Slip energy drive system
It seems to be ABB published view that most large drive manufactures have stopped production of slip energy recovery drive systems (SRDS), justifying rationale for this being paraphrased in following terms:
* Popularity of SRDS in the past was due to lower capital cost
* Use of SRDS has decreased markedly since the late 1980s due to:
- VFD alternative becoming more and more cost effective
- Operational limitations and significantly higher maintenance of SRDS compared to VFD alternative
- Diminishing difference in equipment cost between SRDS and VFD alternative.
Power Electronics and Motor Drives handbook authors assert that the importance of the Kramer drive (old non-PWM SRDS) has been reduced in recent years and that SRDS will tend to become obsolete except in very special applications.
MW-range crusher applications may be one of those special applications because MW implies MV for fully rated VFD whereas SRDS-rated rotor circuit is usually LV, which, assuming top crusher rating may be say 4000 HP max, may be hard to justify.
SRS option's attractiveness as one is trading off new induction motor against transformer, losses are lowest, VFD cost is significantly lower, and downtime may be significantly shorter. It seems on paper that SRS option might be most cost effective and serve as plausible going-in position for discussion purposes but specific retrofit situations should of course be evaluated on a case by case basis.
* Popularity of SRDS in the past was due to lower capital cost
* Use of SRDS has decreased markedly since the late 1980s due to:
- VFD alternative becoming more and more cost effective
- Operational limitations and significantly higher maintenance of SRDS compared to VFD alternative
- Diminishing difference in equipment cost between SRDS and VFD alternative.
Power Electronics and Motor Drives handbook authors assert that the importance of the Kramer drive (old non-PWM SRDS) has been reduced in recent years and that SRDS will tend to become obsolete except in very special applications.
MW-range crusher applications may be one of those special applications because MW implies MV for fully rated VFD whereas SRDS-rated rotor circuit is usually LV, which, assuming top crusher rating may be say 4000 HP max, may be hard to justify.
SRS option's attractiveness as one is trading off new induction motor against transformer, losses are lowest, VFD cost is significantly lower, and downtime may be significantly shorter. It seems on paper that SRS option might be most cost effective and serve as plausible going-in position for discussion purposes but specific retrofit situations should of course be evaluated on a case by case basis.
