Parker AC890PX Series, Инженерный справочник

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C h a p t e r 4 : A s s o c i a t e d E q u i p m e n t
4-3
AC890PX AC Drive
External Braking Resistors
Main Points
♦
We recommend using a thermal overload switch to protect the braking circuit. Refer to page 4-5.
♦
Use the DSE 890 Configuration Tool to configure the following parameters in the AC890PX drive:
Set the INT DB RESISTOR parameter (PREF 31.75 in the DYNAMIC BRAKING function block) to FALSE. Also
enter information about the external resistor being used in to this function block. Enable the "Brake Resistor" and
"Brake Switch" trips in the TRIPS STATUS function block (DISABLE TRIPS parameter).
IMPORTANT
The continuous rating quoted is not to be exceeded under repetitive loading.
Calculation
Brake resistor assemblies must be rated to absorb both peak braking power during deceleration and the average power over
the complete cycle.
Peak braking power P
0 0055 n n
t
W
1
2
2
2
b
=
× −
. ( )
( )
pk
×
J
J - total inertia (kgm
2
)
n
1
- initial speed (rpm)
Average braking power P
P
t
av
pk
c
=
x t
b
n
2
- final speed (rpm)
t
b
- braking time (s)
t
c
- cycle time (s)
Obtain information on the peak power rating and the average power rating of the resistors from the resistor manufacturer. If
this information is not available, a large safety margin must be incorporated to ensure that the resistors are not overloaded.
By connecting these resistors in series and in parallel the braking capacity can be selected for the application.