Schneider Electric iEM3200 Manuale Utente

iEM3100 / iEM3200 / iEM3300 series user manual 

Power, energy and power factor

DOCA0005EN-04

105

NOTE: The descriptions in this section assume that you are an electrical energy consumer, not a 
supplier.

This chapter contains the following sections:

A typical AC electrical system load has both resistive and reactive (inductive or capacitive) 
components. Resistive loads consume real power (P) and reactive loads consume reactive 
power (Q).

Apparent power (S) is the vector sum of real power (P) and reactive power (Q):

Real power is measured in watts (W or kW), reactive power is measured in vars (VAR or kVAR) and 
apparent power is measured in volt-amps (VA or kVA).

The meter uses the values of real power (P) and reactive power (Q) on the PQ coordinate system to 
calculate apparent power.

Positive power flow P(+) and Q(+) means power is flowing from the power source towards the load. 
Negative power flow P(-) and Q(-) means power is flowing from the load towards the power source.

S

P

2 

+ Q

2

=

+Q

(+kVAR)

-P

(-kW)

-Q

(-kVAR)

+P

(+kW)

P (+)

S

P (-)

S

P (+)

S

P (-)

S

Q (-)

Q (-)

)

+

(

Q

)

+

(

Q