Carlo Gavazzi SSRs General Product Line Information

2-10 Specifications are subject to change without notice (30.11.2001)

Control input

In most SSRs galvanic separation is
achieved by optocouplers. These opto­couplers, equipped with integrated trigger
circuit (optotriac), provide the switching
function required for the corresponding
load type.

We distinguish between:

- ZS: Zero Switching

- IO: Instant-on Switching

- PS: Peak Switching

- AS: Analog Switching

- DCS: DC Switching

- FS: Full Cycle Switching

Types of SSRs

When applying the control voltage, the AC SSR output is activated
at the first zero crossing of the line voltage. The response time is
hereafter less than a halfperiod, i.e. typically below 10 ms at 50 Hz.

ZS SSRs are employed in a host of applications with resistive loads
(temperature control) and control of incandescent lamps. The ZS
types are the most commonly used SSRs due to their extensive use
with plastic moulding machines, packing machines, soldering ma­chines as well as machines for the food processing industry.

ZS SSRs are used in various applications, such as interfacing resis­tive loads or lighting installations. Due to high surge current- and
blocking voltage capabilities, SSRs of this switching type will also
perform successfully with most inductive and capacitive loads.

Zero Switching SSR (ZS)

For resistive, inductive or capacitive loads

Control
input

Fuse

Varistor

Load

Function

Application

Description

Solid State Relays
General Information

Instant-on Switching SSR (IO)

For inductive loads

The SSR output is activated immediately after applying control voltage.
Consequently, this relay can turn on anywhere along the AC sinusoidal
voltage curve. The typical response time is thus less than 1 ms.
(Relays equipped with reed contacts are inherently instant-on types.)

This SSR is particularly suitable in applications where a fast response
time or phase angle control is desired.

Control
input

Fuse

Varistor

Inductive load

Line
voltage
(VAC)

Control
input

Load curent
(AAC)

Line
voltage
(VAC)

Control
input

Load current
(AAC)

t

t

t

t

t

t

Type

Note: For SSR without integrated voltage protection

Specifications are subject to change without notice (30.11.2001) 2-11

DC Switching SSR (DCS)

For resistive and inductive loads

The power semiconductor in the DC switching relay operates in ac­cordance with the control input status. The response time is less
than 100 µs.

DCS SSRs are used with resistive and inductive loads for the control
of DC motors and valves.

When switching inductive loads it will be necessary to interconnect
a free wheeling diode surplus voltage parallel to the load as protec­tion.

Control
input

Fuse

Load

Line
voltage
(VAC)

Control
input

Load
Current
(AAC)

Line
voltage
(VAC)

Control
input

Load
Current
(AAC)

Solid State Relays
General Information

Types of SSRs (cont.)

Function

Application

Description

Type

Peak Switching SSR (PS)

For inductive loads with remanent iron core

The peak switching SSR is designed in a way that the power output
is activated at the first peak of the line voltage upon application of
the control voltage. After the first half period the PS SSR operates as
an ordinary ZS relay. The peak of the inrush current could hereafter
be reduced during the first half-period for inductive loads.

Control
input

Fuse

Varistor

Inductive load

t

t

t

t

t

t

2-12 Specifications are subject to change without notice (30.11.2001)

Types of SSRs (cont.)

Solid State Relays
General Information

Low Noise SSR (LN)

For resistive and inductive loads

System Monitoring SSR (SM)

For resistive and inductive loads

The Low Noise SSR is designed for light industrial environments and
fulfills the generic emission standard EN50081-1. By controlling the
switching mode of the semiconductors, the peak level of the zero
voltage turn-on is minimised, thus reducing the noise emitted by the
SSR.

Low Noise SSRs are particularly suitable for applications where ele­ctromagnetic noise must be limited to avoid interference with other
equipment. In this kind of environment, noise generated by standard
SSRs is considered critical or unsafe. Low noise SSRs can be used
with both resistive and inductive loads.

The system monitoring (sense) SSR provides an alarm output in the
event of a circuit failure. Internal circuits monitor:

- line voltage

- load current

- correction functioning of the SSR

- SSR input status.

The relay is designed for applications where immediate fault detecti­on is required. An alarm output signal is available to determine fault
status.

Function

Application

Description

Type

Holding Current Level

Zero Voltage

Noise Decreased Drastically

Holding Current Level

Zero Voltage

Peak that Generates Noise

Normal
Relay
OFF

Operation
Relay
ON

Line
Voltage
Loss

Line
Voltage
Loss

Load
Open
Circuit

DC
Supply
Loss

DC
Supply
Loss

Relay
Remains
OFF

Shorted
Relay

Shorted
Relay

Line
Voltage

Load
Current

Control

Green
LED

DC
Supply

Red
LED

Alarm
Output

(normally open type)

=Half LED light intensity

~

S

41

32

SSR

Control
Input

N/L

2

L

1

Note: Connection “S” does not apply to SSRs
with integrated heatsink

3+

4-

5 Not Con.

6 Control (High/Low)

7 Alarm (PNP/NPN)

Fuse

Load

L

2

/N

L

1

1

2

On

Alarm

Load Current
Phase
Voltage across SSR

Normal Zero Switching

Low Noise Zero Switching

Specifications are subject to change without notice (30.11.2001) 2-13

Solid State Relays
General Information

Types of SSRs (cont.)

Power output

Depending on the application, various
questions concerning the power output
of the SSR need to be clarified. The most
important parameters are

- Line voltage (load voltage)

- Load current

- Type of load (application)

in order to be able to select the correct
SSR. To avoid unnecessary maintenance
expenses, the selection needs to be as
accurate as possible.

Line voltage

The voltage range of an SSR must be se­lected according to the line voltage in the
application. For the non-repetitive peak
transient voltage of the SSR, both tran­sients from the mains and voltage peaks
from the application need to be consid­ered.

A corresponding protective element like
a freewheeling diode (only DC), a varistor
or a snubber (RC) can be incorporated in
order to protect the output semiconduc­tor.

Load current

The relay must be selected in a way that
the continuous load current in the appli­cation does not exceed the correspond­ing nominal value of the relay. It is impor­tant to take into consideration the con­tinuous load current in relation to the am­bient temperature. With inductive loads,
such as motors, valves, etc., the SSR
must be sized or selected according to
the highest expected surge current.

Since the control input of the analog relay - according to speci­fications 4 to 20 mADC - can be varied, the output operates in
accordance with the phase control principle. The relay is
equipped with a built-in synchronization circuit in order to
achieve phase angle control. The output is proportional to the
input voltage or input current. The transfer function is linearized
and reproducible.

These SSRs are highly advantageous in closed loop applications
or where soft starting can limit high inrush currents.

The Full Cycle SSR uses an analogue switching principle that
provides a number of full cycles that are evenly distributed
over a fixed time period. The number of cycles switched dur­ing the time period is directly proportional to the control input
applied to the SSR.

Since the full cycles are distributed, this SSR provides high ac­curacy in temperature control and creates less noise.
Compared to conventional Burst control, the Full Cycle SSR
reduces the stress on the load by limiting the band within
which the load cycles.

Analog Switching SSR (AS)

For resistive, inductive or capacitive loads

Control
circuit

Inductor

Fuse

Varistor Capacitor

Load

Temp. sensor

Line
voltage
(VAC)

Control
input

Load cur­rent (AAC)

t

t

t

Full Cycle SSR (FC)

For resistive loads

Function

Application

Description

Type

Burst Full Cycle Switching

Analogue Full Cycle Switching

Period

T

T

Supply
(V type only)

T

1

A

3

A

4

T

2

L

1

A

1

A

2

L

2

L

1

L

3

L

2

SSR

+

-

Analogue
Control
Input
I/V type

2-14 Specifications are subject to change without notice (30.11.2001)

Types of SSRs (cont.)

Snubberless Triac

The snubberless triac is a further development of
the triac in which the two thyristors on the chip are
well separated. Consequently, a higher dV/dt capa­bility is achieved.

In this way the internal snubber can be eliminated.

Alternistor

The alternistor is developed especially for industri­al use. The alternistor consists of two antiparallel
thyristors and a gate triac integrated in the same
chip. The thyristors are well separated. The triac
will block uncontrolled turn-on during commuta­tion.

Triac

The triac consists of two antiparallel thyristors
mounted on the same chip in order to give full­wave operation at a single gate.

A snubber is often mounted across the SSR in
order to reduce the dV/dt.

Thyristor (SCR)

The antiparallel thyristor solution is most common
for industrial SSRs. The solution requires two sep­arate SCRs and two trigger circuits, which give
optimum dV/dt capability.

Transistor

The transistor option - often the open collector
configuration - is used in the DC SSRs. A free­wheeling diode is normally mounted across the
transistor to avoid damage from back-EMV from
inductive loads.

The triac SSR is the most cost-effective solution in
applications with low dV/dt demands, e.g. applica­tions with heating elements with almost constant
resistance.

The snubberless triac is one of the latest improve­ments from semiconductor manufacturers.

The elimination of the snubbers also reduces the
leakage current in the switching circuit.

The snubberless triac is common in resistive and
inductive applications (up to 25 A) .

The alternistor output is widely used in SSRs for re­sistive and inductive loads.

The antiparallel SCR SSR is used for all load types,
such as resistive, inductive and even capacitive
loads.

An SCR in a diode bridge is only used in PCB relays
with load currents of less than 2 A.

The transistor is used for DC loads such as DC
motors, solenoids or valves.

Load switching component Symbol Application

Solid State Relays
General Information

Advantages and Limitations

SSRs offer the user many outstanding
features and should be treated as a sepa­rate class of relay. However, due to the de­sign of SSRs, the user is always faced
with a few limitations which are different
from those of electromechanical relays
(EMR). The following outline of advan­tages and limitations of SSRs will serve as
a guide to the professional use of these
devices.

Advantages

* Long life and high reliability - more than

10

9

operations

* No contact arcing, low EMI, high surge

capability
* High resistance to shock and vibration
* High resistance to aggressive chemicals

and dust
* No electromechanical noise
* Logic compatibility
* Fast switching
* Low coupling capacitance

Long life and high reliability

In SSRs from Carlo Gavazzi an optimized
thermal design is achieved by applying
the "Direct Copper Bonding" technology.
This technology finally eliminates the
thermal fatigue between chip (silicon) and
terminals (copper). Furthermore, it re­duces the thermal resistance between
junction and ambient.

The DCB substrate, on which the chip is
soldered, consists of a ceramic insulator
(Al

2O3

) with a layer of copper (Cu) on both
sides. The copper is bonded with the ce­ramic material in order to get similar ther­mal expansion conditions for both mate­rials. Thereby the mechanical stress be­tween silicon chip and copper will be min­imized while the relay is in operation.

The ceramic material provides a 4 kV in­sulation between copper leads and
heatsink. A lower temperature difference
(∆T) on the junction will increase the life­time of the relay, and an increase of the

switching frequency can help to achieve
a more reliable application.

No contact arcing

No contact arcing will occur since switch­ing takes place inside the semiconductor
material, which changes from a non-con­ductor to a conductor at the signal of the
control input. Line and load radiation are
reduced considerably because the SCRs,
alternistors or triacs are basically current
latching devices, which will turn off as
soon as the current is near zero. This is
known as "zero crossing turn off". This
greatly reduces the radiated electromag­netic interference (EMI), and this reduc­tion of EMI is often well received by the
equipment designers.

High resistance

SSRs with optocoupler inputs are fully
embedded in the housing material and
consequently, since no moving parts are
used, they are highly resistant to vibra­tions and shock.