Another Vfd Thread

[Deerslayer]

Here is where I posted a link to both the eBay sale & a manual.

mksj
No doubt about the VFD your talking about. I don't use a resistor for breaking. Mine is set very low & only set to break for half a second. It doesn't kick in until the spindle is almost stopped. Mine steps down over 3 seconds then breaks for one second just to stop the last few seconds of it winding down. It isn't realy noticeable. I had the breaking set higher but the VFD screams in a really high pitch when it is. I found that (iirc) .5% is enough to stop it & that is where it is for now. If I get smarter about it later on I might try some changes.

I don't see your link?

 

[kingmt01]

Sorry. I was half asleep. I guess I didn't post it.

http://www.hobby-machinist.com/threads/2-2kw-vfd-3-phase-3hp-motor.41077/

It is in pretty simple English. Not knowing anything about it I was able to get it set up. I bet most people's horror stories are actually from not knowing what they are doing. Each time I read through the manual things become a little more clear.

You don't always get what you pay for. Just because you pay more doesn't make it better.

 

[HMF]

In the Electrical Knowledge Base above this forum we have:

http://www.hobby-machinist.com/library-articles/how-to-wire-a-vfd-to-your-machine.26/

 

[alloy]

I completely agree with joshua43214 about Automation Direct VFD's.

I bought 2 Hitachi VFD's fr my Bridgeport, one for the spindle motor, and one for the power feed. I took them both out to Jim's Dawson's place and he worked on them for a decent amount of time working on setting them up. I looked pretty hard at the instructions and being totally electrically challenged I couldn't make had or tails of the manual.

When I got the E-head for my newest mill I had to buy a DuraPulse sensor-less vector VFD to run the Baldor Super-E motor. I was at Jim's and with reading the well written manual and after asking a few questions Jim answered I was able to set up the VFD, all except one thing. I bought a braking resistor and no matter what we did braking wouldn't work.

I finally had to call Automation and the tech knew exactly what the problem was. I looked through the entire manual page by page for every mention on braking and there was nothing about turning on braking with a resistor. As it turns out it was labeled "overload protection". The tech was fast and spoke english.

On my Bridgeport the Hitachi VFD for the spindle motor literally blew up. A big fireball shot out the side of it, and I was stuck. Jim had a VFD from Automation and I got it from him and later replaced it.

Yes the VFD's from Automation cost more, but in my humble opinion they are worth it.

 

[95ttoplt1]

I'm new so be gentle, and I'm certainly not trying to hijack.

What VFD from automation direct are you guys using? I was just looking for one for a 1.5hp J head BP. Seemed like the GS2 for 2 hp was $250, seems very competitive with a RPC??

Am I missing something? All the searching turns up that VFD's are uber expensive. That seems very competitive with the RPC's, with lots of benefits.

Oh, what is resistor brakeing?

 

[JimDawson]

I am using the 3HP GS2 units, and Alloy has a 3 HP GS3 on his Kent. We went with the GS3 on the Kent because it is direct drive, no change belts or verispeed, so better low end torque with the vector drive GS 3 unit.

A breaking resistor is attached to the VFD to dissipate power during breaking, it allows faster stops. When breaking, the motor becomes a generator and feeds power back into the VFD. The resistor gives the power somewhere to go. Most VFDs will adsorb some power without tripping out, but you can't stop as fast as with a breaking resistor installed. My 3 HP mill for example takes about 4 seconds to stop without the resistor installed, but will stop in about 1.5 seconds with the resistor.

 

[alloy]

I'm no expert, but benefits of a VFD over an RPC are fingertip speed control, and more energy efficient. You don' have a motor turning all the time soaking up power even when the spindle isn't turning. And the added benefit of braking.

You can get a breaking resistor for less then Automation charges. I've got both of my resistors off Aliexpress for 1/3 the price. You just need to read the specs on the VFD and find the correct resistor for that unit.

 

[mksj]

Am I missing something? All the searching turns up that VFD's are uber expensive. That seems very competitive with the RPC's, with lots of benefits.

There are really inexpensive VFDs, direct from China, but it is hard to know what you are getting and what recourse you have if it doesn't work or fails. The price and size of VFDs have come down, and they do have many programmable features, the break point is probably around 3Hp on a VFD vs. store bought RPC. If you have a lot of 3 phase machines than an RPC would be more cost effective. It you need variable speed on a particular machine, it still doesn't rule our running a VFD off of your RPC.

Braking resistors are available on eBay for about $20 for up to a 500W resistor.

 

[95ttoplt1]

Thanks, that clears up a lot of nagging questions.

 

[alloy]

Forgot to mention an added feature of the GS3 is a simulated tachometer output. Since I have no vari speed or pulleys to change belts for speed, a tach is mandatory for my mill.

It took a little time setting up, but we have the tach reading within about 10 RPM of the actual spindle speed.