4th Generation IGBT for Jaguar inverters

Edited by the Engineeringtalk editorial team Dec 14, 2000

Future IMO Jaguar inverters will incorporate the very latest state-of-the-art power devices from the world's leading designer, manufacturer and supplier of power semi-conductors.

Future IMO Jaguar inverters will incorporate the very latest state-of-the-art power devices from the world's leading designer, manufacturer and supplier of power semi-conductors.

The 4th Generation IGBT has evolved from tried and tested technology that for the last decade at least, has been the de facto standard in industrial electronic motor drives.

About five years ago, the first Intelligent Power Modules (IPM's) were introduced.

These were financially extremely competitive over a wide power range when compared to discrete IGBT's which required a lot of external circuitry in addition to sophisticated cooling, driving and protection arrangements.

Moreover, the IPM's combination of power devices and associated ancillary circuitry to one chip, gives a much more efficient, designer-friendly and complete solution to the drives' power stage.

The 4th Generation IPM to be used exclusively in future Jaguar inverters has many clear advantages when compared to the discrete devices still used by so many European and American drive manufacturers.

These include: * Only Silicon semi-conductor chips are used * Excellent noise immunity * Individual junction temperature detection * Very low losses * Reduction in leakage current A brand new monolithic driver IC has been developed and incorporated within the module and contains all the main device protection functions.

All the upper IGBT's have one dedicated driver each, while the lower devices share one between them.

This has major advantages and overcomes the switching difficulties associated with discrete devices, resulting in a 20% reduction in on-state losses when compared with 3rd Generation devices.

All of this reduces heat losses within the device and so extends module operating life expectancy considerably.

The actual IGBT and flywheel diodes will be mounted directly onto the copper heatsink with only the substrate layer between them.

This efficiently eliminates the thermal resistance which causes over temperature problems typical in other types of power module.

Also, because the high frequency switching actions within the IPM are now in much closer proximity to the ground plane, electro-magnetic emissions are lower than for previous, like-for-like power ratings.

Another feature of the new IPM is the incorporation of internal shunt resistors which obviate the need for large (and inaccurate) Hall effect CT's in the inverter output stages.

This allows for precise voltage drop measurements across the resistances proportional to load current, and hence faster response to instantaneous overcurrent, such as short circuit or earth fault conditions.

The torque vector control measurements are also referenced here.

Further advances have seen the incorporation of voltage spike suppression by high gate resistance and soft switching the collector current under fault conditions.

This again, considerably increases the life of the devices.

Overheating, the biggest single cause of IGBT failure in inverter drives has now become a thing of the past.

Earlier designs incorporated a single thermistor bead mounted in close proximity to the devices, usually bonded directly to the heatsink.

Any internal device which was overheating would need to see the excess temperature energy disperse itself through the device, base board, thermal compound and penetrate deep into the main heatsink before the thermistor and associated circuits could respond.

Indeed, by the time the drive tripped, permanent damage could have occurred within the devices due to thermal destruction or degradation of the silicon junctions due to an excessive time constant With the 4th Generation IPM, a junction temperature diode is created with an extra pair of polysilicon wafers as part of the device internal architecture, so enabling much faster recognition of abnormal temperatures at the actual junction of all 6 IGBT devices.

To date, some 5,000 next generation Intelligent Power Modules have been incorporated into the new Jaguar VXM's sister product which was introduced recently into the Asian market with spectacular performance in the MTBF figures to date and impressively low, overall product failures relating directly to main power device failure.

Feedback is positive and encouraging when compared to failure analysis of other types of device commonly used in the field of general purpose inverter drives.