To Know

4 comments

Rate

sri audhi Member Join Date: Jul 2010 Posts: 7	To Know 07/26/2010 11:37 AM
	Dear sir, Its is possible, when the 3phase motor works in three phase electric line continuously, suddenly the power from one phase was failed, during that time we can operate that 3phase motor, by changing the one of the power phase line act as a failure phase. if there is any device is found by electrical engineering. kindly give the information about the device name and specification. thanking you regards E.gunasekar __________________ sri audhi
	Register to Reply

Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

These comments received enough positive votes to make them "good answers".

kvsridhar Guru Join Date: Sep 2009 Location: Temporarily at Ashburn, VA Posts: 2744 Good Answers: 164	#1 Re: To Know 07/26/2010 12:31 PM
	Dear Mr Gunasekar, It is never good practice to run a 3φ motor on two phases. You need to check why the third phase is not coming. It has to be due to blown fuse right? If the upstream device was a circuit breaker, the supply would not be there on any phase even if one phase had a fault. So, you need to check and correct that situation first. The fuse might have blown due to a single-phase to earth short-circuit, or even due to a bad fuse. Do not find a cure. Follow prevention. __________________ Nothing worthwhile can ever be taught, it can only be learnt.
	Register to Reply

JRaef Guru Join Date: Sep 2006 Location: California, USA, where the Godless live next door to God. Posts: 4665 Good Answers: 804	#2 Re: To Know 07/26/2010 3:20 PM
	Not sure of what you are asking, you are likely not a native English speaker. But what I think you are asking is if there is a device that can add in a lost phase so that 3 phase motors can continue to operate? If so, there is. Many VFDs (Variable Frequency Drives) can operate with only 2 of 3 phases coming into them and continue to deliver 3 phase power to the motor. But in order to accomplish this, the size of the VFD must be at least double that of the motor FLC. The reason is, your single phase power draw from the two remaining lines will increase by the sq. rt. of 3 (1.732) plus the single phase input will require additional capacitance on the bus to handle the ripple. So for example if you have a motor with a FLC of 20A, you must use a VFD rated for 40A if you want it to run continuously if a phase is lost. The exception is that under 2kW at 230V, many VFDs are capable of operating from single phase power without over sizing. This is, of course, a very expensive way to go if you have no additional benefit from running at reduced speed. __________________ All I every really wanted to be, was... A LUMBERJACK!.
	Register to Reply Good Answer (Score 2)

sri audhi Member Join Date: Jul 2010 Posts: 7	#3 In reply to #2 Re: To Know 07/27/2010 2:43 AM
	dear sir, Thanks for your advise.which is very much useful for me. In my friend industry, they are using 15H.P capacity 3phase motor. When i entered to that industry suddenly One phase failed due to general reason. but the 3 phase motor runs without any interruption by using some device. so that i what to know that device. so that i am asked this question to you. once again thank you for your advise. E.gunasekar __________________ sri audhi
	Register to Reply

msamad Guru Join Date: Feb 2009 Location: Houston, USA Posts: 946 Good Answers: 244	#4 In reply to #3 Re: To Know 07/27/2010 7:31 PM
	Maybe it is Neutral Compensator. See this link: http://statictransformers.com/NC.htm See this from the link: "Neutral Compensator generates the third phase when only two are available. This voltage is of course lower than would have been in the healthy phase, but is good enough to drive your three phase machines of capacity of approximately 12 KW". - MS __________________ "All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
	Register to Reply

These comments received enough positive votes to make them "good answers".

Copy to Clipboard

JRaef (1); kvsridhar (1); msamad (1); sri audhi (1)

You might be interested in: DC Motor Drives, Motor Test Equipment, Motor Repair Services

	Got Something to Say?
	Ask a Question Start a Discussion

	Aerospace
	BioMech & BioMed
	Chemical & Material Science
	Civil Engineering
	Communications & Electronics
	Education and Engineering Careers
	Electrical Engineering
	General Discussion
	Instrumentation
	Manufacturing
	Mechanical Engineering
	New Technologies & Research
	Software & Programming
	Sustainable Engineering
	Transportation

	Site Directories
	Forum Directory Blog Directory User Group Directory RSS Feeds CR4 Rules of Conduct CR4 FAQ Site Glossary Who's Online (79 right now) Show Members