Page 295 - Electric Drives and Electromechanical Systems

Appendix 1: Units and conversion factors 293

Moment of Inertia

SI units Conversion factors
7
kgm 2 Kilogram metre squared 1kgm 2 ¼ 10 gcm 2
3
gm 2 Gram centimetre squared 1ozin s 2 ¼ 27.0616 10 kg m 2
Energy

SI units Conversion factors
J Joule 1J ¼ 1Ws
kW h Kilowatt hour ¼ 2.7778 10 7 kWh
¼ 9.4781 10 4 Btu
6
1kWh ¼ 3.6 10 J
3
¼ 3.14121 10 Btu
Power
SI units Conversion factors
W Watt 1W ¼ 1J s 1
kW Kilowatt ¼ 0.73756 lb ft s 1
1hp ¼ 735.5 W
Rotational Power
Relevant equations Units
Derived as the product of torque and the angular speed:
Power (P) ¼ Torque (T) Angular speed (n)
P ¼ Tn W; Nm; rad s 1
P ¼ 0.10472 T n W; Nm; rev min 1
P ¼ 7.3948 10 4 Tn W; oz in; rev min 1
Derived Motor Constant - Torque

Unit Conversion factors
Nm A 1 Newton metres per amp 1 NmA 1 ¼ 141.612 oz in A 1
Derived Motor Constants - Voltage

Unit Conversion factors
1
1 1
V (rev min ) Volts per revolutions per minute 1 V rev 1 min ¼ 9.55 10 3 V rad s
Derived Motor Constant - Damping
Unit Conversion factors
1
N m rad s Newton meter per radian per second 1 N m rad 1 s ¼ 0.105 Nm rev 1 min