Unbalanced Vibrating Motor Braking

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Anonymous Poster #1	Unbalanced Vibrating Motor Braking 08/02/2019 10:39 PM
	I have 2 numbers 3 phase ac, 50hz, 415v,1.67kW unbalanced vibrating motors operating in parallel through a vfd danfoss fc360. I have a dc injection device connected to the motors through a contactor. When vfd stops, dc injection starts to stop the motors quickly in order to eliminate abnormal vibration of the vibrating trays. These trays are held at the base with spring at bottom. Now, one of the motors getting stopped as desired but the other is not even though their starting, stopping and braking are common. I have checked the connection of the braking device as well as the motors. Even tried swapping the motors to check connection issues. But still the same motor which were working as desired, is still working as desired and the other is not. I want to ask is there any mechanical problems be there? But it looks like mechanical systems are ok. Springs are good so the base also. Any kind of help will be appreciated. Thanks.
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SolarEagle Guru Join Date: Mar 2007 Location: by the beach in Florida Posts: 33392 Good Answers: 1817	#1 Re: Unbalanced vibrating motor braking 08/02/2019 10:50 PM
	You must have an open circuit in the DC...possibly an overload is stuck open from overheating....with the motor disconnected, check continuity of the motor windings...then apply brake and check DC voltage level on braking circuit...with the motor connected, apply brake and check amp draw on braking circuit... https://www.motioncontroltips.com/what-is-dc-injection-braking-and-how-does-it-compare-with-other-methods/ __________________ All living things seek to control their own destiny....this is the purpose of life
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HiTekRedNek Guru Join Date: Oct 2006 Location: 44.56024"N 15.307971E Posts: 8277 Good Answers: 270	#2 Re: Unbalanced vibrating motor braking 08/03/2019 5:33 AM
	Plugging is widely used in elevators and instrument controls, so the technology is mature.The DC must be missing or the motor would definitely stop. May be an internal connection in the motor terminal box or the motor stator,since the problem follows the motor. I suspect the motor might actually be single phasing,and because they stop and start together,it might not be readily noticed. Check the current on all three legs of the suspect motor. __________________ "A man never stands so tall as when he stoops to help a child." "Never argue with a stupid person.They will drag you down to their level and beat you with experience" "To create an apple pie from scratch, first you must create a universe"
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