In case of power adapter ( step-down) transformers, :?

In case of power adapter ( step-down) transformers, is it correct to say that current drawn from secondary winding should not affect the current drawn by primary from mains supply ?... if not why ?

In other words, power consumption of a device should totaly be determined by primary winding only and not by secondary winding and circuit connected to it. Is this correct ?

6 Answers

  • Anonymous
    1 decade ago
    Favorite Answer

    This is not correct. Increased current in the secondary winding creates increased current in the primary winding. A transformer is an inductive load. Basically, a larger current draw in the secondary winding reduces the inductance of the transformer allowing more current in the primary winding. If a transformer has no load in the secondary the primary coil will draw minimum current. As the secondary load increases the primary current increases to the point that it either overheats and fails or the minimum inductance prevents increased current.

    This is always true except for one situation, a transformer with a constant voltage output. These transformers are special and used only in situation where you want to stabilize the voltage. They work by saturating the core of the transformer. A capacitor is added to a saturating winding. This prevents changes in the voltage applied to the primary winding from causing a voltage change in the secondary winding. Current draw in the primary winding is constant because the core is saturated magnetic flux wise so increased current in the secondary winding won't cause increased current in the primary winding. The transformer can still only deliver so much power. This type of transformer isn't very efficient.

  • 1 decade ago

    1. The current drawn from the primary is directly proportional to the current drawn by the secondary.

    2. Current consumption is determined by the load (device) impedance or the current drawn by the device. The winding(s) has nothing to do with power consumption.

  • 1 decade ago

    It trasnforms both current and voltage. The more current drawn from the secondary the more drawn by the primary. A transformer with a 120V primary and 12V secondary, with a 1A load applied to it, will draw 100ma plus any current lost in the process.

    Power consumption of a device is what the device will draw to work.

  • ?
    Lv 6
    1 decade ago

    Wires has the best answer. A load on the secondary will

    cause the primary to draw (demand) more current to meet

    the loads' demand for operation. Power consumption of the

    Transformer is determined by the load on the secondary.

    Directly proportional. A power transformer will produce heat

    because of eddy currents in the iron lamination. Laminating

    of pieces of iron is used to reduce the effects of these eddy

    currents as opposed to a solid piece of iron. I hope this will

    be of an easier understanding and a better answer.

    Source(s): > 36 yrs. Electronic Experience.
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  • dinovi
    Lv 4
    4 years ago

    First attempt putting a load (like a 12v automobile interior or brake lamp)on that 19V 3A adapter and degree the voltage. maximum less costly adapters are basically a transformer and a bridge rectifier, so the output voltage is going to the height fee of the AC out, really of RMS, at the same time as that is unloaded. Any furnish it extremely is marked for 3 amps or extra and 12-20 volts DC out might want to desire to do the activity for you although because all that is doing is performing as enter to the interior, nicely-regulated, potential furnish. make positive you get the polarity proper.

  • Anonymous
    1 decade ago

    no, "power in = power out".

    If your load is 100 watts (on the secondary) the draw on the primary is 100 watts (plus any losses, efficiency etc)

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