Just Wired Up A Vfd.

[Bob Sorenson]

The last couple of months I've read every thread relating a vfd. Having a grizzly 10 x 20 lathe, I decided to change over to 3 phase one horse d80 frame ( exact replacement ) size motor and a KBMA adjustable frequency drive.
I have all of the parts here now, so I set it up on my backbench to test.
Adding to my materials list was 20 feet of 14/3 so wire and eight feet of 14/4 so cable. The 14/3 is for power from the outlet to the control box, and the 14/4 wire is to go between the motor and control box. Also used two 20 amp twist lock connectors to be used on the 3 phase, wiring (so I could remove the motor if I wanted to).
Wired it all up using a very good KBMA manual. On the bench, every thing works good.
The manual does not mention a breaking resistor.

My question to anyone who might know about my setup, and adding a breaking resistor. Really don't know even if I need the quick breaking system except for 1. An emergency stop and 2. to assist in thread making.

Thanks in advance for any help.
By the way my background is putting out fires, and electrician.

 

[JimDawson]

Assuming you have the KBMA-24D, it looks like the only option for breaking is DC injection (factory programming option). There doesn't seem to be any provision for a breaking resistor. Normally you would find an additional pair of power terminals that would be labeled B1 & B2 or something like that.

 

[Eddyde]

A 20 amp circuit 1 hp motor should use #12 wire. #14 is for max ¼ hp motor.

 

[AaronD]

Eddyde, on 120v your figures are close but it seems that OP is using 240v single phase input. He is fine operating his 1hp motor and VFD on the wire size and connectors purchased.

Helpful rules I have always followed

Watts/volts=amps

Approx 750w per HP

 

[Eddyde]

The calulations don't matter, if its a 20 amp circuit code says it must be #12 wire. It's probably fine to use #14 from the VFD to the motor, provided its a short run, but the wire from the mains to the VFD should be #12, if its on a 20 amp breaker.

 

[ch2co]

My G0602 with 1hp 3ph through a VFD is wired with 10ga. wire, coming off of the mains box. About 60 ft. of wire running through conduit. My VFD manual recommended
using a #8 ground for the circuit why? I don't know, but thats what I used. The rest of my house is severely underwired, being built in the late 1940's. The recommended wiring is overkill to be sure, but who knows what else might be added to that circuit in the future. These aren't production lathes running under full power for hours (days) at a time, so lighter wire would probably do just fine, but if I'm going to put the time into routing conduit, pulling the wire, adding a sub box etc. I happily spend a few extra bucks to not have to do it all over again in a couple of years when the 10-22 becomes a 12-48 or something to that ilk.

CHuck the grumpy old guy

 

[JimDawson]

Also used two 20 amp twist lock connectors to be used on the 3 phase, wiring (so I could remove the motor if I wanted to).

Guys, this is the only mention in the OP's post about amps. He doesn't say anything about the circuit protection, or the system voltage.

By the way my background is putting out fires, and electrician.

The last sentence in his post makes me assume Bob knows ampacities and circuit protection.

 

[ARKnack]

The calulations don't matter, if its a 20 amp circuit code says it must be #12 wire. It's probably fine to use #14 from the VFD to the motor, provided its a short run, but the wire from the mains to the VFD should be #12, if its on a 20 amp breaker.

Actually flexible cords are a bit different. Table 400.5 in the NEC show 14awg good for either 15 or 18 amps. If the cord only has 2 current carrying conductor its good for 18 amp. From the plug to VFD in this case (hot & neutral). I do not know what the input amperage requirement is for this vfd. If it is less the 18 amps he good. If more then he needs a larger cable.
14awg with 3 current carrying wires is allowed 15 amps. This would be from vfd to motor. A 1hp 3ph motor only draws about 3.6 amp @ 220vac.

 

[AaronD]

I did a little bit of...I know...assuming in my reply. Although it was based on info provided by OP.

14/3 SO contains 3 wires.
The choice of wire told me 240v single phase input VFD, although I guess we could make an assumption that this would also work to carry the neutral to 120v input VFD...
14/4 SO carries an additional wire (3 hots, plus ground)

I guess we really need to know more info from Bob. Specifically the drive model

 

[ARKnack]

True. One mistake that is often made is the number of wires. 14/3 has three wires as you stated but it only has 2 current carrying conductors. A 1hp vfd I believe comes with both 120/240v input. Mine did. I had to switch mine to 240v because the vfd kept tripping the GFI breaker. I am also making a lot of assumption. So Bob will have to chime in but I think we are discussing something completely different from his question. Funny how we can get off on a tangent.