(1) Heating element loads: The current of a wire-wound resistive element can reach 1.4 times its rated value after being energized (e.g., heating/air conditioning equipment). If the grid voltage increases by 10%, the current will increase significantly. Thorough analysis is required to select the appropriate contactor rated current.
(2) Lighting devices: The inrush current of an incandescent lamp reaches 15 times its rated current when switched on. The current increases dramatically when the voltage increases by 10%, classifying it as AC-5b. Other lighting fixtures are classified as AC-5a due to their inrush current value, starting time, and power factor ≠
(3) Low-voltage transformer loads: The peak current reaches 15-20 times its rated value when switched on (related to winding and core characteristics). For example, during a short circuit operation on the secondary side of a welding machine transformer, the primary side switch bears strong current stress.
(4) Capacitor loads: The transient charging current is extremely high when switched on, accompanied by high-frequency oscillations, placing stringent requirements on electrical switches.
(5) Motor load: Wound-rotor motors belong to AC-2 category (rotor circuit resistance limits current, and starting time is extended as the load increases); squirrel-cage motors have an effective value of 4 to 8 times the impact current when starting directly, and the current becomes steady-state after decay.
