Rockwell Automation 20D PowerFlex 700S AC Drives with Phase II Control Reference Manual User Manual
Page 25
Rockwell Automation Publication PFLEX-RM003E-EN-E - January 2011
25
Detailed Drive Operation Chapter 1
resistor vendor as the energy rating (in Joules) or a 1 second power rating (in
Watts) with typical values in the range of 30 to 100 times higher than the
resistor’s continuous power rating.
• Parameter 416 [Brake PulseWatts] = (Resistors peak energy in Joules)/1 s;
where the resistor package’s peak energy rating is obtained from the
resistor manufacturer.
When the resistor package’s peak energy rating cannot be obtained, there are a
few other ways to approximate parameter 416 [Brake PulseWatts]:
1.
[Brake PulseWatts] = 75,000 (watts/lbs) x Resistor element weight (lbs);
where 75,000 represents a specific heat of 0.11 cal/Kg
°
C (steel or
nichrome) and a temperature rise of 350
°
C, and the resistor element
weight is the total weight of the resistor wire element in pounds (not the
entire weight of the resistor cage).
For example a resistor with a nichrome element that weights 10 lb would
have:
2.
[Brake PulseWatts] = (Time Constant) x parameter 417 [Brake Watts];
where the Time Constant equals the amount of time for the resistor to
reach 63% of its rated temperature with applied rated watts (parameter
417 [Brake Watts]).
Parameter 417 [Brake Watts] sets the continuous watts for determining the
protection for an external brake. Enter the continuous watt rating of the resistor
cage (found on the resistor cage nameplate or from the resistor manufacturer) for
this parameter. This parameter is active only if the configuration is selected for an
external brake ([Brake/Bus Cnfg] bit 1 set to 1). When the internal brake resistor
is used then the protection is determined from the drive-internal values.
Parameter 369 [Brake OL Cnfg] determines how the drive reacts when the brake
protection is exceeded. Regardless of the setting in [Brake OL Cnfg], the drive
prevents the 7th IGBT from switching when the brake resistor protection,
determined in [Brake PulseWatts] and [Brake Watts], is exceeded. Some possible
settings for this parameter are:
Par 369 [Brake OL Cnfg] Setting
Drive Operation
0 - “Ignore”
The drive does not generate the “Brake OL Trip” fault or alarm.
1 - “Alarm”
The drive generates a “Brake OL Trip” alarm but does not
generate the “Brake OL Trip” fault.
2 - “FltCoastStop”
The drive generates the “Brake OL Trip” fault and issues a coast
stop.
3 - “FltRampStop”
The drive generates the “Brake OL Trip” fault and issues a ramp
stop.
4 - “FltCurLimStop”
The drive generates the “Brake OL Trip” fault and issues a
current limit stop.
Parameter 416 [Brake PulseWatts]
75,000
10
×
750,000 Watts
=
=