4.2 Eskom uses a 1MVA transformer to supply electricity to Willows community. The electricity cost price is R2.50 per kWh. The load supplied by the transformer varies as shown below. The purchasing price of the transformer is R350 000. The transformer has a full load copper loss of 2.2 kW and the iron loss of 4.18 kW. A certain load varies as follows for 269 days per annum: 550 kVA at a power factor of 0.819 lagging for eleven hours per day. 120 kVA at a power factor of 0.836 lagging for six hours per day. 450 kVA at unity power factor for remaining hours of a day. For the remaining time of the year, the load varies as follows: ➢ 290 kVA at a power factor of 0.822 lagging for eight hours per day. ➢ 25 kVA at a power factor of 0.866 lagging for eight hours per day. ➢ No load for eight hours per day. Correct every question to two decimal places : 47.Determine the daily copper losses at 450 kVA (kWh) 48.Determine the daily copper losses at 290 kVA (kWh)
4.2 Eskom uses a 1MVA transformer to supply electricity to Willows community. The
electricity cost price is R2.50 per kWh. The load supplied by the transformer varies as
shown below. The purchasing price of the transformer is R350 000. The transformer
has a full load copper loss of 2.2 kW and the iron loss of 4.18 kW.
A certain load varies as follows for 269 days per annum:
550 kVA at a power factor of 0.819 lagging for eleven hours per day.
120 kVA at a power factor of 0.836 lagging for six hours per day.
450 kVA at unity power factor for remaining hours of a day.
For the remaining time of the year, the load varies as follows:
➢ 290 kVA at a power factor of 0.822 lagging for eight hours per day.
➢ 25 kVA at a power factor of 0.866 lagging for eight hours per day.
➢ No load for eight hours per day.
Correct every question to two decimal places :
47.Determine the daily copper losses at 450 kVA (kWh)
48.Determine the daily copper losses at 290 kVA (kWh)
49.Determine the annual cost of iron losses (Rands) .
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