Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

12.5 Electric Motors 361

TABLE 12.3 Examples of Motors used in Different Applications

Electrical Power

Requirements

Load Motor Type Starting Ability Starting Current Size hp Phase Voltage

Type (1) (Torque) (2) (3) (4) (5) (6)

Shaded-pole Very low Low .035 –.2 kW Single Usually 120

induction 1/2 to 1 times (1/20 –1/4 hp)

running torque

Split-phase Low High .035 –.56 kW Single Usually 120

Easy

1 to 1 times 6 to 8 times (1/20 – 3/4 hp)

Starting

running torque running current

Loads Permanent-split, Very low Low .035 –.8 kW Single Single voltage

capacitor- 1/2 to 1 times (1/20 –1 hp) 120 or 240

induction running torque

Soft-start Very low Low 5.6 – 25 kW Single 240

1/2 to 1 times 2 to 2 times (7 –50 hp)

running torque running current

Capacitor-start, High Medium .14 – 8 kW Single 120 – 240

induction-run 3 to 4 times 3 to 6 times (1/6 –10 hp)

running torque running current

Repulsion-start, High Low .14 –16 kW Single 120 – 240

induction-run 4 times 2 to 3 times (1/6 – 20 hp)

running torque running current

Difficult Capacitor-start, High Medium .4 – 20 kW Single 120 – 240

Starting capacitor-run 3 to 4 times 3 to 5 times (1/2 – 25 hp)

Loads running torque running current

Repulsion-start, High Low .8 –12 kW Single Usually 240

capacitor-run 4 times 2 to 3 times (1–15 hp)

running torque running current

Three-phase, Medium High .4 – 300 kW Three 120 – 240;

general-purpose 2 to 3 times 3 to 6 times (1/2 – 400 hp) 240 – 480

running torque running current or higher

1

2

1

2

1

2

1

2

1

2

1

2

1

2

R

Split-phase

R

Repulsion-start induction Capacitor-start

Centrifugal

switch R

Repulsion-induction Capacitor-motor

Schematic Diagrams for AC Motors

Source:From Electric Motors, Fifth Edition, 1982. Copyright © 1982 AAVIM. Reprinted by permission.

Continued

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