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Fluke 434/435
Users Manual
13-4
Available function keys:
F1
Selection of signals to be displayed: V displays all voltages,
A displays all currents. A (L1), B (L2), C (L3), N (neutral)
give simultaneous display of phase voltage and current.
F3
Return to Meter screen.
F4
Access to trend screen.
F5
Switch between HOLD and RUN of screen update.
Switching from HOLD to RUN invokes a menu to select
immediate (NOW) or TIMED start time which allows you
to define start and duration of the measurement.
Tips and Hints
The voltages and currents in the Meter screen can e.g. be used to check if power applied
to a 3-phase induction motor is in balance. Voltage unbalance causes high unbalanced
currents in stator windings resulting in overheating and reduced motor life. The Negative
Voltage component Vneg. should not exceed 2 %. Current unbalance should not exceed
10 %. In case of too high unbalance, use other measuring modes to further analyze the
power system.
Each phase voltage or current can be split-up into three components: positive sequence,
negative sequence, and zero sequence.
The positive sequence component is the normal component such as present in balanced 3-
phase systems. The negative sequence component results from unbalanced phase-to-
phase currents and voltages. This component for instance causes a ‘braking’ effect in 3-
phase motors: this will result in overheating and life reduction.
Zero sequence components may appear in an unbalanced load in 4 wire power systems
and represent the current in the N (Neutral) wire. Unbalance exceeding 2 % is considered
as too high.
Additional to unbalance percentages (%, relative reading), you can select absolute
readings. This type of readings is of use for measurements in power distribution systems
where negative sequence protection relays with adjustable tripping characteristics are
used. These relays are used to protect three phase generators. In this case it is practical to
measure the absolute value of the negative sequence current component (Aneg).