two unrelated questions for yas

I want to find what would be considered the max freq that a motor can be run at but cant seem to find it when searching the threads. Prolly just typeing something wrong??

Next is a panelview question. I am going into the control tags and making new ones for time date etc. And I mad hem reference the program which I have on the plants master clock. I made these DINT instead of INT but later read that it should be INT. What problems would I have with them as INT as opposed to DINT? I dont see any so far, but as the name suggests 'newbie'. So maybe I am missing something.

Thanks

You should verify max frequency / rpm with the motor manufacturer. Most will let a 4-pole motor (1800 rpm nominal) go to 75 Hz at least. However, I've had some motor manufacturers balk at using 2-pole motors (3600 rpm nominal) at anything over 60 Hz.

Most industrial grade motor bearings are rated 3600RPM, that is why this is the normal upper speed limit.

If a motor is rated for INVERTER duty, it usually has the MAX speed on the name plate. There are SSSOOOO many motors that are made to run beyond base speed these days. I have seen many 60 hertz motors run to 120 hertz regularly. They do not last as long as one rated for that speed.

An example of inverter duty ONLY is the BLACK MAX series by Marathon. By name plate they are rated 1735 to 1765 and show as high as 5200 as a flash speed and some are rated 4200 continuous. These motors cannot be started across the line.

To truly know the motors MAX speed, you need the mfgrs. data sheet for the motor. They are quite easy to get. Most are available on the web site for the mfgr or thru any authorized rep. Many electrical shops have stacks of manuals with these data sheets to help them correctly size motors. Some shops do not actually know they have the books as motor sales reps will drop them off and the folks there do not realize what they just got handed to them. I find that many engineering groups at plants also have these manuals and do not know they have them. Information is easy to get, you just have to look around a wee bit.

Jim Dungar said:

Most industrial grade motor bearings are rated 3600RPM, that is why this is the normal upper speed limit.

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I agree with Jim's reply entirely. I was told the same thing by a motor expert (in tech support). This being that the max speed rating of the bearings end up being the limiting factor at the high end.

As electrical people (engineers, technicians, electricians) we tend to get caught up in only the "electrical" issues. The reality is that the physics hauntingly come into play on every application. This includes friction, vibration, heat, etc.

For example, I had a former client (OEM) who would try to run cylinders at a very fast cycle time on an assembly machine. Those poor cylinders beat themselves to death in a relatively short time. The cause was that the machine designer thought cam-driven "pick and place" units were too expensive.

These guys eventually change their thinking when nothing lasts and buy the "expensive" devices that work reliably, while looking bad to the end customer the whole time. Some commercial says: "Pay me now or pay me later."