Or does it only work with a DC motor?
You can get a transformer to work on DC provided that the DC is varying (or pulsing) . Consider how the coil in a car steps up the 12VDC of a battery to thousands of volts for the spark plugs by pulsing DC through the primary of the coil.. Because the DC motor has a commutator its DC output will resemble that of a full wave rectifier. The variations in the DC will be passed to the secondary of the transformer. Despite feeding a transformer input with pulsating DC, the output of the transformer will be AC so you will need a full or half wave rectifier and it would also help to place a capacitor across the rectifier output to smooth the DC.. Also the power (E * I) input is the same as the output, meaning that if you take 1 V @ 10A (10W) on the input and step it up to 10V at the output you will still have 10W of power at the output which means that the current will drop to 1A. 1V @ 10A in stepped up to 10V @ 1A. Finally as current is supplied from your tiny generator (motor) that current flow will create a counter electromotive force. Simply, as you supply current from your generator it will get harder to turn the generator. Your generator might be turning in a slight breeze now only because there is zero load on it. Once you connect a load (transformer / led etc) you will find that it will take more effort (breeze) to turn the generator. Despite all of the above the step up conversion of the fullwave DC won't be very efficient . Instead of a DC hobby motor as your generator try using a Servo / stepper motor instead. There is no commutator in these types of motors so you should be able to get an AC sine wave output which will be more efficient in stepping up with a transformer.
A permanent magnet motor is a DC motor. You'll do a lot better with an automotive alternator. The voltage regulator, (needed), is built in and they are fitted with pulleys for speed multiplication, (also needed).
It is possible, but most such motors are small and will produce little power. There is also the question of variation in speed, which will change both the voltage and frequency of the generated power, rendering it unsuitable for domestic use without conditioning. Commercial wind turbines are designed to run at a constant speed; the blade angle can be changed to increase the power if the wind velocity increases.
