Section VIII
Trouble-Shooting Guide
006-0007129 10/12/2018
Rev B
58 of 60
UPS-1500 3-Phase Guide
www.synqor.com
• A newly started load disturbs the existing UPS loads.
A common problem can occur when the UPS is running and powering one or more loads
connected to its AC OUTPUT, and then an additional load on the AC OUTPUT is turned “ON”.
If this newly started load draws a large current surge at startup, it can cause the current limit
of the UPS’s AC OUTPUT to be triggered, which in turn causes the output voltage to drop.
The drop could cause existing loads to be disturbed. Furthermore, if the voltage drops far
enough below the rated limit, the UPS will turn “OFF” its AC OUTPUT and initiate a new start-
up sequence. This latter action could cause an interruption on the existing running loads.
If power disruption to the loads is a problem, the solution is to make sure loads with large
startup surges are started first, and then proceed to start the rest of the loads.
• One of the 3-Phase AC INPUTS to the UPS is missing or out of range.
The UPS will detect a missing or out of range input phase and proceed to switch to the DC
INPUT source if present, or if not present, to the battery backup. The UPS will continue to
monitor the INPUT AC source and proceed to switch back automatically to the 3-Phase INPUT
source once the problem has been corrected.
• INPUT Cable wire resistance is too high:
The resistance of the INPUT power (AC or DC) cable is to high due to an excessive cable
length combined with an inappropriate cable size, loose panel/breaker terminals, connector
contamination or corrosion. The accumulated resistance in the cable, drops the INPUT AC or
DC voltage into the UPS below the rated limit during normal load conditions. This problem
is more common in DC INPUT cables, since the DC INPUT current is high (as much as 65 A at
full power) and the DC INPUT voltage is low (as low as 22 V). The phenomenon that may be
displayed is as follows:
Assume for simplicity that the AC INPUT source is not present and DC INPUT source is present
and within the specified voltage range. At standby, the UPS does not draw any or little power/
current from the DC INPUT. The voltage drop across the DC INPUT cable from the source to the
UPS is therefore negligible at this point.
