Hello I’m faced with an task of replacing a VFD with external brake resistor, the original drive is a UNIDRIVE 1405 and it’s obsolete. The VFD drives a 4KW motor that is used for lifting a injection head up and down at a continuous motion and speed. Motor is connected to gear box that follows a crank arm. The replacement VFD is a PF 70 CAT#(). The issue that has me scratching my head is size of the brake resistor that is at the below attached picture, why would the brake resistor be such a big size? I always thought that the resistor should be sized to the VFD. All the braking resistors from AB sized for the PF70 are nowhere close to the wattage of the original resistor. Please can anyone help. I’m afraid that is I use the recommended external resistor from AB it might overheat. I’m thinking to just leave the old braking resistor in place and connect it to the new PF 70 but I’m not sure of any limitations.
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