@@jaacoblosov7327 They look identical yet motors are not. 4 pole in most subway cars of this kind, yet 6 pole in Warsaw metro, model 81-572/573. That is what gives it this distinctive dissonant motor sound.
81-572/573 indeed have different motors from 81-717.3, 6 coil motors instead of 4 coil motors like here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-DSUlW8Ysu7Q.html it is not an additional motors but having 2 additional coils on stator causes that dissonant sound. 6 as opposed to 4 stator coils reduces top speed by 1.5x times but increases acceleration and ability to climb slopes 1.5 times given other things being equal. Compare this (in most Eastern Bloc metro trains), 4 coil motor, refer to the right picture www.electronics-tutorials.ws/wp-content/uploads/2013/08/io31.gif In Warsaw 81-572/573 trains motors are approximately like this previews.123rf.com/images/efes/efes1303/efes130300041/18702692-dc-motor-6-poles.jpg
