92 Rockwell Automation Publication 750-PM001N-EN-P - February 2017
Chapter 3 Drive Port 0 Parameters
385 DB ExtPulseWatts
Dynamic Brake External Pulse Watts
Sets the thermal transient response of the external dynamic brake resistor defined by
the maximum allowable power to the dynamic brake resistor for 1 second without
exceeding the resistor’s element temperature. This parameter is only valid when an
external dynamic brake resistor is selected (P382 [DB Resistor Type] = 1 “External”). If
this value is not available from the resistor vendor it can be approximated by 1 or 2
below:
1. [DB ExtPulseWatts] = 75,000 x weight (lb), where weight is the weight of the
resistor wire in pounds (not the weight of the entire resistor).
2. [DB ExtPulseWatts] = Time Constant x Brake Watts, where the Time Constant equals
the amount of time to reach 63% of its rated temperature while the maximum power
is applied to the resistor and Brake Watts is the maximum continuous power rating of
the resistor.
Many external resistor pulse watts settings are provided in the PowerFlex Dynamic
Braking Resistor Calculator, publication PFLEX-AT001
, or consult the resistor
manufacturer for this specification.
Note: If the value of this parameter is set equal to the value of P384 [DB Ext Watts], an F5
“Overvoltage” fault can occur.
Important: If customer supplied protection is to be used in place of the drive’s
calculated resistor thermal protection, set the [DB ExtPulse Watts] to its maximum
value.
This information may show up on your resistor in Joules or Watt-seconds. Use that value
in this parameter. Contact the resistor manufacturer if that information is not provided.
Units:
Default:
Min/Max:
Watt
2000.00
1.00 / 100000000.00
RW Real
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No. Display Name
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Description
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Data Type
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