Depending on operation conditions and specific requirements different types of Alternators can (or should) be used for Wind Turbine (Wind Power Generator):
• Axial Gap Alternator. Synchronous low speed alternator with permanent magnets. Compact inexpensive design, $400-800 per 1 kW of power. Output voltage is VAC (voltage of alternating current) of non-stable frequency and amplitude. Complex electronic regulator costs extra $400-800 per 1 kW of power. The alternator can be used in autonomous systems. Extra equipment is required for synchronizing with grid frequency.
• Alternator with Combined Excitation. Low speed alternator with permanent or electric magnets. Additional regulating winding is stabilizing the output voltage (VDC 24V, 48V, 96V, etc.) under electronic control. The cost of alternator is $700-1200 per 1 kW of power. Simple (analog of automobile) electronic device for stabilizing of voltage costs $50-100 per 1 kW of power. The alternator can be used in autonomous systems. Extra equipment is required for synchronizing with grid frequency.
• Asynchronous Alternator. The advantage of this type of alternator is the ability of exchange of active and re-active energy with automatic stabilizing of frequency and amplitude of output voltage (according to the nature of such electric machine). It makes this alternator attractive for grid tied applications. The output voltage is VAC of alternating current matched in frequency and amplitude with the grid. The cost is $500-800 per 1 kW of power. For autonomous application additional regulator is required ($400-800 per 1 kW of power).