If you are driving a PM motor with a VFD with no feedback of any kind, you are basically treating it as a big stepper motor in microstepping mode. As you suspect, overload would cause a catastrophic failure - not just loss of torque, but rapidly alternating torque tending to bring the motor to...
Some vector drives will keep the "magnetization current" active even when there is no request for orthogonal "torque current". This way, when there is a request for torque current, there is not the delay in getting the rotor to magnetize.
One of the trickiest things about "sensorless"...
The "VC" in 1 and 2 stands for "vector control". This is closed-loop control of the motor as opposed to the open-loop V/F (voltage/frequency) control of 3.
As to the first letter, different companies use different terminology. "S" is probably for "Space" as "Space Vector Control" is a term...
In the standard operating range of induction motors, torque and slip frequency have an approximately linear relationship.
In open-loop control -- DOL or V/Hz -- as the load torque varies, the speed, and so the slip frequency will change until the generated torque balances the load torque.
In...
About a decade ago, I stumbled on this issue. I spent some time on it, but was too busy to go into depth.
There is a very tight relationship between these "length-of-day" variations and certain components of "atmospheric angular momentum". It appears that a lot of the variation has to do with...
A few years ago, I got a great tour of the southern end of the Pacific Intertie HVDC line in Los Angeles, which typically brings power from the big dams on the Columbia River south to the big population centers.
The thing I found most interesting was how they handle the loss of one of a pair...
We have many customers who output microstepping pulse trains at over 1 MHz. It's not unusual at all. Of course, you need to check what the maximum frequency your drive can accept is, and make sure your pulse width is short enough that you actually have distinct pulses at the higher frequencies.
"Is there really much difference between a brushless servo motor and a stepper motor other than the controller?"
Not really. Both are AC synchronous motors. You are correct that the real difference is in the control. We have multiple customers who buy standard stepper motors, add an encoder on...
The dynamics of stepper motor torque generation are those of a lightly damped spring. Imagine pulling impulsively on a wheeled cart using a Slinky.
This diagram shows the lightly damped response of a stepper motor to full-step commands (left).
If you issue a subsequent step command increment...
There's probably been more nonsense offered about "inertial matching" issues than any other in all the years I have been in servo control. There is really nothing "optimal" about a 1:1 ratio.
In the real world, what you typically need to worry about most is how your resonant and anti-resonant...
The roads along the Charles River between Boston and Cambridge -- Storrow Drive on the Boston side and Memorial Drive on the Cambridge size -- have underpasses with less than 10-foot clearance. These roads pass by major universities -- Boston University, MIT, and Harvard.
Of course, move-in and...
I'm afraid the information given to you is true. As an old product, near obsolescence, it is build-to-order and not a stocked product. I have looked to see if we have any "off the record" parts, but no luck so far.
Curt Wilson
Omron Delta Tau
Bill:
You've done exactly the transformations I recommend to people trying to understand field-oriented control of induction motors. I almost put these in my last comment, but didn't have the time. I would go one step further and express the slip in Hz as well as RPM.
The next step is to...
Bill:
With an induction motor, any time you use negative slip (electrical frequency less than mechanical frequency), the motor becomes a generator. With a synchronous motor, any time you use a negative torque angle (electrical angle lagging mechanical angle), the motor becomes a generator.
So...
Perusing a Tesla forum, I see that Tesla cars have a warning light that comes on at low outside temperatures, telling you that the regenerative braking capability is reduced. This is due to the reduction in charging rate of the battery at lower temperatures.
Bill, as far as the motor and inverter stage are concerned, you can develop as much braking torque as motoring torque. It's highly symmetrical. (And that's neglecting the help of friction losses in decelerating.)
I'm not an expert on batteries, as the systems I deal with regularly have...
The limiting factor on the deceleration is almost always the rate at which the storage devices on the DC bus can accept current, not the motor or the inverter. Capacitors have a far greater charging rate than batteries, but a good-sized battery bank can absorb at a pretty good clip.
My hybrid...
My field is positioning servo control. Most commonly used now are permanent magnet synchronous ("brushless DC") motors, but also brush DC and AC induction motors. In all cases, we decelerate all the way to a stop by regeneration alone. (Many precision systems use air bearings, so don't even have...
The most likely thing is that you have an unsigned 16-bit value (range 0 - 65535), where a value of 0 corresponds to 4mA, and a value of 65,536 (2^16) would correspond to 20mA. You can linearly interpolate between these. It is possible that the numerical values actually correspond to a greater...
For those of you unfamiliar with the area, the crash site is very near (~2 miles north) of the site where the 1980s TV show MASH was filmed. Many of you will remember the iconic opening scene with the helicopters coming into the medical camp with mountains in the background. The hills where the...
