) none of the above 2. The primary and secondary of a transformer are ……… coupled. (i) electrically (ii) magnetically (iii) electrically and magnetically (iv) none of the above 3. A transformer is an efficient device because
1. The yoke of a d.c. machine is made of (i) silicon steel (ii) soft iron (iii) aluminium (iv) cast steel 2. The armature of a d.c. machine is made of (i) silicon steel (ii) wrought iron (iii) cast steel (iv) soft iron 3. The coupling field between electrical and mechanical systems of a d.c.
1. An ammeter is …………… instrument. (i) an indicating (ii) an integrating (iii) a recording (iv) none of the above 2. The controlling torque of an indicating instrument ………. as the deflection of the moving system increases. (i) remains unchanged (ii) decreases (iii) increases (iv) none of the above 3. When the pointer of an
Electrostatic voltmeters are based on the fact that an electric force (attraction or repulsion) exists between charged plates or objects. An electrostatic voltmeter is essentially an air condenser ; one plate is fixed while the other, which is coupled to the pointer, is free to rotate on jewelled bearings. Electrostatic Voltmeter Working Principle When p.d.
1. In Fig. given below, the magnetic circuit is the path (i) DAB (ii) ABCDA (iii) ABC (iv) ABCD 2. If l is the magnetic path in the above Fig., then magnetising force is (i) Nl (ii) Nl x l (iii) l ÷ NI (iv) NI ÷ l 3. The reluctance of the magnetic circuit
1. The force between two electrons separated by a distance r varies as (i) r2 (ii) r (iii) r-1 (iv) r-2 2. Two charges are placed at a certain distance apart. A brass sheet is placed between them. The force between them will (i) increase (ii) decrease (iii) remains unchanged (iv) none of the above
1. A kilowatt hour is the unit of (i) energy(ii) power(iii) electric charge(iv) electric current 2. Heat produced in a conductor depends (i) inversely on time(ii) directly on time(iii) both (i) and (ii)(iv) none of the above 3. If potential difference across a conductot of a material of resistivity ρ remains constant, then heat produced