Technical data

1
How do I put the power supply in the
constant current mode?
The power supply cannot be “put”
into the constant current mode. The
output settings of the power supply
combined with the ohmic value of
the particular load determine
whether or not the power supply
is in constant current.
ie: The power supply inherently
resides in the constant voltage
mode. If the output voltage were set
to 24 volts and a 6 Ω load were
placed across the output terminals,
Ohm’s Law would require that
4 amps would flow (24 V/6 Ω). This
presumes that the constant current
setting of the power supply were set
to a value greater than 4 amps; lets
say 5 amps. Now, if the 6 Ω load were
replaced by a 2 Ω load, Ohm’s Law
would suggest that 12 amps (24 V/
2 Ω) would flow. However, the power
supply is set to go into constant cur-
rent at 5 amps. Therefore, the actual
output voltage would be 10 volts
(2 Ω x 5 A). The power supply will
now remain in constant current for
values of load = 0 Ω≤R < 4.8 Ω. Once
the ohmic value of the load becomes
greater than 4.8 Ω (24 V/5 A), the
power supply will again revert to
constant voltage operation at the
value of 24 volts.
Agilent Technologies
Power Products Catalog 2002-2003 For more detailed specifications see the product manual at www.agilent.com/find/power
107
Applications Information
2
I have 208 vac, 3␾ phase power; can it be
used to operate a product requiring 208 V
single phase?
Yes, see below.
3
Why are the required Watts and
VA so different?
Watts is a scalar quantity which is
frequently used to measure system
efficiency. It is the energy supplied
by the utility company over a given
period of time and is commonly
referred to as power. Except for
heavy industrial users, the utility
company only bills users for the
watts consumed. Watts are directly
convertible into mechanical work or
BTUs (British Thermal Units) of
heat. Wasted power is paid for a
second time in terms of additional
loading on the user’s air-conditioning
system. Mathematically, it is a scalar
quantity resulting from the vector
product of two vector quantities
(volts and amps). It is NOT the
simple algebraic product of the
rms volts times rms current.
VA on the other hand IS the scalar
quantity resulting from multiplying
the magnitudes (rms) of the vector
Note: Connections are made
from phase to phase.
Instrument requires an
ac input voltage in the
window 191-250 Vac
Earth
(Safety Ground)
NL
120 Volts (Typ) 208 Volts (Typ)
Rear of Instrument
C Phase
A Phase
B Phase
Assume V (nominal) = 208 Vac
208 V @ 8% low = 191 V
208 V @ 12% high = 233 V
(Instrument operates between 191 & 250 Vac)
instrument will not operate on a 120 Vac line
10 Most frequently asked questions
about using dc power products
657xA/667xA Connection to a 3-phase line
10 Most frequently asked questions about using dc power products
ac Power and Load Connections
Agilent Application Notes
Power Products Terms