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Inverter, Atex motors, star, delta

  1. Oct 31, 2014 #1
    Dear Friends,

    I need technical solution for my problem;

    I have two motors, type:

    1. HCT/ATEX 45-2T-2 (R/MIN=2800), (400V-3,60A), (KW-1,50)
    2. HCT/ATEX 45-2T-3 (R/MIN=2860), (400V-5,00A), (KW-2,20)

    Also, every motor has its own inverter:
    Inverters are from INVERTEK DRIVES (Optidrive).

    My project is to provide thoose two motors working in first (lower speed) all the time , and sometimes they need to work in second speed (higher - maximal possible).
    Those speeds must be provided by changing frequency with inverter.

    My questions are:
    1. How to know which maximal frequency (Hz) are motors made for? - ( I think maximal frequency would be the higher speed)or they can work on any frequency?
    2. Also how to make electrical diagram correctly ( If I have inverters; do I use only delta connection or I can use only star connection. Or I need to use star for start and delta for running?
    3. Can somebody help me to design electrical diagram?

    I hope you can understand my problem, also I will be very happy if somebody can solve my problem, I am affraid of making false wiring diagram.

    With kind regards,

  2. jcsd
  3. Nov 1, 2014 #2

    I get you technical charactertistics of fans,
    also maximamal airflow (m3/h) for every fan is:

    MAX1. 10650 m3/h
    MAX2. 12750 m3/h

    I realised that with fvd I will use only one type of connection or star or delta.

    If I want provide those two maximal airflows, which type of connection should I use? (What frequeny would it be?)
    If I want half (m3/h)/2 I change only frequency; nothing else?

    Summary which type of connection and what frequency would it be for lower speed, what frequency would it be for higher speed?

    Do you need any additional informations to provide me an answer?
  4. Nov 2, 2014 #3
    The speed of motor depends on both operating frequency and voltage. 400V,50 Hz,2800 rpm rated motor will run at rated speed at 400V/50Hz and at 50% of rated speed at 200V/25Hz. If this voltage/frequency ratio is kept constant the motor will operate very close to full nominal torque. Inverter drive controls frequency and voltage to mantain desired ratio. The parameter to set in the inverter drive is the "Base frequency" in "Motor settings". It should be said that , if the converter output voltage does not match nominal motor voltage, specifying correct converter isn't just done by matching watts, but should be done by matching to the motor full load current.
    1.Motor rating plate tells you that. For a 3 phase motor, max rotor rpm frequency is given by n=60f/p where f is the mains frequency (Hz) and p is the number of pole pairs. p=1, 3000 rpm correspond with mains frequency 50 Hz. Nothing dangerously will happen if try to run (unloaded) motor with f=55 Hz, but at say 100 Hz things might start getting flying apart.
    2. Generally, data on the rating plate correspond with mains voltage and mains frequency motor is connected to.In a star windings connection, the mains voltage (ULN of the inverter output), is reduced by factor 1/√3 on the individual motor windings. For example, if the motor rating plate data reads DY 230/400 V, and you want to run it at 400 V, you are not allowed to connect windings in delta.
    3. Sorry, not me
  5. Nov 2, 2014 #4
    This is vfd I use:


    Also in attachment you can see specification of motor.

    I would like motor to run with maximal posible m3/h and sometimes half max=about 10000 and half 5000.

    I see i need to use star connection and which parameters should be to provide my needs?

    Kin regards
  6. Nov 2, 2014 #5
    This data doesn't help much to adress your question. RPM of motor for max possible m3/h and RPM for half of it and if RPM/2 corresponds to half of m3/h for your fan is more important info to know.
  7. Nov 2, 2014 #6
    Sorry to mix up your pot more, Joe, but you need a fan curve and some understanding of your back pressure to understand what a good motor speed is. It's been a long time since I've worked with fans, but I remember that for a given type, like a squirrel cage of ducted, there tended to be a similar curve between various ones. Thus, you can kinda guess the speed need for a 1/2 max if you know the back pressure. Also from rusty memory, most of my back pressure tended to increase to the square of the flow. That's assuming your just blowing through simple ducts. What it means is you only experience 1/4 the back pressure at 1/2 flow as you do at full flow. Which is pretty sweet when you consider the energy savings. Since you can buy air handlers with variable speed motors, you may be chasing a problem that your local Tran, Lennox, or Carrier distributor can fix for you.
  8. Nov 3, 2014 #7
    I understand thank you very much
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