Emerson 10-30kVA installation manual UPS Input Configuration, Cabling Guidelines

Electrical Connections

2.1.2UPS Input Configuration

Figure 2 illustrates the NX in a split bypass (dual-input) configuration. In this configuration the Static Bypass and the Maintenance Bypass lines are supplied from a separate feed from the Main input. Both sources must be protected externally with properly sized protective devices. By default, the unit ships with internal links installed between the Bypass input and Main input (Single Input configuration). To wire the unit as a dual input UPS, remove the links and wire the bypass to the input bus bars, then wire the Main input directly to CB1 (see Figure 3).

Figure 2 Single module block diagram—dual input configuration

	SW1/D	Maintenance Bypass
	SW1/C	Contactor	Static Switch
Bypass Input
	Rectifier	Inverter	Contactor	SW1/A	UPS
AC Utility Input					Output
	CB1
Neutral Wire	Discharge	Battery		SW1/B
		Charger
	Battery

2.1.3Cabling Guidelines

The following are guidelines only and are superseded by local regulations and codes of practice where applicable.

1.Take special care when determining the size of the neutral cable, as current circulating on the neutral cable may be greater than nominal current in the case of non-linear loads. Refer to the values in 6.4 - UPS Electrical Characteristics.

2.The ground conductor should be sized according to such factors as the fault rating, cable lengths and type of protection. The ground cable connecting the UPS to the main ground system must follow the most direct route possible. Control wiring and power wiring must be run in separate conduit. Output and input cables must be run in separate conduit.

3.Consider using paralleled smaller cables for heavy currents—this can ease installation.

4.When sizing battery cables, a maximum voltage drop of 4VDC is permissible at the current ratings in Table 10. For terminal connection sizing, see Table 10.

5.In most installations, especially parallel multi-module systems, the load equipment is connected to a distribution network of individually protected busbars fed by the UPS output, rather than connected directly to the UPS itself. When this is the case, the UPS output cables can be rated to suit the individual distribution network demands rather than being fully load-rated.

NOTE

If more load is added to the distribution panel, the unit’s cabling must be resized.

6.When laying power cables, do not form coils; this will help avoid increasing formation of electromagnetic interference.

NOTE

Left-side access may be required when making power connections. Cable connections should be made before a cabinet is attached to the left side of the NX or before the UPS is placed where another obstruction, such as a wall, is against the NX’s the left side.

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