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3RW3 semiconductor motor control unit
SIRIUS System Manual
8-20
GWA 4NEB 430 0999-02b
Correction factors
If the minimum clearances are violated, in a combination of a soft starter
with a circuit breaker, fixed correction factors must be used to determine
the rated current for the device and the switching frequency.
The following variables can be modified by means of correction factors:
• Rated current for the device
• Switching frequency
• Current setting of the circuit breaker
• Current setting of the overload relay
Correction factor for the
rated current of the
device
A factor is specified by which the device rated current of the soft starter is
reduced.
Example:
Correction factor for the rated current of the device = 0.9
Selected device = 3RW3014-1CB14 (under normal conditions at 40 °C a
device rated current of 6 A)
This results in an actual device rated current of:
0.9 x 6 A = 5.4 A
Correction factor for
switching frequency
The switching frequency is the maximum permissible number of starts per
hour. This value must be adjusted by the specified correction factor. The
number of permissible starts per hour is given in Table 8.7.1, Control electro-
nics/power electronics, in Section 8.7, Technical specifications.
The specified correction factors refer to the following operating conditions:
S4 operation, 40 °C ambient temperature, 30% duty cycle
Example:
Correction factor for the switching frequency = 1.5
Selected device = 3RW3014-1CB14 (has a maximum switching frequency of
30 starts per hour under the conditions specified above)
This results in a corrected switching frequency of:
1.5 x 30 = 45 starts per hour
To increase the switching frequency, it is also possible to use a larger
device.
Correction factor for the
current setting of the
circuit breaker
In combinations of a 3RW30 soft starter and a 3RV1 circuit breaker, the set
value of the circuit breaker may have to be corrected appropriately. The cor-
rection factor specifies the extent of the change.
Example:
Correction for the current setting of the circuit breaker: 1.1
Selected device = 3RW3014-1CB14
The connected motor has a motor rated current of 5 A.
The set value of the circuit breaker must be changed to:
1.1 x 5 A = 5.5 A