S811+ Operating Configuration
40
S811+ Soft Starter
MN03900001E—November 2012
The table below notes the values of Initial Torque settings as
a percentage of Locked Rotor Current.
Initial Torque Settings
The National Electrical Code requires that all alternating
current motors of 1/2 horsepower and higher must have
code letters on the data plate indicating motor current in a
locked rotor condition. This code denotes the
Kilovolt-Ampere per horsepower of the motor.
The KVA
hp
value is obtained from NEMA and/or NEC
publications. The table below is provided as a reference.
Locked rotor current of a three phase motor may be
calculated using the following formula:
Example:
To calculate the locked rotor current range of a
50 horsepower motor operating at 460 volts with
a code letter B, proceed as follows;
To determine the expected Initial Current value of the above
example, apply the corresponding current reduction value
base on the initial Torque setting of the soft starter. Using
the default Initial Torque value of 45%, the expected current
will be 67% of the above values, or 132.26 amps to 149.02
amps respectively.
Note:
The current in the motor circuit will be subject to the
total impedance of the motor circuit, so actual values
may be slightly different than calculated values.
Code Letters
Torque
Setting
Current as %
Locked Rotor
Initial Motor Torque
85%
92%
Maximum
71%
84%
56%
75%
45%
67%
Default Value
36%
60%
33%
57%
Wye-Delta Equivalent
27%
52%
19%
44%
Current Limit Minimum
14%
37%
1%
10%
Minimum
Locked Rotor Current =
Horsepower x KVA
hp
x 1000
E x 1.73
Locked Rotor
Current (minimum) =
50 x 3.15 x 1000
= 197.91 Amps
460 x 1.73
Locked Rotor
Current (maximum) =
50 x 3.54 x 1000
= 222.42 Amps
460 x 1.73
Code
Letter
Kilovolt-Ampere per hp with Locked Rotor
Minimum
Maximum
A
0
3.14
B
3.15
3.54
C
3.55
3.99
D
4.0
4.49
E
4.5
4.99
F
5.0
5.59
G
5.6
6.29
H
6.3
7.09
J
7.1
7.99
K
8.0
8.99
L
9.0
9.99
M
10.0
11.19
N
11.2
12.49
P
12.5
13.99
R
14.0
15.99
S
16.0
17.99
T
18.0
19.99
U
20.0
22.39
V
22.4
>22.41