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A diode rectifier is the lowest cost
and most simplistic type of exciter.
This type of exciter is a combination
isolation transformer with numerous
taps and a non-regulated diode rectifier.
The voltage output of the rectifier
is a direct ratio of AC input to DC
output. The exciter output voltage
can only be adjusted by changing transformer
taps. The current passed to the field
is a function of the exciter voltage
and field resistance (Ohm’s
law E=IR). The transformer taps can
only be changed with the motor and
exciter off line. Standard taps provided
are five 5% full current capacity
taps below the nominal voltage. Total
of six taps provided. Kinetics manufactures
all our own transformers, with copper
conductor as our standard, from 1
to 2000 KVA up to 15 KV class. Providing
additional taps to the primary or
secondary of the transformer is an
available customer option.
A full current rheostat can be added
to the output of a diode rectifier
for manual voltage adjustment to the
motor field. In many cases the cost
of adding a rheostat exceeds the cost
of a SCR regulated rectifier.
Depending on the field application
control scheme, a CP exciter may or
may not be applicable. Care needs
be taken to assure compatibility between
the exciter and field application
controls.
"CP" exciters tend to be
used on motors below 500 Hp. Units
are available for single phase or
three phase input at a customer’s
request.
The Kinetics models MVR & CVR
are heavy duty, AC line regulated
"CP" diode rectifiers designed
and rated for highly inductive loads.
A robust design enables units to withstand
the spikes and surges commonly associated
with synchronous motor field applications.
• Model MVR 1 to 20 KW in
capacity at 125 or 250 VDC nominal
• Model CVR 22.5 to 2000 KW
capacity
Units are with standard features
of AC line protection, EPT exciter
power isolation transformer, AC surge
suppression, semi-conductor fusing,
diode rectifier, DC surge suppression,
DC bleed resistance, annunciation
and enclosure or chassis assembly
for mounting in a switchgear cell.
Kinetics exciter units are designed
specifically for the high transient
power spikes and surges associated
with highly inductive loads. The rectifier
is protected with robustly rated MOV
surge suppressors, a DC bleed resistance
and diodes with a minimum peak inverse
voltage (PIV) rating of 8 times the
AC RMS voltage into the diode primary.
"CP" exciter models MVR
& CVR can be supplied as an excitation
system when combined with Kinetics’
field application panel model SYNCHAPP-C
for brush type motors and/or Kinetics’
KinetSync digital logic annunciation
and control module.
Cautionary
notes:
1) Diode rectifier exciters may not
incorporate the use of solid state
SCR switching for field application.
A CP exciter field application method
must be a contactor application system.
2) For retro-fit applications, where
only the exciter is being replaced,
the application control scheme must
be confirmed to be suitable for a
constant potential exciter. For application
information, please reference our
engineering library, of our web site,
for a white paper titled: Application
of Regulated & Non-Regulated Rectifiers
to Synchronous Motor Field Excitation
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