72V Engine Mounted Generator

An engine-mounted 72 V generator puts a permanent magnet alternator directly on the prime mover you already have, in place of a conventional alternator and its rectifier. Innotec Power winds these heads for a 72–84 VDC output, which is the charging window of a 72 V battery bank, so the head feeds the bank without an inverter stage and without a separate charger.

The construction is the same across the range: brushless and bearing-less, with no slip rings, no exciter and no diodes inside the machine. On flywheel-mounted builds the rotor runs on the engine’s own bearings, which removes the last consumable from the alternator entirely.

72 V heads are built in three drive configurations. The flywheel-mounted units are the same 310-series machines used inside the 14 kW and 25 kW complete DC generator sets, supplied on their own when you are mounting to your own engine.

Duty points between and around these are wound to order — the frames run from the 145 series up to the 360, and the winding is chosen from your speed and voltage rather than picked off a shelf.

At 72 V the current is a third of what the same power costs at 24 V, which is most of the reason to specify this bus. A 14 kW head delivers roughly 170–195 A across the 72–84 V window, and a 25 kW head roughly 300–345 A. Cable, glands, fuses and contactors all come down accordingly.

Output can be configured two ways. With a regulator the head holds a constant terminal voltage, which suits a fixed DC load. Without one it is set to a charging range and taken straight to the bank, with engine or drive speed varied to follow the charge curve. Peak efficiency is engineered above 90%, and the machines are built for high vibration, high ambient temperature and continuous duty.

The same machine can be specified to work in both directions. In starter/generator duty it cranks the prime mover, switches to generation once running, and recovers energy under braking in hybrid drivelines. That removes the separate starter motor and its ring gear, and it takes the starting torque demand off the engine. It is worth raising early — the winding and the controller are chosen differently for dual-direction duty.

To quote a 72 V head we need the duty point in kW, the shaft speed or speed range, the mounting interface (flywheel diameter and bolt pattern, SAE housing, J609 face or foot), the cooling available, and whether you want a temperature sensor and position feedback. Tell us the battery chemistry too, because it sets the charging window inside the 72–84 V range.

Related: the complete 72 V DC generator sets, the 72 V PTO generator range, 48 V and 96 V engine-mounted heads, and the DC generator head overview. The same 72 V frames also run as motors across the 72 V motor range.