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energy saving?

Created by: innovations at: 6/20/2010 1:02 PM (7 Replies)

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6/20/2010 1:02 PM	Rate (0)
innovations Experienced Member Joined: 5/21/2008 Last visit: 5/31/2025 Posts: 93 Rating: (0)	dear all, one general query if i run a machine (having acmotor)by DOL starteror AC drive . with the same load conditions & at same speed will energy be saved when machine runs on ac drive ? pl. give your suggestions. sehgal

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6/20/2010 1:58 PM	Rate (0)
Vithani Platinum Expert Joined: 7/8/2009 Last visit: 6/7/2025 Posts: 1977 Rating: (479)	Of course.. Because when you will run machine on DOL, it will having an inductive load which causes lagging power factor which means more power required as Total Power will be Active Power + Reactive Power But when you run machine on AC Drive, it will work as Resistive load for a network which in turn result in to Higher (Almost Unity) power factor which means you will draw lesser power from supply because you only need active power that time... Regards, Devesh
	I dont Like people driving Fast, thats the reason I overtake them ;)
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6/21/2010 6:46 AM	Rate (0)
Mehta Posts: 80 Rating: (7)	Powersaving always take place if AC drive is used instead of DOL.However it could be little or partial depend upon application type. If application type is variable torque like Fan and compressor than power saving will be high as per load-unload cycle using AC drive.In this case by controlling speed of motor resulted in power saving. In case of Constatnt torque application little power saving take place due to following reason. - Ac drive having capacitor bank and it improves power factor. - Current peak during starting is approx 2*motor current or less depend upon ramp time and other setting.However in case DOL it could be 6 times.
Mehta Posts: 80 Rating: (7)
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6/22/2010 6:37 AM	Rate (0)
RBM Bronze Member Joined: 8/21/2008 Last visit: 7/25/2025 Posts: 141 Rating: (6)	Hi, Icompletelyagree with what vithani had said. But i would like to add one more point to that. The drive never improve the supply power factor. ie, suppose if the input power supply has a 0.85 lag in th line, the load connected to the drive will be having a power factor near to unity. But still the supply power factor will be remaining the same. But on starting with the DOL starting, this power factor directly reflects to the input supply line. This has an energy saving but it cant be generally to a high value. (under DOL starts, the power factor drops more when the motor runs at very low loads) As Metha said, significant energy saving is done on varying the speed of the motor. Normally every motor selection may be of a higher size load and this selection of motors will always be opted to work at maximum load condition. But this maximum load wont be there all the time. Hence using a VFD to varying the speed (variation in the load current) considerable amount of energy can be saved. But if you load is always a full load application, the only energy saving will be in the from of taking active power from load. rgds, RBM
	Last edited by: RBM at: 6/22/2010 6:58 AM
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6/22/2010 7:23 AM	Rate (0)
Vithani Platinum Expert Joined: 7/8/2009 Last visit: 6/7/2025 Posts: 1977 Rating: (479)	sehgal dear all, one general query if i run a machine (having acmotor)by DOL starteror AC drive . with the same load conditions & at same speed will energy be saved when machine runs on ac drive ? pl. give your suggestions. sehgal Well, I was knowing that But what Sehgal asked was, energy saving with the same load condition and at same speed So I replied that only.. Devesh
	I dont Like people driving Fast, thats the reason I overtake them ;)
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6/22/2010 3:44 PM	Rate (0)
innovations Experienced Member Joined: 5/21/2008 Last visit: 5/31/2025 Posts: 93 Rating: (0)	dear all, thanks a lot for suggestions byu all ! forum is a life line for techbees. sehgal

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6/23/2010 3:06 PM	Rate (0)
dchartier Grandmaster Joined: 9/27/2006 Last visit: 9/19/2025 Posts: 12415 Rating: (2718)	Hello sehgal; Siemens USA gives access to some documents (whitepaper, FAQs, applications, demos from Hannover Mess) that might give you more ideas on energy savings with AC drives: https://www.sea.siemens.com/us/Products/Drives/Pages/drives-home.aspx?HTTPS=REDIR Hope this helps, Daniel Chartier

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This contribution was helpful to 1 thankful Users Vithani

6/24/2010 2:09 PM	Rate (0)
Vithani Platinum Expert Joined: 7/8/2009 Last visit: 6/7/2025 Posts: 1977 Rating: (479)	Check out this forum Nice Details regarding Energy Saving has been provided https://www.automation.siemens.com/tf/WW/en/Posts/17194 Regards, Devesh Vithani
	Last edited by: Vithani at: 6/24/2010 2:10 PM I dont Like people driving Fast, thats the reason I overtake them ;)
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