Half wave and full wave rectifiers?

Discussion in 'Power Electronics' started by Loz2212, Oct 16, 2018.

  1. Loz2212

    Thread Starter New Member

    Oct 9, 2018
    25
    1
    Hi guys,

    Just trying to brush up on my knowledge with the products at my new work. We supply electromagnetic safety brakes and clutches.. I'm fine with all that sort of lol.

    However, they offer DC rectifiers in both full wave and half wave... I kinda understand them also... However the half wave is half the voltage??? I understand it only supplies half the sinewave as the reverse cycle is blocked by the diode - however, I thought the amplitude would still be the same? Just less of it, so to speak.

    Also, what is the benefit of half wave over full wave? Why would you spec a half wave rectifier or is it just for the purpose of lowering the voltage?

    Our brakes are 207vdc coil and 104vdc.. I guess a half wave is used for the latter.

    Any help would be greatly appreciated.
     
  2. MrChips

    Moderator

    Oct 2, 2009
    18,711
    5,943
    The peak voltage is the same for half-wave and full-wave rectifiers.
    What is different is the RMS voltage which is what matters in this case.

    I did not check the math given below.

    [​IMG]

    [​IMG]
     
    Loz2212 likes this.
  3. crutschow

    Expert

    Mar 14, 2008
    22,234
    6,486
    Not likely.
    Is this filtered (steady) dc that goes to the coils?
     
  4. Loz2212

    Thread Starter New Member

    Oct 9, 2018
    25
    1
    Yes, it goes through a separate, purpose built rectifying unit. 230vac in and dc out. I can't vouch for the filtering tolerance but I'm 99% sure the half wave runs the 104v brakes and the full bridge runs the 207v brakes. I may well be properly wrong though lol
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    18,235
    5,597
    Industrial DC clutches and brakes rarely use filtered DC, generally just a bridge rectifier.
    Max.
     
  6. Loz2212

    Thread Starter New Member

    Oct 9, 2018
    25
    1
    I'm sure that is correct. It does say bridge rectifier on the unit so I assume it's just the diode configuration without the capacitor etc?

    I was more wanting someone to clarify that a half wave will give 0.45 the AC input voltage and the bridge gives 0.95. This seems correct with the 104v and 207v having a supply voltage of 230vac. They can switch between 207v for pulling the brake off and 104v for holding. Assuming this switching is between half wave and bridge rectification.

    Thank you.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
    18,235
    5,597
    'Pulling the Brake off'?
    Do these have double coil? Normally there is only one coil on brakes from my experience, they drop back or release as soon as the power is removed?
    Is this a particular application?
    Max.
     
  8. Loz2212

    Thread Starter New Member

    Oct 9, 2018
    25
    1
    They are spring applied and come off when energised. I use the term pull very loosely.

    The higher holding torque brakes have a stiffer spring arrangement so an over-excitation of the voltage for a few milliseconds gives it that initial shove.
     
  9. BR-549

    AAC Fanatic!

    Sep 22, 2013
    4,917
    1,342
    Show us the data sheets on both brake units. Do you make the power units also?
     
  10. Loz2212

    Thread Starter New Member

    Oct 9, 2018
    25
    1
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
    18,235
    5,597
    Unless designed to engage with the higher voltage and then be retained by the half wave supply when seated?
    Max.
     
  12. Loz2212

    Thread Starter New Member

    Oct 9, 2018
    25
    1
    That was my guess Max. Just thought I'd see if you guys would agree with my logic there.
     
  13. BR-549

    AAC Fanatic!

    Sep 22, 2013
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    1,342
    That's disappointing. Still don't have a clue to your product. Where is your product used? Who uses your product.

    What are you braking? Are you moving? What is power source?
     
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