Thanks a bunch!
Between the several replies, I found way to do this researching your suggestions, not to mention learning something in the process. I'm using psychrometrics initially, then having the supplier evaluate afterwards. The ARI 360 standard also pointed me to ASHRAE Standard 37, which...
Hello all,
Is there a method to verify the actual performance of a packaged unit? I have a 15 ton roof-mount on a metal building (insulated) that doesn't seem to be working as well as it should. Total heat losses for the building, including sun load are calculated to be 38KW.
The unit is new...
Hello,
It's been a while since I was last here!
I hope someome can point me in the right direction. I need to find a spec for LV (690) bus bond testing. I'm having a hard time finding specifics for conducting the test. The closest is ASTM B539-02, but it doesn't mention a standard for minimum...
I have some experience with low (480 - 600) voltage power factor correctors. The capacitor bank failures I have encountered were caused by overvoltage or heat.
The caps should be taken off line when inductive loads are minimal, as a transient rise in voltage can occur. If your facilty is on a...
I have some experience with FIDs, TCDs, and gas chromatographs. Also photo ionization detectors(PIDs). Most of them were designed for the natural gas industry.
The FIDs were mainly used in open environments for leak detection. They burned, within a closed cell, a mix of hydrogen and some inert...
What is the encoder resolution? I once saw a problem where the encoder resolution (2048) was finer than the mechanical backlash of the gears. At low speeds, the drive saw a greater percentage of speed error (the gear slop being constant), and would become erratic trying to corect for it...
Someone on this board a little craftier than me may be able to answer that, but the easiest way to find the no-load current is to ask the manufacturer. I've tried to calculate this in the past and have never been 100% accurate. There's just too many variables.
When I can't get the unloaded(or...
The smaller the motor, the more of the "voltage doubling" effect will occur. Also true for cable length. At 3/4 Hp, you should be able to find an off-the-shelf output filter to reduce voltage spikes at the motor.
Just read through this thread...
Someone I work with sometimes (at another location) had a simialr experience. I don't know all the details but this is what I do know:
It was a crane (not a bridge crane though)
drive 3 "blew up" energized but not running
drive 1 and 2 had been running...
What do you want to test for?
I worked for a manuf. that made large inductors. We built a test fixture with caps, variac, transformer, a CT, and motor starter. We'd connect the inductor, charge the caps to twice the inductor voltage rating, and close the starter. This put the inductor in a...
I'd recommend using a cap rated above the mains voltage by at least 10%. There will be times when you get a transient rise in voltage at the cap. Keep in mind this will reduce the nameplate KVAR rating of the cap when used at the lower voltage.
Hey Skogs..
Isn't it not advisable to increase a motor beyond it's voltage rating? True, if you want to run a 60 Hz motor at 50 Hz, you'd decrease the volts along with the frequency. Above the rated frequency, don't you want to stop at the rated voltage and run in constant HP (reduced torque...
Just found this forum and thread...
leanne, you're right about that! More and more, customers are requesting copies of completed test procedures, observing tests, etc.
>>...mag amps (no load current) was 1.89A. The nameplate value is 0.92A....<<
That means almost twice the magnetizing current needed. You may have an over-saturated rotor. I sugest you run the (unloaded) motor open loop, measure the current, and enter that value as your mag amps.
