E-Stop with inverter

We have a simple winding machine, which is run using a omron CPM2A.

The winding machine simply rotates a big wheel by a set number of turns. Once the set number of turns is reached it stops.

The turning of the 'big wheel' is controlled using a 7.5KW motor/gearbox controlled by a Lenze 8200 vector Inverter. this enables us to offer variable speed option.

Currently the Estop for this system seems to be simply wired into the PLC, with no hardwired emergency stop fucntion.

I am trying to hardwire an emergency stop in with a safety relay, however having not controlled inverters before I am not sure what the best way to do this is. Should I simply use the safety relay to activate a contactor which cuts the 3phase into the inverter? Or should I use the dc brake coil fitted into the motor. If I use the brake then I must have power to the inverter... which to me isnt a hardwired emergency stop.

Does anyone have experience working with this inverter (or any inverter really) and know the best wire to implement the emergency stop?

Thanks in advance

Ben

One method I've used is a controlled stop and then drop a contacter between the motor and VFD, or a contacter from input power to the VFD, or both. I think VFD (and servo) mfgs grimace when talking about cutting off the motor connection from the VFD, so a controlled stop first meets them halfway (cat 4 stop I believe?) so thats not to rough on the VFD internals. The brake resistor will dissipate the retained energy faster so thats a good thing.

One of the guys here that work for a VFD mfg will probably have the right skinny on it.

Hi

I'm sure that a high inertia load such as a winder needs to be ramped-down via the inverter to a safe, controlled stop. In this case the winder is under control 'til it stops before all motive power is removed. The PLC should still be powered up in the event of an e/stop with power removed from the outputs at the necessary instance. Perhaps a Master Control Relay has a delay-off contact that allows the inverter to ramp-down before shutting off. Most inverters prefer to remain powered with isolation points downstream.

Take care. Regards - silva.foxx

Are there any brakes ? Is the winder behind guards which remain locked until rotation stops ? What are the implications of an unexpected start ? A review of EN60204 will point you in the right direction for the complete story.

I think Lenze (mine 9300) have like an EM-STOP terminal 28. It is not Emergency stop, but handy terminal to lock inverter.

On the 9300's its always better to ramp down the drive using an input on the drive assigned to cw/quickstop or ccw/quickstop. This ramps the drive to zero at maximum current limit. Monitor the drive zero speed relay digital output. Once zero speed relay is active then remove your direction and inhibit input from the drive. No contactors and unit is safe !!!

Note:

If you remove the power to the inveter, you have to wait for about 3 min, before you put on the power again, if not you can damage the inveter.

silva.foxx said:

Hi

I'm sure that a high inertia load such as a winder needs to be ramped-down via the inverter to a safe, controlled stop. In this case the winder is under control 'til it stops before all motive power is removed. The PLC should still be powered up in the event of an e/stop with power removed from the outputs at the necessary instance. Perhaps a Master Control Relay has a delay-off contact that allows the inverter to ramp-down before shutting off. Most inverters prefer to remain powered with isolation points downstream.

Take care. Regards - silva.foxx

Click to expand...

Pilz have a unit that is designed for this sort of application, it has a set of timed contacts so on intital stop you run the inverter down then the timer removes the main contacts on the relay which you can use for removing power from the inverter via a contactor

SimonGoldsworthy said:

Are there any brakes ? Is the winder behind guards which remain locked until rotation stops ? What are the implications of an unexpected start ? A review of EN60204 will point you in the right direction for the complete story.

Click to expand...

Simon hit the nail on the head here. You really will need to review guaring, interlocks and the whole ball game rather than just adding proper e-stop to the drive. Its a minefield and unless done properly if you alter the machine and it doesn't comply then in the event of an accident you may be personnally liable.

See EN954 and EN60204 as further reading.

Also check to see if there are any special standards that apply to your machine as these would also apply.

Whoa.... necroposted by mjoubert


I would have hoped benjo would have sorted his problem after 15 months...

Slow ramp maybe ?