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Soft Starters for High Voltage AC motors


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Have anyone got any information regarding motorstarters for high voltage motors?


What would the hypothetical commercial value potential of such a device be in your opinion? As far as I know, high voltage motors today are doing without softstarters altogether. Why is this the case? If I had a technology that could make such devices feasible, would this be something to pursue?

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Hello Otto


Welcome to the forum.


There are a number of manufacturers of soft starters up to around 11KV with names such as Alen Bradley, Motortronics, Solcon coming to mind immediately.


I do not know the current pricing of these devices, maybe someone else can shead some light on that.


Certainly, if you have an alternative technology, there would be interest. Especially if it resulted in a lower cost than the existing technology which uses multiple SCRs in series on each phase.

- Tell us more!!


Best regards,

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  • 4 weeks later...

Hello Otto,


Up until recently one could only purchase 'standard' specification MV & HV motors and had to consider starting alternatives that would provide best possible performance.


More recently however, some manufacturers of MV and HV motors have advertised that they are capable of manufacturing MV & MV motors to customer/application specifications, thus enabling the desired starting perfomance to be achieved without the use of soft starters.


Needless to say, these motors are generally more costly than standard variations so it's important to consider all options.




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Hello Otto,


First you must define what you mean by "High Voltage". In the US (that is where I am), High Voltage is described as OVER 15kV, and few motors are used at those voltages. 1kV - 15kV is considered Medium Voltage.


The practical limit on solid state technology for the time being is 15kV class starters (13.8kV utilization), and they are being done quite regularly. The problem is the cost. When compared to other starting technologies available at 10-13.8kV , solid state appears somewhat intimidating to the person signing the check, and they require significant "justification" from the engineer. The main reason for this is the fact that almost all of the components necessary for, lets say a reactor starter, are required for the solid state as well, except for the reactor being replaced by the more expensive SCRs. While it is true that solid state provides many benefits, the net result is that it costs upwards of twice what a reactor starter would cost at 13.8kV.


What I also find is that in many cases with 10-15kV class motors, they are often started and stopped only for maintenance purposes, making it difficult to quantify any real cost advantages over electro-mechanical. The driving factor in increased attention lately has been the rash of power outages in the US and elsewhere. Unscheduled re-starts after a power failure can be very hard on a motor that may have been designed for 2-3 starts/year!


I feel confident that the first 25kV starter will be built in the next 2 years. Technically it could be built today, but first it needs to be sold, which means finding a buyer willing to be the test case! ;b;

"He's not dead, he's just pinin' for the fjords!"
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