Recommended starting methods for LSPM motors (Line Started Permanent Magnet)

[S_S_IBRAHIM]

DO these types of motor (Line Started Permanent Magnet ) can work efficiently with VFD ?

 

[BrianPetersen]

It would help if you explained the application. Is this a tiny synchronous motor that operates the hands of an old fashioned clock through an extremely high-ratio (but low-inertia) gear reduction, or is it a massive motor the size of a house that operates something (?) synchronously, or somewhere in between, or what is it? Explain yourself.

Permanent magnet motors in my field of understanding are also called "brushless DC" motors or "servo" motors, and in this day and age, they are electronically commutated. There's an example of such a motor, and a highly specialised drive that operates it, in my driveway, in the form of the drive unit for my Chevrolet Bolt.

So. Explain yourself.

 

[waross]

Most of the "line started" (12 V DC line) DC motors that I am familiar with move things like seats and mirrors in my car.
They would not work with a VFD.
Echoing Brian;
We need more information.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[FacEngrPE]

An attempted web search for "line-start permanent-magnet synchronous motor (LSPMSM)" finds mostly research papers, demonstration videos, a few nitch products, and some hopeful postings about products in R&D.
From the standpoint of using a VFD with a LSPMSM, it should be similar to any AC motor having a Permanent magnet roter. If the VFD is suitable, the documentation will indicate that a setting for PM mode is available.
PM motors are reported to have very fast accelerations when started across the line.

http://www.vfds.org/why-does-a-permanent-magnet-ac-motor-need-a-vfd-596666.html

The LSPMSM likely is similar to a PM motor but designed to have an acceleration that is tolerable when started across the line.

So if the plan is to use a PM mode VFD why not use the more available PM AC motors intended for use with a VFD?

 

[Gr8blu]

SS Ibrahim The "industrial grade" line-start permanent-magnet motors (up to several hundred kW) are out there: at least one North American and a couple of European manufacturers have patents on the internal design of both the rotor and stator. The bottom line is that the rotor design has to be a cross between an old-school squirrel-cage induction machine and a modern (interior) permanent magnet machine. The (copper) cage creates the initial starting / break-away torque to get the rotor moving in a line-start application. If the machine is designed (and manufactured) correctly, it will certainly operate on an adjustable speed drive - pretty much the same way as a squirrel-cage induction from standstill, with a switch in control scheme to permanent-magnet mode at some fairly low frequency condition (below 10 Hz, I believe).

Then again - why choose this design if you're using a VFD in the first place? Why not just a squirrel cage induction or a (solely) permanent magnet design? Both are cheaper, more reliable, and more readily available compared to the combination required for LSPM.

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