Document oDQ24ZkjYNxG89VEgjorx2BgR

616 CHAPTER 35 , 1946 Guide Typical Specifications for Wound Rotor Motors f208] ________ ....................................RPM, {gjjj Cycles, Volts, ||| Phase, Wound Rotor l55oJ Induction Motors For Driving................................................ Motor Shall Be Arranged for (Application) {vertteal*3*} ^ount`n And Shall Be Provided With A..................................... -.............. ^' (Open, Splashproof, etc.) Type of Enclosure, NEMA Insulation and |g[^!ve| Bearings. Typical Specifications for Synchronous Motors ..............Hp,____ ___ RPM, ......... Per Cent P.F.,............ Volts, |}Phase- {go} Cy**. Belted Synchronous Motors of the Coupled Type for Driving. ^Engine (Application) Motor Shall be Arranged for {vertiVal*3'} OPerat'on ai>d Shall Be Provided With A................................... -............... .....................Type of Enclosure. Motor Shall be Capable (Open, Splashproof, etc.) of Developing A Starting Torque of ............ Per Cent Full Load Torque, A Pull-In Torque of ------------ Per Cent Full'Load Torque, And A Pull-Out Torque of................ Per Cent Full Load Torque. The Motor Field Shall Be Excited From A {Direct Connected Exciter' Belted Exciter Which M-G Set Exciter d-c Bus f^ot} e Inc'uded With The Motor. the power factor. With purchased power, if the rates include a clause embodying a penalty for low power factor, or a bonus for high power factor, the saving in power costs may often make a very good return on . the investment required for the corrective equipment. Synchronous motors are used to drive fans,' blowers, pumps, compres sors and other applications. Compressor applications having a high peak torque require the use of flywheels to smooth out power peaks; and should always be referred to the electrical manufacturer for recommen dations. Synchronous motors are provided with built-in damper windings on the'rotor and operate during the starting period similarly to squirrel-cage . motors. After the motor is nearly up to speed, field excitation is applied and the motor draws into step at synchronous speed. After excitation is applied the motor runs at exactly constant speed and will remain at this speed uiitil a load approaching the pull-qut load is reached, whereupon . the motor pulls out; of synchronism and stops. . In applying synchronous motors consideration must be given to the ' torque the motor can develop on pull-in, that is, at the instant when field Motors and Motor Controls 617 excitation is applied. Table 2 tabulates typical application requirements of synchronous motor drives, listing starting, pull-in, and pull-out torques. Typical specifications for synchronous motors are shown on page 616. Multi-Speed motors provide flexibility in many types of drives. Syn chronous motors can be furnished only with a 2 to -1 ratio-in speed, single winding. Squirrel-cage induction motors may be 2, 3 or 4 speed. Two-speed, induction motors are usually of single winding type, having a 2 to 1 speed ratio such as 600 rpm and 1200 rpm,or may be double . winding. Three-speed induction motors are always two winding,' and four-speed motors are usually two winding with a 2 to 1 speed ratio Table 2. Typical Application Requirements of Synchronous Motor Drives Showing Starting, Pull-In and Pull-Out Torques Application Method of Connecting Motor to Load Starting Conditions Torques Start Pull- Pulling in Out Remarks CO c Exhaust and t Ventilating Coupled or Belted Usually Loaded 50 60-125 150 WR* of Fan Must be Considered Cycloidal Positive CO Coupled or Engine Type 41 Blowing Engines O Reciprocating Engine Type Unloaded Unloaded 40-60 40-60 150 Two-Speed Motors Sometimes Used 40 40-60 150 Turbo High Speed Direct Connected or Step Up Gear' Unloaded 30 (Intake Closed) 50 150 WR} of Blower Must be Considered iAir Engine Type Unloaded 40 40 150 Flywheel Effect Important Ammonia and High Speed--Belted Unloaded 40 40 150 Flywheel Effect O Ammonia 3 LO.f Booster Low Speed--Engine Type (By By-Pass) Occasionally Coupled Important ` 6o Freon U High Speed--Belted Low Speed--Engine Unloaded 45 60 150 Flywheel Effect (By By-Pass; Important Gas High Speed--Belted Reciprocating - ' Low Speed--Engine - Unloaded 40 40 150 Flywheel Effect (By By-Pass) 'Important