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Auto Electricals from Bosch

Bosch Alternators

For close to a hundred years, Robert Bosch GmbH has been a world leader in Auto Electricals. The first batch of high-voltage Magnetos were delivered from Bosch, way back in 1902. This led to the development of high-speed automotive engines. In the years that followed, Bosch pioneered many a breakthrough development that spurred the phenomenal growth of the automotive sector. The thrust on quality, reliability and innovation endeared the Bosch name to millions of customers worldwide. Inspired by its principal’s worldwide success, Bosch Ltd. started its auto electricals operation in 1989. Today, Bosch Ltd. manufactures a wide range of Starter Motors and Alternators at its state-of-the-art plant in Naganathapura, near Bangalore, catering to the ever-increasing demands of the Indian automotive industry. A national field-service network has been set-up to provide comprehensive service support for all Bosch Ltd. products. A strong in-house Auto Electricals R&D set-up, supported by the rich experience and vast infrastructure of Robert Bosch GmbH helps Bosch Ltd. to offer the latest and the best technology to Indian customers.

Starter motor

Internal-combustine (IC) engines must be started by separate system because they cannot self-start like electric motor or steam engines. When starting these engines, considerable resistance resulting from compression, piston friction and bearing friction (static friction) must be overcome. Frictional resistance is highest at low temperatures. The starter (also known as the “starting motor”) must rotate the flywheel at a minimum starting speed overcoming these resistances. It must also continue to support rotation during initial combustion to maintain momentum until the engine can sustain operation.

Bosch Self Starters


Motor vehicles need their own efficient, reliable & constantly available source of energy for ignition, lighting, starting motor etc. When the engine is stopped, the battery represents the vehicle’s energy source, the alternator is the on-board “electricity generating plant” when the engine is in operation. The task of the alternator is to supply power to all current consuming loads. Alternator output, battery capacity & power demand of the loads must be matched to each other as ideally as possible so that the entire system is reliable & trouble-free in operation.

The requirements of an alternator are:

  • Supplying all connected loads with direct current.
  • Additional power reserves for the fast charging of the battery – even when continuous loads are switched on and when the engine is only idling.
  • Keeping the alternator voltage constant over the entire engine speed range.
  • As maintenance-free as possible in operation.
  • Rugged construction to withstand all external loading caused by vibration, changes in temperature, dirt, damp, fuel & lubricants.
  • Low weight & compact dimensions.
  • Low noise.
  • Long life.

Function :

The basis for the generation of electricity is formed by electromagnetic induction i.e. when an electric conductor cuts through the lines of force of a magnetic field, a voltage is induced in the conductor. It is immaterial whether the magnetic field remains stationary while the conductor moves, or vice versa.

The generation of three phase current in alternator takes place in conjunction with a rotary motion. There are three identical, independent windings which are arranged at 120° from each other. According to the law of induction, as the rotor rotates, sinusoidal alternating voltages & alternating currents of identical magnitude & frequency are generated in the windings.

The result is a constantly recurring rotation. The resulting three phase alternating current known as three phase current is rectified through semiconductor diodes since it cannot be supplied directly to the electrical loads or the battery.