I have 3 different working motors ranging from 1kw to 2 kw (on 220V AC, 1 phase), they all use running capacitors. I tried 2 different AC ammeters on them and I get bad readings between 0 to 1 amp, when I should read at least 5 amps.

I cant figure out what's going on, but I guess it has to do with the running capacitors, in one instance when the motor has the running capacitor disconnected ( and therefore the motor cant spin) I get a realistic 6 amp reading.

So do you know what's messing up the AC amp readings and how could I measure the amps that the motors use ?

  • 3
    \$\begingroup\$ Are the motors fully loaded? If not then you will not measure the 5A or 10A that you expect. A motor draws current proportional to the mechanical load that is on it. \$\endgroup\$
    – Steve G
    Jul 18, 2016 at 9:37
  • 2
    \$\begingroup\$ if the motor was running unloaded, 1A sounds about right. \$\endgroup\$
    – user16324
    Jul 18, 2016 at 9:37
  • \$\begingroup\$ the motor wasnt loaded, after applying a bit of load manually the amp needle rised a bit, thanks a lot for your help ! \$\endgroup\$ Jul 18, 2016 at 10:00
  • \$\begingroup\$ fully loading these motors is difficult, isnt there another way to calc their amperage/ power ? \$\endgroup\$ Jul 18, 2016 at 10:19
  • 1
    \$\begingroup\$ Without some kind of LOAD on the motor, "their amperage/ power " is UNDEFINED. That makes no sense. The "amperage/ power" DEPENDS on how much is the load on the motor. You are asking an impossible question. Like "How much does a box weigh?" without knowing what is INSIDE it. \$\endgroup\$ Dec 16, 2016 at 1:33

1 Answer 1


The motor should be loaded in order to measure it's amperage.


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