SynQor MPC-1500 Series, Operator'S Manual, Page: 46 / 48

Section VII Trouble-Shooting Guide
006-0006452 MPC-1500 Operator Guide Rev P 46 of 48 03/03/2021 www.synqor.com
▪ A newly started load disturbs the existing MPC loads.
A common problem can occur when the MPC is running and powering one or more
loads connected to its AC OUTPUT, and then an additional load of the AC OUTPUT is
turned on. If this newly started load draws a large surge current at start-up, it can cause
the current limit of the MPC’s AC OUTPUT to be triggered, and the AC OUTPUT voltage
will then drop. This drop could cause the existing loads to be disturbed. Furthermore,
if the voltage drops far enough, the MPC will turn off it AC OUTPUT and initiate a new
start-up sequence (after 0.1 seconds). This latter action would cause the power flow to
the existing loads to be interrupted.
If this disruption of existing loads is a problem, then the solution is to make sure the
loads that display this start-up surge characteristic are all started first, or that all loads are
started at the same time.
• Cable wire resistance is too high:
As mentioned in the section “Power Cables Wire Size”, the resistance of a power cable’s wires
gives a voltage drop from the upstream to the downstream end of the cable. This voltage
drop, if large enough, will cause the either MPC to determine that the voltage at its AC INPUT
or its DC INPUT is below its minimum specified value, even though the corresponding voltage
at the source of AC or DC power is within the specified range.
This problem is particularly possible for the DC INPUT, since the DC INPUT current is so high (as
much as 65 A at full power) and the DC INPUT voltage is so low (as low as 22 V).
The phenomenon that may be displayed is the following.
▪ Assume the AC INPUT source is not present, but the DC INPUT source is.
▪ The MPC, before it turns on, does not draw any power or current from the DC INPUT, and
therefore the voltage drop across the DC INPUT cable is zero.
▪ The MPC sees that the voltage at the DC INPUT is within its specified range, and enables
its outputs.
▪ As the load then draws power, the MPC begins to draw current from the DC INPUT cable.
This current causes a voltage drop to appear across the cable.
▪ If the voltage at the DC source is close to, but still above, its 22 V minimum, but the voltage drop
across the cable is large enough for the voltage at the DC INPUT of the MPC to fall below 22 V,
then the MPC will determine that the DC INPUT is out of range and will shut down.
▪ Since the MPC no longer draws current from the DC INPUT, the voltage drop across the DC
INPUT cable goes back to zero volts.