AC Controls

Multi-Speed Starters (NEMA Sizes 0–4)

General / Dimensions

Full-voltage AC magnetic multi-speed controllers are designed to control reconnectable squirrel-cage induction motors for operation at two, three or four different constant speeds depending on the construction of the motor. These controllers are available in combination and non-combination types.

The speed of an induction motor is a function of the supply frequency and the number of poles of the motor winding. To obtain different speeds with a fixed supply frequency, the number of magnetic poles of the motor must be changed. Characteristics at any speed are similar to those of a single-speed motor. There are two basic methods for providing multiple combinations:

JSeparate-Winding Motors have a separate winding for each speed. This motor construction is relatively simple, and a wide variety of speeds can be selected. Separate winding motors with delta connected motor windings require one corner to be opened on each unused winding.

JConsequent-Pole Motors have a single winding for two speeds. Extra winding taps are brought out for reconnection for different numbers of stator poles. The controller is more complicated, and speed range is lim- ited to a 2-to-1 ratio.

Two-speed consequent-pole motors have one reconnectable winding. Three-speed motors have two windings, one of which is reconnectable. Four-speed motors have two reconnectable windings. Each unused delta connected winding must have one corner open.

Torque Characteristics

Multi-speed motors are divided into three application groups:

JConstant Torque: HP output varies directly with speed, while torque remains constant. A constant torque motor rated 100 HP at 1200 rpm delivers 50 HP at 600 rpm. This type is applicable to conveyors, mills, dough mixers, reciprocating pumps, and other similar loads.

JVariable Torque: HP varies as square of speed, while torque varies directly with speed. A variable-torque motor rated 100 HP at 1200 rpm delivers 25 HP at 600 rpm. This type is applicable to drives having fan or centrifugal pump characteristics.

JConstant Horsepower: Motor deliv- ers rated HP at all full-load speeds, while torque varies inversely as speed. This type is applicable to cutting tools, lathes, spindles, etc.

Starter Types (NEMA Sizes 0–7)

Single Winding (Consequent Pole) Variable Torque

Single Winding (Consequent Pole) Constant Torque

Single Winding (Consequent Pole) Constant Horsepower

Two Winding (Separate Winding) Variable Torque

Two Winding (Separate Winding) Constant Torque

Two Winding (Separate Winding) Constant Horsepower

Note — Reversing types, reduced voltage types, and three or four speeds are also available.

Enclosures

Type 1: General Purpose

Type 3R: Outdoor Raintight

Type 12: Dusttight — Industrial Use

Type 4: Watertight Stainless Steel or Watertight Painted Sheet Steel

Ratings

Table 15.33 3-Phase Multi-Speed Starter

NEMA

 

Maximum Horsepower

Starter

Half

 

 

 

Size

Size

200V

230V

460/575V

0

 

3

3

5

1

 

7.5

7.5

10

 

1 3⁄4*

10

10

15

2

 

10

15

25

 

2 1⁄2*

15

20

30

3

 

25

30

50

 

3 1⁄2*

30

40

75

4

 

40

50

100

Dimensions

Table 15.34

 

Combination

 

Multi-Speed Starter

 

 

 

 

 

Dimensions in Inches (mm)

 

 

 

Size

A

B

 

C

NEMA 1

 

0

–1 3⁄4

25.75

16.00

 

7.63

 

(654)

(406)

 

(194)

General

 

 

 

 

 

 

 

Purpose

 

2

– 3

31.50

19.00

 

7.63

Enclosures

 

(800)

(483)

 

(194)

 

 

 

 

 

 

 

 

NEMA 12

 

0

–1 3⁄4

28.50

16.00

 

7.69

 

(724)

(406)

 

(195)

Industrial

 

 

 

 

Use

 

2

– 3

34.25

34.25

 

7.69

Enclosures

 

 

 

(870)

(870)

 

(195)

 

 

 

 

 

15

Controls AC

CSI Section 16160

Siemens Electrical Products and Systems

305

 

Specification Guide