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A book about electrical machines states as below

what happens in a generator of this sort when the load is increased? When
the load supplied by the generator is increased, IL (and therefore IA) increases. As
the armature current increases, the lARA drop increases, so the terminal voltage of
the generator falls.

What I don't understand is what is meant by increasing the load? If the load is increased shouldn't the current through it (IL) decrease? How can IL increase when the load is increased?

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  • \$\begingroup\$ Load increases = load resistance decreases, load -power- and -current- increases. \$\endgroup\$
    – Pentium100
    Commented Jun 5, 2013 at 13:57
  • \$\begingroup\$ @Pentium100 how can the load resistance decrease? what is the connection between increasing the load and decreasing the load resistance \$\endgroup\$
    – DesirePRG
    Commented Jun 5, 2013 at 14:02
  • \$\begingroup\$ Some are compound wound, with a series winding to help correct for increased load and additional line loss. \$\endgroup\$
    – Optionparty
    Commented Jun 5, 2013 at 14:18
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    \$\begingroup\$ @DesirePRG, it's just a term. High load = the generator has to work hard to power it, that means that the power output is high. Conversely, low load means that the generator does not have to work as hard = lower power. If the voltage is constant then higher power means higher current and lower resistance. Say you connected a second device to the output of the generator - that means the generator has to supply more power and that the total resistance of the load (both devices in parallel) is lower. \$\endgroup\$
    – Pentium100
    Commented Jun 5, 2013 at 14:42
  • \$\begingroup\$ @Pentium100 You should make this an answer. \$\endgroup\$
    – Pablo Maurin
    Commented Jun 5, 2013 at 16:26

3 Answers 3

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"Load" is a term for how hard the device has to work to power whatever is attached to it. "High load" means the output power is high, "low load" means the output power is low. You can increase the load by, say, connecting a second device to the output of the generator. Assuming the voltage is constant, the current will be higher (since there are now two deices powered by the generator). That means that the equivalent resistance of both deices in parallel will be lower than that of a single device.

So, increasing the load means decreasing the resistance of the load. This may be counter intuitive, but usually devices are not rated in resistance - they are rated in input current or power, so the "load" follows that. If I have a 1kW load attached to the power supply and now increase it to 2kW, the current will increase (assuming the voltage stays constant).

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The 'load' is the power drawn from the generator. Once you get that definition, the rest should be clear.

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When load is increased the armature current is increased and the terminal voltage and speed decreased due to the voltage drops in the armature resistance and armature reaction

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