Motor-Drive Discussion
While Russ is getting the data I requested, there is an opportunity to clear up some terminology and other items.
First, the term "inverter duty" is mostly snake oil due to its loose definition and irresponsible application by some manufacturers. For example, Baldor will put an inverter duty sticker on an ordinary TEFC or ODP motor for no better reason than that it has Class F insulation. At the other extreme is Reliance which reserves such a title for motors with auxiliary blowers or those like TENV motors capable of continuous rated torque duty at near zero speed. To protect yourself, you need to match the motor to the drive output technology as well as select the motor design to survive thermally at all expected speeds and loads, especially low speeds.
Second, while there are some variations between manufacturers, the general rule is that a motor that meets MG1.31 insulation standards will not need motor lead reactors or wave traps unless lead length exceeds 250 feet. There are some exceptions. Also, you can expect line reactor manufacturers and drive manufacturers selling reactors to recommend shorter lengths but, again, this is largely snake oil.
Third, variable torque loads like most fans and centrifugal pumps have a horsepower-speed characteristic curve that declines as a function of the cube of the speed and a torque-speed curve that declines as a function of the square of the speed. This means that at one-half speed, the horsepower is down to one-eighth and torque is down to one-quarter of what it was at full speed. In view of this rule, a fan or pump turning at one-quarter speed is down to one-sixtyfourth HP and one-sixteenth torque which, for the motor, is very close to operating at no load. There is absolutely no load-related reason why an ordinary TEFC motor should run hot or even warm at one-quarter speed on this kind of load. Sure, the motor's shaft-driven fan is not turning very fast but the motor is doing almost no work.
Fourth, motor amps is a poor way to measure motor load. This is due to the lead amps consisting of two components, magnetizing amps and torque-producing amps. These components are vectors at 90 degrees from each other so they do not add arithmetically. You can find magnetizing amps on the job-site by uncoupling the motor and running it at full voltage and frequency. This no-load current usually comes to about 20-25% (premium efficient motors are at the low end, standard efficient are near the high end) of nameplate amps. Calculating torque-producing amps from the total amps requires triangulation to solve. This is what "vector drives" do to measure torque. A far better way to measure motor shaft load or torque is to use a strobe light and find shaft speed. Assuming 60HZ, a four pole motor will turn right at sync speed of 1800 rpm with no load, a two pole will be at 3600 rpm, etc. As the motor load increases, the shaft speed will drop linearly until, at rated output, the speed will be right at nameplate rpm and amps will also be right at nameplate.
For example, the nameplate of a 100hp motor reads 1760 rpm. Since this is clearly a four pole motor, no load speed will be at 1800 rpm and full load speed will be at 1760 rpm. Torque calculates to 300 ft-lbs at full load. If you measure shaft speed while working and find the speed is 1780 rpm, you can be sure that the load is taking 150 ft-lbs torque out of the motor--one-half the speed drop will be one-half the rated torque. Since most modern drives will do a rough calculation of torque for you and display it, the above measurement technique is really only useful for motors on across-the-line starters.
Let's see what Russ comes back with for nameplate data and we'll take this further at that time.