If you are a student engineer you need to develop an analytical approach to problem solving. So what have you thought about?

You've got a chain conveyor :

have you been and looked at it in operation, particularly when starting?

have you understood how it works?

do you understand the way the electric motor works?

have you thought about how the manufacturer selected to motor?

(hint, F = mu x N)

have you thought about the starting characteristics of the conveyor?

You're looking to use a soft start :

do you understand how a soft start works?

do you know the characteristics of the unit you propose to use?

Now the real bit :

is the characteristics of the motor output when driven by a soft start compatible with the required input of the chain conveyor ???

If yes then

use a soft start,

else

use something else

So start thinking and analysing like an engineer, and good luck. ■

If this is a soft start only, my understanding of these is that you can only adjust ramp up time and some current parameters.

This would imply that you are jogging the drive to inspect. Otherwise I would think you are just slowly going up to full speed.

What Hp are you looking at? If under 10 Hp the price difference will be small between a soft start & a real VFD.

With a VFD, watch the speed turndown ratio & make sure it will give you the inspection speed you think you need. Since you are presumably inspecting empty your Hp draw and motor heating should not be an issue for a short term inspection on a relatively short conveyor.

This is a much better idea than the old creep drives with sprockets & over running clutch. ■

Just a thought, as it's 40 hp do you have a fluid coupling in the drive unit?? ■

I'm interested how a soft start can set a motor speed?

Are you intending to jog the conveyor loaded or empty? ■

Umm.

But surely unless you have enough current fed to a 3 phase motor it won't generate enough torque to start it rotating and turn over even an empty chain conveyor. Of course it all depends on how much torque you need to turn over your empty conveyor. As I said in my first post it's just F = mu x N, and T = F x r (which, me being old, I was doing aged 15)

The best solution is to get the local rep to bring you a unit for trial. If it works you buy it and perhaps a few more, if it doesn't you thank him for his visit but don't waste any money, just a bit of your time but you've gained some education. ■

Someone may correct me if I am wrong but my experience with softstarts is that if there is no load it will go across the line start sooner than you may want it to.

If you set the ramp time too high there may not be enough torque to get the conveyor moving at all.

If this is for a maintenance inspection service I would look at a totally independant drive system such as a secondary (maintenance) drive with a much larger reduction reducer to slow it down to the speed you want it to go. Since it is for maintenace you could use the same starter switched to the maintenace drive. Only need a switch and a new cable running to the new drive. ■

My classic experience with a soft start was someone setting it up, with guidance from the salesman, with a low start voltage and long ramp time. The result was a machine that would not start because the thermal overloads tripped out before it got moving!

Solution, increase the start voltage significantly and reduce the ramp time significantly. Not much of a soft start in the end.

Call me old fashioned, but I prefer fluid couplings. ■

As its only for turning over an empty conveyor and there's no fluid coupling why not make up an adaptor to connect a power drill (or similar) onto the motor fan extension shaft. One guy can turn the machine over while another does the checks. ■

But not if the overloads are separate items from the sort start

In my experience there is not a lot of difference between static and dynamic friction in chain conveyors so most of the torque you need to "unstick" a chain conveyor is needed to keep it going i.e. it's a constant torque machine. It's also a "low inertia" machine as compared with the drive motor unlike centrifugal bucket elevators.

Yes, the "drill" is the inspection drive that turns the motor and hence the conveyor. A bit more high tech (and less hard work) than turning the motor fan by hand!! ■

I'm with Gary Blenkhorn and the original designer. If the chain is jammed onto the sprocket and the 'ramp up' business clears the jam the machine will carry on with maybe a few fingers in the chain. The existing system is there because it needs to be. Don't let a bunch of sparkies take over mechanical design work. People finish up in mechanical design because they were athe only ones who listened to the applied maths teacher at school! All the others fell by the wayside. ■