DC ALTERNATORS

The conventional method to have auxiliary DC Supply for battery charging & other DC Loads is to use a diesel generating set of constant speed & a rectifier unit.

Integrated Electric developed a variable speed DC Alternator for coupling with Diesel engine as a source of DC auxiliary power. The principle of working is as under. The basic generator will be just like any brushless AC Generator consisting of main stator, Main rotor, Exciter stator & Exciter rotor. The generator is of three phase, variable speed, variable kW output, 

For. Example the DC Alternator is capable of delivering:

• 2 kW at 750 RPM

• 4 kW at 1500 RPM

• 8 kW at 3000 RPM

The control panel consists of a basic digital automatic voltage regulator. Diode bridge to convert AC To DC, DC Choke, DC Capacitor bank, a key board for programming the desired DC Output voltage, Battery current, Total overall current.

SYSTEM FEATURES

• The DC Alternator delivers constant DC Voltage at the terminals up to its rated load battery current or total full load & subsequently the voltage drops depending upon load & hence protect the Engine, Alternator & the load.

• User settable DC Output voltage, DC Battery current & DC Overall current

• The control panel gives signal to electronic governor of the engine to operate at sub-synchronous (settable) and super synchronous speeds (settable) to get optimum fuel consumption & hence increase efficiency of the system & further increases the life of the engine

• Ripple will be less than 100 mV with battery & less than 300 mV with out battery

I.   The rotor of the revolving field generates a rotating flux which induces the following emf’s in the stator. The alternator builds up voltage with the help of residual magnetism & mainly from the permanent magnets housed in the exciter stator..

• 3 Ph. AC from the main armature windings.

• 2 Ph. AC from the auxiliary winding.

II.   The 3 Ph.AC from the main stator is fed to the Diode bridge.

III.   The automatic Digital voltage regulator (AVR) receives the following signals.

• DC Output voltage.

• 2 phase AC from the auxiliary winding.

• Speed feedback for frequency roll off

• DC Battery Current feedback.

• DC Total current feedback

The AVR uses these signals to compute the amount of excitation required to maintain the terminal voltage up to its rated current rating & reduce the terminal voltage on further loading of DC Alternator & hence protect the DC Alternator from over loading. The digital AVR also monitors the total overall load current & gives feedback signal to electronic governor to change the speed depending on load.

IV.   The Exciter field induces 3 phase AC at 100Hz. in the exciter rotor.

V.   The rotating diodes mounted in the exciter rotor rectify the AC voltage to DC Voltage and supply it to the Main rotor field winding 

VI.   This regeneration continues and till the rated DC output voltage is achieved. The output voltage will be maintained at its rated value up to its rated current as indicated on the name plate of the DC Alternator.

Ordering Details