In general terms, VFDs are limited to running motors as small as 10% of the VFDs amperage rating.  For example, a 100Amp VFD can protect a motor as small as 10Amps. This changes slightly on the SP100 bypass package. The SP100 utilizes an Electronic Motor Protection Relay (EMPR) for motor protection in the bypass mode. Therefore, motor capacity is limited by the range of the EMPR. Refer to the below EMPR adjustment ranges on the two smallest SP100 packages. 

230VAC Model: LSLV0055SP100-2CEND3

GMP60-T 60A has a 5~60A adjustment range.

480VAC Model: LSLV0055SP100-4CEFD3

GMP60-T 30A has a 3~30A adjustment range.

Based on the NEC FLA Motor Table this means you can apply as low as 1.5HP motors.