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trol and power sections are run off the phase voltage. The IGBT is operated in such a manner that
the rectified sinewave voltage is applied to the load, which is wired between terminals 1D and D,
and the amplitude of this voltage can be altered by a control signal between terminals 3 and 4 of
X102.
JUMO, FAS 620, Edition 02.03 39
5 Power units on single/3-phase supplies
When using an IGBT power unit the current drawn from the supply is not the same as the current in
the load. If we neglect the losses in the power unit, the maximum input (supply) current can be cal-
culated as:
Pnom/Load[W]
(19)
IIN = --------------------------------------------------------------------------------------
Supply voltage to power section
The maximum load current is given by
Pnom/Load[W]
(20)
ILoad = -----------------------------------
Load voltage
Example: a heater element with a power rating of 5000W and a nominal voltage of 120V AC is driv-
en by an IGBT power unit that has a 230V AC supply to the power section.
The current through the heater element is:
5000 W
ILoad = -------------------- = 41.7 A
(21)
120 V
But the current that is drawn from the supply is:
5000 W
-
IIN H" --------------------- = 21.74 A
(22)
230 V
5.2.2 IGBT power units on 3-phase supplies
IGBTs can also be used in a 3-phase system, to achieve symmetrical loading of all three phases.
The circuit layout for this is quite simply 3 x single-phase sections (phase-N or phase-phase) con-
nected to the individual phases of the 3-phase supply.
40 JUMO, FAS 620, Edition 02.03
6 Filtering and interference suppression
To suppress RF interference, such as is generated by thyristor power units operating with phase-
angle control, the electrical equipment must be fitted with interference suppression devices.
The control electronics of JUMO power units meets the EMC requirements of EN 61 326.
However, electrical modules such as thyristor or IGBT power units do not have any purpose by
themselves. They provide a function as part of a complete system or installation. For this reason,
the manufacturer of the complete system or installation must provide suitable filters to suppress in-
terference from the power section of the power units.
There are a number of specialist companies that provide appropriate ranges of filters to deal with
any interference problems. Such filters are usually provided as complete modules, ready to be
wired into the system.
JUMO, FAS 620, Edition 02.03 41
6 Filtering and interference suppression
42 JUMO, FAS 620, Edition 02.03
7 Abbreviations
iTh1 = current through thyristor 1
iTh2 = current through thyristor 2
IOld = current through an old heater element
INew = current through a new heater element
IL = current in a supply phase
ILoad = load current
IIN = current in supply
ILoad = amplitude of the load current
IS = current through the power unit
POld = power in an old heater element
PLoad = power in the load
PNew = power in a new heater element
RC = cold resistance of a heater element
Rh = hot resistance of a heater element
TC = temperature coefficient (heater elements)
VOld = voltage on an old heater element
VN = phase-N voltage
VL = phase-phase voltage
VLoad = load voltage
VLoad max = maximum load voltage
VS = load voltage of the power unit
V~ = supply voltage
Vpk~ = peak amplitude of the supply voltage
W = set value (setpoint)
x= actual value
y= output level
yR = controller output level
± = phase angle
±Start = firing angle for 1st half-cycle in burst-firing mode
É t = phase angle at time t
JUMO, FAS 620, Edition 02.03 43
7 Abbreviations
44 JUMO, FAS 620, Edition 02.03 [ Pobierz całość w formacie PDF ]