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Forums13
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Most Online117 Jan 16th, 2020
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#18033 - 09/19/16 01:20 AM
Re: Potential disaster averted
[Re: Chris]
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Joined: Aug 2011
Posts: 563
uppo72
addict
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addict
Joined: Aug 2011
Posts: 563
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Problem is that both the STR and RU contactors are fed directly from the main line. When the contactor fused the only way to shut it down was shunting the main line. I am unfamiliar with this unit, but are you saying the 3 ph goes thru STR and then RU? The reason why I ask this is the whole purpose of have 2 or 3 contactors is so if 1 does get stuck, is then the run timer trips, stops the control run up, which then would trip 'all' driving relays ie STR and UP. Unless STR is star and UP is delta. If that is the case, then this is a poor design of the 3 phase control. Also over temp thermistor should do the same thing. Every hydro that I have worked on has a MC contactor, then the star/delta changeover system which can protect for this problem. Also having a soft starter also needs to have an input to say the run timer and over temp has tripped or else the same situation will happen. The best advantage of a S/S is for motor life without the in rush current breaking down motor insulation.
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#18053 - 09/20/16 12:46 AM
Re: Potential disaster averted
[Re: Chris]
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Joined: Aug 2011
Posts: 563
uppo72
addict
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addict
Joined: Aug 2011
Posts: 563
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Line feeds both STR and RU simultaneously, they switch the motor from wye to delta. The good news is all the cars in the store (4)are now getting soft starts. As for the fire system, the only reason that I can figure that the system didn't trip was that this particular unit was directly under the outside vent.(which is very large due to multiple power units in the room)I have been a volunteer firefighter for 20 years and this one is sure strange. I think the lid on the tank probably stopped the oil from catching fire by excluding the oxygen, I'm sure it had reached its ignition temp! Yep genuinely poor design without another contactor in series for protection.
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#18077 - 09/21/16 06:40 AM
Re: Potential disaster averted
[Re: uppo72]
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Joined: Aug 2011
Posts: 563
uppo72
addict
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addict
Joined: Aug 2011
Posts: 563
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When talking about the ac ripple of a tacho, are we talking about a ripple where the commutation is a perfect dc line? Doh! put this in the wrong thread!!
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#18447 - 10/24/16 02:31 AM
Re: Potential disaster averted
[Re: uppo72]
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Joined: Oct 2016
Posts: 38
Philelevman
newbie
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newbie
Joined: Oct 2016
Posts: 38
St Louis Mo
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I am pushing the soft starts every day. Better protection and no movable parts. The only way to go.
Philelevman
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