Emerson E300 Series - Page 420

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420 E300 Design Guide
Issue Number: 1
Figure 8-35 Under-voltage and power supply control
Under-voltage system
The under-voltage system controls the state of Under Voltage (L19) which is then used by the sequencer state machine. Each under voltage
threshold detection system includes hysteresis of 5 % of the actual threshold level therefore:
* Hysteresis is 5 % subject to a minimum of 5 V
When Under Voltage (L19) = 1 the sequencer state machine will change to the UNDER_VOLTAGE state and when the UNDER_VOLTAGE state is
active it is not possible to enable the drive inverter. The under-voltage system operates in different ways depending on the setting of LV Supply Mode
Enable (O12).
If the low under-voltage threshold is used or if back-up supply mode is selected the internal drive power supplies are normally powered from the 24 V
supply input (i.e. Digital I/O 13). User Supply Select (O10) should be set to one to select this supply and its monitoring system. (It should be noted that
in Regen mode LV Supply Mode Enable (O12) is not present, and so back-up supply mode cannot be selected.)
It should be noted that the under-voltage threshold used with a thyristor based charge system and the charging rate (Slow Rectifier Charge Rate
Enable (O17)) are automatically saved within the rectifier units each time the value is changed because these will be required at the next power-up
before the drive control system is active. These values will be retained when they are changed 128 times. If any more changes are made between
power-up and power-down the new values are not retained.
Standard mode: LV Supply Mode Enable (O12) = 0
If Low Under Voltage Threshold Select (O13) = 0 then the under voltage threshold is defined by Standard Under Voltage Threshold (O11). If Low
Under Voltage Threshold Select (O13) = 1 then the under voltage threshold is defined by Low Under Voltage Threshold (O14).
Frame size 06 drives and smaller have a d.c. link charge system based on a charge resistor and shorting contactor that is in circuit for both the a.c.
and d.c. inputs of the drive. The charge system is generally active (contactor open) when Under Voltage (L19) = 1 and inactive when Under Voltage
(L19) = 0. The exception is that there is a delay of 50 ms while the contactor changes state and during these periods Under Voltage (L19) = 1.
If the d.c. link voltage is above the under-voltage threshold and Under Voltage (L19) = 0 a large surge of current can occur if the a.c. supply is
removed and then reapplied to the drive. For a given level of supply voltage the worst case surge occurs when the supply is applied at the point where
one of the line voltages is at its peak. The surge is proportional to the difference between the d.c. link voltage before the supply is reconnected and
the
mag
nitude of the supply voltage. The minimum setting and default for Standard Under Voltage Threshold (O11) corresponds to the lowest d.c. link
voltage level where the maximum allowed a.c. supply voltage can be applied without damaging the drive or rupturing the recommended supply fuses.
Therefore it is safe to adjust the under-voltage threshold using the Standard Under Voltage Threshold (O11).
If the under-voltage threshold needs to be lower than the minimum of Standard Under Voltage Threshold (O11), then the Low Under Voltage
Threshold (O14) should be used. It is important that the difference between the under-voltage threshold level and the peak of the supply voltage is
never larger than the difference between the minimum Standard Under Voltage Threshold (O11) and the peak of the maximum allowed a.c. supply
voltage for the drive.
D.C. Bus Voltage (J65) Under voltage detection
Vdc Active
Threshold ≤ Vdc No change
Vdc ≥ Threshold x 1.05* Not active
Standard Under-voltage
Threshold (O11)
Low Under-voltage
Threshold (O14)
0
1
O
19
Under Voltage
Active
Low Under-voltage
Threshold Select (O13)
Under -voltage and power supply control
D.c. link voltage (J65)
+
-
0
1
Backup Supply Mode Enable
(O12)
Under-voltage control logic
O
15
Under
-voltage
System Contactor
Close
Under
-
voltage
System
Contactor Closed
(O16)
Final drive enable
Slow Rectifier Charge Rate Enable (O17)
User Supply Select(O10)