Danfoss FC 300 Design Manual page 45

FC 300 Design Guide
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:
As can be seen, the brake resistance depends on the intermediate circuit voltage (U
The AutomationDrive FC 301 and AutomationDrive FC 302 brake function is settled in 4 areas of mains:
Size
AutomationDrive FC 301 /
AutomationDrive FC 302 3 x 200-240 V
AutomationDrive FC 301 3 x 380-480 V 778 V
AutomationDrive FC 302 3 x 380-500 V* 810 V/ 795 V
AutomationDrive FC 302 3 x 525-600 V 943 V
AutomationDrive FC 302 3 x 525-690 V 1084 V
* Power size dependent
NB!
Check that the brake resistor can cope with a voltage of 410 V, 820 V, 850 V, 975 V or 1130 V - unless Danfoss brake resistors are
used.
Danfoss recommends the brake resistance R
that the frequency converter is able to brake at the highest braking torque
(M ) of 160%. The formula can be written as:
br(%)
η is typically at 0.90
motor
For 200 V, 480 V, 500 V and 600 V frequency converters, R
107780
V R rec
200 : = Ω
P motor
375300
Ω 1)
V R rec
480 : =
P motor
464923
V R rec
500 : = Ω
P motor
630137
V R rec
600 : = Ω
P motor
832664
V R rec
690 : = Ω
P motor
1) For frequency converters ≤ 7.5 kW shaft output
2) For frequency converters 11 - 75 kW shaft output
NB!
The resistor brake circuit resistance selected should not be higher than that recommended by Danfoss. 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).
Brake active Warning before cut out
390 V (UDC) 405 V
810 V
840 V/ 828 V
965 V
1109 V
, i.e. one that guarantees
rec
R rec
η
at 160% braking torque is written as:
rec
480
MG.33.BC.02 - VLT ® is a registered Danfoss trademark
3 Introduction to AutomationDrive FC 300
2
U dc
R br
Ω =
P peak
where
P = P x M [%] x η x η
peak motor br motor
).
dc
Cut out (trip)
410 V
820 V
850 V/ 855 V
975 V
1130 V
2
U dc x 100
Ω =
P motor x M br x
(%)
VLT
is typically at 0.98
VLT
428914
Ω 2)
V R rec
: =
P motor
[W]
VLT
x
motor
3
45