Can isolation switches in low-voltage electrical systems operate with normal load current while carrying load?
First, let's take a look at the definition of the standard 50054 term:
2.0.34 Isolation switch - a switch that can meet the isolation requirements of the isolator when in the disconnected position.
2.0.35 Isolation Electrical Device for Isolation Electrical appliances with isolation function.
Article description: From 2.0.33 to 2.0.36, we used to classify low-voltage switchgear into three categories: isolating switches (unable to connect and disconnect load current and short-circuit current), load switches (unable to connect and disconnect short-circuit current), and circuit breakers (able to connect and disconnect load current and short-circuit current). However, this classification has changed in the product standards, and can now be explained using Table 1 of the "Summary Table of Electrical Device Definitions" in the current national standard "Low Voltage Switchgear and Control Equipment Part 3: Switches, Isolators, Disconnectors, and Fuse Combination Electrical Appliances" GB14048.3-2008 (equivalent to IEC 60947-3:2005):
From the definition of electrical appliances and this table, it can be seen that switch devices that only have isolation function are called "isolators"; A "switch" is a switching device that can connect load current, short-circuit current, and disconnect load current but cannot disconnect short-circuit current; A switch with isolation function is called an "isolation switch". Switches, isolators, and isolating switches can be combined with fuses to form a fuse combination electrical device.
First, let's take a look at the definition of the standard 50054 term:
2.0.34 Isolation switch - a switch that can meet the isolation requirements of the isolator when in the disconnected position.
2.0.35 Isolation Electrical Device for Isolation Electrical appliances with isolation function.
Article description: From 2.0.33 to 2.0.36, we used to classify low-voltage switchgear into three categories: isolating switches (unable to connect and disconnect load current and short-circuit current), load switches (unable to connect and disconnect short-circuit current), and circuit breakers (able to connect and disconnect load current and short-circuit current). However, this classification has changed in the product standards, and can now be explained using Table 1 of the "Summary Table of Electrical Device Definitions" in the current national standard "Low Voltage Switchgear and Control Equipment Part 3: Switches, Isolators, Disconnectors, and Fuse Combination Electrical Appliances" GB14048.3-2008 (equivalent to IEC 60947-3:2005):
From the definition of electrical appliances and this table, it can be seen that switch devices that only have isolation function are called "isolators"; A "switch" is a switching device that can connect load current, short-circuit current, and disconnect load current but cannot disconnect short-circuit current; A switch with isolation function is called an "isolation switch". Switches, isolators, and isolating switches can be combined with fuses to form a fuse combination electrical device.
Summarize two knowledge points:
In the past, we used to classify low-voltage switchgear as isolating switches that could not break load currents. However, this classification has changed in product standards. It can be seen that isolating switches are a combination of "isolators+switches" that can break load currents, that is, they can operate with loads
We must pay attention to the legend symbol in the design, which includes a circle and a vertical (or horizontal) graphic symbol. If there is no small circle, the vertical (or horizontal) graphic symbol is the isolation switch. Do not use the symbol of the isolation switch instead of the symbol of the isolation switch in the design.