Romanization of Greek Greek numerals which employed the entire alphabet, including the nonstandard letters digamma, stigma, or sigma-tau (placed between epsilon and zeta), koppa (placed between pi and rho), and sampi (placed after omega). As revised in 2001, ELOT 743 provides for the uncommon characters to be given (in Greek) as $ for stigma, + for koppa, and / for sampi. These symbols are not given lower-case equivalents. When used as numbers, the letters are used in combination with the upper "keraia" numeral sign ⟨ʹ⟩ to denote numbers from 1 to 900 and in combination with the lower "keraia" ⟨͵⟩ to denote multiples
Cogging torque however, at high speed the motor moment of inertia filters out the effect of cogging torque. A summary of techniques used for reducing cogging torque: Almost all the techniques used against to cogging torque also reduce the motor counter-electromotive force and so reduce the resultant running torque. A slotless and coreless permanent magnet motors does not have any cogging torque. Model railway motors usually have a 2-pole permanent magnet and 3, 5 or 7 poles on the armature to reduce cogging torque. Cogging torque Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets