Switching Inductive Loads - Siemens SITRANS RD300 Operating Instructions Manual

SIT SITRANS RD300RANS RD300

Switching Inductive Loads

The use of suppressors (P/N 7ML19306AL) is strongly recommended
when switching inductive loads to prevent disrupting the
microprocessor's operation. The suppressors also prolong the life of the
relay contacts. Suppression can be obtained with resistor-capacitor
(RC) networks assembled by the user or purchased as complete
assemblies. Refer to the following circuits for RC network assembly and
installation:
Choose R and C as follows:
R: 0.5 to 1  for each volt across the contacts
C: 0.5 to 1 µF for each amp through closed contacts
Notes:
1. Use capacitors rated for 250 VAC.
2. RC networks may affect load release time of solenoid loads. Check
to confirm proper operation.
Install the RC network at the meter's relay screw terminals. An RC
3.
network may also be installed across the load. Experiment for best
results.
Note:
Relays are de-rated to 1/14th HP (50 watts) with an inductive load.
Page 10
AC and DC Loads Protection
Low Voltage DC Loads Protection
SITRANS RD300 – OPERATING INSTRUCTIONS
C
C
R
R
Use a diode with a reverse
breakdown voltage two to
three times the circuit
voltage and forward current
at least as large as the load
current.
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