Electronics > Projects, Designs, and Technical Stuff

3-phase motor, phase failure detection?

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filssavi:
Yea I haven’t commented on that but I would not touch that crane with a 10 Km pole, the fact that you are just a single phase fault away from a potentially fatal catastrophic failure is worrying at best, it probably violates a very long list of legally mandated standards and will result in criminal charges in most countries.

There should be a mechanical brake somewhere that gets released through some sort of safety relay connected to a safety interlock loop, that makes shure, among other things that all three phases are energised.

It this is a task from your employer, and the problem is not considered dangerous enough to either delay the product release, or maybe even recall the product I personally would seriously consider searching for a different job

WattsThat:
This is not a one-off, roll your own project. If you aren’t licensed, insured and work in this field, stay the hell away from it.

Regenerative (4 quadrant) AC drives are the de-facto standard for crane operation. This is a job for a crane company, period. The big players in AC drives (ABB and Siemens) have crane specific software that implement all the required safety features and other high end requirements like anti-sway. These drives are only sold to licensed, trained companies that design, fabricate, install and maintain crane systems.

Cranes are a very serious business, treat them with the respect they deserve and don’t believe for a second it is a simple matter of just detecting one failure method the customer has asked you to implement. The only drive system that scares me more than a crane is an elevator...

andy3055:

--- Quote from: Snake____1 on June 30, 2020, 06:20:34 am ---Thanks for all the replies!
Thing is: This is a crane hoist motor, if a contactor switch burns out and the operator tries to hoist a load it will disengage the brake and the load will fall to the ground. The cranes are normally pre-current protector, so this does not have that. The motor has a cone shaped rotor and stator so it will move axially 2-3mm when energized to disengage the brake.
I have attached a proper schematic.
I have in-fact thought of rolling my own protection circuit, but this will take time as CE/UL are mandatory. This is a time sensitive matter, so if some off-shelf product exists that would be great.
The system is 400v 50hz, the motor is 2/8pole (2speeds).

--- End quote ---

Rolling out your own? Are you willing to take the risks? When things go wrong due to industrial accidents, the results are deadly. I hope you are thinking of this seriously! Think of what is happening to Boeing.

wizard69:
Phase detection relays of all sorts are available.    The problem you have is detection after the contractor which means the phase detector will not be "Good" until after an attempt to energize the motor is made.   Usually this requires a time delay from switch on until verification. The obvious problem here is the potential for uncontrolled movement over that short period of time.   In this case forward and reverse would likely mean two phase detection relays.

As others have indicated there are all sorts of standards, both local and international that one needs to comply with when dealing with lifting machines.   As others have indicated I wouldn't touch this with a 10 foot pole, a fantastic errors and omissions insurance program and all the other corporate protections.   It is something for a specialist to address.   In fact I'm very concerned that a third party is even being involved here as the crane manufacture would be the best organization to address this.   Sounds really fishy to me.

Even buying phase detection hardware will not be easy as I would expect a need to have such hardware validated for use in a crane.   You would have to check with the manufacture of the phase detection hardware to see if they even permit it to be used in such a case.


--- Quote from: Snake____1 on June 30, 2020, 06:20:34 am ---Thanks for all the replies!
Thing is: This is a crane hoist motor, if a contactor switch burns out and the operator tries to hoist a load it will disengage the brake and the load will fall to the ground. The cranes are normally pre-current protector, so this does not have that. The motor has a cone shaped rotor and stator so it will move axially 2-3mm when energized to disengage the brake.
I have attached a proper schematic.
I have in-fact thought of rolling my own protection circuit, but this will take time as CE/UL are mandatory. This is a time sensitive matter, so if some off-shelf product exists that would be great.
The system is 400v 50hz, the motor is 2/8pole (2speeds).

--- End quote ---

capt bullshot:

--- Quote from: Snake____1 on June 30, 2020, 06:20:34 am ---Thanks for all the replies!
Thing is: This is a crane hoist motor, if a contactor switch burns out and the operator tries to hoist a load it will disengage the brake and the load will fall to the ground. The cranes are normally pre-current protector, so this does not have that. The motor has a cone shaped rotor and stator so it will move axially 2-3mm when energized to disengage the brake.
I have attached a proper schematic.
I have in-fact thought of rolling my own protection circuit, but this will take time as CE/UL are mandatory. This is a time sensitive matter, so if some off-shelf product exists that would be great.
The system is 400v 50hz, the motor is 2/8pole (2speeds).

--- End quote ---

So, this falls into a category I'm familiar with ;) - "Functional Safety", laws, regulations, standards, certification, ... and worst case prosecutor, lawyers, judge, liabilities, ...
It's grown to a real big thing in comparison to some decades ago.
Just one advice left: If you aren't a professional safety engineer, stay away. If you can't, ask for assistance from a professional safety engineer or whatever in your country is the equivalent to our German "Berufsgenossenschaft"  (workers' compensation board) - basically a thing that work with insurance of the workers, risk management etc.

If you want to do that from scratch or buy something, you'd have to go through quite an assortment of failure analysis and risk management stuff and be able to prove that you've done that according to the applicable standards. It might result in a quite simple result, but with a lot of paperwork behind. If you can't provide the paperwork in case of an accident, you're toast.

As this looks like it's safety relevant, CE/UL is mandatory anyway, but not sufficient.

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