In electrical design, the use of fuses as distribution line protection, many electrical designers often aR, gG ,gL, aM type fuse confused use, resulting in the distribution line can not be effective protection. So what do these symbols mean?

These symbols represent the operating class of the fuse.

Fuses are classified according to their function. In this case, the first letter indicates the functional class, and the second letter indicates the object to be protected.

Letter 1
a Partial range protection (back-up fuse)
g Full-range protection (general-purpose fuse)

Letter 2
G Cable and conductor protection (general application)
M Switching appliance protection (protection of motor circuits)
R Semiconductor protection (for rectifier protection)
L Cable and conductor protection (according to DIN VDE)

gL (DIN VDE)/gG (IEC) Full-range cable and conductor protection
aM (DIN VDE/IEC) Local range motor circuit protection
aR (DIN VDE/IEC) Localized semiconductor protection
gR (DIN VDE/IEC) Full range of semiconductor protection