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Idiomas disponibles
Idiomas disponibles
TH
TH
TH
TH
TH
TH
TH
TH
THRE
TH
TH
TH
THREE PHASE POWER UNBALANCE
TH
TH
RE
RE
RE
RE
RE
REE
RE
RE
RE
RE
RE
RE
RE
E
E
E
E
E
E
E
E
E
E
E
E
E
PH
PH
PH
PH
PH
PH
PH
PH
PH
PH
PH
PH
PH
PHAS
AS
AS
AS
AS
AS
AS
AS
ASE
AS
AS
AS
AS
AS
E
E
E
E
E
E
E
E
E
E
E
E
E
PO
PO
PO
PO
PO
POWE
PO
PO
PO
PO
PO
PO
PO
PO
WE
WE
WE
WE
WE
WE
WE
WE
WE
WE
WE
WER
WE
A full three phase supply consisting of three individual
transformers or one three phase transformer is recom-
mended. "Open" delta or wye connections using only
two transformers can be used, but are more likely to
cause poor performance, overload tripping or early mo-
tor failure due to current unbalance.
Check the current in each of the three motor leads and
calculate the current unbalance as explained below.
If the current unbalance is 2% or less, leave the leads as
connected.
If the current unbalance is more than 2%, current read-
ings should be checked on each leg using each of the
three possible hook-ups. Roll the motor leads across the
starter in the same direction to prevent motor reversal.
To calculate percent of current unbalance:
A. Add the three line amp values together.
Starter Terminals L1
Motor Leads
R
T3
Example:
T3-R = 51 amps
T1-B = 46 amps
T2-W = 53 amps
Total = 150 amps
4 ÷ 50 = .08 or 8%
IN
IN
IN
IN
IN
IN
IN
IN
IN
INSULATION RESISTANCE READINGS
IN
IN
IN
N
N
SU
SULA
SU
SU
SU
SU
SU
SU
SU
SU
SU
SU
SU
SU
LA
LA
LA
LA
LA
LA
LA
LA
LA
LA
LA
LATI
LA
TI
TI
TI
T
TI
TI
T I
TI
TI
TI
TI
TION
TI
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
ON
R
R
R
R
R
R
R
R
R
R
R
R
R
R
ES
ES
ES
ES
ES
ES
ES
ESIS
ES
ES
ES
ES
ES
ES
IS
IS
IS
IS
IS
ISTA
IS
IS
IS
IS
IS
IS
IS
TANC
TA
TA
TA
TA
TA
TA
TA
TA
TA
TA
TA
TA
Normal Ohm and Megohm Values between all leads and ground
Condition of Motor and Leads
A new motor (without drop cable).
A used motor which can be reinstalled in well.
Motor in well. Readings are for drop cable plus motor.
New motor.
Motor in good condition.
Insulation damage, locate and repair.
Insulation resistance varies very little with rating. Motors of all HP, voltage and phase ratings have similar values of
insulation resistance.
Insulation resistance values above are based on readings taken with a megohmmeter with a 500V DC output.
Readings may vary using a lower voltage ohmmeter, consult factory if readings are in question.
R
R
R
R
R
R
R
R
R
R
R
R
R
UN
UN
UN
UN
UN
UN
UN
UN
UN
UN
UN
UN
UN
UNBA
BA
BA
BA
BA
BA
BA
BA
BA
BA
BA
BALA
BA
BA
LA
LA
LA
LA
LA
LA
LA
LA
LANC
LA
LA
LA
LA
NCE
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
E
E
E
E
E
E
E
E
E
E
E
E
E
Hookup 1
L2
L3
B
W
T1
T2
÷ 3 = 50 amps
– 46 = 4 amps
NC
NC
NC
NC
NC
NC
NC
NC
NC
NC
NCE
NC
NC
E
E
E
E
E
E
E
E
E
E
E
E
E
RE
RE
RE
READ
RE
RE
RE
RE
RE
RE
RE
RE
RE
RE
ADIN
AD
AD
AD
AD
AD
AD
AD
AD
AD
AD
AD
AD
IN
IN
IN
INGS
IN
IN
IN
IN
IN
IN
IN
IN
N
GS
GS
GS
GS
GS
GS
GS
GS
GS
GS
GS
GS
GS
B. Divide the sum by three, yielding average current.
C. Pick the amp value which is furthest from the average
current (either high or low).
D. Determine the difference between this amp value
(furthest from average) and the average.
E. Divide the difference by the average. Multiply the
result by 100 to determine percent of unbalance.
Current unbalance should not exceed 5% at service
factor load or 10% at rated input load. If the unbalance
cannot be corrected by rolling leads, the source of the
unbalance must be located and corrected. If, on the three
possible hookups, the leg farthest from the average stays
on the same power lead, most of the unbalance is coming
from the power source.
Contact your local power company to resolve the imbal-
ance.
Hookup 2
L1
L2
L3
W
R
B
T2
T3
T1
T2-W = 50 amps
T3-R = 48 amps
T1-B = 52 amps
Total = 150 amps
÷ 3 = 50 amps
– 48 = 2 amps
2 ÷ 50 = .04 or 4%
Ohm Value
20,000,000 (or more)
10,000,000 (or more)
2,000,000 (or more)
500,000 - 2,000,000
Less than 500,000
Hookup 3
L1
L2
L3
B
W
R
T1
T2
T3
T1-B = 50 amps
T2-W = 49 amps
T3-R = 51 amps
Total = 150 amps
÷ 3 = 50 amps
– 49 = 1 amps
1 ÷ 50 = .02 or 2%
Megohm Value
20 (or more)
10 (or more)
2 (or more)
.5 - 2
Less than .5
7
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