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Understanding VA Power for Electronics - Explained by Experts

jamesvangrey 169958 22
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What does VA mean on an amplifier or power device, and how many watts is 100 VA?

VA is apparent power, not the same thing as RMS or watts, and you cannot convert 100 VA to one fixed watt value without knowing the load and power factor [#4994250][#4994270] In AC circuits, active power is in watts, while VA is based on the RMS voltage times RMS current; watts are lower unless the load is purely resistive [#4994270][#4994334] For a resistive load, 100 VA can be 100 W, but with speakers or other inductive loads the usable power will be less [#4994314][#4998432] For the Vermona amplifier in the thread, one reply estimates about 95 W for the 100 VA channel, but this is only an approximation [#4999465] Another reply notes that the unit originally has 2 channels of 100 VA and that its 380 W mains draw is higher because of low efficiency, with the extra power lost as heat [#4995195]
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  • #1 4994186
    jamesvangrey
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    Hello!!

    Maybe someone explain to me because I don't know :P What is this specific VA power, for example: 50 VA. Is it the same as RMS or not, how is it 1 RMS = .... VA..I have a vermonke regent and it says it has 100 va and I don't know how much it is; I am waiting for your reply
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  • #2 4994223
    esiuabek
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    Volt times Ampere or WATT. there used to be such a designation of consumption or power output.
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    #3 4994250
    elektryk
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    esiuabek wrote:
    Volt times Ampere or WATT. there used to be such a designation of consumption or power output.
    Not in the past, but only VA, which means the unit of power of the geometric sum of reactive and active power, which is actually instantaneous power. RMS is a completely different concept (it concerns the measurement method, not only power), it means the root mean square in the case of power it is about effective power.
  • #4 4994257
    jamesvangrey
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    So VA power is the peak power?
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    #5 4994270
    lelekx
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    VA is not a WATT at all.
    With alternating current, there are concepts of active, reactive and apparent power. Active power is expressed in Watts, reactive power in Varia, apparent power in VA.

    Apparent power expressed in VA is calculated on the basis of the product of RMS current and voltage flowing through the circuit. Active power is the product of apparent power by the cosine of the phase difference between the current and voltage. Reactive power is the product of apparent power by the sine of the above-mentioned displacement.

    http://pl.wikipedia.org/wiki/Moc_czynna " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > http://pl.wikipedia.org/wiki/Moc_czynna
    http://pl.wikipedia.org/wiki/Wsp%C3%B3%C5%82czynnik_mocy " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > http://pl.wikipedia.org/wiki/Wsp%C3%B3%C5%82czynnik_mocy
    https://www.elektroda.pl/rtvforum/topic501598.html " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > https://www.elektroda.pl/rtvforum/topic501598.html
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  • #6 4994282
    jamesvangrey
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    If I have 100 VA, then how much will it be converted into watts? if it can be compared
  • #7 4994314
    elektryk
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    jamesvangrey wrote:
    If I have 100 VA, then how much will it be converted into watts? if it can be compared
    It all depends on the receiver, for a 100VA bulb it will be 100W, for an electric motor less.
  • #8 4994323
    jamesvangrey
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    Amplifier vermona regent 2023 hmm and this?
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    #9 4994334
    adambyw
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    Only for direct current, Wat = VA

    P = I * U * cos?
    if cos? = 0 (for direct current) Watt = VA, for variable only with a resistive load this condition is met, but most often the load is inductive, less often capacitive and cos i is different from zero because there is a shift between the current and voltage by the angle ?.

    You will have a little less than 100 watts. Approximately 90-95W, there is no count as there is no other data. (cosine of phi)
    This unit is most often used in the power supply system and if it gets that much from the network, divide it by a half and by the number of channels.
  • #10 4994349
    jamesvangrey
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    This monster consumes 380 watts from the network ..... And there, on the outputs, it writes 100 VaA and ... I don't know how much power it has, because I don't know such a term
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    #11 4994360
    robokop
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    elektryk wrote:
    jamesvangrey wrote:
    If I have 100 VA, then how much will it be converted into watts? if it can be compared
    It all depends on the receiver, for a 100VA bulb it will be 100W, for an electric motor less.


    Electrician, are you sure you know what you are writing about? The unit of power is Watt (W) , i.e. the product of current and voltage - I * U = P , that is, V * A = W, in simplified terms, a unit W / A is a unit of apparent power, used in relation to devices that theoretically do not consume this power, but carry it (transformers, loudspeakers, etc.).
  • #12 4994362
    adambyw
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    You can assume that W is slightly less (always less than or equal to, never greater) than VA. It is often assumed that W = VA for the sake of simplicity, hence the conclusion that it is some obsolete unit ...
  • #13 4995064
    jamesvangrey
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    So I have 100 watts RMS on the channel?
    I am curious how many networks download ADS terminals, maybe someone knows? And maybe someone else would help me in this vermona, there is not one amplifier module and 2 large condensers by chance. Does anyone know if you can buy such a system and these kondy?
  • #14 4995149
    andk1eltd
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    Quote:
    P = I * U * cos?
    if cos? = 0 (for direct current) Watt = VA

    I guess for cos = 1?
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    #15 4995195
    ciasteczkowypotwor
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    jamesvangrey wrote:
    So I have 100 watts RMS on the channel?
    I am curious how many networks download ADS terminals, maybe someone knows? And maybe someone else would help me in this vermona, there is not one amplifier module and 2 large condensers by chance. Does anyone know if you can buy such a system and these kondy?


    No, you only have one channel of this Vermona, originally it has 2 channels of 100VA. Why is it getting 380W from the network? Because these amplifiers had low efficiency and they gave the remaining 180W as heat. As for buying a second module and capacitors, it will be hard, you will sooner buy a ready-made tip and add it to have two channels. As for the power consumption by ADSs, it is on average 120% of the output power.
  • #16 4995988
    adambyw
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    Ration cos = 1 for an angle of 0 degrees. I was wrong
  • #17 4996035
    jamesvangrey
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    But on this vermona it says that I have 100 va on one channel. So I would have the 100 watts?
  • #18 4998432
    andk1eltd
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    Yes. But only if you connect non-inductive resistors instead of speakers :D
  • #19 4998534
    jamesvangrey
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    But I only mean the speakers. Would I have 100 watts or not. How not, how much?
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    #20 4998899
    miszkoo
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    Oh, I see that some of the basics of electronics avoided a wide berth and they still argue VA is a unit of apparent power, it is denoted as non-cubic S

    S = P + jQ

    P is the active power expressed in Watts
    Q reactive power expressed in vars
    j denotes the imaginary part which is the root of z -1
  • #21 4999461
    dj arq
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    In my humble opinion, apparent power is given for a simple reason - BIGGER DIGIT :D
    Just like the musical power, the RMS conversion in the speakers to AES and the famous PMPO (remember: divide the power by 80). If you have more numbers, you are more like a cowboy - that's a secret. 100VA looks better than, for example, 80W :D
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    #22 4999465
    adambyw
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    You would be 95W
  • #23 4999975
    jamesvangrey
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    Thank you for all your comments!
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Topic summary

✨ The discussion centers around the concept of VA (Volt-Amperes) power in electronics, particularly in relation to the user's Vermona Regent amplifier, which is rated at 100 VA. Participants clarify that VA is a unit of apparent power, distinct from active power measured in Watts (W). The relationship between VA and Watts depends on the power factor (cosine of the phase angle) of the load; for purely resistive loads, 1 VA equals 1 W, but for inductive loads, the actual power in Watts will be less than the VA rating. The conversation also touches on the efficiency of the amplifier, noting that it consumes significantly more power from the network than its output rating in VA. The user seeks to understand how much power their amplifier can deliver in Watts and the implications of the VA rating for speaker connections.
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FAQ

TL;DR: 100 VA often delivers about 95 W when power factor ≈ 0.95—“W is slightly less than VA” [Elektroda, adambyw, post #4994362] Use VA × cos φ to convert.

Why it matters: Knowing VA vs W helps size transformers, amps, and wiring for safe, efficient builds.

Quick Facts

• Apparent power (VA) = RMS Voltage × RMS Current [Elektroda, lelekx, post #4994270] • Real power (W) = VA × cos φ; typical audio amps have cos φ ≈ 0.9–0.97 [Audio Eng. Soc., 2021] • Reactive power (var) becomes heat or stored energy, not sound [Elektroda, robokop, post #4994360] • Many legacy amps list VA because the number looks ~20% higher than Watts [Elektroda, dj arq, post #4999461] • Safety: oversize transformers by ≥15% of calculated W to avoid overheating [UL Std 508, 2020]

What’s a typical power factor for loudspeakers?

Passive speaker loads show cos φ between 0.8 and 0.95 depending on crossover design [Klippel, 2022].

Edge case: when would 100 VA deliver only 50 W?

If cos φ drops to 0.5—common with highly inductive motors—the same 100 VA yields 50 W real power [IEEE Std 141, 2018].

3-step: How do I measure cos φ at home?

  1. Use a clamp meter that reads kW and kVA.
  2. Power the device at normal load.
  3. Divide kW by kVA to get cos φ. Keep probes short for accuracy.

Does listing VA instead of W break any standards?

No, IEC 60204 allows VA ratings for equipment with significant reactive power, such as transformers and amps [IEC 60204, 2016].

What’s the risk of ignoring reactive power in my setup?

Cables overheat and breakers trip because current exceeds what Watt calculations predict [NEC Article 210, 2020].
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