Why DC motors have open slots?

DC overvoltage test to a minimum of 29 kV Winding resistance measurement Stator slot wedge tightness Stator core low energy stator core flux

it was an economically produced item with no longevity built into it when it was manufactured Note the lack of slot wedges and slot insulation

slot lotus The use of slot wedges made of magnetic material in a synchronous and induction motor or generator makes Wedges for Stator and Rotor Slots of DC Motors

slot bonus 100 to 3x In this context, the opportunity to employ magnetic or semi-magnetic wedges in surface-mounted permanent magnet machines with fractional-slot concentrated