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Electrical functions
3.15
Parallel operation
3.15.1 Redundant operation
Up to 2 Power Supply Units can be used in redundant
operation. If you need more than 2 units operating redun-
dantly, please contact Delta.
An Or-ing circuit is built-in to prevent that the redundant sys-
tem fails when a single unit fails.
The maximum start-up load of the redundant system may
not exceed the maximum output current of a single power
supply, otherwise the redundant system may not power-up.
3.15.2 Special requirements for parallel operation
Up to 8 Power Supply Units of the same Maximum DC
output power can be used in parallel operation.
When you need to exceed the maximum output current of
one of the Power Supply Units during start-up, you have to
ensure that one of the following conditions is fulfilled:
1.
When you can ensure that the input voltages come in
simultaneously on both PSU: Set "Remote ON/OFF" to
ON (Y-Model: shorted, I-Model: open) before you apply
the input voltages.
2.
If you cannot ensure that the input voltages come in
simultaneously: Set "Remote ON/OFF" to OFF (Y-
Model: open, I-Model: shorted) before you apply the
input voltages. After the input voltages are available,
set „REMOTE ON/OFF" simultaneously to ON for both
Power Supply Units.
For more information about the REMOTE ON/OFF function,
see "3.11 Remote ON/OFF", p. 8.
Remote Sense+
Remote Sense-
Power
supply
CS bus
unit
Vout+
Vout-
Remote Sense+
Remote Sense-
Power
supply
CS bus
unit
Vout+
Vout-
Fig. 15: Active Current Sharing (CS) bus - functional diagram
10
3.16
Current sharing
The Power Supply Unit has an Active Current Sharing
circuit for the Main DC Output, in order to ensure output
current balance during parallel operation.
An One-wire Current Share bus (CS bus) is used to achieve
current sharing between the Power Supply Units. For par-
allel operation, the CS buses of all Power Supply Units of
the redundant system have to be connected. The CS Bus
is connected to the signal connector J3 Pin 11 (CURRENT
-SHARE_V).
The voltage at the CS pin will vary linearly with load current
on Main Output; and will be 6 V at rated load current, when
the output voltage is at its rated value.
The difference in output voltage can impact the current
sharing accuracy. All outputs fo the Power Supply Unit
are factory-set within rated voltage ±50 mV. If you need to
adjust the output voltage in the end user application, adjust
the output voltage of each power supply to the same volt-
age level which will be used in parallel. It is recommended
to set the output voltage within ±50 mV of the target volt-
age.
Parallel units share load current within ±10% of each other.
The maximum error has to be calculated as follows:
Maximum error =
I
The current of the Power Supply Unit with
PSUmax
the highest current
I
The current of the Power Supply Unit with
PSUmin
the lowest current
This applies for all loads greater than 25% rated output of
each Power Supply Unit.
See Fig. 15, p. 10.
IMA-x1000-xx-Series_Application_Note_V4.0_XX_EN_2019-08-19
I
- I
PSUmax
PSUmin
I
PSUmax
Vin+
Load
Vin-
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