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694 CHAPTER 35 1949 Guide Table 10. Typical Specifications fob Wound Rotob Motor. Control^ , Control for Wound Rotor Motor Control for .. Applications Shall Consist of a Safety (Fan, Pump, etc.) Disconnect Switch, a Mounted Across the Line Starter Providing Over- load Protection, Low Voltage {r^1011}, and a Secondary {Ipe^Re^ilating} GontroUerforf^^^^o^J. primary and Secondary Contrdl Shall Be Interlocked so as to Provide Complete Control from the Rheostat "Handle. Table 11. Typical Specifications for Synchronous Motor Control Synchronous Motor Control for..................................... Motors Shall Provide for (Application) SSduSd^tage} Starti"S andSha11 Be {S&t}- CBedi^d Voltage Autotransformers Starting Shall Be Obtained by Means of * Resistors And Shall Limit Reactors The KVA Inrush to a Maximum of___ per cent of Full Load KVA.) The Control Panel Shall Be For {^bboard} A-nWy And Shall Be of Construction. It Shall Provide Overload, Under Voltage Protection And After Pull- ing Out of Step Will g-^onUe} The Motor., . Table 12. Typical Specifications fob Single Phase Motor Control Control For Single Phase............................... ................Motors: Shall Consist ^of a (Fan, Pump, etc.) {Magnetic} Type {R^uced VoltTge) Starter Providing Overload Protection (And Low Voltage); And A Separate Safety Disconnecting Switch. ' .. high motor power factor and efficiency. The gearing efficiency is also high, usually about 98 per cent for a single reduction of the helical or spur type, that is, a 2 per cent loss for one reduction or 4 per cent loss for a double reduction. Consequently, the over-all performance of'the gear' motors is much higher than a combination of open gearing; belting,: countershaft, or other arrangement, which would otherwise be required;: Gear motors are used extensively to drive numerous types of slow speed drives. Besides being more effective than other combination drives in: saving space, they are important in reducing maintenance and operating hazards.' ' . '' = = ': Motors and Motor Controls' LINE 12 COMBINATION LINESTARTER LINE 695 ' tINE 2 MANUAL STARTER Fig. 12. Recommended Controls for Wound Rotor Motors Arrangements 2, 3 and 4 are optional for motors up to 71 hp, 220 volts. Fig. 13. Recommended Controls for Single Phase Motors GLOSSARY General Definitions - NEMA is the abbreviation for the National Electrical Manufacturers Association. Speed Regulation (d-c motors) is the change in speed between no-load and full-load,' expressed in per cent of full-load speed; for example, a motor having a no-load speed of 1200 rpm and a full-load speed of 1140 rpm would.have a speed regulation of 5.6 per cent. Slip (a-c induction motors) is the difference between the motor speed and syn chronous speed expressed in per cent of synchronous speed, e.g., a 1200 rpm motor operating at 1140 rpm would have a slip of 5 per cent. Torque is an expression of the turning effort developed by the motor at the shaft and is usually expressed in ounce-feet for fractional horsepower motors and in poundfeet for motore of larger ratings. Primary is the term usually applied to the high voltage or line side of a transformer or motor. In the case of the wound rotor motor the primary iR the stator, winding. Secondary is the term usually applied to the low voltage or load side of a trans former or motor.. In the case of the wound rotor motor the secondary is the rotor winding. ? ^ NEMA Classification of Motor Enclosures Open motors (40C rise, rated load, 50 C rise, service factor load) are self-ventilated machines having no restriction to ventilation other than that necessitated by me chanical construction. Protected motors (50 C rise) have all ventilating openings in the frame protected by perforated covers. Semi-Protected motors (50 C rise) have the ventilating openings in the top half of the frame only protected by perforated covers. Drip Proof motors (50 C rise) are so constructed that drops of liquid or solid par ticles falling on the machine at any angle not greater than 15 deg from the vertical' cannot enter the machine either directly or by striking and running along a hori zontal or inclined surface. ,. Splash Proof motors (50 C rise) are so constructed that drops of liquid or solid particles falling on the machine or coming towards it in a straight line at any angle not greater than 100 deg from the vertical cannot enter the machine either directly or by striking and running along the surface.