G3H203SNDC524 Datasheet, PDF (5/12 Pages) Omron Electronics LLC – Solid State Relays Technical Information

Forward and Reverse Operation of
Single-phase Inductive Motors
L
Motor
C
Note: 1. The voltage between the load terminals of either SSR 1 or
SSR 2 when turned OFF is approximately twice as high as
the supply voltage due to LC coupling. Be sure to use an
SSR model with a rated output voltage of at least twice the
supply voltage. For example, if the motor operates at a sup-
ply voltage of 100 VAC, the SSR must have an output volt-
age of 200 VAC or higher.
2. Make sure that there is a time lag of 30 ms or more to switch
over SW1 and SW2.
ON/OFF Control of Three-phase
Inductive Motors
Motor
Input signal
source
R
Three-
S
phase
power
supply
T
Forward and Reverse Operation of
Three-phase Inductive Motors
Make sure that signals input into the individual SSRs are proper if the
SSRs are applied to the forward and reverse operation of a three-
phase motor. If SW1 and SW2 as shown in the following circuit dia-
gram are switched over simultaneously, a phase short-circuit will
result on the load side, which may damage the output elements of
the SSRs. This is because the SSR has a triac as an output element
that is turned ON until the load current becomes zero regardless of
the absence of input signals into the SSR. Therefore, make sure that
there is a time lag of 30 ms or more to switch over SW1 and SW2.
The SSR may be damaged due to phase short-circuiting if the SSR
malfunctions with noise in the input circuit of a SSR. To protect the
SSR from phase short-circuiting damage, a protective resistance R
may be inserted into the circuit.
The value of the protective resistance R must be determined accord-
ing to the withstanding inrush current of the SSR. For example, the
G3NA-220B withstands an inrush current of 220 A. The value of the
protective resistance R is obtained from the following.
R > 220 V x √2/200A = 1.4 Ω
Considering the circuit current and weld time, insert the protective
resistance into the side that reduces the current consumption.
Obtain the consumption power of the resistance from the following.
P = I²R x Safety factor
(I = Load current, R = Protective resistance, Safety factor = 3 to 5)
Selecting an SSR for Different Loads
The following provides examples of the inrush currents for different
loads.
Load
AC Load and Inrush Current
Solenoid
Incan-
descent
lamp
Motor
Relay
Capacitor
Resis-
tive
load
Inrush Approx. Approx. Approx.
current/ 10 times 10 to 15 5 to 10
Normal
current
times times
Wave-
form
Approx.
2 to 3
times
Approx. 1
20 to 50
times
832
Solid State Relays Technical Information