When rewinding the exciter rotor for a synchronous motor or alternator, avoid the common mistake of assuming the exciter poles are the same as the main rotor poles. First, count the stationary exciter field coils. The exciter rotor must be wound for the same number of poles as the exciter fields. Second, divide slots by poles to make sure the coil pitch passes the sanity check and to avoid future confusion for others. If the exciter rotor has half as many coils as slots, convert it to a conventional lap winding just as you would do for a conventional stator.