VFD for EOT crane LT

If the crane is going to operate continuously VFD should not be required. and besides the LT power is 0.75hp... which is quite low and doesnt lead to significant cost saving.... VFD's are opted when varied speed operation is envisaged.

I think it will not be worth to go for VFD.

I'm afraid I disagree - the whole point about VFD in cranes is about firstly preventing shock load on sudden start up which can put extra loading on supporting steel work and secondly controlling the pendulum effect of the payload. In general terms in material handling 'gently does it' and we would always recommend variable speed drives in order to get controlled acceleration and deceleration. Your crane supplier should advise you - Roger Pask - Handlingconcepts.co.uk

Low hp VFD's are not very expensive. The new sensorless vector provide very smooth control with variable speed.

The one draw back is that cranes and hoists often require regenerative power so you need to have either braking grids or a regenerative power circuit.

We have used AC drives on dockside cranes lifting and lowering over 40 tons in the big containers.

Safety cicuits also need to be in place to provide braking in case of power loss or drive failure.

Just being able to set the aceleration/deceleration time, max speed will provide a level of flexability, that will more than justify the cost!

Most vfd's will have the ability to switch between various set-ups w/the flick of an external switch. this provision allows fast travel [for unloading trucks], slow for critical placement.

I am not familliar with the type of crane your are asking about. However we have used VFD's on bridge and monorail cranes with good success. Here are some things that might cause you problems:

1.) Overhauling load. GW already mentioned this. Having used fully regenerative drives on some applications, I would not recommend the additional expense in this case. I would stick with a standard drive with a built in brake chopper and an external dynamic braking resistor.

2.) Clean power. If this crane has power festooned to it, you should be OK. Many times cranes are supplied with power through some conductor bar and collector shoe arrangement. As the collector shoes travel down the bar, the connection can be a little intermittant. This can cause your drive to trip. To overcome this problem, you might consider doubling the collector shoes (i.e. two sets).

3.) Sizing. I agree with your crane supplier, use a 3hp drive

If you are interested we can recomend a control system using VFD with anti sway system for your crane