New to me RF 45 ..... In the shop

[MashingMetal]

Some of these motors are star wound. They need a fairly balanced 3 phases to work properly. The VFD would be the better option unless you buy a commercial rotary phase converter that has this built in.
I have both in my shop and the VFD are nice for specific motors that you want to control.

 

[Bandit]

I'm not sure I follow all that. I don't know why sourcing switches from the VFD is a problem. I think it's an advantage.

No VFD I ever saw would start after a power outage without first turning it off. VFDs contain all the safety features normally implemented through relays and control systems.

Please be careful about VFD’s not starting after a power outage! Some units can be programmed to restart after a power outage, and can be set up to restart motor after a programmed amount of time when power returns, in hand with ramp ups of speeds to last operating speed, or near no ramp up to last speed.
Most all of our pumps, air blowers could/would do this, and all of this was utilizing mag switch’s in the controls, NOT requiring switching to off manually before restarting.
This was checked when doing a backup power test, power from diesel generator.
Now if VFD’s all have capability or not, I do not know. Possibly depending on switching wired in, controls,— (safety’s), and if has the ability of needed programming, and programming done. ( used VFD? Could be a surprise). At least 4 different makes/brands and sizes had this ability that we were using.
a question for a much more knowledgeable person or electrician, with VFD experience, more then mine!

 

[BaitMaster]

Sinking or sourcing refers to the type or configuration of the transistors used for the low voltage DC inputs.

Sinking = NPN transistor = “switching the negative”.

Sourcing = PNP Transistor = “switching the positive”.

Some VFD’s have configurable input types with a jumper or small switch, allowing you to select which type works better for your application.

Most “North American” or European drive brands default to sourcing.

A lot of Japanese brands default to sinking.

Most full featured VFDs have restarting after a power outage as a selectable option. So certainly be careful with that one. A live test shouldn’t harm anything. A contactor on the line side is a way to ensure it does not restart, but word of warning, the contactor should not be used to start and stop the drive under normal circumstances. It can be used as an E-stop or a power outage safety mechanism. If used as an Estop mechanism most drives also have options for configuring this as well.

The low voltage inputs should be used to start, stop, and control the operation of the drive under normal circumstances.

Hopefully this helps you out.

@Susquatch that should answer everything?

 

[Susquatch]

Please be careful about VFD’s not starting after a power outage!

That is true. Good point. On mine, it is a user choice. But that still meets the safety requirements. Any control system for a system without a VFD can do the same thing. The only difference is hardware control system design vs VFD Programming.

The point is that the VFD replaces the system in the control box.


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[Susquatch]

Hopefully this helps you out.

@Susquatch that should answer everything?

Yup. I just wasn't sure where the terms came from or what they meant in the context of electrical control systems.

Your explanation makes absolutely perfect sense to me. Especially since those are the two main ways of powering a relay even without a VFD.