3/16

sames

PM2102DPD

http://www.sames.co.za

PRELIMINARY

Figure 4: Current sensing using a CT

Figure 5: Current sensing using a shunt

Figure 3: Voltage divider circuit

NEUTRAL

LIVE IN

R1

R2

R3

R15

R11

R12

C7

IVP

GND

P1

J16

RA

RB

R1 = R3 = 82k

and

R2 = R15 = 100 k .

Resistors R6 and R7 (figure 4 and figure 5) define the current at

the current sense inputs of the SA2102D. The PM2102DPD

module uses a 625µ

shunt.

At I

(80A) the voltage drop

across the shunt will be 50mV. To ensure proper current

sensing it is advisable to use a shunt that will give a voltage

drop of at least 20mV at I

. The resistor values are calculated

for an input of 16µA

on the current sense inputs at I

(see

Figure 5). The design equation is as follows:

R6 = R7 = (I / 16µA) x R

/ 2

I = Line current

R

= Shunt value

Also see the section on

.

Provision is made for the use of either a Current Transformer

(CT) or a Shunt on the application module. The module is by

default setup for a shunt, which must be removed if a CT is

chosen as the sensing device. When using

a CT, the

terminating resistor (R16), phase compensation capacitor (C7)

and jumper (J5) must be inserted. The jumper references one

side of the CT to ground for sensing. The current sensing

resistors (R6 and R7) must be changed according to the

equation stated below (see Figure 4):

R6 = R7 = (I / 2500 / 16µA) x R

/ 2

I = Line current

CT ratio = 1:2500

W

W

W

Current Sense Input

SETUP EXAMPLES

Sensing Method (CT or SHUNT)

ma

x

ma

x

RM S

m a

x

LSH

terminating

L

SH

L

L

The capacitor C7 is inserted to correct or compensate for the

phase shift caused by the current transformer. The following

equationshows how to calculate the capacitor value for a

phase shift of 0.18 degrees.

C = 1/ (2 x x Mains frequency x R12 x tan (Phase shift angle))

Also see the section on

.

A CT with a low phase shift and a ratio of 1:2500 is

recommended for optimum module performance.

p

C = 1/ (2 x x 50 x 1M x tan (0.18 degrees))

C = 1.013µF

p

SETUP EXAMPLES

CT

LIVE IN

LIVE OUT

R6

R7

CT +

CT-

R16

GND

J5

LIVE IN

LIVE OUT

Shunt

R6

R7

IIN

IIP