Selection of Inverter for Hoist
Posted 26 March 2004 - 11:09 AM
Posted 28 March 2004 - 07:10 PM
The next thing to insist on is commonly referred to as a "Torque Proving" feature, although the name may be different among manufacturers. This provides for testing that the motor is at 100% torque at zero speed BEFORE the mechanical holding brake is released. It seems like a given, but not all inverters, even Closed Loop Vector, are capable of this. Without it the load may begin to drop slightly before the inverter can calculate the proper output vector, then the motor may become incapable of stopping a moving load on the fly!
You must also carefully consider the input signal requirements. If you are retrofitting an existing hoist control, the voltage levels of the inputs must be capable of matching the existing control system. this seems like a minor issue but it is one that can cause lots of problems right at the very end of the project cycle (I have learned this the hard way!)
Posted 11 August 2005 - 08:02 AM
Posted 16 August 2005 - 06:38 AM
Posted 16 August 2005 - 11:57 PM
The drive spec does state that the speed accuracy is slightly worse with out the encoder, but we're only talking a fraction of a % of the motor slip frequency.
In general, when putting a drive onto a hoist do your self a favour and use one with an active front end. The drive may cost a bit more but it is worth it for the peice of mind, you don't have to worry about sizing brake choppers and resistors or install extra fuses and cables. You just commission the drive and let it do its thing.
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