48V Starter-Generator: Types and Structure

The automotive industry is constantly evolving and introducing new technologies to make cars more efficient and environmentally friendly. One such innovation is the MHEV technology, which includes a starter generator and a lithium-ion battery operating at 48V. The starter generator is responsible for starting the engine, generating electricity, creating additional torque during hard acceleration, and recovering braking energy. An engine with a starter generator can be switched off during a short stop, e.g. at traffic lights, and then restarted within a fraction of a second. The «soft hybrid» technology provides 10 – 15 per cent fuel savings, and most importantly -– reduced emissions.

The technology is designed to reduce the emissions of harmful substances into the atmosphere.

There are currently two principle starter-generator designs: belt starter generator (BSG) and integrated starter generator (ISG). The belt starter generator is integrated into the Front End Accessory Drive (FEAD). In this version, the starter generator replaces the conventional alternator in terms of role and installation.

Audi belt starter-generator

The integrated starter generator (ISG) replaces the engine flywheel, which provides higher power output and torque compared to a belt starter generator. However, the installation of an integrated starter generator is accompanied by significant engine modifications. In fact, you get a completely new engine. The belt starter generator is therefore more common due to its ease of integration into existing engines.

Mercedes-Benz-S400-BlueHyrbid Integrated Starter-Generator

How is a belt-driven starter generator designed?

The belt starter generator is structurally a three-phase alternating current (AC) motor with a built-in inverter. Depending on the capacity, the starter generator can be air-cooled or liquid-cooled.

Continental 48V belt starter generator

The belt starter generator is controlled and communicates with the engine control unit via the CAN bus. The starter generator also controls the coolant pump itself (if liquid-cooled) using pulse width modulated (PWM) signals.

. Disassembling a belt-driven starter-generator is not a trivial and time-consuming task. Under a single cover on the housing there are power electronics.

Seal electronics starter generator 48V Jeep Wrangler 2019–2021
On the power electronics side, the three-phase bridge, DC centre capacitor and external interface equipment are located. The power electronics has three H-bridges, one per phase. Each phase is welded to the motor controller busbars.

If you disconnect a pair of busbars from the controller, you can access the control board, bearing assembly and rotor. The control board is covered by a plastic cover welded to the housing cover. It is not possible to get to the control board without destroying the plastic cover.

Conclusion

Despite the great growth in the popularity of electric vehicles, automakers continue to improve internal combustion engine vehicles on the path of reducing CO2 emissions and fuel economy. The development of «soft hybrids» technologies with 48V power systems will create serious competition to the more complex and expensive high-voltage power systems of plug-in hybrid (PHEV) cars and electric vehicles.

The development of soft hybrids

With the development of 48V power systems, there is a need for more sophisticated and costly high-voltage power systems for plug-in hybrid (PHEV) cars and electric vehicles.

This article was written using material from https://transistor-man.com/everything_etorque.html