Frequency Inverter / Variable Speed Drive (Vsd); Ignition Electrodes And Transformers - Unigas N880X Manual

1.2

.Frequency inverter / Variable Speed Drive (VSD)

A VSD is one of the strongest EMC sources in a boiler house, so the following is recommended:
Earth
Use only VSD with EMC- filter!
Cable from VSD to the fan motor (Line voltage)
Use a complete separate and shielded cable from the VSD to the fan motor! Connect the shield at VSD- and at the motor- side with PE.
Details and further information see related VSD- documentation.
Cable from LMV5 to VSD (Low voltage)
Use a shielded cable from LMV5 to VSD. The shield of this cable has to be connected only at LMV5 side with X73.6 (FE), not at the VSD side:
1.3

Ignition electrodes and transformers

The Ignition is also one of the strong EMC sources, so the following is recommended:
•
Keep the cable loop/length in the high voltage ignition circuit as short as possible.
•
Use special EMC-ignition cable
•
Avoid capacitive and inductive coupling to other signal paths.
•
Use separate wiring for the ignition high voltage cable, with max. possible distance to other cables and to the burner housing.
•
e.g.: use a electrical insulating conduit or distance parts (e.g. plastic material), see also Appendix "Example for wiring, earthing and
shielding the LMV5-System"
•
Prefer a double pole ignition (see drawings below).
•
When using a double probe ignition, the cables should be run close together to ensure that the area of emissions is as small as possible.
Double pole ignition: recommended
High
Voltage
ignition
trasformer
If a single pole ignition must be used, it is very important to have a low impedance at the mechanical connections (no insulation material, e.g.
paint), because than you get a good current path from the ignition spark back to the ignition transformer, that results in low EMC-emissions:
If you have high impedance at the mechanical connections, e.g. caused by paint, you get bad multiple current paths from the ignition spark back to
the ignition transformer, that results in high EMC-emissions
VS
LMV5x
5
LMV5
hi ld
Note: If the LMV5 is mounted in a cabinet, alternative to
(X73.6 / FE), also a connection with the PE- rail in the
cabinet is possible
Low impedance, no
electrical insulating
material (e.g. paint)
Current path
back to
ignnition
trasformer
gas train
VSD