When appliances are first turned on, they often draw more electricity than when they are running continuously. This initial surge in electricity consumption is known as "inrush current" or "starting current," and it occurs due to several factors:
Charging Capacitors: Many appliances, such as motors, compressors, and electronic devices, use capacitors to store electrical energy temporarily. When the appliance is switched on, these capacitors need to charge up quickly to provide the initial power required to start the device. This charging process demands a higher current draw from the electrical supply.
Motor Starting: Appliances with electric motors, like refrigerators, air conditioners, washing machines, and vacuum cleaners, require higher current to overcome the inertia and start the rotation of the motor. Once the motor is up and running, it requires less power to maintain its operation.
Cold Resistance: Some appliances, particularly those involving heating elements (e.g., ovens, toasters), experience a temporary increase in resistance when they are cold. Higher resistance means they draw more current until they heat up to their operating temperature, after which the resistance decreases, leading to a decrease in current draw.
Magnetic Induction: Inductive loads, like transformers and certain motors, produce a higher inrush current due to the magnetic properties of their coils. This is a transient phenomenon that occurs when power is first applied to the inductive load.
It's essential to consider these inrush currents when designing electrical systems and selecting circuit breakers or fuses. Circuit breakers need to be rated to handle the momentary surge in current during appliance startup without tripping unnecessarily.
While the inrush current can be significant for a brief moment, most appliances are designed to handle these higher loads without causing any harm to the electrical system. Once the appliance reaches its steady-state operation, the power consumption returns to a more typical level.