HDD Spindle Motor
The hard drive spindle motor is three-phased which provides stability of magnetic disks rotation mounted on an axis (spindle) of the engine. The stator of the engine has three windings included by a star with the tap in the middle, and a rotor contains a permanent section magnet. To provide small palpation on big turns, hydrodynamic bearings are used in the engine.
The start of the spindle motor is made after full internal diagnostics of the hard drive. At first spindle motor is spun in the forced mode without the analysis of rotation speed of magnetic disks; therefore, the computer power supply should have a reserve of peak power, and after the removal of magnetic heads from the parking zone the speed of rotation is controlled by a servo marking signal, recorded at store manufacturing. Electronics marks out servo marks located between sectors from the general stream of the readout data and stabilizes the constant speed of rotation according to them. Stability of rotation is especially important with the increase of density of data recording on a magnetic surface of disks.
The speed of rotation of magnetic disks is one of the major characteristics of the performance of a hard drive. Its increase reduces the time necessary for information search and increases the speed of reading and record. Usually, the speed of rotation of magnetic disks in disk drives with PATA and SATA interface is from 4200 to 10000 revolutions per minute, and inexpensive server systems of data storage (SCSI) it reaches 15000 turns. The increase in the speed of rotation is limited by a problem of the high thermal emission and cost of manufacturing of qualitative bearings. Disk drives with the speed of rotation of magnetic disks of 7200 revolutions per minute and above require the application of a computer case with the thought-out design of passive cooling or the use of the system of active cooling of hard disks drives.