DOL starter 7.5HP, 3 ph motor

[Brightspark2]

And just to confirm i ran down and checked, i could turn the blades by hand when unplugged so no brake present.

That doesnt proove a motor doesnt have a brake squire...motors can be stopped by dc injection...

 

[Brightspark2]

The motor is a David Brown....

There not bothered what youve called the motor wade, they want to know the manufacturer....





Well I laughed I to myself...

 

[Knobhead]

That doesnt proove a motor doesnt have a brake squire...motors can be stopped by dc injection...

If you’ve worked on paddle mixers you will know they stop dead, no need for a brake.
It’s a bog standard DOL starter, no mention of the capacitors required for “plug” braking or a second contactor for reverse braking.

David Brown will have bought in a standard flange mount motor to put on one of their gearboxes. Chances are Wade has looked at the gear box plate.
I’ve worked with DB for near 30 years, they made an 18 ton pinion gear and a 25 ton girth gear for us. I think they know what they are doing.

 

[wade88]

That's the only plate i could see on the whole unit tony. Just a whopping great David Brown tag.

Ok, well thanks for the info guys, I know what I need to do with this one now.

Interestingly enough, I had left a similar post about contactors when i first joined this forum, and i even drew a diagram...clearly all such things have eluded me now, buty i shall repost it as its not indifferent to this scenario (includes limit switch etc).

I drew this Nov 2011, have had not done anything similar since.

- - - Updated - - -

Hasten to add I don't draw electrical diagrams....

 

[Spoon]

Dont you need a safety relay now?

 

[wade88]

Well there is no safety relay in the existing circuit mate? The safety cut out just runs through the contactor

 

[wade88]

I wanted to tap your brain on safety relays anyway, meant to ask last week.

For a basic circuit as this with integrated safety cut out. Can you show me what safety relay you would purchase and how you use them. Something i have notice you mention quite often, i also went to the packing expo in Birmingham last week and wondered around a few robotics stands that specialised in safety innovation and automation, but none of it made a great deal of sense to me.

 

[wade88]

Would i be after a single pole auxiliary, for a single safety circuit.

 

[Spoon]

We use safety PLC here now. There are lots of safety relays and I suppose it depends on what category of stop you require as to which type of relay you use.
This all depends on the risk assessment that should be done on the mixer (if you are upgrading the mixer to current regs).
But if what Tony says is true for your mixer and that the motor will stop straight away when the lid is lifted then there may be no need for a safety relay.. All depends on the risk assessment mate.

 

[wade88]

Alright thanks mate. I write the risk assessments here... *Gasps of horror* so I shall make that decision once we review the frequency of use, nature of use, and human input based around the safe system of work that I write subject to the new product.

Thanks lads

 

[joel89]

Lol.

A1/A2 will be your coil and is energised by the control circuit as my previous post............voltage needs to be checked as it could be a 230v or a 415v coil and that would be your control circuit voltage so you don't really want to be taking that to your lid switch

or 110v ac...

 

[joel89]

i always use schiender xps 2 wire control safety relay... pretty easy to wire really ! but of course be aware whatever your control voltage this needs to be the same (i.e) 24vdc, 48vac, 110vac, 230vac, 400vac?

you have a reset pb.. and connect all your outgoing control wires to the bottom of this so when you hit the e-stop it kills everything in the panel hope this helps regards
Buy Safety Relays XPSAC emergency stop relay,110Vac 3NO Telemecanique XPSAC3421 online from RS for next day delivery.

 

[joel89]

you basically feed your control lines (generally 2) in most basic start stop circuits, connect the stop relay coil (a1 + a2) through the stop button so that when you hit e-stop it will kill all control (with the estop being n/c contact) and also take the 2 control wires which come into the bottom of the esr through the estop they are really easy to wire up !

ensure the esr is protected on the incoming and outgoing sides of the supply i.e 2a circuit breaker or less!!
could you not just use the old fashioned NVR Coil?

 

[Knobhead]

We use safety PLC here now. There are lots of safety relays and I suppose it depends on what category of stop you require as to which type of relay you use.
This all depends on the risk assessment that should be done on the mixer (if you are upgrading the mixer to current regs).
But if what Tony says is true for your mixer and that the motor will stop straight away when the lid is lifted then there may be no need for a safety relay.. All depends on the risk assessment mate.

Paddle mixers depending on the product plasticity will normally stop dead IF LOADED.
Unloaded they will run on.

This is where common sense has to play its card.
Most of my work has involved centrifugal fans up to 2500HP. Are you going to try to stop that quick?

No amount of safety relays can take out kinetic energy. 20 minutes for a 2000HP fan to stop due to the fan impellor acting as a flywheel.

 

[Spoon]

Paddle mixers depending on the product plasticity will normally stop dead IF LOADED.
Unloaded they will run on.

This is where common sense has to play its card.
Most of my work has involved centrifugal fans up to 2500HP. Are you going to try to stop that quick?

No amount of safety relays can take out kinetic energy. 20 minutes for a 2000HP fan to stop due to the fan impellor acting as a flywheel.

As you say Tony, you have worked with these mixers before. I haven't. Common sense works with most people but not all and unfortunately you have to allow for the thicko's who want to put their hands into things and press buttons for no reason.
If I was to put my name down on the re-design of this mixer I would use a locking solenoid on the lid and monitor to see is the mixer is still moving. I'd keep the lid locked until the mixer stops.
Just out of curiosity, how to the modern mixers work? Do they lock the lid while the mixer is moving?

Regarding the fans, don't they have guards to stop people touching the fans with their hands?