E stopping invertor driven motors

[TF and the wire]

What the correct way for an emergency stop or the opening of a guard to stop an invertor driven motor. Is the opening of a contactor supplying the 3 phase to the invertor a bit too drastic especially as the motor will still be connected and running when the supply is suddenly interrupted. I know that ofetn the drive will go into undervoltage error. Or perhaps a timed safety relay that instantaneously opens the enable signal to stop the motor followed a half a second later by the removal of the 3 phase as above.

 

[Darkwood]

Repeated stopping like this can damage the inverter, or knacker the program, you can find safety relays that send a signals a split second before cutting the power to the contactor but their are a few models of inverters that can be signalled with e-stop and are acceptable as a safety stop system but with the xmas spirit amidst my presence i cant remeber which ones.

Additional this isnt as straight forward to answer as might seem, a safety assesment needs to be done as to the dangers associated with how the motor stops in an emergency like whether it needs braking or is coasting acceptable, each situation requires different measures and simply de-energising the contactor coil isnt considered fail-safe incase the contactor is jammed in. As mentioned a safety relay with either dual channel or single channel isolation would be best as these are self monitoring but the whole subject requires alot more knowledge than a simple answer given on a forum, what is good for one installation is dangerous in another so lack of parameters means i cant give a definitive answer.

 

[Guest123]

DC braking springs to mind.

But as DW said need to know a bit more, as brake resistors may need to be fitted and numerous other bits and bobs depending on set up.

 

[TF and the wire]

The application I am considering (even on Xmas day) is simply a section of roller conveyors that will stop almost immediately once power or the run signal is removed.

I am considering a Powerflex 40 which has a terminal that needs 24v to run and am considering breaking that just before dropping out the main contactor.

I have had similar drives go into undrevoltage error when just the mains have been removed by an E-stop, requiring the electrician to be called over to the machine to turn off/on to clear the fault.

I was just wondering whether the E stop could be used to just break the signal above, leaving the mains on.

 

[Darkwood]

This set-up would only be considered as a funtion stop system as that is all you are doing removing the run command voltage or signalling a stop voltage, it dosnt meet the requirements of a e-stop system as its not fail-safe as a program error is possible or broken wire etc as mentioned before their are inverters that can be stopped this way but you will have to source them, they self monitor the run or stop command or even seperate e-stop command and have passed reqiurements that need to be met for such a system, you might consider using a dual channel safety relay and fit a contactor on the outgoing side of the inverter which pulls in on the run command, a safety relay could break its coil circuit as well as breaking run command both through seperate channels so if one fails their is a back up.

You would need to review the inverter instructions to see if an outgoing contactor would work or speak to tech' as some inverters wouldnt work correctly as i mentioned before you need to establish all the limitations, do a safety assesment then decide what system would be acceptable once this has been established pick an appropriate safety relay and inverter.

 

[xraytek]

I have had similar drives go into undrevoltage error when just the mains have been removed by an E-stop, requiring the electrician to be called over to the machine to turn off/on to clear the fault.

With the Powerflex drives there are parameters that can be adjusted to prevent an undervoltage fault in the event of drive power being reinstated before it finishes completely powering down.

You need to set 'Auto restart tries' to a value other than the default of zero, and 'Auto restart delay' to zero instead of the default which I think is 1 second.

As far as I am aware the Powerflex cannot automatically resume running on power up, but is ok to interupt power to the drive while it is running.
If power to the drive is lost as a result of an e-stop and re-energised before the drive completely powers down, the motor will start when the run command is broken and then remade.
Or at least it will if the parameters are set as I mentioned.

Hope that helps.

 

[ericks]

As you have indicated, it is an emergency stop. It should only be used in emergency situations.
It is fine to use the e/stop circuit to drop out the supply to the Inverter Drive. But it would not be
suitable for regular starting and stopping. Most Drives will auto reset at a loss of supply if the supply
is off long enough, so that the Drive completely powers down.

 

[boatnik1]

I have used a Warner clutch/brake in similar situations. on/off sw only actuates the clutch and disengages the brake and vice versa. Cutout sw drops out the clutch and instantly brakes the driven machine while the motor keeps running continuously, therefore no effect on inverter
Suppliers all over the UK and world. Based in Bishop Aukland UK.

Warner Electric - Clutches / Brakes designed for your needs

 

[Wazzajnr]

I normally use an estop relay with both instantaneous contacts and timed contacts. The inst contact breaks the enable which is configured to put the drive into "fast stop" then depending on the inertia load (i.e. how long it takes the motor to stop) the delay then breaks the mains to the drive.
Control techniques drives enable input is fully safety certified and can be used for this as can some of the siemens units.

 

[Quadrant]

What the correct way for an emergency stop or the opening of a guard to stop an invertor driven motor. Is the opening of a contactor supplying the 3 phase to the invertor a bit too drastic especially as the motor will still be connected and running when the supply is suddenly interrupted. I know that ofetn the drive will go into undervoltage error. Or perhaps a timed safety relay that instantaneously opens the enable signal to stop the motor followed a half a second later by the removal of the 3 phase as above.

HI
Wire your e/stop through your drive control cucuit.Never disconnect the out put of an inverter unless it is interlocked to switch the run signal off.Eventually you will smell that expensive electronic burn smell,TOO LATE.
Roy