Toshiba G8000 Series installation manual Grounding configuration without input neutral

11.6.2 Grounding configuration without input neutral

When the neutral line cannot be fed to the bypass input from the input source which is wye-connected, the neutral terminal in the UPS cabinet must be connected to the ground bus in order to stabilize the UPS potential as shown in Figure 11.10. Thus, the jumper cable should stay on. See Figure 11.9 for the jumper cable location.

However, there will be circulating current between the UPS and the bypass, whenever the UPS transfers to/from the bypass. And the current will flow through the ground path instead of neutral line like that in Figure 11.8.

Input Source

3

N

3

G

	< UPS Cabinet >
3
N
3	3
	N
G	G

3

N	To the
G	Load

Keep the

Cable on

Figure 11.10 - Grounding configuration without input neutral.

If a ground fault interrupter is installed, the system is likely to trip the interrupter during transferring to/from the bypass circuit. It is recommended to put 0.5 sec or longer delay on the ground fault interrupter.

11.6.3Recommended configuration with delta-input

If the input source has a delta-connection (3-phase 3-wire) without ground, the neutral terminal in the UPS cabinet must be connected to the ground bus as shown in Figure 11.11.

So, the jumper cable should stay on. See Figure 11.9 for the jumper cable location.

Input Source

3

3

G

	< UPS Cabinet >
3
N
3	3
	N
G	G

3

N	To the
G	Load

Keep the

Cable on

Figure 11.11 - Grounding configuration with non-grounded delta-input.

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