0
\$\begingroup\$

The switch I'm going to use is MTS-202 [Datasheet].

The ratings is 6A/125V and 3A/250V. Most switches are rated like that, as voltage increases they pass less current.

Does it means that I can connect voltages at 500V/1.5A?

What about DC voltages? is the same rule applies?

\$\endgroup\$
3
  • \$\begingroup\$ Related question: electronics.stackexchange.com/questions/421137/… \$\endgroup\$
    – ErikR
    Commented Jun 7, 2021 at 6:35
  • 1
    \$\begingroup\$ For high AC current or voltage consider using an SSR (solidstate relay) instead of a mechanical switch. An SSR can switch at the zero-crossing of the waveform resulting smoother switching. \$\endgroup\$
    – ErikR
    Commented Jun 7, 2021 at 7:48
  • 1
    \$\begingroup\$ No you can't. And if the switch isn't rated at 500V, be aware it may fail connecting 500V to your finger. \$\endgroup\$
    – user16324
    Commented Jun 7, 2021 at 12:56

2 Answers 2

2
\$\begingroup\$

The ratings you see are a combination of voltage and current. They originate as well from a combination of phenomena:

  1. voltage withstanding capability that is the ability to keep isolated two terminals across the gap of the open contact; of course there re margins dictated by standards, so that some overvoltage level and some impulsive overvoltage level are dictated for a given rated voltage (e.g. your mains voltage). Whe the manufacturer says "250 Vac", knows that thee test passed was e.g. 1500 Vrms for 1 minute, that is suitable for 250 Vac, no more than that.
  2. wearing of contacts and load handling: in this case you get a combination of voltage and current, as you see in your case. There are some assumptions behind: number of operation allowed before degradation (e.g. expected life), that is lower for higher rating using the same technology; but they also assume some kind of load (such as AC11, and similar notations, standing for a proportion between inductive and resistive parts, in some cases including also capacitive). Here you have some margin: provided you do not go beyond safety ratings (see 1), you can increase the current slightly, e.g. if you know that the load is almost resistive, if you put a snubber across contacts (with snubber galvanic isolation is gone, however).
  3. the evil DC operation: DC waveforms can wear your contacts much faster, as they do not cross zero (as for sinusoidal waveforms) and can easily create arcing. DC capability depends strongly on contact technology. If not written explicitly, do not assume it can handle DC: for example, even 28V/1A dc is a burden for these types of switches. (I used in a hurry a much bigger one, but not good -- I swear --, to switch two relays with 12V DC coil and it broke after 6 months, maybe after 100 operations or so).
\$\endgroup\$
1
\$\begingroup\$

You can't exceed the datasheet ratings.

If there is no other mention, then those are the limits you are given, and you can't switch more than 6A at 125VAC or 3A at 250VAC.

The datasheet does not rate usage over 250VAC or any DC ratings, so they are unknown. Usually for a given switch, the DC voltage ratings are lower than AC voltage ratings.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.