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Continuous braking
For continuous braking, a brake resistor should be
selected in which the constant braking power does not
exceed the mean power P
Please contact your Danfoss supplier for
further information.
Optimal braking using resistor
Dynamic braking is useful from maximum speed
down to a certain frequency. Below this frequency
DC braking is to be applied as required. The most
efficient way of doing this is by using a combination
of dynamic and DC braking. See the illustration.
NOTE
When changing from dynamic to DC braking,
there will be a short period (2-6 milliseconds)
with very low braking torque.
How to calculate optimum DC-brake cut in frequency:
Slip S=
Synchronous speed
f=frequency
p = no. of pole pairs
n
= speed of the rotor
n
DC-brake cut in frequency =
Brake cable
Max. length [ft]: 30 ft (10 m)
MG.90.F2.22 - VLT is a registered Danfoss trademark
of the brake resistor.
AVG
[1/min]
Hz
Decentral Solutions
In the great majority of cases, the variable frequency
drive is used by professionals of the trade as a complex
component forming part of a larger appliance, system
or installation. Connect the shield to the conductive
backplate at the variable frequency drive and to the
brake resistor metal cabinet by means of cable clamps.
NOTE
If Danfoss brake resistors are not used,
it must be ensured that inductance for
the brake resistor is low.
175
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