We study the fully nonlinear magnetohydrodynamic (MHD) equations in 3-D driven by a specific time-dependent forcing function, characterized by a frequency, Ω. Stable hydrodynamic solutions exist that are or are not dynamos depending on Ω. We examine the effect of such flows on an imposed large-scale (mean) field and measure the associated α-effect. We find that a significant non-zero α-effect can exist, indicating possible dynamo action on scales larger than the velocity scale, when sometimes no dynamo action exists at the velocity scale itself. Flows exist which are not small-scale dynamos, yet may be large-scale dynamos.
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