Control power PM5000

[p_dejarmy_encos]

Hello,

We're installing several (+20) PM5340 meters in one enclosure, and we wish to account for the power drawn by the meters. The installation guides states that the meter has an AC burden of 5 W/11 VA at 415 Vac 

So, i have some questions:

1. If the Aux power is 120 Vac rather than 415 Vac, does the burden change or is it the same?
2. Why is so much difference in W and VA? Is it a power factor thing?
3. What number would be best for the aux power supply calculation for the enclosure?
4. Why is the DC burden smaller than the AC burden?

Thanks in advance,

[Mehran_Mehrnia · Accepted solution]

Hi @p_dejarmy_encos

1. Burden at 120 Vac vs. 415 Vac:
   The wattage (5 W) remains nearly constant regardless of voltage, but VA (11 VA at 415 V) depends on voltage. At 120 V, the meter draws more current to maintain the same power, so VA will be lower, but current higher.

2. Difference between W and VA:
   Yes, this is due to power factor. Watts (W) measure actual energy used, while Volt-Amps (VA) include both real and reactive power. A low power factor means the meter draws more apparent power than it actually consumes.

3. Aux power supply sizing:
   Use VA for sizing to ensure the supply can handle the total load. For 20 meters:
   20×11 VA=220 VA
   You can also add margin e.g. 30% → 300 VA-rated supply is recommended for safe operation and future expansion.

4. DC burden is lower than AC:
   DC power is more efficient for electronic devices — no need for AC-to-DC conversion, so less internal loss. That’s why the DC burden is 4 W, compared to 5 W for AC.

Best Regards,

-Mehran

L3 Expert Advanced metering