Disadvantage of Electronic Soft Starter

[danamobaddel]

I have a question. Who knows what is disadvantage Electronic Soft Starter against Magnetic Soft Starter?

 

[dpc]

Well there are a lot of different types of "magnetic" soft starters. The fact that they are basically all obsolete for any new installation tells us that the soft starter fares well compared with the old style reduced-voltage starters.

The soft starter generates a lot of harmonic distortion during starting, but the time duration is short so it is not generally an issue.

In general, the soft starter will be less expensive, more flexible, and smaller in size - although a mechanical bypass contactor is still necessary. The old methods (auto-transformer, resistor, part-winding, wye-delta) are dead and I don't see them coming back. My parents had an old telephone with a rotary dial - it's not coming back either.

 

[RonShap]

Depending on the motor size, and reliability needs, it is often cheaper just to get a VFD and use it as a soft starter.

 

[LionelHutz]

Well, a soft-starter is larger. There's not much else for disadvantages.

A VFD can be a cheap option, but you're taking a 5% efficiency hit and using a less reliable device.

 

[jraef]

The one advantage of Autotransformer starting is that the transformer amplifies the motor current when dropping the voltage so you do end up with more starting torque PU of line current. That has to be weighed against the higher cost, larger physical size, higher weight, limited starting time, inflexibility and tendency to wear out when compared with solid state.

I also used to say that any electro-mechanical starting method has the advantage of unsophisticated users being able to watch things happen, which gives some people comfort I guess. But with current Arc Flash regulations, that's no longer possible anyway.

Now if, by saying "magnetic soft starters" you were referring to the one single type still sold in India after being abandon by the rest of the world 50 years ago, but trumpeted as "new" again, I will not further engage. To do so would require I use the term they coined for it, then anyone searching for it will end up being directed to their website because they are the sole manufacturer. That company has used this forum, and others, as a form of free advertising by posting "questions" and eventually dropping their trade name, indirectly driving hits to their site. If they want advertising, they should pay for it like everyone else.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[MatthewDB]

A VFD can be a cheap option, but you're taking a 5% efficiency hit and using a less reliable device.

I'd suggest that anyone who uses a VFD solely to get a motor started should invest in a proper bypass contactor setup. (Make sure you use a mechanically interlocked contactor to ensure you never apply line voltage to the VFD output.)