Application – Single-Phase Motors

Auxiliary Running Capacitors

Added capacitors must be connected across “Red” and “Black” control box terminals, in parallel with any existing running capacitors. The additional capacitor(s) should be mounted in an auxiliary box. The values of additional running capacitors most likely to reduce noise are given below. The tabulation gives the max S.F. amps normally in each lead with the added capacitor.

Although motor amps decrease when auxiliary run capacitance is added, the load on the motor does not. If a motor is overloaded with normal capacitance, it still will be overloaded with auxiliary run capacitance, even though motor amps may be within nameplate values.

Table 15 Auxiliary Capacitor Sizing

MOTOR RATING

NORMAL RUNNING

 

AUXILIARY RUNNING CAPACITORS FOR

S.F. AMPS WITH RUN CAP

 

CAPACITOR(S)

 

 

NOISE REDUCTION

 

 

 

 

 

 

 

 

 

HP

VOLTS

MFD

MFD

 

MIN VOLTS

FRANKLIN PART

YELLOW

BLACK

RED

1/2

115

0

60(1)

 

370

TWO 155327101

8.4

7.0

 

4.0

 

 

 

 

 

 

 

 

 

 

 

1/2

 

0

15(1)

 

370

ONE 155328101

4.2

3.5

 

2.0

3/4

 

0

20(1)

 

370

ONE 155328103

5.8

5.0

 

2.5

1

 

0

25(1)

 

370

ONE EA. 155328101

7.1

5.6

 

3.4

 

 

155328102

 

 

 

 

 

 

 

 

 

 

 

1.5

 

10

20

 

370

ONE 155328103

9.3

7.5

 

4.4

2

230

20

10

 

370

ONE 155328102

11.2

9.2

 

3.8

3

45

NONE

 

370

 

17.0

12.6

 

6.0

 

 

 

 

5

 

80

NONE

 

370

 

27.5

19.1

 

10.8

7.5

 

45

45

 

370

ONE EA. 155327101

37.0

32.0

 

11.3

 

 

155328101

 

 

 

 

 

 

 

 

 

 

 

10

 

70

30

 

370

ONE 155327101

49.0

42.0

 

13.0

15

 

135

NONE

 

 

 

75.0

62.5

 

16.9

 

 

 

 

 

 

 

 

 

 

 

(1)Do not add running capacitors to 1/3 through 1 hp control boxes, which use solid state switches or QD relays. Adding capacitors will cause switch failure. If the control box is converted to use a voltage relay, the specifi ed running capacitance can be added.

Buck-Boost Transformers

When the available power supply voltage is not within the proper range, a buck-boost transformer is often used to adjust voltage to match the motor. The most common usage on submersible motors is boosting a 208 volt supply to use a standard 230 volt single-phase submersible motor and control. While tables to give a

wide range of voltage boost or buck are published by transformer manufacturers, the following table shows Franklin’s recommendations. The table, based on boosting the voltage 10%, shows the minimum rated transformer kVA needed and the common standard transformer kVA.

Table 15A Buck-Boost Transformer Sizing

MOTOR HP

LOAD KVA

MINIMUM XFMR KVA

STANDARD XFMR KVA

1/3

1.02

0.11

0.25

1/2

1.36

0.14

0.25

3/4

1.84

0.19

0.25

1

2.21

0.22

0.25

1.5

2.65

0.27

0.50

2

3.04

0.31

0.50

3

3.91

0.40

0.50

5

6.33

0.64

0.75

7.5

9.66

0.97

1.00

10

11.70

1.20

1.50

15

16.60

1.70

2.00

Buck-Boost transformers are power transformers, not control transformers. They may also be used to lower voltage when the available power supply voltage is too high.

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Franklin 2007 manual Auxiliary Running Capacitors, Buck-Boost Transformers, Buck-Boost Transformer Sizing