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IRPT 4052
During power-up and power-down, or in the event of
overcurrent (OI) or overtemperture (OT), the
latch
inhibits the
PWM gate, deactivating the gate drive circuits and shutting off
the inverter.
The
relay control circuit
delivers an on/off signal via an
opto-isolator to the relay driver which controls the relay (K1).
The relay contact is open during power-up, inserting the resistor
R in series with the DC bus capcitor and limiting the capacitor
charging current. In normal operation, the relay contact is closed.
If the AC line voltage falls below 300V or if one input phase is
lost, or if the DC line voltage falls to less than 82% of the peak
line voltage, the relay contact opens.
The
UV circuit
senses the voltage of the local power supply,
and sends a signal via an opto-isolator to the latch in the event of
undervoltage. The UV circuit normally activates the latch only
during power-up and power-down, preventing the IGBTs from
being turned on when the local power supply voltage is too low
for proper IGBT switching.
The
current signal processing circuit
receives inputs from
current transformers connected in series with the input lines and
the DC bus capacitor. The output of the current signal processing
circuit, IFB, is essentially an isolated replica of the inverter input
current. An isolated current feedback signal, I
FB
, is provided as
an output of the IRPT4052A. If the inverter current exceeds the
trip level of 45A, I
FB
also activates the latch.
The
thermistor
activates the latch if the temperature of the
IMS substrate exceeds a set level. The 15V isolated power sup-
ply used to power the IRPT4052 should be the same as the one
for the PWM generation, otherwise the protection functions will
be disabled.
The
switching power supply
delivers a nominal 18V DC out-
put, referenced to the negative DC bus, N. This feeds the gate
drive, relay control and under voltage (UV) circuits, which are
optically isolated from the control input section, and therefore
require their own local power source.
Figure 3. IRPT4052D Driver-PlusBoard