gefran TPD32-EV-...-2B, Instructions Manual

Page: 485 / 504

—————— Instruction manual ——————
485
Valid formulas
Vb@Id
N
= (Id
N
/ (Iprim / Isec)) x Rb and Gain_required = Vf@Id
N
/ Vb@Id
N
.
Calculation example A
IdN = 2000A, CT = 2400A / 0.5A; Rb = 5 Ohm.
Vb@IdN = (IdN / (2400 / 0.5)) x Rb = (2000 / 4800) x 5 = 2.08333V;
Gain_required = Vf@IdN / Vb@IdN = 0.612 / 2.08333 = 0.29376; therefore
Binary_switch_setting = 51.2 / 0.29376 = 174.29 which is rounded off to 174 and converted into binary format
as 000010101110 . i.e.:
SW3-1 SW3-2 SW3-3 SW3-4 SW4-1 SW4-2 SW4-3 SW4-4 SW4-5 SW4-6 SW4-7 SW4-8
OFF
MSB
OFF OFF OFF ON OFF ON OFF ON ON ON OFF
LSB
Calculation example B (extreme case)
Id
N
= 85A, CT = 2000A / 1A; Rb = 2.5Ohm.
Vb@Id
N
= (Id
N
/ (2000 / 1)) x Rb = (85 / 2000) x 2.5 = 0.10625V;
Gain_required = Vf@Id
N
/ Vb@Id
N
= 0.612 / 0.10625 = 5.76; therefore
Binary_switch_setting = 51.2 / 5.76 = 8.88888 rounded off to 9 and converted into binary format as
000000001001
.
Calculation example C
IdN = 16000A, CT = 20000A / 5A;
Using an internal 2.50-Ohm RB, inserting a second CT2 with a ratio of 5 A/1 A.
The new Iprim/Isec is the total of 20000 A / 1 A;
Vb@Id
N
= (Id
N
/ (20000 / 1)) x Rb = (16000 / 20000) x 2.5 = 2V;
Gain_required = Vf@Id
N
/ Vb@Id
N
= 0.612 / 2 = 0.306; therefore
Binary_switch_setting = 51.2 / 0.306 = 167.32 rounded off to 167 and converted into binary format as 000010100111 .
Calculation example D
Burden resistor connected to terminals XCT and CT with a 5 A secondary current. Applying the same criteria
for the burden resistor, the ideal burden resistor value is 2.5 Ohm / 5 = 0.5 Ohm. The nearest value for the EIA
E96 series is 0.499 Ohm ±1% but the more commonly used 47 Ohm ±1% can of course also be used.
Id
N
= 8000A, CT = 10000A / 5A, Rb = 0,47Ohm.
Vb@Id
N
= (Id
N
/ (10000 / 5)) x Rb = (8000 / 2000) X 0.47 = 1,88V;
Gain_required = Vf@Id
N
/ Vb@Id
N
= 0.612 / 1.88 = 0.3255319149; therefore
Binary_switch_setting = 51.2 / 0.3255319149 = 157.281; rounded off to 157 and converted into binary format as 000010011101 .
n
ote
:
When choosing the external burden resistor, bear in mind the possibility of substantial power
dissipation. In this example, the power at the rated current is already approx. (1.88)
2
/ 0.47
= 7.5 W without taking into account any overload conditions or the advisability of not using
resistors at more than half of their rated power.
Table A.1.6.3.1: Calculation of the configuration of dip-switches SW3-1 to SW4-8 for standard TPD32-EV-.. drives with external bridge
Rated arma-
ture current
CT
transformer
Jumper J4 (on
the FIRXP-XX
card)
Jumper J5 (on
the FIRXP-XX
card)
Vb@IdN Gain
required
Binary
switch
setting
Binary
number
SW3-1, ..SW3-4,
SW4-1, ..SW4-8
(on the FIRXP-XX card)
[ a
dc
] (Rb=5Ω) [V
dc
] [MSB … LSB]
1000 1600/0,4 OFF ON 1,250000 0,489600 105 1101000 000001101000
1010 1600/0,4 OFF ON 1,262500 0,484752 106 1101001 000001101001
1200 1600/0,4 OFF ON 1,500000 0,408000 125 1111101 000001111101