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From: "John Jardine"
Subject: Re: AC Motor Soft Starter
Date: Fri, 27 Dec 2002 19:42:48 -0000
NNTP-Posting-Date: 27 Dec 2002 22:37:14 GMT
X-Newsreader: Microsoft Outlook Express 5.00.2615.200
Oppie wrote in message
> There are several commercial units available. Do a search for 'reduced
> voltage motor starter' or 'soft start' and you should come up with a
> The soft starter in general reduces the voltage to the load during run-up.
> This is often done by a current sensing relay which switches in a limiting
> resistor while the current is above threshold. When the load comes up to
> speed, current draw is reduced and relay cuts out providing full voltage
> the motor. More sophisticated controls have phase control to reduce the
> voltage and sense what is happening to the load for safety.
> For valid response address, remove the '1' following oppie
> "Rudolf Usselmann" wrote in message
> | Hi !
> | I'm looking for a single phase 220V Soft Starter for
> | a 3.5HP Electrical Motor.
> | Anybody know where to get these things from ?
> | (Either fully build or as a kit).
> | Many Thanks !
> | rudi
Be aware that an AC induction motor soft-start is not as 'soft' as what you
may wish for. I.e it's not as soft as for a DC motor or as soft as an AC
motor fed via an electronic inverter. The soft start just takes the sharp
edge off the mech/elec loading at switch on.
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