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Shunt Regulator Operation
Refer to Chapter 4 for an explanation of the shunt regulator circuitry. The
nominal data for the shunt regulator is as follows:.
Overvoltage Trip Point
DC Bus Shunt "ON" Point
DC Bus Shunt "OFF" Point
Nominal DC Bus Voltage
DC Bus Undervoltage Detect
The shunt regulator behavior is modified by an adjustable duty cycle timer.
The timer is used to model the shunt resistor temperature. A selector switch
(SW1) determines the temperature level and therefore the average power
level at which the drive will fault. When this level is reached, the drive will
be forced to fault on an overvoltage. This action would be equivalent to
turning the shunt regulator off.
The Duty Cycle Selector Switch is located on top of the drive near terminal
Block, TB5 (see Figure 1.1). The switch has 16 positions designated "0 to
F," with "0" being the lowest value and "F" the highest. The higher the
setting, the higher the average power seen by the shunt resistor. The Duty
Cycle Selector Switch settings for various drive/shunt combinations are
shown in Tables 10.A and B.
Important: Accurate operation of the Duty Cycle Timer is dependent on
the shunt resistor value. Do Not substitute alternate values.
Important: Setting SW1 higher than the rating of the shunt resistor may
cause a blown fuse, resulting in repeated overvoltage faults. This will occur
until the fuse is replaced and/or the switch is set correctly (see Table 10.B).
Table 10.A provides the required Duty Cycle Selector Switch settings and
resistor power trip points for factory supplied configurations. An optional
external resistor assembly (catalog number 1391-MOD-SR22A) is
available for the 22.5A 1391-DES.
Table 10.A
Maximum Switch Settings and Trip Points for Factory Supplied Configurations
Configuration
1391-DES15 w/ standard 16 ohm internal resistor
1391-DES22 w/ standard 12 ohm internal resistor
1391-DES22 w/ 9 ohm external resistor (1391-MOD-SR22A)
1391-DES45 w/ standard 5 ohm external resistor
* Denotes SW1 setting at time of shipment. User must reconfigure drive when using optional
1391-MOD-SR22A.
ATTENTION: The designated settings for the factory supplied
!
configurations must be used or damage to the drive may result.
Chapter 10
Transformers and Shunt Regulators
= 405V DC 2.5%
= 386.4V DC
= 366.9V DC
= 300V DC
= 145V DC 20%
SW1 Switch
Nominal Trip
Setting
Point
B*
164w, 10%
B*
162w, 10%
F
386w, 10%
D*
715w, 10%
10-3
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