If the secondary of a transformer is left open-circuited (Figure 6), primary current is very low and is called the no-load current. No-load current produces the magnetic flux and supplies the hysteresis and eddy current losses in the core.
The no-load current (IE) consists of two components: the magnetizing current (Im ) and the core loss (IH). Magnetizing current lags applied voltage by 90°, while core loss is in phase with the applied voltage (Figure 1b). VP and VS are shown 180° out of phase. IH is very small in comparison with Im , and Im is nearly equal to IE . No-load current, IE , is also referred to as exciting current.
Figure 1 : Open-Circuit Secondary
Example:
When the secondary of a 120/440 V transformer is open, primary current is 0.2 amps at a PF of .3. The transformer is a 5 kVA transformer. Find: (a) IP , (b) IE (c) IH , and (d) Im
Solution :
(a) Full Load Current = KVA Rating / Vp
(b) IP at no load current is equal to IE
(c) IH = IE Cos θ = IE x PF
IH = 0.2 x 0.3 = 0.06 amps
(d) Im = IE Sin θ
θ = across 0.3 = 72.5°
Im = 0.19 amps
The conveyor sorting machine is widely used in the packing industries using the PLC program…
Learn the example of flip-flop PLC program for lamps application using the ladder logic to…
In this article, you will learn the STAR DELTA programming using PLC controller to start…
Lube oil consoles of rotary equipment packages in industrial process plants are usually equipped with…
Rotating equipment packages such as pumps, compressors, turbines need the lube oil consoles for their…
This article explains how to blink lights in ladder logic with a detailed explanation video…