San (letter) San (letter) San (Ϻ) was an archaic letter of the Greek alphabet. Its shape was similar to modern M, or ϡ, or to a modern Greek Sigma (Σ) turned sideways, and it was used as an alternative to Sigma to denote the sound . Unlike Sigma, whose position in the alphabet is between Rho and Tau, San appeared between Pi and Qoppa in alphabetic order. In addition to denoting this separate archaic character, the name "San" was also used as an alternative name to denote the standard letter Sigma. The existence of the two competing letters Sigma and San is
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