How To E-Stop A Powerflex Drive
How To E-Stop A Powerflex Drive
(OP)
I'm working on a vfd estop application for the first time. I have a belt conveyor driven by a Powerflex 700. Lanyards on the conveyor are for estop.
I'm having trouble understanding exactly what dictates requirements for an estop. Is it acceptable to simply turn off the Enable control signal to the drive, ... or must I install a contactor between the drive and the motor with some sort of relay management module to disconnect the drive safely?
Whatever the answer is... what code dictates my requirements? I have been digging through MSHA, NFPA, and NEC for something, but I have done nothing more than confuse myself.
Thanks,
Eric





RE: How To E-Stop A Powerflex Drive
Depending on the application, contacts for a "Soft" E-stop may be placed in series with the stop/run terminals (a Soft E-stop permits a more orderly shutdown.)
***Check with the drive manufacturer and make them tell you where to place the contactor. They do not all have the same answer.
RE: How To E-Stop A Powerflex Drive
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I don't suffer from insanity. I enjoy it...
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
Aside from that, cbarn2450 is correct in that putting a contactor on the output side is generally risky to the drive. As you will find however, some people consider that to be secondary to life safety requirements if there is a possibility of contact with the motor conductors after the E-stop is activated. I doubt if that is a concern for a conveyor drive. Killing input power will still prevent the drive from running on and carrying someone into a rock crusher or shredder etc., which is what those cable switch systems are about.
My opinion is that I don't think a base block stop command is adequate for life-safety purposes, but again, this has been debated often. I recently attended a presentation on the SIL-2 conformance capability of the new Schneider VFD which they claim is exclusive to them, but I went away unconvinced. To put it another way, if I fall on a belt and grab the cable, I want an air gap in front of the power source to that motor, not a legal conformance document that my widow can use to sue someone after I have been turned into pink goo!
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: How To E-Stop A Powerflex Drive
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
You have to determine what sort of stop is required in an emergency. The actual function of your VFD will come a few steps after you have determined the method of stopping. The advent of 'safe-stop' in a VFD means you have a tested and verified method of removing power to the motor, but you still have to determine how you are going to stop the motor and how quickly. Treat the application as you would for a traditional E-stop (without VFD) and if it had a suitable safety category built into the VFD then you can integrate it.
If you do not have the "safe-stop" function in your powerflex then removing the power to the input of the drive should be looked at in the event of an emergency stop as removing the supply to the motor could mean that the VFD is still 'running' even though the motor is not physically connected.
RE: How To E-Stop A Powerflex Drive
ht
David Baird
Sr Controls Designer
EET degree.
Journeyman Electrician.
RE: How To E-Stop A Powerflex Drive
I just got of the phone with a friend who works at a mine, so he deals with this issue as it relates to conveyors every day with MSHA. He says MSHA has no requirements for motor power removal per se, but the cable e-stop must be a maintained device requiring physical reset by hand. How it is done at the VFD is strictly up to the user's safety protocol. Most users he has worked for allow the VFD to turn off without the need for an additional isolation contactor, because a common way of handling e-stops like that is to use a Master Control Relay (MCR) that kills control power to everything simultaneously. He suggests that you call your local MSHA inspector anyway just to make sure, because he is going to be the AHJ.
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: How To E-Stop A Powerflex Drive
Hardware Enable Circuitry (Vector Control Option Only)
By default, the user can program a digital input as an Enable input. The
status of this input is interpreted by drive software. If the application
requires the drive to be disabled without software interpretation, a
“dedicated” hardware enable configuration can be utilized. This is done
by removing a jumper and wiring the enable input to “Digital In 6” (see
below).
1. Remove the I/O Control Cassette &
cover as described on page 1-16.
2. Locate & remove Jumper J10 on the
Main Control Board (see diagram).
3. Re-assemble cassette.
4. Wire Enable to “Digital In 6” (see
Figure 1.8).
5. Verify that [Digital In6 Sel],
parameter 366 is set to “1, Enable.”
This is a hardware Stop Not a program stop which makes it a good E-stop circuit.
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
Very true. Here is an extract from the Siemens 'Standard drive' operating manual (without safety integrated):
"This equipment must not be used as an "Emergency Stop Mechanism" (see EN 60204, section 9.2.5.4).
Emergency Stop facilities according to EN 60204, IEC 204 (VDE 0113) must remain operative in all operating modes of the control equipment. Any disengagement of the Emergency Stop facility must not lead to an uncontrolled or an undefined restart of the equipment"
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
Unless you have a certified 'Safety Integrated: safe stop (here in Europe it would be classed as a category 3 safety level within EN954-1), you cannot use the function (shutting down the gate driver circuit) as a safe stop. I'm not sure if A-B have this in the Powerflex700 but lowdere advised his particular model does not have it.
More and more drive companies are building this in. Siemens, Danfoss and Control Techniques are three that I know do in 'standard drives'as an option.
RE: How To E-Stop A Powerflex Drive
RE: How To E-Stop A Powerflex Drive
then in the Self-Help area box under 'Product Name or Part number'copy and paste this part number: 6ZB5000-0AA02-0BA1.
This will take you to the page where the Siemens Safety Systems manual can be downloaded (22MB I'm afraid). Of course it's only Siemens products but included is a wealth of technical detail that explains fully most areas of safety and what you should do.
Hope this helps!
RE: How To E-Stop A Powerflex Drive
"Safe Off Option, the first offering available within the DriveGuard™ series of safety solutions, prevents a drive from delivering rotational energy to motors by integrating a safety circuit with the drive’s power switching signals. This solution meets EN 954-1, Category 3."
The only difference between what I am doing and this is that I am using a seperate safety relay to break the power to the SCR's.