Harmonics -Softstarter
Harmonics -Softstarter
(OP)
Dear Folks,
Pl. clear the doubt on softstarters. Does soft-starter for motor generate harmonics, if it operates at full output voltage (no voltage reducing condition)and without by-pass contactors?
Advanced thanks..
Pl. clear the doubt on softstarters. Does soft-starter for motor generate harmonics, if it operates at full output voltage (no voltage reducing condition)and without by-pass contactors?
Advanced thanks..





RE: Harmonics -Softstarter
Soft starters reduce the voltage during start by phase controlled SCRs in series with each phase applied to themotor, or each winding of the motor. This does cause harmonics during start and during soft stop.
During run, provided that there is no energy saving algorithm in operation, the soft starter does not produce harmonics. If an energy saving algorithm is in operation, the voltage to the motor can be reduced by the SCRs and at this time, harmonics are produced.
The harmonics produced by soft starters are primarily low order odd harmonics due to the symmetric operation of the SCRs and the inductive nature of the motor.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: Harmonics -Softstarter
So, Softstarter will act like a back-to-back doides during running and no harmonics will be generated if there is no energy saving algorithm. Thanks for your information.
How energy saving algrorithm works for soft-starter without frequency control (v/f control)?
RE: Harmonics -Softstarter
This has been commercialized by a number of manufacturers and claims have been made that it will save vast amounts of energy. The reality is that with three phase motors, the efficiencies are already high, the iron loss is small and the energy savings are very small relative to the rating of the motor,and only achieved when the shaft load of the motor is very low. There are few truely viable applications that provide reasonable payback periods.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: Harmonics -Softstarter
In addition, could you pl. clarify that what is the fault current contribution of Softstarter drives and VFD if there is a fault on line side?
Advanced Thanks...
RE: Harmonics -Softstarter
The fault current contribution with a soft starter is up to the same as a full voltage starter.
The fault current of a standard VFD is 0, and a regenerative (active front end VFD) is current limited by the drive to less than 150% of the drive rating.
Best regards,
Mark Empson
http://www.lmphotonics.com