Hi, I need some advice with variable frequency drive parametrizing. The thing is, we had to replace a Sew Eurodrive vfd which is used to drive a crane lift motor. But, even though the new vfd is the exact the same as the old one and we downloaded all the parameters, from it, it doesn’t work properly.
The problem is when we want the crane to go up, it goes down a little bit first as the brake loses and then starts going up. And it goes down rapidly as it falls on its own weight.
Can anyone explain me what parameter of vfd we have to regulate in order to prevent lift motor slipping when it begins running? My guess is tourqe, but I am bot sure

 

What releases the brake, I assume this is a physical brake and not a function of the VFD?

 

It is released by the vfd’s output signal, when vfd starts running the motor

 

What releases the brake, I assume this is a physical brake and not a function of the VFD?

Yes it’s a physical brake attached on the motor. It is released by the vfd, when vfd starts operating.
By the way, there is a box of braking resistor connected to vfd. Don’t they have sth to do with my problem?

 

The braking resistors are for operating when braking (stopping) the motor.
So I assume you are using one of the outputs on the VFD for the brake which comes on "At zero speed" for e.g.?

 

SEW drives are highly configurable in terms of hardware and make excellent drives for lift applications when configured correctly. The motors can have a number of different brake styles which need to correspond to the type of brake controller in the drive. Some applications may utilize a simple digital output to power a contactor which releases the brake. Others may have a dual-output PWM control which is capable of doing fancy things like reversing polarity at key moments to add/cancel residual magnetism for faster brake response.

You need to confirm that the new drive matches the old one exactly, down to the down to the installed options. It could be that your old drive had a braking option that the new one lacks, and therefore the brake is not being controlled properly.

SEW is very good about documenting systems and packages that they deliver. You can put a SEW motor or drive part number into their website and it will tell you exactly what options were installed, and in most cases this part number is all you need to get an exact replacement. But if an option was added or changed by the end user or 3rd party after delivery, it will not be reflected in the part number. So it is possible you ordered an exact replacement which was not actually an exact replacement.

Does the old drive still power on? Can you connect to it, upload the configuration to a new/empty project, and compare to the program you downloaded into new one? Usually the MoviTools software will alert you when you download an existing program into a new drive if the technology options do not match. This warning is presented in the typical "do you want to proceed, yes/no?" style of pop-up box that we are all conditioned to blindly click through "yes, yes, ok, accept, ok, yes, ok, let's get on with it..." so it would be understandable if you missed it.