Hello !

I'm having a bit of a problem with my current limiting resistors, I'm using Oatley electronics driver board with Oatley electronics constant current supply for steppers and 20V 40A power supply.
Constant current supply is rated at 2.5A with current limiting resistors to suit a motor. Value is worked out using formula: 1.25/stepper current rating. They are two 5W resistors that can be connected in parallel or series to get the correct rating.
Now, the motor that I want to use is rated at 50V 3.5A. I spoke to the designer of the board and I was told that extra amperage is ok if I provide adequate heatsink. Using the formula, I worked out that current limiting resistors should be 0.357 Ohm (1.25/3.5=0.357).
I managed to get the motor turning, driver transistors are cool, but current limiting resistors are getting so hot that they melt the solder on the pcb.
What am I doing wrong ? Should I use larger resistors (more wattage) ?

Thanks for help !