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842 CHAPTER 39 1951 Guide Table 5. Classification of Motors POWEB Ttpb Speed Full. Voltage Starting Torque Starting Current Hp Range Ttpb of Application See Footnote! Constant Speed Drives d-e Polyphase Single phase a-o 1. Shunt Constant Normal Normal (with controller) All (o) Fans and (e) centrifugal pumps and centrifugal compressors 3. Compound Variable Hlrh Normal (with controller) All (6) (c) () Recipromtinff mimm and frequent or hard starting 3. Series Variable High Normal (with controller) Small (d) Fans directconnested 4. Squirrel-cage gwnoml pilN poee Design A Constant Normal 1- High 6-8 2.5 times times All (a) Fans and (c) centrifugal pumps and centrifugal compressors 6. Squirrel-cage Constant Design B Normal 1- Normal 6-6 Medium 216 times Small (a) Fans and centrifugal pumps and centrifugal compressors 6. Squirrel-cage Constant Design C High 2-2J Normal 5-6 Medium tunes . times Small 9) Reciprocating pumps () and eompressors started loaded 7. Wound rotor Constant or High 1-2.6 Low 1-3 All variable times tames (with secondary oontrol) (o) Hoists (5) reciprocating pumps and compressors (c) and frequent () or hard start 8. Synchronous Exactly eon- Normal high speed stant 0.76-1.75 times Normal 6-7 Medium times Large (a) Fans and centrifugal pumps and eentrifugal compressors 0. Synchronous- Exactly ooh- Low 0.3-0.4 Low 3-4 Medium low speed stant. times -times Large (a) Reciprocating compressors starting unloaded 10. Two value ca- Constant padtor Normal' Small (6) Pumps and compressors 11. Permanent Constant split capaci tor Low Normal Fractional (a) Fans, Blowers 13. Capacitor start Constant Moderate Normal Small Frao- (a) Fans and tional pumps 13. Repulsion In- Constant duetion High 14. Split phase Constant Normal and ad- justable Normal Normal Medium Small Fractional (a) Fans (6) pumps and compressors (o)Fans (6) pumps and compressors (d) fans--direct t Applications: . Drives having medium or low starting torque and inertia (WR*) such as fans and centrifugal pumps or reciprocating.pumps and compressors started unloaded. . Drives having.high starting torques, such as reciprocating pumps and compressors started loaded.- - e. Similar to (a) except where frequent orhard starting (large WR*) requires a higher starting and accelerat ing torque. - 4. Fans direct connected, . e. Stoker drives. Motors and Motor Controls 843 Powsb Table 5. Classification of Motors--(Concluded) Ttpb Speed* Characteb- istzcs Full Voltage Starting Torque Starting Current Hp Range Ttpbof See Footnote! Adjustable Speed Drives 15. Shunt field Constant adjustment d-C 16. Armature re Variable sistance ad justment Normal ^ | Normal (with oc ntroller) I Normal Normal (with ocmtroller) All All (a) Fans and () centrifugal pumps (a) Fans and () centrifugal pumps 17. Variable vol Constant tage control 18. Squirrel-cage high sup. Transformer adjustment Variable Normal Normal (with oo ntroller) Normal Normal All Medium irmul] (d) Fans and centrifugal pumps (a) Fans Poly phase a-e 19. Squirrel-cage separate winding or regrouped poles' Constant multi speed Normal or Normal or An high low (a) Fans (b) pumps and (e) compressors 20. Wound rotor Variable High Low au (with seoondi ,ry control) . (o) Fans (6) centrifugal pumps and compressors 21. Repulsion Variable High Single Phase. a-o 22. Capacitor low torque tapped winding 23. Capacitor tow torque transformer adjustment Variable two speed Variable Low Low Normal Normal Low and (o) Fans, centrif Fractional ugal pumps' (b)oompreesors Fractional (d) Fans, direct Low Fractional (d) Fans 24. 8ptit phase regrouped poles --' Constant Normal Normal Fractional (d) Fans from 15 min to 2 hr, depending on the size), the horsepower rating required will usually not be less than this constant value, regardless of other parts of the cycle. If the driven machine is to operate at more than one speed, the horsepower re quired at each speed must be determined.. 4. Torqite. The torque required to operate the driven machine at every moment between initial breakaway and heal shutdown is important in determining the type of motor. .A torque-speed curve is desirable and sometimes essential. x The starting torque or breakaway torque required by the driven machine may be as low as 10 percent, as in the case of medium-sized centrifugal pumps, or as high as 225 to 250 percent of full-load torque, as in the case of a loaded reciprocating two- cylinder compressor. The breakaway torque may vary greatly at different times because of frequency of start, temperature changes, type and amount of lubricant, etc. The motor torque available at the shaft must be well above the torque requirea by the driven machine, taking into consideration these variables as well as the pos sibility of low voltage and the type of starter used. The torque required after breakaway for acceleration to full speed varies with dif ferent driven machines, remaining at a rather high value throughout acceleration for such-machines as loaded compressors and plunger pumps. The torque delivered by the motor must at all points, up to full speed, be in excess of the torque required