
soft starters and delta motors
#1
Posted 06 January 2006 - 03:44 PM
#2
Posted 06 January 2006 - 07:37 PM
Welcome to the forum.
There are harmonics produced during start due to the fact that the current waveform is being distorted. This occurs with both inside delta (6 wire) control and line control. I have not heard of it causing any issues before.
The harmonics are only produced during soft start and soft stop so are for a very short period of time except for units that have an energy saver function operating. If there is an energy saver feature, this will reduce the voltage when the motor is at reduced load and this will also cause harmonics to flow. This is then a continuous case and if there is a heating problem, it could become and issue. - harmonics create losses and sometimes the losses outweigh the savings!!
Best regards,
Mark Empson | administrator
Skype Contact = markempson | phone +64 274 363 067
LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters
#3
Guest__*
Posted 06 January 2006 - 08:29 PM
harmonics, especially the odd harmonics, (3rd, 9th, 15th,...) are actually additive in
the neutral of three phase wye circuits. This is because the harmonic number
multiplied by the 120 degree phase shift between the three phases is a integer
multiple of 360 degrees, or one complete cycle. This puts the harmonics from each of the
three phase conductors “inphase” with each other in the neutral.
#4
Posted 06 January 2006 - 08:32 PM
Best regards,
Mark Empson | administrator
Skype Contact = markempson | phone +64 274 363 067
LMPForum | Power Factor | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | Pressure Transducers | Smart Relay | GSM Control | Mark Empson Website | AuCom | Soft Starters
#5
Posted 17 March 2006 - 08:12 AM
I suppose that one tiristor from bridge of soft-starter was broken down and it is the reason of third harmonic...:cool:
#6
Posted 18 March 2006 - 12:33 AM
#7
Posted 20 March 2006 - 07:59 AM
Sorry me, my english is bad.
If you have big 3rd harmonic, it is problem of incorrect work, because we need a generator of 3rd harmonic. In usual work we can have different harmonics, but they will be very small. In this case the generators can be two motors and two soft-starters and may be a power supply (power line). I would start a check with line after that motors after that soft-stars.
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