Maharashtra HSC Electrical Maintenance (Bifocal) case studies
Maharashtra HSC Electrical Maintenance (Bifocal) · Put your knowledge to work in context.
The Maharashtra HSC Vocational (Bifocal) Electrical Maintenance subject is a state-board higher secondary vocational course that pairs a general academic programme with trade-specific electrical training. It suits students who want a school-leaving qualification that opens directly into electrical apprenticeships, industrial maintenance jobs, or further diploma study, rather than a purely academic science stream. The Maharashtra HSC Electrical Maintenance (Bifocal) case studies are 5 cases and about 4,745 words.
1Rewound 30 kW Pump Motor Tripping on Overload
A dairy plant's 30 kW, 415 V, 3-phase, 4-pole squirrel-cage motor (nameplate FLC 54 A, efficiency 89%, power factor 0.86) drives a centrifugal pump. After a local rewind, it trips the 63 A thermal overload relay after 6–8 minutes at a steady valve position.
963 words, about 5 min235 mm² Submain Through an Insulated Wall
A 415 V, 3-phase submain is to be run from the main switchboard to a new workshop distribution board. The design current is 70 A, the route is 60 m, and the cable is 4-core 35 mm² copper PVC-insulated, armoured, clipped to a wall.
870 words, about 4 min3ACB Trips Before 250 A MCCB on a Submain Arcing Fault
A 630 kVA, 11 kV/415 V distribution transformer (6% impedance) feeds a main 1000 A air circuit breaker. The ACB's long-time setting is 0.9 In, short-time pickup 2.0 In with a 0.2 s time delay, and instantaneous is switched off.
932 words, about 5 min4Unbonded Earth Electrodes at a 250 kVA Package Substation
A 250 kVA, 11 kV/415 V package substation serves a small industrial estate. The transformer neutral, transformer tank, LT panel body and lightning arrester are each connected to a separate 3 m galvanized iron pipe electrode.
943 words, about 5 min5VFD Overvoltage Trip on a High-Inertia Induced-Draft Fan
A 30 kW, 415 V, 4-pole induced-draft fan is driven by a 37 kW VFD. The fan has a high inertia; coast-down from 50 Hz takes about 70 s.
1,037 words, about 5 min