Big motor question.

[flyingsparks]

I have been asked about installing a large motor to drive a forage wagon which basically has a load of blades which chops up silage. The motor specified is about 40kW, and will run through a gearbox reducing down about 1:7. My quesion is with star delta starting is this motor likely to struggle to start, or should there be a clutch mechanism to allow the motor to start up fully and then engage drive?

Forage Wagon similar to this, basically instead of tractor driven PTO will be electric motor.

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[RF Lighting]

First question is can the existing supply take this load? I'm assuming you're on a rural farm? Be careful here as a few of the farms I look after suffer really badly with volts drop when you start to properly load their supplies up.

It might be an idea to chat to the DNO first off to see if their supply will cope.

The gear box has a reasonable ratio so you should have a decent amount of torque availible at the blades any way, so I'd have thought a star - delta starter should be fine.

 

[flyingsparks]

Thanks RF. As it happens he phoned me this afternoon to say that the cost of the gearbox was too much and they are rethinking their plans. This is all prototyping/experimental!

It is a rural farm yes, will contact DNO if they decide to go ahead with this system.

 

[ricicle]

It may be better with a VSD but sit down when you get a quote for one !

 

[Aragorn84]

Surely a diesel engine running on red is a far better idea?

Means you can move it around if needed, and likely to be far cheaper than huge electric motors and whatnot when you can get one from a scrapped transit van or old landrover for about 50quid.

 

[bernardgreen]

The diesel engine is probably the best option as the machine is ( apparently ) designed to run from a tractor and will have all the necessary gearing and couplings already fitted.

 

[stillp]

Also please be aware of the Machinery Directive, implemented in UK law as The Supply of Machinery (Safety) Regulations 2008. There's plenty of guidance on the BIS web site and at http://ec.europa.eu/enterprise/sect...inery/guide-appl-2006-42-ec-2nd-201006_en.pdf

These regulations apply even though the machine is not being supplied on the open market.

 

[flyingsparks]

RE the diesel engine, this machine will chop up silage to feed into an anaerobic digester, which produces methane. This then runs an engine and generates electricity and sends it back to the grid. Therefore the electric motor was effectively going to run at a cheaper rate than a diesel engine.

 

[stillp]

An electric motor would also be easier to stop if you need to interlock it with covers preventing access to the dangerous bits.

 

[bernardgreen]

Use a dual fuel engine, start on liquid fuel and then when possible switch to run on methane,

 

[flyingsparks]

The methane engine is already in and working, they are looking at ways to make the process of feeding silage into the digester easier/quicker.

Not sure how a dual fuel engine would work as this one is basically (I think from memory) a diesel engine which has had spark plugs fitted. (To put it very simply!)

 

[ericmark]

Not seen many Diesel engines that run at 540 RPM. I would have thought gear box 5:1 would be needed be it electric or diesel? May be petrol engine converted to run off methane gas? CH4 instead of C8H18 should work?

I would say pulley and belts with tension roller would both give reduction and allow start off load. It's a lot of weight to get moving and a soft start is expensive.

 

[flyingsparks]

I think there may be a a bit of confusion. The methane engine litterally only produces electricity through a generator, the majority of which is exported. This motor I was asking about is to chop the silage to feed into the digester plant. The methane from this plant is piped directly into the methane engine.

I think your pulley idea Eric is not a bad shout. Easily able to allow the motor to run up to speed before putting it under tension, and gearing is still easy to achieve.

 

[ericmark]

The methane engine is already in and working, they are looking at ways to make the process of feeding silage into the digester easier/quicker.

Not sure how a dual fuel engine would work as this one is basically (I think from memory) a diesel engine which has had spark plugs fitted. (To put it very simply!)

Field Marshal tractor? Glow plug or cartage start. I would look at narrow boats for gear box and drive disconnection the old velvet drive should work well. Bedford TK military version had multi fuel engine 300 cu in but don't think it would run on gas. National mining engines ran on coal gas remember one a college foot bore and stroke but at 150 RPM a little on the slow side.

 

[ericmark]

Come on whole hog have a sterling engine running from the heat off the digester!

Look at compressor pulleys about right ratio.