Main circuit parameters:
Rated voltage: The voltage level that the cabinet is designed to work at (such as: 380V AC, 400V AC, 415V AC, 690V AC, 220V AC, 110V AC, etc.). It must match the power supply grid and motor voltage.
Rated current: The maximum operating current that the main circuit (contactor, circuit breaker, thermal relay main terminal, etc.) can safely carry for a long time. Usually selected according to the rated current of the controlled motor, and a certain margin is left (such as 1.2-1.5 times the rated current of the motor).
Short-time withstand current: In the event of a short circuit fault, the main circuit components (especially the circuit breaker) can withstand the maximum short-circuit current (unit: kA) without damage within a specified time (such as 1 second).
Rated frequency: Usually 50Hz or 60Hz.
Controlled motor power: The maximum motor power that the cabinet can safely and reliably control (unit: kW or HP). This is determined by the rated voltage, rated current and heat dissipation capacity.
Control circuit parameters:
Control voltage: The working voltage (such as AC 220V, AC 110V, AC 24V, DC 24V, DC 48V, etc.) provided to the control circuit (contactor coil, relay, indicator light, PLC, etc.). Usually converted from the main circuit through a control transformer or switching power supply.
Control current: The working current requirement of the control circuit components (mainly contactor coils).
Protection level: The level of protection of the cabinet shell against the intrusion of solid foreign objects and liquid splashing (such as IP20, IP54, IP65, etc.). IP20 is often used inside the distribution room, and IP54/IP65 is used in industrial sites where dust or water spray may occur.
Core component parameters:
Main contactor:
Rated working current/voltage.
Coil voltage.
Electrical life (number of operations).
Mechanical life (number of operations).
Protection circuit breaker/fuse:
Rated current (In).
Breaking capacity (Icu/Ics).
Tripping characteristics (e.g. D type for motor starting).
Thermal relay:
Setting current range (must cover motor rated current).
Tripping class (e.g. Class 10, Class 20 - indicates the time of tripping after overload).
Whether it has phase loss protection.
Auxiliary components: Voltage and current specifications of buttons, indicator lights, terminal blocks, etc.
Function parameters:
Control mode: Local (buttons on the cabinet), remote (terminal block wiring), automatic (PLC/DCS signal control).
Protection function: Standard: short circuit protection (circuit breaker/fuse), overload protection (thermal relay/motor protector), undervoltage protection (contactor characteristics). Optional: phase loss protection (integrated in thermal relay or separate relay), stall protection (motor protector required).

Starting characteristics:
Large starting current: This is the most significant feature. The starting current is usually 5-8 times (or even higher) the rated current of the motor. It will cause an impact on the power grid, which may cause a voltage drop and affect other equipment on the same power grid.
Large starting torque: The starting torque is about 1.5-2.5 times the rated torque. This is an advantage for loads that require high starting torque (such as crushers and compressors that start with load), but it is too large for light loads such as fans and water pumps.
Short starting time: Since it is full-voltage input, the motor accelerates quickly and the starting time is usually completed within a few seconds (depending on the load inertia).
Structural characteristics:
Simple: Few core components (circuit breaker/fuse + contactor + thermal relay + button indicator light) and compact structure.
Reliable: Mature component technology, few failure points, and high reliability.
Low cost: Low component cost, simple cabinet structure, and lowest overall manufacturing cost and maintenance cost.
Easy to maintain: The structure is clear, and component replacement and troubleshooting are relatively easy.