Danfoss VLT AQUA Drive FC 202 Design Guide

T
ta
tc
tb
to ta
tc
tb
to ta
130BA167.10
Load
Time
Speed
Figure 3.18 Brake Resistor Duty Cycle
Calculate the intermittent duty cycle for the resistor as
follows:
Duty cycle=t
b
/T
T =cycle time in seconds
t
b
is the braking time in seconds (of the cycle time)
Danfoss oers brake resistors with duty cycles of 5%, 10%,
and 40%. When a 10% duty cycle is applied, the brake
resistors absorb braking energy for 10% of the cycle time.
The remaining 90% of the cycle time is used to dissipate
excess heat.
Ensure the brake resistor is dimensioned for the required
braking time.
Brake resistance calculation
To prevent the adjustable frequency drive from cutting out
for protection when the motor brakes, select resistor values
on the basis of the peak braking energy and the
intermediate circuit voltage. Calculate resistance of the
brake resistor as follows:
R
br
 = 
Udc
2
P
peak

 Ω
The brake resistor performance depends on the DC link
voltage (U
dc
).
U
dc
is the voltage at which the brake is activated. The FC-
series brake function is settled depending on the line
power supply.
line power supply input
[V AC]
Brake
active
[V DC]
High
voltage
warning
[V DC]
Over
voltage
alarm
[V DC]
FC 202 3x200-240 390 405 410
FC 202 3x380-480 778 810 820
FC 202 3x525-600
1)
943 965 975
FC 202 3x525-600
2)
1099 1109 1130
FC 202 3x525-690 1099 1109 1130
Table 3.18 DC link Voltage (U
dc
)
1) Enclosure sizes A, B, C
2) Enclosure sizes D, E, F
Use the brake resistance R
rec
, to ensure that the adjustable
frequency drive is able to brake at the highest braking
torque (M
br(%)
) of 160%. The formula can be written as:
R
rec

Ω = 
U
dc
2
x100
P
motor
xM
br( % )
xη
VLT
xη
motor

η
motor
is typically at 0.90
η
VLT
is typically at 0.98.
When a higher brake resistor resistance is selected, 160%/
150%/110% braking torque cannot be obtained, and there
is a risk that the adjustable frequency drive cuts out of DC
Link overvoltage for protection.
For braking at lower torque, for example 80% torque, it is
possible to install a brake resistor with lower power rating.
Calculate size using the formula for calculating R
rec
.
Adjustable frequency drive D and F enclosure sizes contain
more than one brake chopper. Use a brake resistor for
each chopper for those enclosure sizes.
The VLT
®
Brake Resistor MCE 101 Design Guide contains the
most up-to-date selection data, and describes the
calculation steps in more detail, including:
•
Calculation of braking energy
•
Calculation of brake resistor peak power
•
Calculation of brake resistor average power
•
Braking of inertia
System Integration
VLT
®
AQUA Drive FC 202
62 Danfoss A/S © 09/2014 All rights reserved. MG20N622
33

Danfoss VLT AQUA Drive FC 202 Specifications

General

Brand	Danfoss
Model	VLT AQUA Drive FC 202
Category	DC Drives
Language	English