Electric Loads - Classification and behaviour

Load - Definition

An Electrical Load is any device or component that taps energy from an electrical network.  Examples of domestic loads are domestic appliances, such as bulbs, fans and air conditioners.  Industrial loads include motors, heaters and lighting loads.

Electric loads have a range of power ratings from very low bulbs to motors which draw megawatts of power.

The vast majority of electric loads are motor loads.  The following is a classification of the types of electric loads and their quantity.

Motor devices                     - 70%
Heating and lighting loads  - 25%
Electronic devices               - 5%

Sensitivity to voltage and frequency variations

Loads are sensitive to both voltage and frequency

Motor loads are sensitive to both frequency and the voltage variations. A change in the frequency can cause the motor speed to increase or decrease.  Motor speed is directly proportional to the frequency.

When the voltage drops, a motor draws more current.  The power drawn varies as the square of the voltage.  Power is proportional to V2

Loads can be further classified based on the size, number of phases (single or three phase), and the duty cycle (constant use or intermittent use)