Table 1. Characteristics and Applications of D.C. Motors, 1–300 Horsepower
Maximum Momentary Running Torque
Speed Regulation
Speed Control a
Starting Duty
Type
Applications
Basic speed to 200% basic speed by field control Basic speed to 60% basic speed (lower for some ratings) by field control Basic speed to 2% basic speed and basic speed to 200% basic speed Basic speed to 125% basic speed by field control From zero to maximum speed, depending on control and load
Shunt-wound, constant- speed
8 to 12%
Drives where starting requirements are not severe. Use constant-speed or adjustable- speed, depending on speed required. Centrifugal pumps, fans, blowers, conveyors, elevators, wood- and metalworking machines Drives where wide, stepless speed control, uniform speed, constant-torque acceleration and adaptability to automatic operation are required. Planers, milling machines, boring machines, lathes, etc. Drives requiring high starting torque and fairly constant speed. Pulsating loads. Shears, bending rolls, pumps, conveyors, crushers, etc. Drives where very high starting torque is required and speed can be regulated. Cranes, hoists, gates, bridges, car dumpers, etc.
Medium starting torque. Varies with voltage supplied to armature, and is limited by starting resistor to 125 to 200% full-load torque
Shunt- wound, adjustable speed Shunt- wound, adjustable voltage control Compound wound, constant- speed
10 to 20%, increases with weak fields
125 to 200%. Limited by commutation
Up to 25%. Less than 5% obtainable with special rotating regulator Standard compounding 25%. Depends on amount of series winding
Heavy starting torque, Limited by starting resistor to 130 to 260% of full-load torque Very heavy starting torque. Limited to 300 to 350% full-load torque
130 to 260%. Limited by commutation
Series- wound, varying- speed
Very high. Infinite no-load speed
300 to 350%. Limited by commutation
a Minimum speed below basic speed by armature control limited by heating.
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