Protective Ground Connections; Ac Supply Requirements; Line Reactors - Emerson FXMP25 User Manual

4.2

Protective ground connections

The field controller must be connected to the system protective ground of the AC supply.
The protective ground wiring must conform to local regulations and codes of practice.
See section 4.3.1 MOV protective ground disconnect on page 17 for possible
exceptions.
Ground loop impedance
The ground loop impedance must conform to the requirements of local safety
regulations.
The field controller must be connected by a protective ground connection capable of
WARNING
carrying the prospective fault current until the protective device (fuse etc,) disconnects
the AC supply. The protective ground connections must be inspected and tested at
appropriate intervals.
4.3

AC supply requirements

For detailed information regarding AC supply requirements, please refer to section
8.4 AC supply requirements on page 54.
4.3.1 MOV protective ground disconnect
In some special circumstances, for example during a high potential test or in certain
situations with IT supplies and multiple generators there may be a requirement to
disconnect the MOV protective ground connection. If the MOV protective ground
connection is disconnected the immunity of the field controller to high voltage pulses is
reduced. It is then only suitable for use with supplies having overvoltage category II, i.e.
not for connection at the origin of the low voltage supply within a building. If the MOV to
protective ground connection is not required then do not make a protective ground
connection to the FXMP25.
4.4

Line reactors

The FXMP25, in common with all naturally commutated SCR drives, causes voltage
notches at the input supply terminals. To avoid disturbances with other equipment using
the same supply, the addition of external line inductance is strongly recommended in
order to restrict the depth of notches imposed. This is generally not necessary where a
dedicated transformer is used to supply the FXMP25.
The following recommendations for added line inductance, have been calculated based
on the power drive systems standard: EN 61800-3:2004 "Adjustable speed electrical
power drive systems - Part 3: EMC requirements and specific test methods".
Table 4-1 Minimum values of L
Field output
current
A
25
On typical field windings or high inductance loads the output current is smooth DC and
NOTE
therefore the rms input current is approximately equal to the DC output current.
The above assumes the supply has 1.5 % impedance and a minimum supply rating of
5 kA.
FXMP25 User Guide
Issue Number: 3
and inductor current rating for a typical application
add
System voltage
400 V
μH
230
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Typical current
480 V
μH
290
rating
A
26
17