Terminal Block Selection: Accurate Selection Based On Parameters Such As Current And Voltage
Terminal blocks are the core components of electrical connections, and their selection requires comprehensive consideration of current, voltage, environment, and mechanical parameters to ensure connection reliability. The following is a precise selection guide based on key parameters:
1、 Current parameters: Core carrying capacity
Rated current (In)
The selection should be based on the maximum continuous operating current of the circuit, with a 20% -30% margin reserved. For example, if the circuit design current is 20A, terminals with a rated current of ≥ 25A should be selected (such as Phoenix PT1.5/X series, rated 24A).
Attention: When multiple wires are connected in parallel, the current carrying capacity should be calculated based on the total cross-sectional area after parallel connection to avoid local overheating.
Temperature rise control
The temperature rise of the terminal at rated current should be ≤ 55K (when the ambient temperature is 40 ℃, the surface temperature of the terminal should not exceed 95 ℃). If the ambient temperature is high or the ventilation is poor, the rated current needs to be reduced (such as when the ambient temperature is 60 ℃, the rated current needs to be reduced to 80%).
2、 Voltage parameters: insulation and withstand voltage guarantee
Rated voltage (Un)
It needs to be higher than the maximum operating voltage of the circuit. For example, a 220V AC circuit should choose terminals with a rated voltage of ≥ 300V (such as the Weidmuller TOPJOB series, rated at 690V).
Key point: Special DC terminals should be selected for DC circuits, as DC arcs are more difficult to extinguish and require higher insulation materials.
Impact withstand voltage (Ui)
It is necessary to meet the transient overvoltage that may occur in the system (such as lightning strikes and switch operations). For example, industrial control systems need to select terminals with impulse withstand voltage ≥ 6kV (in accordance with IEC 60664-1 standard).
3、 Adaptation of environmental and mechanical parameters
Protection level (IP)
Outdoor or humid environments require IP65 or higher rating (such as Wanke 221 series, IP68 protection) to prevent dust and moisture from entering and causing short circuits.
temperature range
Wide temperature terminals should be selected for extreme temperature environments. For example, outdoor equipment in the north needs to choose terminals with a temperature range of -40 ℃ to+105 ℃ (such as the Phoenix UT series).
vibration and shock
Anti vibration terminals (such as the Weidmuller SAKDU series, which have passed the IEC 61373 vibration test) should be selected for scenarios such as rail transit and engineering machinery.
4、 Selection Example
Home distribution box: 20A/220V circuit, choose Phoenix PT1.5 (rated 24A/400V, IP20).
Industrial control cabinet: 10A/380V three-phase circuit, choose Wanke 2273 series (rated at 24A/690V, IP65).
New energy vehicle battery pack: 200A/600V DC circuit, choose Taike EV series (rated 250A/900V, IP6K9K).
Tip: After selection, it is necessary to conduct type tests for verification, including salt spray tests (in coastal areas), thermal cycling tests (in high temperature environments), etc., to ensure long-term reliability.
