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Which VFD will do what I'm trying to accomplish?

Peroni

Cast Iron
Joined
May 18, 2007
Location
Yadkinville, NC
I've got a lathe that right now is forward rotation only. I'd like to add reversing capabilities and instead of adding a reversing contactor I thought about a VFD instead. It would let me do a couple other things that would be helpful but I'm not sure which VFD to get.

Motor is a 7.5hp Westinghouse Life-Line CSP 3 phase and 23 FLA. I already have 3 phase input from a 15hp rotary converter. Believe I need 3 wire control function as there will be 3 momentary push buttons for forward, stop, reverse. I'd like to add a speed pot(but don't know what resistance value to get) and be able to program the VFD for 50% over and under the motor's nominal speed. There is a low voltage indicator light that needs to be lit when the motor is running. And it would be nice to be able to tap into a low voltage DC source to power a tachometer.

I don't need anything like dynamic braking or instant start/reverse or spindle jog capabilities. Just simple motor direction and speed control. The selection of VFD's is overwhelming and I'm not sure which one will do what I want. Reliability is more a concern over price.

Suggestions?
 
Just about any VFD should be easily able to do those things. Mostly, those are things that all VFDs "just do".

It may take some programming, to set what the buttons do by selecting a particular control mode. That's entirely normal.

Most VFDs do have a voltage available for small auxiliary items, typically 24V, sometimes 20V. Whether a particular VFD can power the device you mention depends more on how much current the device needs. Mostly you can count on 20 or 30 mA, some can supply up to 100 mA.

There are generally two voltages. A 10V which is specifically for the speed control, and the 24V (or whatever) that is general purpose.

The control potentiometer is "usually" between 2k ohms and 10k ohms, with a 5k covering most. But look at the manual to determine that for any particular unit.

You will want to look at the manual anyway, before buying, to be sure you are getting a general purpose VFD with easily programmed features you want. Most any reputable source will probably have the manual on-line.

There are some cheap sources selling ones with special programming that are not suitable for general use. Those folks won't help you out at all, either. Stay away from the really cheap stuff.
 
Can you run a VFD off a rotary converter?

If I were spending the money on a VFD, I'd see if someone makes one rated 7.5hp with single phase input and eliminate the RPC. Sell the RPC and offset the cost of the VFD.

Most VFD's can do what you want. Those functions are pretty simple.

Call your local motor shop and see if they can recommend something.
 
Can you run a VFD off a rotary converter?

If I were spending the money on a VFD, I'd see if someone makes one rated 7.5hp with single phase input and eliminate the RPC. Sell the RPC and offset the cost of the VFD.

Most VFD's can do what you want. Those functions are pretty simple.

Call your local motor shop and see if they can recommend something.


Yes, you can run a VFD off a rotary phase converter.
Many people do, some without realizing they are…
 
Yes, you can run a VFD off a rotary phase converter.
Many people do, some without realizing they are…

There may be a degree of derating when running a 3 phase input VFD off of an RPC, so I would suggest allowing a bit of headroom (10-20%) in the VFD sizing. This also depends on the VFD, type of load and duty cycle. So I would use something like the Hitachi WJ200-075LF (10 Hp) if running off of the RPC, or the WJ200-110LF (15 Hp) if running off of single phase (assume a derating of 2 for this VFD). The functions you are asking the VFD to perform are quite rudimentary, the issue is that 3 wire control with momentary buttons does not typically work the way you are envisioning. Momentary buttons are used for the start stop and the 3rd wire (sustained) is the direction. I do recall seeing a VFD that had momentary run F/R and momentary stop, I think it was some generic Chinese variant. What I typically do if ones wants momentary buttons for FOR/STOP/REV is use two 2 pole latching relays which latch the relays closed when the F or R button is pressed and the stop breaks the latch/power to the relays. So one side (set of contacts) is the powered latch and the other side of contacts executes the run direction command with VFD programmed for 2 wire control. I interlock the relays so only one can operate at a time. This can also be done with lighted (LED) buttons if desired. If using the VFD internal low voltage power supply, many have very limited current.

The WJ200 VFD's have a 100 mA 24VDC power supply, so this can be used to power the relays (standard relays are around 50-75 mA) or one can used a small external 24VDC power supply.

I did check one other VFD brand which is Lenze (AC-Tec) and they do have a 3 wire control that operates with 3 momentary buttons. They are good reliable VFDs, although a bit minimalist as to higher level VFD functions but would work well in your application. I do not know their derating if operated off of single phase (it indicates 1.73 online), but you can check on the links below for the specific VFD and see what they recommend. They are also available in NEMA4 enclosures.
10 HP 3 phase input ESV752N02TXB | AC Tech |
15 Hp 3 phase input ESV113N02TXB | AC Tech |
 
Some headroom is good anyway. Not HP, but current. Always check that the current rating for the VFD is at least a ittle above what your motor calls for.
 
Just to add

FWD STOP REV from the lathe apron controls into the VFD is well worth the trouble.

And the switches are already there!
 
I would not use the little membrane switches on the CHI-COMM vfd. Those are only good for 1000 operations. Wire external push button switches made by Allen-Bradley.
 
The A510-2010-C3-UE will work off of a RPC, but will need to upsize to the A510-2015-C3-UE if running off of single phase. A510 series appears to be a heavy duty version of the E510, but operationally similar with some PLC functions. I have not looked at the manual if it can be configured with momentary buttons as you have described. Otherwise one can use two dual pole relays with a latching function. They do indicate that they have 2-wire control with hold using momentary buttons for FOR, REV and STOP.
 
I thought the A510 series would work good as they seem to have a fairly wide range on the input voltage compared to other makes. +10% -15% falls within the range of my RPC. I was reading through the manual and (if I understand what I read correctly) it does appear I can use momentary push button switches with it.
 








 
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