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How can I measure the voltage in a stand alone motor start capacitor with ratings of 440 volts @ 60 uF avoiding destroying the DVM? We were given a formula for determining the power in a cap, but were not told how to measure the capacitor without changing the out the caps conditions or blowing up the multimeter?

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    \$\begingroup\$ What in the world sort of DMM are you trying to do this with? One of those Horror Fright ones? \$\endgroup\$ Commented Oct 22, 2017 at 22:49

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Motor start capacitors are only used on AC motors and there will be an AC voltage across it.

  • To measure the voltage across the capacitor use a multimeter or voltmeter with a 1000 V safety rating.
  • Switch the meter to the next AC range higher than 440 V.
  • Connect the probes safely to the capacitor with the power switched off.
  • Stand back, switch on, take the readings and switch off before disconnecting.

Do not try this with a $5 meter. Both meter and probes need to be adequately rated with a recognised safety mark.

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  • \$\begingroup\$ No ac this is DC and start caps exist out side of motors and ac circuits thanks though I have a friend who has a pile of DVM'S. From measuring caps .I just was trying to get a head of the problem .jim \$\endgroup\$ Commented Oct 24, 2017 at 6:28
  • \$\begingroup\$ What sort of 440 V DC motor uses a start capacitor? Please put all the information in the question. \$\endgroup\$
    – Transistor
    Commented Oct 24, 2017 at 7:08

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