3 phase electrical ammeter

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Need some help on trying to figure out an ammeter for a 3 phase electric motor. Motor is a Baldor EM2334T 20hp electric motor. 3 phase wired for 480 volts and rated at 24 amps. There is an analog Simpson ammeter with transformer installed now. 0-150 is the range. Question is, should the load on the motor max out at 24 amps per the meter? Or 48 amps per the meter since its monitoring one input leg? I'll describe the wiring as best as I can. Powered by a 36kva generator. There are 3 "hot" lines going into the magnetic switch and there is also a ground wire with nothing spliced into it. Just a dedicated ground.

 

[SoCalDave]

If name plate states 24 FLA @ 480vac/3phase you should have a reading very close to that on all three legs under full load. No load amps will be much less but rule of thumb is all three legs should be within 10% of each other.
Hope this helps.

 

[hallett21]

You should read pretty close to 24 amps per phase.


Sent from my iPhone using Tapatalk

 

[highvoltagehands]

Hey Ad,

Motor ammeter current(amperage) reading should be close to 24 amps when running @ FLA(full load amps) 20HP at 480 Volts.
Motors normally don’t operate constantly at FLA, they normally operate @ RLA(Running Load Amps) which is lower amperage than FLA.
Motor ammeter reading will vary based on motor status.
Motor Amperage at startup under full load, will spike well above 24 amps as the motor gets up to full running speed at full load.
Motor amperage will then drop to RLA as motor operates at normal constant load.
Motor amperage will also change as motor load drops or increases accordingly.
Motor amperage will also change based on circuit feeder voltage. If voltage is higher or lower than 480v, the motor current(amperage) drawn will constantly be lower or higher accordingly.
Hope this helps. Good luck.

Hud

 

[Sleek-Jet]

Highvoltage, is your name really Hud?

 

[Sherpa]

Lock rotor amps (amp draw on start up) will usually be about 2-3X higher than full load amps. fyi. sounds like you're just wanting to know full load amp draw.

is this just for business knowledge?? Because it if's for charging somebody power usage, you've got to install a revenue-certified amp meter.

 

[Racey]

Need some help on trying to figure out an ammeter for a 3 phase electric motor. Motor is a Baldor EM2334T 20hp electric motor. 3 phase wired for 480 volts and rated at 24 amps. There is an analog Simpson ammeter with transformer installed now. 0-150 is the range. Question is, should the load on the motor max out at 24 amps per the meter? Or 48 amps per the meter since its monitoring one input leg? I'll describe the wiring as best as I can. Powered by a 36kva generator. There are 3 "hot" lines going into the magnetic switch and there is also a ground wire with nothing spliced into it. Just a dedicated ground.

When you are measuring 3 phase the amperage is rated per leg. So a 24 amp motor is rated for it's full load amperage at 24 amps on each leg, no matter which wire you clamp you will get the same amperage.

As noted you will only see 24 amps at FULL LOAD, if the motor is just on and free wheeling you won't see anywhere near that kind of amperage.

 

[highvoltagehands]

Highvoltage, is your name really Hud?

Yep. I’ve only met one other Hud, kinda.

 

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Thanks for the replies everyone. Got the answer I needed. The motor is on a concrete saw that sees variable loads. That's the reason for the ammeter. So I know how much to load it but not overload it. The one on it currently is 0-150 range and it doesn't really do any good having that big of a swing. I'll replace with a 0-50 range.