API St 547:2005 pdf download
API St 547:2005 pdf download.General-purpose Form-wound Squirrel Cage Induction Motors-250 Horsepower and Larger.
Note: When motors supplied under this standard are to be applied on a non-sinusoidal source and/or an adjustable speed application, the manufacturer should be consulted to determine if the motor will operate successfully over the required speed range. Refer to NEMA MG 1 Part 30. Proper selection of the motor and drive is required to avoid the following conditions:
I. Motor rms current exceeding the continuous sinusoidal nameplate rating due to excessive voltage harmonics or improper volt/hertz levels.
2. Excessive winding temperature due to insufficient cooling, excessive torque levels, or improper volt/hertz levels; and increased losses due to harmonics.
3. Insufficient motor accelerating torque at reduced speeds due to insufficient volt/hertz levels or limitations in the drive’s short- time current capacity.
4. Increased noise levels due to increased fan noise (above base speed), excitation of mechanical resonances, and/or magnetic noise caused by supply source harmonics.
5. Mechanical fiuilure of the motor or coupling due to torque pulsations, operation at or near mechanical resonances, or excess speed.
6. Winding failures due to repetitive high-amplitude voltage spikes created by the drive’s carrier frequency and motor feeder cable system.
7. Damage to the motor and drive due to improper application of power factor correction capacitors or harmonic filters.
8. Higher motor temperatures that may limit application in Division 2 or Zone 2 hazardous (classified) locations.
9. Shaft-to-bearing voltages/currents resulting from common mode currents tiowing through stray system capacitances to ground via the bearings. These currents are induced from the ASD’s high rate of change (dv/dt) of output voltage.
10. Extended operation at slow speed.
2.2.2 MOTOR DESIGN AND STARTING CHARACTERISTICS
2.2.2.1 Where applicable, motors shall meet the requirements for Design B torque-current characteristics based on the power/speed ratings defined per NEMA MG I Part 12. Type test and/or design information shall he supplied when requested to verify design characteristics.
2.2.2.4 When the motor speed-torque curve at the conditions specified in 2.2.2.3 is plotted over the load speed torque curve, the motor developed torque shall exceed the load torque by a minimum of 10% (motor rated torque as base) at all locations throughout the speed range up to the motor breakdown torque point.
2.2.2.5 When specified and when the purchaser provides a specific load torque and inertia condition other than above, the motor manufacturer shall evaluate and design the motor starting capability for a minimum 10% of rated full load torque margin at 80% rated voltage against the specific load requirements, prior to final purchase agreement.
2.2.2.6 The machine shall he designed for a lifetime minimum of 5000 full voltage starts. Design features outlined in section 2.3 shall he demonstrated in the stator construction and/or documented as part of the design. Rotor design shall have proven field service and shall he demonstrated or documented to include features of 2.4.5.
2.2.2.7 With rated voltage and frequency applied, motors shall not exceed a maximum locked-rotor current of 650% of the full-load current.
2.3 WINDING AND INSULATION SYSTEMS
2.3.1 Stator windings shall have an epoxy base, vacuum pressure impregnated, nonhygroscopic insulation system, including lead and coil connections. Bus bars shall also he insulated. As a minimum, the insulation system shall meet the criteria for Class F insulation listed in NEMA MG I or EEC 60034-1 as applicable. The allowable temperature rise above ambient, 40°C (104°F), shall not exceed that listed for Class B insulation. For ambient temperatures above 40°C the allowable temperature rise shall he reduced by the amount equal to the temperature above 40°C, so as not to exceed the total temperature limits (ambient, rise and hot spot) for Class B insulation.
