Description of All Types

Class 8600 / Refer to Catalog 8600CT9601

Reduced Voltage Starting of Squirrel Cage Motors

A squirrel cage motor draws high starting current (inrush) and produces high starting torque when started at full voltage. While these values differ for different motor designs, for a typical NEMA design B motor, the inrush will be approximately 600% of the motor full load amperage (FLA) rating, and the starting torque will be approximately 150% of full load torque at full voltage. High current inrush and starting torque can cause problems in the electrical and mechanical systems, or may even damage the materials being processed.

 

When a motor is started at reduced voltage, the current at the motor terminals is reduced in direct proportion to the voltage reduction, while the torque is reduced by the square of the voltage reduction. If the “typical” NEMA B motor is started at 70% of line voltage, the starting current would be 70% of the full voltage value (that is, 0.70 x 600% = 420% FLA). The torque would then be (0.70)2 or 49% of the normal starting torque (that is, 0.49 x 150% = 74% full load torque). Therefore, reduced voltage starting provides an effective means of reducing both inrush current and starting torque.

 

If the motor has a high inertia or if the motor rating is marginal for the applied load, reducing the starting torque may prevent the motor from reaching full speed before the thermal overload relays trip. Applications that require high starting torque should be reviewed to determine if reduced voltage starting is suitable.

Square D™ offers several types of electromechanical as well as solid-state reduced voltage starters that provide different starting characteristics. The following describes the 8600 series of reduced voltage starters.

Electromechanical Reduced Voltage Starters

Class 8606—Autotransformer Starter: Autotransformer starters provide reduced voltage to the motor terminals during starting through the use of a tapped, three phase autotransformer. Taps on the autotransformer allow for selection of the motor with 50%, 65%, or 80% of line voltage values supplying 50%, 65%, or 80% of the current inrush seen during a full voltage start. The resulting starting torque will be 25%, 42%, or 64% of full voltage values, as will be the current draw on the line. Thus, the autotransformer provides the maximum torque with minimum line current.

 

Class 8630—Wye-Delta Starter: Wye-delta starters can only be used on wye-delta motors which have six leads that allow for motor winding to be connected in either a wye or delta configuration. During start up, the windings are connected in the wye, resulting in 58% of line voltage applied across two windings. This reduces both inrush and starting torque to 33% of the delta connected values. After a set time delay, the motor leads are switched to the delta connection. The wye-delta starter is available in both open and closed transition configurations. Closed transition starters are supplied with an additional contactor and resistor bank used to keep the motor windings energized for a few cycles until the transition from wye to delta is complete.

 

Class 8640—Part Winding Starter: Part winding starters can be used only with part winding motors. During a part winding start, only one winding is energized, reducing the inrush current to 60–70% (depending on the motor design) and starting torque to 50% of normal starting values with both windings energized. Most (but not all) dual voltage 230/460 volt motors are suitable for part winding starts at 230 volts.

Specifications

Starter Characteristics

Characteristic

Full Voltage

Autotransformer, Class 8606

Wye-Delta Class, 8630

Part Winding, Class 8640

Solid-State ATS46

Voltage at Motor

100%

50% / 65% / 80% (tap setting)

100%

100%

Ramped Up

Line Current (% Full Load Current)

600%

150% / 250% / 380%

200%

390%

150% to 700% (adjustable)

Starting Torque (% Rated Torque)

150%

40% / 60% / 100%

50%

70%

0% to 100% (adjustable)

Start Time (Factory Setting)

6–7 s

10 s / 15 s (open/closed transition)

1–1.5 s

10 s
(adjustable 1–60 s)

Advantages

  • Simple

  • Economical

  • High Starting Torque

  • High torque/amperage

  • High inertial loads

  • Flexibility

  • High inertial loads

  • Long acceleration loads

  • Good torque/amperage

  • Simple

  • Small size

  • Greatest flexibility

  • Smooth ramp

  • Solid-state overload relay

  • Diagnostics

Disadvantages

  • Abrupt starts

  • Large current inrush

  • Large size

  • Low torque

  • No flexibility

Not suitable for:

  • High inertial loads

  • Frequent starting

  • SCR heat dissipation

  • Ambient limitations

Motor

Standard

Standard

Special

Special

Standard

Line Voltage Codes (60 Hz)

Line

Control

Code

208

240

380
480
600

208

240

380
480
600

V08

V03

V05
V06
V07

Coil Voltage Codes (60 Hz)

Line

Control

Code

208

240

240

480

480

480

600

380

other

120

24

120

24

120

240

120

110/50

specify

V84

V82

V80

V83

V81

V87

V86

V95

V99

Form Codes

Form Description

Form Code

Fused CPT for timing relay only

F4T

Fused CPT for all coils

F4T40

Separate control of timing relay only

S

Separate control for all coils

Y195


How to Order

  1. Specify the Class Number and the Type Number.

  2. If all coils are at the line voltage, and not Sizes 6 or 7, select the voltage code from Line Voltage Codes (60 Hz) (Sizes 6 and 7 are supplied with a fused transformer with 120 Vac as standard).

  3. If the coils are at a different voltage than line supply, or Size 6 or 7, select a voltage code from Coil Voltage Codes (60 Hz) and also select a Form code from Form Codes (note that a Form code may be used with any voltage code, except as noted).

See 380 Vac, 50 Hz Starters, Maxiumum Horsepower Rating for sizing of 380 V starters.

24 V coils are not available on Sizes 4–7.

Factory Modifications (Forms): see Factory Modifications (Forms).

380 Vac, 50 Hz Starters

The Class 8600 starters are available for 380 Vac, 50 Hz applications. 380 Vac, 50 Hz Starters, Maxiumum Horsepower Rating provides maximum horsepower ratings. To determine the Type number, select the second digit based on the NEMA size. Select the fifth digit based on the horsepower requirement. Specify V05 voltage code.

380 Vac, 50 Hz Starters, Maxiumum Horsepower Rating

Autotransformer, Class 8606

Wye-Delta, Class 8630

Part Winding, Class 8640

Max. hp

NEMA Size

Max. hp

NEMA Size

Max. hp

NEMA Size


25
50
75
150
300


2
3
4
5
6

15
40
75
150
250
500

1YD
2YD
3YD
4YD
5YD
6YD

15
40
75
125
250
500

1PW
2PW
3PW
4PW
5PW
6PW


50 Hz Control Voltage

Coil Voltage Codes (50 Hz)

Hz

V

Code

V

Code

V

Code

V

Code

60
50

120
110

V02

240
220

V03

480
440

V06

600
550

V07

The starters in this section can also be operated at 50 Hz at the coil voltages listed in Coil Voltage Codes (50 or 60 Hz). For additional coil voltage availability, contact the Customer Care Center (CCC) at 1-888-778-2733.

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