Electric motor with 1/rev torsional output
Electric motor with 1/rev torsional output
(OP)
I've never studied motors. Is it possible to get a steady rpm, with a variable 1/rev torsional output??
Want to build a bench test setup for testing a mechanical device.
Help !
Steady rpm in the neighborhood of 1500 + or - say 20% or so (not critical). One per rev on the order of 1/3rd hp.
Want to build a bench test setup for testing a mechanical device.
Help !
Steady rpm in the neighborhood of 1500 + or - say 20% or so (not critical). One per rev on the order of 1/3rd hp.





RE: Electric motor with 1/rev torsional output
Bill
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"Why not the best?"
Jimmy Carter
RE: Electric motor with 1/rev torsional output
Do you mean "torque inversely proportional to RPM"? (But you are calling for a "steady" RPM in which case both the RPM and the torque are going to be constant?)
Explain what you mean. Or perhaps, explain what it is that you are trying to do.
If push comes to shove, a modern servo drive can generate any motion profile you want that is within the capacity of the motor to do, or generate pretty much any torque relationship that is within the capacity of the motor. Servo drives can have a "positioning mode" in which they will apply as much or as little torque as it takes to follow a specified motion profile, or a "torque mode" in which they apply a torque that you specify regardless of the speed that the motor wants to go in order to apply it - provided, of course, that you remain within the capability of the system to do it.
RE: Electric motor with 1/rev torsional output
RE: Electric motor with 1/rev torsional output
RE: Electric motor with 1/rev torsional output
RE: Electric motor with 1/rev torsional output
But be very careful to define the cycle, load inertia, etc., VERY well; there is a LOT of variation in servo response capabilities!
For instance, we work daily with AC servo drives in the size you are talking about, capable of 800hz velocity loop bandwidth; not many, if any, other AC servo drive is capable of this (yet). Most work well up to about 100hz area. You are asking for a maintained constant speed with some undefined (as yet) sine/triangle/step? torque disturbance 1/rev @ 1800rpm, 30 times/sec, or a full cycle every 33 msec or less. And you want to be able to match that torque disturbance closely, so assume you are willing to accept only 10 'corrections' during that cycle, you are asking for a velocity loop response of 300hz or more.... You will require a VERY good servo system to accomplish this. Now if you were running only 180 rpm, any old servo would likely do.
We had an application similar to this where we were to simulate cam shaft loading for an engine test stand - again running at these type speeds. So a torsional torque was put into the servo each rev, and I must say, it was very nearly undo-able without overheating the servo motor! What appeared on the surface as a simple application like this had a lot of bandwidth requirement!
In addition, you do not say what your system inertia is. Since T=jw/t, where Torque required to move an inertia of j over a speed change of w rad/sec in time t, understanding total inertia is critical to determine your response need. In your application inertia may be your friend - or your enemy, depending exactly on what you are doing.
I would recommend you pass your specifics by some of us who help design such systems; besides, it is a free service a lot of us provide!
www.KilroyWasHere<dot>com
RE: Electric motor with 1/rev torsional output
At 1/rev, you ought at least to consider the possibility of mechanical torque modification (a suggestion borne of 20 minutes spent truing the front wheel on the Lad's bicycle to stop it scuffing the brake blocks).
A.
RE: Electric motor with 1/rev torsional output
The cost appears to be cheaper with nuts and bolts than than with electrons flowing from - to + on the battery. (Just kidding!)
RE: Electric motor with 1/rev torsional output
www.KilroyWasHere<dot>com
RE: Electric motor with 1/rev torsional output
www.KilroyWasHere<dot>com
RE: Electric motor with 1/rev torsional output
Cost mechanically: Guesstimate about $300-400.
Been doing calculations using a steady rpm of 60 rev/sec, driving low inertia. On top of this #'s indicate an 'inertia load' of about 10-28 ft-lbs peak in a sign wave at one/rev (60 Hz). Or 20-56 ft-lbs peak to peak.
This help any?
RE: Electric motor with 1/rev torsional output
www.KilroyWasHere<dot>com
RE: Electric motor with 1/rev torsional output
RE: Electric motor with 1/rev torsional output
www.KilroyWasHere<dot>com