Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 22 replies
  • Subscribers 32 subscribers
  • Views 2898 views
  • Users 0 members are here
Options
You may also be interested in
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Swimming pool 3 phase motor trips occasionally on earth leakage RCD

CliveS
We have a new 4 kW 3 phase pump motor at the local pool which has a new variable speed drive unit attached and occasionally it trips out on the RCD which I assume is 30mAmp .  The connections are star inside the motor but not earthed which should have stopped it tripping.

We are not sure what to do, we could run the motor flat out and delta connect the windings possibly or some suggest disconnecting the RCD as the circuit is completely separate from normal wiring.  Would this option contravene any of our regs?
Parents
  • 0
    I think they were hoping to encourage the manufacturers to switch to making  more efficient  EL3 motors, with the VSD clause as the way to allow old designs to be sold out.

    - so for your 4kW unit,


    3 figures are for 2, 4 or 6 poles though I suspect yours is 2.


    Efficiency level 3 would allow

    85,8    86,6    84,6 percent efficient, so a ~ 15%  can be burnt off as heat if you use a VSD.


    or

    Efficiency level 2 would be

    88,1    88,6    86,8 percent efficient,  and so if the motor is improved to more like ~12% off as heat and then you do not need   VSD.

    Of course what has happened, is that re-tooling factories to stamp out motors with more generous  metal is not in the motor maker's interest, as they do not pay the electricity bill, so they keep making the inefficient ones and then later the buyer has to add the price of the VSD.


    Depending how many hours the motor runs, and the local price of electricity, the capital cost of the motor (with or without VSD ) may not be the largest cost.

Reply
  • 0
    I think they were hoping to encourage the manufacturers to switch to making  more efficient  EL3 motors, with the VSD clause as the way to allow old designs to be sold out.

    - so for your 4kW unit,


    3 figures are for 2, 4 or 6 poles though I suspect yours is 2.


    Efficiency level 3 would allow

    85,8    86,6    84,6 percent efficient, so a ~ 15%  can be burnt off as heat if you use a VSD.


    or

    Efficiency level 2 would be

    88,1    88,6    86,8 percent efficient,  and so if the motor is improved to more like ~12% off as heat and then you do not need   VSD.

    Of course what has happened, is that re-tooling factories to stamp out motors with more generous  metal is not in the motor maker's interest, as they do not pay the electricity bill, so they keep making the inefficient ones and then later the buyer has to add the price of the VSD.


    Depending how many hours the motor runs, and the local price of electricity, the capital cost of the motor (with or without VSD ) may not be the largest cost.

Children
No Data

Community Rules & Guidelines