Manual

www.schaeferpower.de
Technical Notes Technical Notes
Operational Characteristics
AC or DC input DC output
inrush current
Power factor correction (PFC)
Power supplies draw line current in pulses from the input
supply
. Should it be required, a PFC will integrate these pulses
to be both, effectively sinusoidal in shape, and in phase with
the AC input supply. The result of this integration, be it active
or passive, is the reduction of the harmonic distortion and
allows a more effective loading of the input source.
Spike suppression
High input voltage spikes generated in the supply system that
could disturb oper
ation of the unit or cause damage will be
absorbed by a varistor across the input lines.
Input under and over voltage turn off
The input voltage range of the unit is defined as the voltage
limits at which it will operate. Should the input be reduced to
a specific voltage, the unit will turn off by switching off the
power circuit. The same applies to an increase in the input
voltage. Once a preset value is reached then the power circuit
will be switched off. It must be considered that the switching
off of the power circuit does not mean a removal of the input
circuit from the power supply.
Thermal shutdown with auto restart
The higher power Schaefer modules are fitted with a thermal
shutdo
wn. In the event of a temperature rise above a preset
value, the unit will turn off. This safety feature will then
remain active until the point of temperature measurement has
reduced significantly. The time duration for this to be reached
is dependent upon the environment and level of cooling.
Temperature derated load
It is the responsibility of the client to reduce the loading of the
Schaefer product with respect to the temperature (derated
load: 2.5 % / °C from +55 °C operating temperature). The
maximum operating temperature of +75 °C must lead to the
unit being switched off.
Efficiency
The optimum efficiency is obtained through a high input
voltage measured against a high output voltage at maximum
power rating.
Soft start
The application of the input power permits the unit to
generate a secondary output. The switching on of the primary
power circuit is controlled and gradually increased to allow
a controlled charging of the secondary capacitors. The time
duration for the secondary capacitors to be charged is defined
as the soft start.
No load operation
Single output converters require no minimum load for
operation within tolerance. Multi output converters require
the main output be loaded. Semi-regulated auxiliary outputs
may also require a minimum load to be applied.
Short circuit protection
The main output of a converter will be immune against
a momentary or continuous short circuit. The secondary
current limitation will not permit the sustained output current
to be higher than the calibrated setting, and it will actively
reduce the output voltage in accordance to the overload. The
removal of the overload / short circuit will result in the output
voltage being increased to the calibrated value. Regulated
auxiliary outputs will also reduce the output voltage / current
in accordance to their overloading. The characteristic may
vary according to the circuit employed.
Over voltage protection (OVP)
The main output voltage is measured, either internally or
thr
ough sense leads. This measured value is compared
against a calibrated value. When the calibrated value has
been reached, this circuit turns off the primary power circuit.
Once the measured value has reduced below the calibrated
value, the primary power circuit is permitted, once again, to
be activated. The high power units have an additional feature,
which will shut down the primary power circuit after a
continued OVP operation.
The input power must be re-cycled
in order to remove the unit from shut down.
voltage adjustment [V] 5 9 12 15 24 28 48 60 110 200 220 400
Over voltage protection [V] 6.5 12 15 18 30 35 60 70 140 220 280 440
Sense leads
Through the use of sense leads, an output voltage may be
r
egulated to a point outside of the unit. The sense leads should
be connected to the power connection at the point of load
under regard of polarity. There should be a non-interruptible
connection between sense and load points. Interruption
may lead to damage or the activation of the OVP circuit. The
units, which have sense leads, have the ability to regulate to
a higher voltage at the output connection. This increase is
largely dependent upon the unit. The details may be found in
the respective unit specification. Parallel operation with sense
leads allows a common point for the units to regulate their
voltages to. Units whose output voltage has been calibrated
to be near identical will now be able to supply a common
load.
De-coupled outputs will be sensed both, before and after the
decoupling diodes, which in turn will lead to an output
voltage regulation, specifi c to load and unit. Sense leads
are typically employed with a decoupled output voltage of
less than 40 VDC. The current sharing option will effectively
override the sense lead output voltage setting, but the point
at which the output voltage is regulated, will be the point of
sense lead connection.
-
+
-S +S
LOAD
+
-
When the module is connected to the input power, the
primary capacitors will be charged by a high current pulse. The
magnitude of this pulse depends mainly on the input supply
system. With a thermistor (temperature dependent resistor)
in series with the input, this current pulse can be reduced,
as the thermistor has a relatively high value of resistance as
long as it is cold. This resistance becomes very low as the
thermistor heats up. If the input power is interrupted for a
short period of time not allowing the thermistor to cool
down, and the primary capacitors are discharged, the current
limitation function of the thermistor will not be effective. The
thermistor is standard on mains input models up to 45 Amps
input current. For higher input current there are two further
alternatives available: Schaefer PFC or an electronic current
limitation.