Gefran GT 25A, GT 40A, GT 50A, GT 60A, GT 75A Data Sheet

Main applications

• Plastics extrusion lines
and injection moulding
machines

• Polymerization plant for
synthetic fibre production

• Rubber moulding
machinery

• Driers for ceramics and
components for the
building industries

• Chemical and

pharmaceutical industries

• Industrial electric furnaces

• Food processing plants

GT 25 / 40 / 50 / 60 / 75 / 90 / 120A

SOLID STATE RELAYS WITH ANALOG CONTROL

Main features

• Command input from analogue voltage
or current signal or potentiometer.

• Switching at voltage zero crossing.

• Partialization of wave train power with

dynamically optimized time cycle.

• Antiparallel double SCR

• 2 led for supply indication, “ON” state,

1 optional LED for load interrupt alarm

• 4000V isolation between input circuit
and power output

• MOV (varistor)

• Optional monitoring of interrupted load

PROFILE

The GT family of solid-state relays has
been designed with the aim of providing
very accurate control of the load thanks
to an analog control input, in voltage
at 0…5V; 0…10V or in current at
0…20/4…20mA or a potentiometer (from

1KΩ to 10 KΩ).

The electronic design ensures that the
cycle time for proportioning the power is

automatically optimized.

Il numero di periodi che il GT fornisce

al carico (“treni d’ onda”) per un

certo valore di segnale di ingresso, è
calcolato in modo da essere il minimo
possibile, pur mantenendo la precisione

necessaria.

The number of cycles that the GT

supplies to the load (wave trains) for

a given input signal is calculated to be
the minimum possible to maintain the

necessary accuracy.

The GT can be used in three phase
systems, using master-slave control
architecture in which the control signal

drives only one GT (master) and this unit

supplies the synchronized signals to the

other slaves. Two GS modules can also
be used as slaves (logic control).
A load interrupt control option (HB)

is available without having to use an
external current transformer; alarm limit

is settable with trimmer and yellow LED
signal, with voltage-free contact, normally

open.

The GT solid-state relay has a green
LED to indicate the presence of the
24Vac power supply and a red LED
to indicate the switching based on the

analog control input signal.

The LED signal will be continuous (off at

minimum, on at maximum) at the ends of
the scale, pulsing for intermediate values.

The units offer optional accessoires for
panel mounting, fuses and fuseholders,
current transformer, isolation

transformers.

Use the relè with an opportune heatsink

(see section accessories).

TECHNICAL DATA

General features

Category of use AC1
Nominal voltage

- 480Vac (max. range 24...530Vac)
Nominal frequency: 50/60Hz
Non-repetitive voltage: 1200Vp
Zero switching voltage: ≤ 20V
Voltage drop at nominal current ≤

1.4Vrms
Power factor = 1

Control inputs

Voltage: 0...5Vdc, 0...10Vdc

(impedance ≥100KΩ)

Current: 0...20mA, 4...20mA

(impedance 125Ω)
Potentiometer: da1K a 10KΩ

(auto-fed by GT)

Outputs

GT 25 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
25A
Non-repetitive overcurrent t=20 ms: 400A

2

I

t for blowout: ≤ 645A2s

dV/dt critical with output deactivated:
1000V/µs

GT 40 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
40A

Non-repetitive overcurrent t=20 ms: 600A

2

I

t for blowout: ≤ 1010A2s

dV/dt critical with output deactivated:
1000V/µs

GT 50 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
50A
Non-repetitive overcurrent t=20 ms: 1150A

2

I

t for blowout: ≤ 6600A2s

dV/dt critical with output deactivated:
1000V/µs

GT 60 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
60A
Non-repetitive overcurrent t=20 ms: 1150A

2

I

t for blowout: ≤ 6600A2s

dV/dt critical with output deactivated:
1000V/µs

GT 75 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
75A
Non-repetitive overcurrent t=20 ms: 1300A

2

I

t for blowout: ≤ 8000A2s

dV/dt critical with output deactivated:
1000V/µs

GT 90 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
90A
Non-repetitive overcurrent t=20 ms: 1500A

2

I

t for blowout: ≤ 11200A2s

dV/dt critical with output deactivated:
1000V/µs

GT 120 (SCR version)

Nominal currents of the device with
opportune heatsink in continuous work:
120A (complete with fan and standard
thermostat).
Non-repetitive overcurrent t=20 ms: 1500A

2

I

t for blowout: ≤ 11200A2s

dV/dt critical with output deactivated:
1000V/µs

Isolation

Rated isolation voltage input/output:
4000Vac

Power supply:

24Vac ±10%, 50/60 Hz

Absorption: 1.5VA
Max. isolation voltage: 300Vdc

Options:

Interrupted HB load alarm.
Controls the load by measuring current
on a shunt inside the device.
The alarm limit is set with a multirev
monorev trimmer.
The alarm output is obtained by means of
a solid state relay.
The contact is normally open (max. 30V,
150mA, conduction resistance 15W).

Thermal features

GT 25

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 1.25 K/W
Rth junction/ambient: ≤ 12 K/W

GT 40

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 0.65 K/W
Rth junction/ambient: ≤ 12 K/W

GT 50

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 0.35 K/W
Rth junction/ambient: ≤ 12 K/W

GT 60

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 0.35 K/W
Rth junction/ambient: ≤ 12 K/W

GT 75

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 0.3 K/W
Rth junction/ambient: ≤ 12 K/W

GT 90

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 0.3 K/W
Rth junction/ambient: ≤ 12 K/W

GT 120

Junction temperature: ≤ 125°C
Rth junction/case: ≤ 0.25 K/W
Rth junction/ambient: ≤ 12 K/W

Solid State Relay Dissipated Power
Calculation

Singol-phase static relay

Pds = 1.4 * IRMS [W]

IRMS = singol phase load current

Heatsink thermal resistance
Calculation

Rth = (90°C - T.amb. max) / Pd

where Pd = dissipated power
T.amb.max = max air temperature inside
the electrical cabinet.
Use a heatsink with thermal resistance
inferior to the calculated one (Rth).

Ambient conditions

• Working temperature: 0 to 80°C.

• Max. relative humidity: 50% at 40°C

• Max. installation altitude:

2000m asl

• Pollution level: 2

• Storage temperature: -20..85°C

Installation notes

- The heat sink must be grounded.

- The device must be protected by an
appropriate high-speed fuse (accessory).

- Applications with solid state power units
must also include an automatic safety
switch to cut out the load power line.

- Protect the solid state relay by using an
appropriate heat sink (accessory).
The heat sink must be sized according to
room temperature and load current (see
the technical documentation).

- Procedure for mounting on heat sink:

The module-heat sink contact surface
must have a maximum planarity error
of 0.05mm. and maximum roughness of

0.02mm. The fastening holes on the heat
sink must be threaded and countersunk.
Attention: spread 1 gram of
thermoconductive silicone (we

recommend DOW CORNING 340

HeatSink) on the dissipative metal
surface of the module.
The surfaces must be clean and
there must be no impurities in the
thermoconductive paste.
Alternately tighten the two fastening
screws until reaching a torque of 0.60
Nm for the M4 screws and 0.75 Nm for
the M5 screws.

Wait 30 minutes for any excess paste to

drain.
Alternately tighten the two fastening
screws until reaching a torque of 1.2 Nm
for the M4 screws and 1.5 Nm for the M5
screws.

We advise you to randomly check for

proper installation by dismantling the
module to make sure there are no air
bubbles under the copper plate.

Limits of use

• dissipation of thermal power of device
with restrictions on temperature of
installation site.

• requires exchange with outside air
or an air conditioner to transfer
dissipated power outside the panel.

• installation restrictions (distances
between devices to guarantee dissipation
by natural convection).

• max. voltage limits and derivative
of transients in line, for which the
solid state unit has internal protection
devices (depending on model).

• presence of dispersion current
< 3mA for SCR version GS
< 4mA for TRIAC version GS
(max. value with rated voltage

and junction temperature of 125°C).

WORKING TYPOOLOGY

“Zero crossing” with variable cycle time

Examples of the operation of the GT for different values of the input drive signal and the consequent different cycle times
(100msec and 40msec respectively).

V

V

Example of input at 20% = 2V (IN 0-10V) or 4mA (IN 0-20mA)
V=Voltage across load

Logic output control for GT

Example of input at 50% = 5V (IN 0-10V) or 10mA (IN 0-20mA)
V=Voltage across load

GT thermal protection

Control
input

ON

OFF

t

Red LED ONRed LED

Thermal alarm

t

V = Load voltage

t

Thermal protection
activation