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Drive In Hoist Application


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#1 Ramasubramanian

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Posted 30 November 2007 - 10:08 AM

Dear Friends,

A 15kw motor driven hoist is connected through a VFD. The application being tough we had connected VFD of capacity 18.5kw and started using the hoist. It takes a load of 3 ton and beyond it does not hold the load. What is the reason for that. Some one says that it has to be used with Dynamic Breaking Unit and DB Resistor. Please explain.

#2 anu_rags

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Posted 30 November 2007 - 12:19 PM

In hoist application, regeneration takes place from the motor side while lifting. Therefore the DC voltage will increase till a limit and then the VFD will trip under DC bus overvoltage. In order to dissipate this excess energy, Brake Chopper and Resistor is required. You need to size the DBR as per your application requirement.

Regards,
Anurag

#3 Ramasubramanian

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Posted 04 December 2007 - 08:47 AM

Drive for hoist application
QUOTE (anu_rags @ Nov 30 2007, 05:49 PM) <{POST_SNAPBACK}>
In hoist application, regeneration takes place from the motor side while lifting. Therefore the DC voltage will increase till a limit and then the VFD will trip under DC bus overvoltage. In order to dissipate this excess energy, Brake Chopper and Resistor is required. You need to size the DBR as per your application requirement.

Regards,
Anurag



#4 marke

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Posted 04 December 2007 - 09:01 AM

Hello Ramasubramanian

Can you give us more detail on the problem that you are having.
QUOTE
beyond it does not hold the load

Do you mean that it will not hold the load stationary, or that it will not lift the load, or it will not lower the load in a controlled fashion?

There are a number of scenarios and if you can give us more detail, it will be easier to give you a meaningful answer.

Best regards,




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