Siemens EF 784 Series Bedienungsanleitung PDF herunterladen (Seite 7)

Relays and Timers

1-800-633-0405

eRL-38

Book 2 (14.1)

Prices as of October 22, 2014. Check Web site for most current prices.

Protection Device Selection Guide

Part Number Price Description

Nominal Input

Voltage

Dimensions

& Package

Mating

Socket

AD-ASMD-250

$9.75

Protection diode module for 784 and 75 series relays. Plug-in modules come in package

of 5.

6-250VDC

Figure 1

783-3C-SKT

784-4C-SKT-1

750-2C-SKT

750-3C-SKT

AD-ASMM-24

$8.00

MOV module for 784 and 75 series relays that operate at 24VAC coil voltage. Package

includes 5 modules.

24VAC/VDC

AD-ASMM-120

$8.00

MOV module for 784 and 75 series relays that operate at 120VAC coil voltage. Package

includes 5 modules.

120VAC/VDC

AD-ASMM-240

$8.00

MOV module for 784 and 75 series relays that operate at 240VAC coil voltage. Package

includes 5 modules.

240VAC/VDC

AD-BSMD-250

$8.00 Protection diode module for 782 series relays. Plug-in modules come in package of 5. 6-250VDC

Figure 2 782-2C-SKT

AD-BSMM-24

$8.00

MOV module for 782 series relays that operate at 24VAC coil voltage. Package includes 5

modules.

24VAC/VDC

AD-BSMM-120

$8.00

MOV module for 782 series relays that operate at 120VAC coil voltage. Package includes 5

modules.

120VAC/VDC

AD-BSMM-240

$8.00

MOV module for 782 series relays that operate at 240VAC coil voltage. Package includes 5

modules.

240VAC/VDC

Figure 1

Figure 2

1.37

(34.7)

1.45

(38.8)

0.384

(9.82)

0.490

(12.4)

0.900

(22.8)

0.34

(8.63)

M.O.V .

DIODE

Packaged M.O.V.s and Diodes

Accessory dimensions

inches [mm]

Overview

Metal Oxide Varistors (MOV) and

Diode circuits are offered as convenient

plug-in modules. Plugging a module

into the relay socket connects the circuit

in parallel with the relay coil. No addi-

tional wiring is required.

Modules fit within the maximum dimen-

sions of the relay and socket.

Features

• MOVs protect by shunting potentially

damaging electrical spikes away from

the relay coil. Ideal for AC and DC

applications.

• Diodes protect external drive

circuitry from inductive voltages

generated when removing coil voltage.

Ideal for DC applications.

Polarity sensitive.

Application

Many PLC systems control one or more

inductive load devices. These inductive

loads (devices with a coil) generate

transient voltages when they are de-en-

ergized with a relay contact. When a

relay contact is closed it “bounces”,

which causes the coil to energize and

de-energize until the “bouncing” stops.

The transient voltage which is gener-

ated is much larger in amplitude than

the supply voltage, especially with a

DC supply voltage.

When switching a DC-supplied induc-

tive load the full supply voltage is always

present when the relay contact opens

(or “bounces”). When switching an

AC-supplied inductive load, if the

voltage is not zero when the relay

contact opens, there is energy stored

in the inductor that is released

when the voltage to the inductor is

suddenly removed. This release of

energy is what produces transient

voltages.

When inductive load devices (motors,

motor starters, interposing relays,

solenoids, valves, etc.) are controlled

with relay contacts, it is recommended

that a surge suppression device be

connected directly across the coil of the

field device. If the inductive device has

plug-type connectors, the suppression

device can be installed on the terminal

block of the relay output.

Metal oxide varistors (MOV) and

diodes are devices which provide good

surge and transient suppression of AC

and DC powered coils.

1 2 3 4 5 6 7

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