Help figuring out "coast stop" on Toshiba VFD

I don't have the model off-hand but my Toshiba VFD I got for my lathe does not have a function/setting for a coast stop. IE, I can't just set a function and have it coast to a stop, it always wants to do a controlled ramp-down stop at the time interval I set. ETA, this unit is quite old, I got it pretty cheap used. Trying to make it work to avoid the cost of a new unit (they get expensive once you go north of 3 hp).

There is a provision for a coast stop that must be as follows:
#1 FWD/RVS command is given & motor starts, #2 auxiliary input commanding coast-stop is triggered, #3 FWD/RVS command is trigger off and motor coasts to a stop. Sometime after the FWD/RVS command is triggered off the "aux coast-stop" command must also be triggered off before the motor will start again.

I'm using the drum-switch and control rod on my lathe to give the FWD/RVS commands to the VFD. There are several open terminals on the drum. The drum used to control the electro-mechanical brake, the main motor, and the coolant pump all from the drum switch. I'm now just controlling the brake and a single FWD & single RVS terminal for the inputs to the VFD. But as explained to me by the Toshiba tech, the aux input for the coast stop must be triggered on AFTER the motor has started and remain on until the FWD/RVS contactor is opened, and then the aux must be triggered back off BEFORE the FWD/RVS contactor is closed again. I don't think I can do this with the drum switch without involving a circuit.

My initial thought was a 2nd contactor that closes when either FWD or RVS is closed that charges a capacitor through a resistor. This will allow the cap to charge up after the motor is started, providing the aux signal, and then drain down when the motor is stopped essentially resetting back to the start point. I may have to play with resistor/capacitor sizing to get this to work right, I'm guessing my resistor will have to be quite a bit smaller than whatever internal resistor there is on the aux input line so that I get enough voltage to come through...

Am I on the right track?

I have used that strategy, but using a small DC relay, no reason to use a contactor to control a VFD input. There is a delay in charging, and the off delay is determined by the size of the capacitor. There are also very inexpensive dual relay boards (some even with separate timers), I use one where I needed a timing difference for each relay, and used different RC combination. Was cheap and works, but for a few bucks more and you can get programmable ones. You can use a DC relay(s) and use a small bridge rectifier to convert low voltage AC to unfiltered DC. Alternate is to use a timing relay like a 821TD10H-UNI which can work with a wide range of voltages and has a number of different on-off delay algorithms that have a wide timing range. There is an ON/OFF sequence delay function (I).

You might try going into the manual, to see if you can just program the Dynamic braking to start as soon as the drive is moved to off. That does away with separate controls. Hitachi has that capability, and makers tend to follow each other.

I don't know of any Toshiba drive sold in the last 20 years or so that was unable to be programmed for Coast to Stop.

I'm also confused by your statement saying it can't, then saying it can...

"...does not have a function/setting for a coast stop. IE, I can't just set a function and have it coast to a stop,"

"... input commanding coast-stop is triggered"

Seems contradictory.

This thread needs a model number, or a link to the appropriate manual.

Agree that "coast to stop" is present on virtually every VFD.

Is it possible that this unit is not a standard unit, but one made for a special purpose? Or that it is standard, but not general purpose, intended instead for hoisting, or some such usage?

Is there an update to your last post here?

http://www.practicalmachinist.com/v...ning-multiple-motors-rotary-converter-343135/

SAF Ω

Group 1
item 26
set value 1 : Coast to stop.

First of all, let me apologize for the delay, busy life, sort of forgot I started this thread asking for help. I appreciate the help so far. I forgot to look at the model info. It requires me crawling under the chip-pan of the lathe to take a look. I'll see what I can find out.

Toms Wheels said:

You might try going into the manual, to see if you can just program the Dynamic braking to start as soon as the drive is moved to off. That does away with separate controls. Hitachi has that capability, and makers tend to follow each other.

Click to expand...

I don't want any braking from the VFD. There is no parameter that just disables the VFD from braking

Jraef said:

I don't know of any Toshiba drive sold in the last 20 years or so that was unable to be programmed for Coast to Stop.

I'm also confused by your statement saying it can't, then saying it can...

"...does not have a function/setting for a coast stop. IE, I can't just set a function and have it coast to a stop,"

"... input commanding coast-stop is triggered"

Seems contradictory.

Click to expand...

Sorry for the confusing. There is a parameter in the manual called "coast stop" but in order to utilize that function you must enable the "coast stop" parameter then, after starting the motor, you must trigger one of the aux inputs that actually tells the vfd this will be a coast-stop (as opposed to a normal dynamic braking stop), then you can turn off the aux input that is commanding the motor to run (either fwd or rev). Then the aux input telling the vfd it will be a coast-stop must be reset before the motor run command is given again.

What I want is a parameter within the programming of the vfd to just set so that when I command the motor to run it runs, and when I turn that command off, it coasts to a stop EVERY TIME. This vfd doesn't have that option. This is an old re-purposed VFD.

SAF said:

Is there an update to your last post here?

http://www.practicalmachinist.com/v...ning-multiple-motors-rotary-converter-343135/

SAF Ω

Click to expand...

I will have more info this weekend. I'm heading to mom & dad for a late Christmas and I'll see what came of it. It's not as pressing now that dad got through this year's use of the equipment.

You might be interpreting an optional configuration with a mandatory one. Post the model number of the drive. I have several older Tosh manuals floating around.

Jraef said:

You might be interpreting an optional configuration with a mandatory one. Post the model number of the drive. I have several older Tosh manuals floating around.

Click to expand...

Toshiba VF-S11

FWIW, I called Toshiba and they stated there was no parameter for coast-stop and the only way to make it coast to a stop was to use the aux input as I outlined above.

Huh. I have never used or programmed one of those. Looks as though in an effort to make it smaller/cheaper, they made some compromises in user friendliness. I can't make heads or tails of what they are saying there, but you are right, this drive doesn't have a simple option for coast to stop, you do have to assign a "STandby" (ST) function to an input to make it do that. Weird.

That said, it does not BRAKE either. The default is for it to RAMP to a stop. That's actually the OPPOSITE of braking. In theory you could just set the decel time to some reasonable value and live with it...

Side note: This is the same drive that Sq. D / Schneider sold as the ATV31 and they dumped that product because people couldn't figure out how to use it. Now I see why. I tried looking this up in their manual too, the PDF manual doesn't give any "advanced" programming instructions, they refer you to a CD they provide with the drive... sheesh.

Jraef said:

That said, it does not BRAKE either. The default is for it to RAMP to a stop. That's actually the OPPOSITE of braking. In theory you could just set the decel time to some reasonable value and live with it...

Click to expand...

I thought I recall seeing mention of braking and sizing the resistor properly but I could be confusing drives...

That being said, ramp stop is fine and dandy until I want to stop quickly and hit the brake that is on the machine, then I have a motor "ramping to a stop" that is fighting the brake.