VFD stop switch

[Scott_M]

Hi Herbie
Glad you are making some headway. There sure is a bunch of stuff to get these set up properly ! But once it is done it is a real dream to use.

Looking at your error code it seems it is over volting. Does it throw the error when you stop the motor ? If so a braking resistor would solve the problem and give you a real fast stop. If you do not want to buy / install a resistor look for a setting like "Coast to stop" and it won't overvolt because of deceleration. Or lengthen your deceleration time.

I have been meaning to ask, What are all those buttons for ?
I know you need FWD, REV and Stop and a Pot for speed control. What are the others for ?
I will add a picture of my lathes control. I have a drum switch for FWD, REV and Stop and the Pot. for speed control. Only 3 wires for the switch and 3 wires for the Pot. Pretty clean and simple.

Scott

 

[Herbiev]

You're quite correct Scott. The error code does come up after stopping. I shall buy a braking resistor and try that out. Not sure what I was going to use the button switches for. I just hooked them up to DI1 to DI5. I tried to program DI2 for reverse but nothing happened. I like your switch. It looks nice and simple.
Perhaps the fact that here in Oz our 3 phase is 415volts and the unit is rated 380volts might cause the error message

 

[toolznthings]

Hi,

On my TECO drives I set the parameter to allow the mill motor to coast to a stop.
This stopped the back feeding to the drive when shutting done from higher spindle speeds. I got the same faults as you even though I set the deceleration time as long as possible. I prefer the coast to stop. Makes tapping with drill chuck easier. Or add breaking resister as suggested.

Brian

 

[Herbiev]

Thanks Brian. I shall try the coast to stop idea until mr resistor arrives.

 

[Scott_M]

Hi Herbie

If you have it found it , it is Parameter b1-07. Set to 1

Scott

 

[kvom]

On my mill's VFD I can get an over-voltage error if milling/drilling with load at too low a spindle speed. In that case the motor stops and the spindle coasts. I have a brake that I can stop it with. That happens below about 500 rpm. Personally I've never had the need for reverse.

 

[mu38&Bg#]

You can use DC injection braking to stop motors fairly quickly. Options are on pg 83. If you need to stop quickly from high RPM (like driving a motor well above nameplate frequency 120 Hz+ or you have a lot of inertia), the braking resistor will allow you to make more start/stop cycles without over heating the VFD/motor. I use DC injection braking on my lathe and exceed the recommended number of start/stops with my AB Powerflex 40 without issue for years now. For my CNC lathe project I do have a resistor to install to allow quick/often braking. DC injection causes all the energy to be dissipated in the motor while the VFD put DC into the motor coils. When using a resistor the motor acts as a generator and a large portion of the energy goes into the resistor.

The only reason you should see overvoltage is if you're reducing speed by reducing frequency. This causes regeneration in the motor and feed current back into the DC bus in the VFD. I'd just turn off this portion of the stopping profile, it's just making the stop time longer. In a large installations with a proper VFD, this current can be fed back into the grid to reduce energy costs.

Greg

 

[mu38&Bg#]

On my mill's VFD I can get an over-voltage error if milling/drilling with load at too low a spindle speed. In that case the motor stops and the spindle coasts. I have a brake that I can stop it with. That happens below about 500 rpm. Personally I've never had the need for reverse.

In this case you should be using a lower gear and overdriving the motor with high frequency to get the highest spindle speed you might use. Torque is reduced at above motor nameplate motor frequency, but chances are that at high RPM you won't need it. In low speed (frequency) use, motor torque (current) is limited and power drops as RPM is reduced. Much more power will be available to cut with if you run closer to nameplate frequency and use a lower gear. The only caveats here is structural integrity of the motor and heating. I'm running up to 120Hz on my old Clausing but that's still 3600 RPM, equal to a two pole motor. Some motors, especially older ones, might run hot at high RPM, but these same motors would run hotter with VFD's in general. My CNC lathe will run up to 200hz (6000RPM) and has a modern ABB motor rated for 6000RPM and inverter(VFD) use.

Greg

 

[kvom]

Nothing to do with overspeeding, as the 2200 rpm I get at 60 Hz is plenty for what I do on the Bridgeport. Normally for low rpm I'd use back gear, but the gearbox has gone walkabout.

 

[mu38&Bg#]

Ah well, when no more gearing is available you don't have much choice.

 

[Herbiev]

Thanks again for the responses. The new code causes it to stop less abruptly but still get error message. I've ordered a 100 ohm 100 watt resistor so we'll see what happens