Interesting. Maybe my system came up with the braking resistance number in the auto tune, but I thought I manually put it in. My resistor is the home made resistor that fit in the rear cavity along with everything else of the VFD conversion. If you want to look at my reference, Part 2 that I posted, you will find VFD program settings as an appendix at the back of the document. The resistor value shone in my table was correct as I went with 50 Ohms. If you have lost it here is another link to the discussion
Your resistor is going to be fine. But if you can get the manual programing work to function I would do so. Why not?
PS. During one of my first jobs (1970) I had to spec and test transformers for a rather complex multi output power supply I was designing. This was for a small electronic publishing equipment house in New Hampshire, while I was in graduate school in Boston. So for a load I took a plywood board and with stand offs I mounted a serpentine resistance wire of some length. I could then just clip the output of the transformer to various points along the wire to see the effect of loading. Due to internal resistance and saturation of the of the transformer windings and core the output voltages from the various secondary windings did not all degrade at the same rates. Obviously the core saturating also cause the voltages from some outputs to be too low while others were meeting spec. Redesigns were required.
I also used this same fixture to test various fuses as to when they would burn out. They were pretty consistent. Most of the common BUSE type fuses would burn out at the same voltage drop ~0.1 volt. Hence, sometimes in a circuit when I need a very small resistor but the exact value is not critical, I just do the calculation and use a fuse as the resistor, choosing the knowledge that at the current load rating occur about 0.1 volt. Hence you know the resistance of the fuse. They are usually much cheaper than purchasing a power resistor and commonly easier to mount. By the way due to the resistance at the contacts, you have to have special equipment to measure the very small resistance of low resistance devices. It is called a 4 point probe and you can usually purchase these as good impedance analyzers. I have one. Typical cost is a few thousand dollars. They will tell you the L, R, and C value of a device at various voltages and a various frequencies. Very handy when you need it.
Dave L.
I assume that you are going to mount your resistor to the inside wall of your enclosure? I looked at the specs. It will be fine. However, I would probably have to break it open to understand their design in detail. The doe not provide any information about frequency dependence,I assume because it is small. All wire wound resistors are similar. One uses a NiCr alloy wire ("resistance wire") and runs current through it. It has kind of high resistance and so one just sizes the diameter to length to achieve the desire resistance value. If you make it bigger in diameter and longer than you can still get the same resistance and it will dissipate more heat before the wire melts. In these types of device the usually bury the wire in a ceramic like material which is enclosed by the outside Aluminum. The design of this stuff sort of determines how fast the head can get out before the wire gets so hot that the housing would crack open. Anyway, 400 watts is way over kill for our application. It never gets hot. These big resistors are really design for process mills etc where the motor is constantly/continuously accelerating and decelerating (braking) with big loads. To test my resistor, I started my lathe up to high speed and shut it down via fast ebrake a bunch of times as fast as I could and then gave my resistors the old heat sensing finger test. They were just starting to get warm. I suspect that even a 50watt resistor would work fine just because of the duty factor of when are running versus how often we apply the break. Also, my design has air flowing over the resistor assembly as it come from the VFD fan. Anyway, my individual resistors were wired up to yield 50 ohms but could have been wired up to yield other values, over all by putting some in parallel with some in series and the package size is still smaller than the commercial ones. While yours looks pretty nicely packaged, they usually remind me of the shape of a bulky Sea Slug. (I scuba dive and so have often seen them(sea slug) inching their way across the ocean sand floor.)
Your resistor is going to be fine. But if you can get the manual programing work to function I would do so. Why not?
PS. During one of my first jobs (1970) I had to spec and test transformers for a rather complex multi output power supply I was designing. This was for a small electronic publishing equipment house in New Hampshire, while I was in graduate school in Boston. So for a load I took a plywood board and with stand offs I mounted a serpentine resistance wire of some length. I could then just clip the output of the transformer to various points along the wire to see the effect of loading. Due to internal resistance and saturation of the of the transformer windings and core the output voltages from the various secondary windings did not all degrade at the same rates. Obviously the core saturating also cause the voltages from some outputs to be too low while others were meeting spec. Redesigns were required.
I also used this same fixture to test various fuses as to when they would burn out. They were pretty consistent. Most of the common BUSE type fuses would burn out at the same voltage drop ~0.1 volt. Hence, sometimes in a circuit when I need a very small resistor but the exact value is not critical, I just do the calculation and use a fuse as the resistor, choosing the knowledge that at the current load rating occur about 0.1 volt. Hence you know the resistance of the fuse. They are usually much cheaper than purchasing a power resistor and commonly easier to mount. By the way due to the resistance at the contacts, you have to have special equipment to measure the very small resistance of low resistance devices. It is called a 4 point probe and you can usually purchase these as good impedance analyzers. I have one. Typical cost is a few thousand dollars. They will tell you the L, R, and C value of a device at various voltages and a various frequencies. Very handy when you need it.
Dave L.
