Starting Time for Induction Motor using DoL.

Maybe a fluid coupling would help. At one time I thought hydraulic pumps/cylinders were involved, but one dam project just blends into another. Perhaps you could start over in your description.

How about not posting anonymously?

I bet it's still the vaporware dam with magic gates. Must be at least 3rd topic started recently.

Either some dams are made by ignorants or you aren't really involved in the engineering.

User hydraulics for dam gates whenever possible.

anons

Because that's just how long it takes.

The document you are reading is generic and covers a wide range of motor applications hence the large difference in start times. A lightly loaded fan motor takes far less time to get up to speed than a heavily loaded motor powering a rock crusher for example.

Part of the problem with "handbook engineers" is that they only look at the page that comes close to what they're looking for. If OP had taken the time, and had the engineering background required, he would have found that pages 1-42 do a fine job explaining the basics of motor starting.

Now that the internet so easily provides a link to all information anyone needs to know about any topic.

Squirrel. [Sorry about that.]

The sheer size of readily available information is so overwhelming it is easy to get distracted away from the critical information.

Squirrel! [So very sorry.]

Some people will go to a forum that has less distractions to direct a clueless individuals to the critical information they need to impress others.

Did someone say "squirrel"?

Sorry for the delay! However it is very interesting redfred, indeed. I find myself a poster in Romanian. Excuse me please for the translation.

SIMPLIFIED SYSTEM GIVES RAPID START:

Doesn't it rather depend on what it's connected to, Murphy? I mean, if it's the rotor of a progressive cavity pump, it will be different to the blade of a huge circular saw, won't it?

Friend,

1. You mis-read the table in the informative AB publication you linked us to. The 5-30 seconds for DOL starting is the range of maximum times suitable for loaded equipment. Alongside this was another column giving the much shorter range of typical times for DOL starting of an unloaded motor.
2. In this post and in your previous thread(s) on the same topic, I have not seen ANY convincing evidence from you to support a start time that is on the long side of these ranges.
3. If you are posting this question again (but in a slightly different form), are you doing this, hoping that someone will agree with you so you can be viewed as "right"?
4. Otherwise, please realize that questions such as yours are often best answered by the "scientific method" of making an assumption, designing an experiment to (safely) test the assumption, collecting the data from this experiment, and then seeing if the assumption is supported or fails. In other words, take what you have learned about motors, starting methods, and electrical safety then appropriately connect a starter between your power source and the motor in question, and try it!

Come back to us after you have done this!

--JMM

Yet another great answer! Regardless if the OP understands your answer, I learned something from your explanation, as I usually do. As I said before, maybe you really wanted to be a LUMBERJACK, but you are a great TEACHER.

if anybody has design guide, then please forward me at Do not post phone numbers or email addresses. The CR4 Admin will delete all phone numbers and email addresses posted in threads or comments. You can share this information via the CR4 internal messaging system.

If we use the NEMA MG1 recommended maximum load inertia moment most of

D.O.L. starting cases duration will not be over 10-12 sec. See NEMA MG1 CH.20.11 maximum load inertia. [Motor inertia moment is approximate 10% of maximum recommended load inertia moment.]

Of course if the voltage will be minimum 80% of rated and the load torque will follow a quadratic rule [with respect to velocity] and the maximum will be only 90% of the motor rated. Less voltage, more starting time.

For 100% rated voltage the starting time will be 5-7 sec.

In my opinion one cannot achieve a constant speed in an elevator using a regular squirrel cage induction motor starting D.O.L.

You have to employ a wound rotor, double-cage or deep bar for such a case. The modern VFD could be better. You can reach the rated speed very rapid and you can continue at constant speed up to the target. The starting time it is the duration from stall to rated [or required] speed, not more.

If you achieved a constant speed elevator then the passengers would have to get onto and off of a moving platform.

You are right, redfred . I mean constant speed between stations. Of course, at the stop-deceleration-it has to be in the same way. See [for instance, nevertheless it is about a dc drive]:

http://www.baldor.com/pdf/manuals/770-397.pdf

Set-Up Information 5-4