Abstract: A commutatorless direct current motor drive system that initiates rotation of a permanent magnet rotor from standstill upon the application of supply potential and then sustains rotor rotation by sequentially energizing the polyphase stator phase windings in response to the alternating current potential waveforms induced in the stator phase windings by the magnetic field of the permanent magnet rotor upon rotor rotation.

Abstract: A valve assembly in an air brake truck system which meets minimum response time specifications required by authorities and the maximum response rate required by the wheel lock control system for efficient operation. The valve assembly varies the effective orifice size between the air supply inlet and the outlet to the relay valve. The high minimum specified rate is provided for a short period of time for initial response and the lower maximum rate for efficient operation is provided for the remainder of the stop. The valve assembly has a timing section and a variable orifice section.