The numerical suffix appended to the class designation indicates whether or not grid current flows in any appreciable portion of the cycle.
数值后缀附加到指定表明阶级与否电网目前的流量在任何可观的一部分周期。
2
For small fields, air is a good insulator-electrons attach to oxygen atoms faster than they are knocked loose by collisions-and electric current cannot flow in any appreciable amount.