Excitation level M
=
⋅
=
12490
49 98
11000
50
1 00
1 1359
.
.
.
(Equation 253)
Example 2
The situation and the data are according to Example 1. In this case, the
manufacturer of the machine allows the continuous operation at 105 percent
of the nominal voltage at the rated load and this value to be used as the
base for overexcitation.
Usually, the U/f characteristics are specified so that
the ratio is 1.00 at the nominal voltage and nominal
frequency. Therefore, the value 100 percent for the setting
Voltage Max Cont is recommended.
If the
Voltage Max Cont setting is 105 percent, the excitation level M of the
machine is calculated with the equation.
Excitation level M
=
⋅
=
12490
49 98
11000
50
1 05
1 0818
.
.
.
(Equation 254)
Example 3
In this case, the function operation is according to IDMT. The
Operating
curve type setting is selected as "OvExt IDMT Crv2". The corresponding
example settings for the IDMT curve operation are given as:
Start value =
110%,
Voltage Max Cont = 100%, Time multiplier = 4, Maximum operate time
= 1000 s,
Minimum operate time = 1 s and Cooling time = 200 s.
1MRS759142 F
Protection functions
REX640
Technical Manual
895