Effective: 08-01-11 - TECO-Westinghouse Motor Company

USEFUL FORMULAS
kW = hp * .746
Torque in lb-ft = hp * 5250
RPM
Motor synchronous speed in RPM = 120 * Hz
Number of Poles
Three-Phase Full-Load Amp = hp * .746
Rated Motor kVA = hp * .746
1.73 * kV * Efficiency Power Factor
*
100 100
Efficiency * Power Factor
kW Loss = (HP * .746) * (1.0 - Efficiency)
Efficiency
Wk 2 Referred to Motor Shaft Speed = [Driven Machine Wk 2 (Driven Machine RPM/ Motor RPM) 2 ]+
Gear Wk 2 at Motor Speed
Accelerating Time = 0.462 (Wk 2 of Motor and Load) RPM 2
Motor Rated kW * 104 * Per-Unit Effective Accelerating Torque
kVA inrush = Percent Inrush * Rated kVA
Approximate Voltage Drop (%) = Motor kVA Inrush * Transformer Impedance (Normally 5% to 7%)
Transformer kVA
Stored Kinetic Energy in kW-sec = 2.31 * (Total Wk 2 ) * RPM 2 x 10 -7
Inertia Constant (H) in Seconds = Stored Kinetic Energy in kW Seconds
Conversion Factors:
hp * .746
CV = (Metric hp) = 735.5 Watts = 75 KW-m/sec
Wk 2 (lb-ft) = 5.93 x GD 2 (kg-m 2 )
( ) ( )
Effective 08-01-11
Supercedes 12-01-09
Derating motor for change in elevation: For each 330 foot increase in elevation above 3300 feet above sea level, derate motor horsepower by 1 percent.
Cooling-water requirements: 2 gpm of water for each kW of loss
Ventilating-air requirements: 100-125 cfm of 40˚C air at 1/2 water pressure for each W of loss
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