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Power Protection and Conditioning
A constant voltage regulator will protect both itself and its
load against damage from excessive fault currents. Fusing
of load currents may not be necessary. The actual value of
short-circuit current varies with the specic design and
rating. Units may be operated indenitely at short-circuit.
This characteristic protects the unit itself as well as the load
and load circuit being served. Typical overload
performance is shown in Figure D.
Motor Loads
Because of the fast response time of the SolaHD circuit, any
current-limiting characteristic must be taken into account
for transient overloads such as motor starting and solenoid
operation. In general, the SolaHD constant voltage regulator
must have a capacity nearly equal to the maximum demand
made on it, even for an instant. To determine the power
rating of the regulator, peak motor-starting current or
solenoid inrush current should be measured or power factor
correcting capacitors should be used to reduce the starting
VA of the load.
Response Time
An important advantage of SolaHD’s ferroresonant
transformer is its fast response time compared with other
types of AC regulators. Transient changes in supply voltage
are usually corrected within 1½ cycles or less; the output
voltage will not uctuate more than a few percent, even
during this interval.
Figure D: Overload Performance
Figure C: Power Factor
Power Factor
SolaHD power conditioners regulate any power factor load.
Output voltage is a function of load current and load power
factor (see Figure C). If lower voltage under lagging power
factor is objectionable, correction may be made with capaci-
tors at the load. “Median” value of output voltage will vary
from the nameplate rating if the load has a power
factor other than that for which the transformer was
designed. Load regulation will also be relatively greater as
the inductive load power factor is decreased (see Figure C).
However, the resulting median values of output voltage will
be regulated against supply line changes at any reasonable
load or load power factor.
Efficiency
The copper magnet wire and lamination material used in
SolaHD ferroresonant products are selected to achieve
efciencies of 90% or higher. Whether or not an external load
is being served, current will be drawn from the line whenever
the primary is energized, since the capacitor remains
connected in the circuit.
Overload and Short Circuits
When the load is increased beyond the regulator’s rated
value, a point is reached where the output voltage suddenly
collapses and will not regain its normal value until the load is
partially released. Under direct short circuit, the load current
is limited to approximately 150-200% of the rated full load
value and the input watts to less than 10% of normal.
Operating Characteristics of the CVS & MCR Series
Except as noted, all characteristics of SolaHD’s CVS products also apply to the MCR series.