Power Supply

Discussion in 'General Electronics Chat' started by viju, Oct 4, 2008.

  1. viju

    Thread Starter Senior Member

    Sep 28, 2008
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    I am supplying a voltage to a hysterisis dynamometer with an Aplab power supply which has Voltage and Current output.It has got two modes - Constant Voltage and another one is Constant Current.I set my power supply voltage to a particular voltage and inject millivolts to the Constant Current input while measuring the torque of a motor.Upon performing this I get a gradual increase in braking.Am I compensating the voltage drop by injecting the millivolts to current input?

    Kindly help me with the theory behind this.

    "Braking type is excitation control"
     
    Last edited: Oct 5, 2008
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
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    Please clarify what you mean by inject millivolts into the constant current input. Your question is really hard to understand, you need to re-explain your setup, the purpose, the results, etc.

    Steve
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Besides what Steve said, don't E-mail me about this again. I have too much in my in-box as it is.
     
  4. viju

    Thread Starter Senior Member

    Sep 28, 2008
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    Wookie: Steve also advised me not to send any PM.I will not make mistake again.Pepole who are desperate will always find way to resolve the problems.That apart my question is:

    As already posted earlier, I am building an DC motor performance testing station.Wherein I measure No load speed,No load current,No load voltage,terminal resistance of that motor,load current,load torque,load volatge,load speed,@ 0.7 Volts maximum current,minimum current and its variation.I have performed the complete PLC programming with an indexing mechanism.I have no problem in measuring the current,voltage,rpm and to the greatest accuracy I an measure them through analog input channel of a PLC.

    In the load test I use Magtrol 6001 Dynamometer with hysterisis braking.My motor specification is @13.5 volts and 80 Nmm applied torque my rpm should be around 2950 with a maximum current of 4.55 amps.Magtrol controller doesn't have external brake on input other than one in front panel.

    Another way of applying torque is to increase the voltage of braking from 0 to 7 volts.
    By performing the load test at rated torque the rpm is not stable.But when I supply some(195 mV) millivolts to the other terminals of my power supply my rpm reading stays stable.I have accidentally found this.Rightnow I have programmed in my PLC to supply 195 milivolts in several steps so that I get gradual increase in torque. But don't understand the theory behind this.

    I can increase the voltgae upto 10 Volts through my PLC output.But it can handle maximum of 15 milliamps.My brake draws nearly 100 milliamps.If some circuit can be desined in such a way that it gets input from my PLC and with gain of 1:1 ratio but with higher current rating at output can solve my problem.Also please help me the theory behind the power supply with which I am doing rightnow.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    "Other terminals" is a vague term at best. Can you provide a schematic for your test set-up? In that schematic, can you indicate what terminals you are speaking of?
     
  6. sam2008

    New Member

    Oct 7, 2008
    3
    0
    Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output load or group of loads is called a power supply unit or PSU. The term is most commonly applied to electrical energy supplies, less often to mechanical ones, and rarely to others.
     
    Last edited by a moderator: Oct 8, 2008
  7. viju

    Thread Starter Senior Member

    Sep 28, 2008
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    SAM thankyou for correcting me.

    Today I did lot of experiments with that power supply unit!!!

    It has got two modes.Constant Voltage and Constant current.And a switch to change the operating mode internal or external.If internal is selected the the output Voltage is the Voltage you set using a trimmer knob.If external mode is selected power supply unit does not output any voltage.Only if some external voltage ( in millivolts) is fed we get the corresponing output.

    I don't have the operating manual with me.Will it be a master / slave PSU?If so how does it function?

    How to attach schematic here?
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
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    Might use a medium power NPN transistor as an emitter follower, in/out ratio will not be quite 1:1, and it will requore an external power supply of about 12-15 v. Simple and cheap.
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
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    use the paper clip icon [​IMG] in the reply window
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    You should have several terminals:
    V+
    V-
    +S or +Sense
    -S or -Sense
    You use the +/-S terminals as sense inputs from the remote load. This is for when you want the voltage regulation as close as possible. The sense lines will carry very little current, so that the voltage drop in your V+ and V- supply wiring can be compensated for. The +S lead gets connected to where you want the +V sense input to come from; same with -S and -V.
     
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