Remote start/stop of drives
Remote start/stop of drives
(OP)
Hi,
I`m quite new in my job and there some couple of things there which look amazing.
All the drives , including conveyors , are remotely started via the SCADA with a soft start and a soft stop via the screen. They only have an emergency stop for all drives , which surprisingly is also wired to the PLC . The only information being sent to the PLC is the run command from each drive.
I am requesting that position detectors , field start/stop, be hard wired for each drive . I am also looking to provide additional inputs for the drive ready state and faulted condition . In addition I am also requesting that the emergency stop be hard wired so as to trip main contator in case of trouble.
The management is not ready to accept these amendments as they will involve extra expenses . The former instrumentation engineer told them that this mode of start/stop were compliant with international standard WHICH I OBVIOUSLY DO NOT BELIEVE.
What are the current standards for remote start/stop of drives and how are they implemented ?
Bob
I`m quite new in my job and there some couple of things there which look amazing.
All the drives , including conveyors , are remotely started via the SCADA with a soft start and a soft stop via the screen. They only have an emergency stop for all drives , which surprisingly is also wired to the PLC . The only information being sent to the PLC is the run command from each drive.
I am requesting that position detectors , field start/stop, be hard wired for each drive . I am also looking to provide additional inputs for the drive ready state and faulted condition . In addition I am also requesting that the emergency stop be hard wired so as to trip main contator in case of trouble.
The management is not ready to accept these amendments as they will involve extra expenses . The former instrumentation engineer told them that this mode of start/stop were compliant with international standard WHICH I OBVIOUSLY DO NOT BELIEVE.
What are the current standards for remote start/stop of drives and how are they implemented ?
Bob





RE: Remote start/stop of drives
But it is not considered good practice to wire the emergency stop via the bus or via the PLC. It shall work directly on the main contactor (or via a relay/auxiliary contactor with forced opening of the contacts).
The emergency stop can (and should) also be connected to the bus/PLC system for indication. But not for stopping.
If you are using one of the newer systems with a SIL level according to your application, then you may also wire the emergency stop directly to your PLC. But only then.
RE: Remote start/stop of drives
For a belt conveyor, it is customary to have an emergency stop pull cord running the length of the conveyor if it is accessible. This pull cord terminates in "pull cord switches" that must be hard-wired.
I'm not an OSHA expert, but I believe this is an OSHA requirement. If the PLC system is designed to be fail-safe, such that it will cause a conveyor to shut down if it fails, then maybe this is acceptable, but it wouldn't be acceptable to me.
RE: Remote start/stop of drives
Without knowing the particulars of all of the decisions that went into the design process of your system, I would be carefull about making a blanket statement. Do a key word search on "VFD emergency stop" in this forum and you will find several lively debates on this subject over the past few years.
"Venditori de oleum-vipera non vigere excordis populi"
RE: Remote start/stop of drives
If it is an enclosed pump system, the "emergency stop" may be a misnomer.
RE: Remote start/stop of drives
I'm just being "meticulous" I guess (meticulous being a more socially acceptable term than the other "Freudian" version I would use in normal conversation).
"Venditori de oleum-vipera non vigere excordis populi"