Connecting Loads For Multi-Pole Relays; Motor Forward/Reverse Switching; Input Circuits; Maximum Allowable Voltage - Omron G9SA Series Manual

C-A-6 Connecting Loads for Multi-pole Relays
Connect multi-pole Relay loads according to diagram "a" below to
avoid creating differences in electric potential in the circuits. If a
multi-pole Relay is used with an electric potential difference in the
circuit, it will cause short-circuiting due to arcing between contacts,
damaging the Relays and peripheral devices.
Power
supply
Load Load Load Load
a. Correct Connection
C-A-7 Motor Forward/Reverse Switching
Switching a motor between forward and reverse operation creates an
electric potential difference in the circuit, so a time lag (OFF time)
must be set up using multiple Relays.
Arc short-circuiting occurs.
M
B
Incorrect
Example of Incorrect Circuit
X
1
X
2
M
B
X
2
X
1
Correct
Example of Correct Circuit
C-A-8 Power Supply Double Break with Multi-pole
Relays
If a double break circuit for the power supply is constructed using
multi-pole Relays, take factors into account when selecting models:
Relay structure, creepage distance, clearance between unlike poles,
and the existence of arc barriers. Also, after making the selection,
check operation in the actual application. If an inappropriate model is
selected, short-circuiting will occur between unlike poles even when
the load is within the rated values, particularly due to arcing when
power is turned OFF. This can cause burning and damage to
peripheral devices.
C-A-9 Short-circuiting Due to Arcing between NO and
NC Contacts in SPDT Relays
With Relays that have NO and NC contacts, short-circuiting between
contacts will result due to arcing if the space between the NO and
NC contacts is too small or if a large current is switched.
Do not construct a circuit in such a way that overcurrent and burning
occur if the NO, NC, and SPDT contacts are short-circuited.
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Load
Load
Power
supply
Load Load
b. Incorrect Connection
ON ON
X
1
ON
X
2
Reverse
Motor
operation
Forward Forward
operation operation
OFF OFF
time time
Arc short-circuiting occurs.
Load
Incorrect
Example of incorrect circuit
X X
1 2
Load
Correct
Example of correct circuit
C-A-10 Using SPST-NO/SPST-NC Contact Relays as an
SPDT Relay
Do not construct a circuit so that overcurrent and burning occur if the
NO, NC and SPDT contacts are short-circuited. Also, with SPST-NO/
SPST-NC Relays, a short-circuit current may flow for forward/reverse
motor operation.
(Short-circuit current)
Power supply
C-A-11 Connecting Loads of Differing Capacities
Do not have a single Relay simultaneously switching a large load and
a microload. The purity of the contacts used for microload switching
will be lost as a result of the contact spattering that occurs during
large load switching, and this may give rise to contact failure during
microload switching.
B Input Circuits
C-B-1 Maximum Allowable Voltage
The coil's maximum allowable voltage is determined by the coil
temperature increase and the heat withstand temperature of the
insulation material. (If the heat withstand temperature is exceeded, it
will cause coil burning and layer shorting.) There are also important
restrictions imposed to prevent problems such as thermal changes
and deterioration of the insulation, damage to other control devices,
injury to humans, and fires, so be careful not to exceed the specified
values provided in this catalog.
C-B-2 Voltage Applied to Coils
Apply only the rated voltage to coils. The Relays will operate at the
must-operate voltage or greater, but the rated voltage must be
applied to the coils in order to obtain the specified performance.
C-B-3 Changes in Must-operate Voltage Due to Coil
Temperature
It may not be possible to satisfy this catalog values for must-operate
voltages during a hot start or when the ambient temperature exceeds
23°C, so be sure to check operation under the actual application
conditions.
Coil resistance is increased by a rise in temperature causing the
must-operate voltage to increase. The resistance thermal coefficient
of a copper wire is approximately 0.4% per 1°C, and the coil
resistance also increases at this percentage.
This catalog values for the must-operate voltage and must-release
voltage are given for a coil temperature of 23°C.
(c)Copyright OMRON Corporation 2007 All Rights Reserved.
ON
X
1
ON
X
2
OFF time
L
C-7