Application notes
PS3031-2440-0000
35
Version: 1.0
4.4
Operation on two phases of a 3-phase system
No external protective devices are required to protect against phase failure.
This power supply can also be operated continuously on two strings of a 3-phase system. However, it is not
recommended for this performance class, since the feeding 3-phase network can become unbalanced.
Fig. 23: Operation on two phases
• When operating on only two strings of a three-phase system, the output power must be reduced
according to the curves below. Exceedance of these limit values over extended periods leads to
thermal shutdown of the system.
• Operation below 340 Vac with an output current of more than 30 A can also cause a thermal shutdown.
• When switching on, there may be some start-up attempts until the output power is fully available.
• EMI behavior, hold-up time, losses and output ripple are different from three-phase operation.
Therefore check the suitability for your individual application.
• The screw of the unused terminal must be firmly tightened.
• This kind of operation is not covered by the UL approval. Additional testing may be required if the
complete system has to be approved according to UL 508 or UL 60950-1.
Fig. 24: When using only two phases: Permissible output current; hold-up time
Fig. 25: Efficiency over output current at 24 V; losses over output current at 24 V
