Panasonic AQ-H Series Manual page 12

Cautions for Use of Solid State Relays
Load Type Description
Heaters (Resistive load)
The SSR is best suited to resistive loads. Noise levels can be
drastically lowered with zero-crossing switching.
Lamps
Tungsten or halogen lamps draw a high inrush current when turned
on (approximately 7 to 8 times the steady state current for zero-
crossing SSRs; approximately 9 to 12 times, in the worst case, for
random type SSRs). Choose an SSR so the peak of the inrush
current does not exceed 50% of the SSR surgeon current.
Motors load
When starting, an electric motor draws a symmetrical AC starting
current some 5 to 8 times the steady-state load current,
superimposed on a DC current. The starting time during which this
high starting current is sustained depends on the capacities of the
load and load power supply. Measure the starting current and time
under the motor's actual operating conditions and choose an SSR
so the peak of the starting current does not exceed 50% of the SSR
surge-on current.
When the motor load is deactivated, a voltage exceeding the load
supply voltage is applied to the SSR due to counter-EMF.
This voltage is approximately 1.3 times the load supply voltage for
induction motors, and approximately 2 times that for synchronous
motors.
Reversible motor control
When the direction of motor rotation is reversed, the transient
current and time required for the reversal far exceed those
required for simple starting. The reversing current and time should
also be measured under actual operating conditions.
For a capacitor-starting, single-phase induction motor, a
capacitive discharge current appears during the reversal process.
Be sure to use a current limiting resistor or reactor in series with
the SSR.
Also, the SSR should have a high marginal voltage rating, since a
voltage twice as high as the load supply voltage develops across
the SSR in the reversal process.
For reversible motor control, carefully design the driver circuit so
the forward and reverse SSRs do not turn on at the same time.
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Solenoids
AC-driven solenoid contactors or solenoid valves also draw inrush
current when they are activated. Choose an SSR such that the peak
of the inrush current does not exceed 50% of the SSR surgeon
current. For small solenoid valves and AC relays in particular, a
leakage current may cause the load to malfunction after the SSR
turns off. In such an event, use a dummy resistor in parallel with the
load.
Using an SSR below the specified load
SSR
Capacitive load
A capacitive load (switching regulator, etc.) draws an inrush current
to charge the load capacitor when the SSR turns on. Choose an
SSR so the peak of the inrush current does not exceed 50% of the
SSR surge-on current. A timing error of up to one cycle can occur
when a switch used in series with the SSR is opened or closed. If
this is a problem, use an inductor (200 to 500 μH) in series to the
SSR to suppress dv/dt error.
Other electronic equipment
In general, electronic equipment uses line filters in the primary
supply circuit.
The capacitors used in the line filters may cause the SSR to
malfunction due to dv/dt turn on when the equipment is turned on or
off. In such an event, use an inductor (200 to 500 μH) in series with
the SSR to suppress dv/dt turn on.
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Dummy resistor
Load
Output Load power supply
ASCTB400E 202201