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7.3.2 Instructions to E21 electromagnetic capability installation
E21 may be installed outside the cabinet. If work environment is poor, keep E21
close to cabinet as much as possible;
Metal housing shall connect to protective ground via earth conductor, and ground
resistance shall be no higher than 0.3 ohm;
Cabinet must be ground well to avoid personal injury or death caused by electricity
leakage;
Power line, encoder cable and signal line must be away from strong current and
inductive load. Do not lay in parallel;
Signal line (I/O port cable) is the shorter the better. If long distance wiring is
required, try to keep away from strong interference source;
Two 24V power supplies are recommended, one for supply power to internal circuit,
the other for IO port power supply.
Encoder cable uses shield line. The shield layer and metal housing connect to each
other in large area. Try to avoid “pigtail” connection.
7.3.3 Install freewheeling diode on relay
When inductive load is cutoff, instant high voltage will generate, such as coil and
contactor of relay.
To avoid damage to system circuit by high voltage, necessary protection measures
must be taken.
E21 output port load is DC relay, protective measures are as follows:
Add bleeder diode on coil, clamp voltage on both ends of coil. But some off-delay will
be caused.
Figure 7-2 Relay coil connect freewheel diode
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