3. Example
A 1kW heater is connected to a 240V supply.
Find the total current taken from the supply
when:
(a) the power factor is one (heater only)
(b) the power factor is 0.7 (caused by
reactance in parallel with the heater)
(c) the power factor is 0.3 (caused by a higher
value of reactance).

4. I = P
VcosΦ

5. I =
1000 = 4.17 A
240 x 1
Answer: when power factor is =
1.0 then I = 4.17A.

6. I =
P
VcosΦ
I =
1000 = 5.95 A
240 x 0.7
Answer: when power factor is =
0.7 then I = 5.95 A

7. I =
P
VcosΦ
I =
1000 = 13.88 A
240 x 0.3
Answer: when power factor is =
0.3 then I = 13.88 A

11. when pf = 1
apparent power (S) = 240 x 4.17
= 1000 VA (1 kVA)

12. when pf = 0.7
apparent power (S) = 240 x 5.95
= 1428 VA (1.43 kVA)

13. when pf = 0.3
apparent power (S) = 240 x 13.88
= 3331 VA (3.3 kVA)