GE AF-650 GP Design Manual page 43

The max. permissible load on the brake resistor is stated as a peak power at a given intermittent duty cycle and can be calculated as:
The brake resistance is calculated as shown:
3
As can be seen, the brake resistance depends on the intermediate circuit voltage (U
The AF-650 GP brake function is settled in 4 areas of mains:
Size
3 x 200-240 V
3 x 380-480 V*
3 x 525-600 V
3 x 525-690 V
* Power size dependent
NB!
Check that the brake resistor can cope with a voltage of 410 V, 850 V, 975 V or 1130 V - unless GE brake resistors are used.
GE recommends the brake resistance R
frequency converter is able to brake at the highest braking torque (M
160%. The formula can be written as:
η is typically at 0.90
motor
For 200 V, 480 V and 600 V frequency converters, R
107780
200 V : R rec =
P motor
375300
V R rec
480 : =
P motor
630137
600 V : R rec =
P motor
832664
V R rec
690 : =
P motor
≤
1) For frequency converters
2) For frequency converters 11 - 75 kW shaft output
NB!
The resistor brake circuit resistance selected should not be higher than that recommended by GE. If a brake resistor with a higher ohmic value is selected, the
160% braking torque may not be achieved because there is a risk that the frequency converter cuts out for safety reasons.
NB!
If a short circuit in the brake transistor occurs, power dissipation in the brake resistor is only prevented by using a mains switch or contactor to disconnect the
mains for the frequency converter. (The contactor can be controlled by the frequency converter).
NB!
Do not touch the brake resistor as it can get very hot while/after braking. The brake resistor must be placed in a secure environment to avoid fire risk
42
Brake active
390 V (UDC)
810 V/ 795 V
943 V
1084 V
, i.e. one that guarantees that the
rec
at 160% braking torque is written as:
rec
Ω
Ω 1)
Ω
Ω
7.5 kW shaft output
2
U dc
R br
Ω =
P peak
where
P = P x M [%] x η
peak motor br
).
dc
Warning before cut out
405 V
840 V/ 828 V
965 V
1109 V
R rec
Ω =
) of
P motor x M br
br(%)
η is typically at 0.98
DRIVE
428914
V R rec
480 : =
P motor
AF-650 GP Design Guide
x η [W]
motor DRIVE
Cut out (trip)
410 V
850 V/ 855 V
975 V
1130 V
2
U dc x
100
x DRIVE x
η η
(%) motor
Ω 2)