Large scale experience with industrial stepping motor controllers and resolver read-out systems at SPS and LEP

Over three hundred stepping motors and two hundred resolvers are used for Beam Instrumentation purposes in SPS and LEP. Most of these instruments are beam intercepting and therefore require very reliable drive electronics. The coincidence of the upgrading of the SPS controls and of the energy upgrade of LEP was the ideal opportunity to standardise the motor control systems for both accelerators and to acquire an industrial system which would fulfil the requirements for the two machines in the most economical way. The interface to the control system had to be compatible with different environments, currently PCs in the SPS and VME crates in LEP and probably other systems in the future. The project was handled as a farming-out project with CERN producing a detailed functional specification and the hardware development being entirely under the responsibility of industry. The first set of motors and resolvers has been equipped with the new control systems and has been running for more than one and a half years without failures. Details of the hardware, software and EMI measurements, and present experience with the system are presented.