Sizing 115v Teco FM50

I want to get a 115v. Teco FM50 to run a 1/2 hp 3ph gear motor currently on a 3ph Teco FM100 for speed control. This is for a infrequent use. The 1hp unit is just a few bucks more than the 1/2hp, is there any reason not to get the 1hp in for possible future use on a larger motor?

I believe the reason why you want to size it as closely as possible is for efficiency. I'm just not sure how much is efficiency is lost and if it matters for your application. What is the motor driving?

The motor powers a sort of winch for steambending wood strips into circles. Not used very often, so efficiency is not an issue. Just need speed control and reversing capability.

No, no reason not to. Just make sure you program the correct motor nameplate data into the drive. The only potential issue is that the programmable Motor Current range for the FM50 is 50-100% of the drive rating. So on a 1HP drive, it SHOULD be able to be turned down to what the FLC is for a 1/2HP motor, but it will actually depend on the FLC of the 1/2HP motor in question.

So for example, the FM50-101 is rated for 4.2A, which means you can turn the motor current protection down to 2.1A. But if your 1/2HP motor has a nameplate FLC of only 1.9A, technically that's too low for the VFD to protect it correctly. You could buy an external OL relay to solve that problem and still allow you the option of using the drive on a 1HP motor in the future, but that wioll cost you more.