9
Power Capacity – “Continuous” and “Surge”
How much load can an XM Series UPS handle? Its power output is rated in VA. .There are two
levels of power rating –a continuous rating and a surge rating. Continuous means the amount of
power XM Series UPS is rated in Watts (VA x 0.7 = Watts), that number generally refers to its
continuous rating. The “Surge Power” indicates the power to handle instantaneous overload for
very short period to provide the higher power required to start certain type of devices and
appliances.
Loads that require “Surge Power” to start
Resistive types of loads (like incandescent lamps, toaster, coffee maker, electric range, iron etc)
do not require extra power to start. Their starting power is the same as their running power.
Some loads like induction motors and high inertia motor driven devices will initially require a
very large starting or “surge” power to start from rest. Once they have started moving and have
attained their rated speed, their power requirement reduces to their normal running power.
TVs and microwave ovens also require surge power for starting. The manufacturers’ specification
of the appliances and devices indicates only the running power required.
If an XM Series UPS cannot efficiently feed the surge power, it may simply shut down instead of
starting the device. If the XM Series UPS surge capacity is marginal, its output voltage will dip
during the surge. This can cause a dimming of the lights in the house, and will sometimes crash a
computer.
