This invention relates to a snubberless inverter circuit. for three-phase induction motor drive with bus bar and component layout.
This invention is of a special design for busbar selection like dimensions (like size / thickness etc.) / shape end layout of busbar along with special design of component layout with specific attention to have an extremely low circuit inductance which enables the inverter to operate without a snubber, thus making it "a snubber less inverter" and gain the advantages in this type of inverter configuration and operation.
The availability of high power rating and economically priced semi-conductor devices has enabled the easy us* of high power switching devices, like Insulated Gate Bipolar Transistor (IGBT), even in mediuim and high power rating inverters of hundreds of kilowatts of power output. The IGBT is a fast turn-off device with high di/dt and dv/dt characteristics. Since the device is a fast turn-off type, the load current is turned off very fast cresting a high di/dt at device turn-off. The high di/dt created by IGBT turn-off results in a large over-voltage across the IGBT due to the stray inductance in the power circuit of the inverter.
According to the present invention there is provided a snubberless inverter circuit device for three-phase induction motor drive with busbar and component layout comprising a three—phase AC voltage input connected to a rectifier having plurality of diodes (D.I-D6) in three phase bridge rectifier configuration to convert AC voltage to DC voltage, said DC voltage is connected to a filter capacitor bank having plurality of capacitors (C1-C6) and is connected to an inverter through a lumped stray inductance, said inverter having plurality of transistor circuits (T1-T6) to convert the applied input DC voltage from said filter into a three phase AC voltage to an electrical load, the said capacitors (C1-C6) in the filter capacitor bank being connected in two groups in series, with three capacitors (C.t , C3, C5; C2, C4, C6) in each group connected in parallel such that the internal lead inductance of each filter capacitor (C1-C6) contributes minimum inductance to the circuit inductance in the commutation path of the capacitors.
The nature of the invention, its objective and further advantages residing in the same will be apparent from the
following description made with reference to the non-limiting exemplary embodiments of the invention represented in the
accompanying drawings.
Figure 1 shows the power circuit diagram of snubberlass IGBT inverter according to the invention.

WE CLAIM:
1. A snubberless inverter circuit for three-phase induction motor drive with busbar and component layout
comprising a three-phase AC voltage input (1) connected to a rectifier (2) having plurality of diodes (D1-D6) in three phase
bridge rectifier configuration to convert AC voltage to DC voltage, said DC voltage is connected to a filter capacitor bank (3) having plurality of capacitors (C1-C6) and is connected to sn
:inverter (5) through a lumped stray inductance (4), said inverter (5) having plurality of transistor circuits (T1-T6) to convert the applied input DC voltage from said filter (3) into a three
phase AC voltage to an electrical load (6), the said capacitors (C1-C6) in the filter capacitor bank (3) being connected in two
groups in series, with three capacitors (Cl, C3, C5; C2, C4, C6) in each group connected in parallel such that the internal lead inductance of each filter capacitor (C1-C6) contributes minimum inductance to the circuit inductance in the commutation path (7)
of the capacitors.
'2. The snubberless inverter circuit as claimed in clalim 1 wherein said load (6) comprises an electrical load of three phase? induction motor.
3. The snubberleas inverter circuit device for three-phase induction motor drive with designed busbar and component layout as herein described and illustrated with the accompanying drawings.