Hi,
Question 40 GK4 asks: A voltage regulator controls generator out put by:

Given answer is D: varying the current flow to the generator field coil.

Does the question relate to an Alternator rather than a Generator or are you using generator as a more generic term? My confusion is because I understand that the generator has a fixed magnet and therefore the voltage can only be altered by the RPM. Whereas the alternator output voltage can be modified through altering the rotating electromagnetic potency.

If you are referring to an Alternator, how does the the regulator work when coupled to a generator? Does it just use solenoids to regulate the output by opening the circuit?

With thanks in advance,
Cam

That question has been changed in the more recent issues of the book. It now reads 'varying the current flow to the alternator field'.

Thanks for the reply Bob. If the aircraft does have a generator does the regulator just cut off the voltage by means of a solenoid when it exceeds a preset voltage or does it do something more clever than that?

As you probably know, generators are yesterday's technology. All modern systems use alternators. The problem with the generator was that the magnetic field strength was fixed because it used a permanent magnet. That meant that if the RPM was too low, there was no way the system could be provided with the rated voltage. The alternator overcomes this problem by changing the magnetic field strength so that at low RPM the magnetic field strength can be increased by feeding more current into the coils thereby compensating for the low RPM. The old generators used an electromechanical voltage regulator that sensed the voltage output by monitoring the strength of the magnetic field in an electromagnet and operating switches to control the current. While this system could guard against over voltage, it couldn't do anything to increase voltage when the RPM was low. Whenever the engine ran at low RPM, the generator voltage dropped below the battery's voltage and the system relied on the battery to maintain the rated voltage output.

My little Pacer had a generator when I first got it, but I have since replaced it with an alternator.

Bob

thanks again,
Cam