The Alternators Rotor is designed to consume a Maximum amount of 6 amps at 12 volts only at short periodes, That is, until the battery becomes charged enough to regulate the current and voltage at the rotor down.
Here is what i mean, The Alternator Monitors the Voltage coming from its stator. Once the stator is connected to the Load, "Battery" Which is sometimes Weak will cause a Drop of voltage at the Stator due to charging of the battery. Once the Internal circuit of the atlernator detects this Load drop more amps is directed to the Rotor, in most cases between 12, or 15 volts is maintained at all times. Once the battery starts to take a charge the internal circuit reduces the voltage and amperage to the rotor, At some point in time there will be low voltage and low current flow to the stator. 5 volts at 2 amps to the rotor at 3500 rpm's is capable of putting out 12.5 volts at well over 35 amps.
The smaller alternators Such as a 50, 55 to 60 and 75 amp alternators will only consume 3 amps of current at 12 volts. This means when you apply 12.5 volts to the rotor at 3 amps, the maximum number of amps that is allowed to flow threw the rotor you will only get out 55 amps of current at 12 to 15 volts. So a 55 amp alternator will Never operate with more than 3 amps consumed at its rotor, and higher output alternators will Never consume more than 6, to 7 amps depending on its rotors resistance.
At 12.5 volts on smaller alternators we know 3 amps is what is consumed. At 12.5 volts on the bigger alternators we know 6 to 7 amps can be consumed. The alternator has a built in fan to help cool its rotor coil. When you go above the threashold of 12.5 volts on any alternator you are forcing more current into a rotor. For example; If you apply 30 volts DC to the rotor of a 55 amp alternator normally designed for 3 amps, you can push in anywhere from 6 to 15 amps Causing the rotor to become hot and frying it. Over time your alternator will become a Dead short and the rotor will become so hot it crystalizes and becomes brittle.
Also, Pulsing the rotor helps to keep the temperature of the rotor down to a minimal, During the Pulse off time current flow and voltage to the fuel cell is not effected because of the 3 phase wiring. Also the Hp "Driver motor" and alternator is in Tune with each other allowing a smooth clean run.
If you have applied 30 volts to your rotor of DC, i am most certain you either smoked your rotor, Or you are going to smoke it. You can read the Cold ohms of your rotor to help determin if it is becomming fried, assuming you know what the value should be. You can also measure amp flow to a Cold rotor using a car battery to determine if the rotor has been abused. And abused rotor will always consume more amps and can never be restored, it keeps getting worse and worse.
It is possible that an alternating current to the rotor could be affective, A variac powering a alternator rotor is never a good ideal "unless you keep the rotor under 12 volts." A pwm using a 12 volt battery to the rotor, Even if you are pulsing 5 volts at 2 amps is better recommended than using a variac. "A variacs Signal is too clean, and is not high in freq "700 hertz"
This is just my comment, by no means be affended by it. Test and research what you can and you can determine what should and should not be done.
