Frequency converter or parallel UPS with SSC

Maintenance (cont.)

Modular UPS with external maintenance bypass

(figure 31)

To service a number of modular UPSs with an external maintenance bypass, it is necessary to isolate them.

◗isolate the UPSs

Proceed in the following order:

◗shut down each inverter (press the "inverter off" button 7 for three seconds),

◗switch to the maintenance bypass whereby the load will be directly supplied by Mains 2 via Q3BP (close Q3BP, then open Q5 in the maintenance bypass cubicle),

◗open input switch Q4S on each UPS;

◗isolate each UPS from Mains 2 by opening the upstream protection devices,

◗open input switch Q1 on each UPS,

◗open output switch Q5N on each UPS.

The UPSs are de-energised (except the Mains 1 cables upstream of the Q1 switches on each UPS), but the load is supplied with Mains 2 power via the maintenance bypass. Complete isolation of the installation requires opening of the upstream protection devices on both Mains 1 and Mains 2.

◗start-up

Once servicing is completed, proceed in the following order:

◗close the input switches Q1 and Q4S on each UPS,

◗close output switch Q5N on each UPS,

◗close output switch Q5N in the maintenance bypass cubicle,

◗open switch Q3BP in the maintenance bypass cubicle,

◗close battery circuit breaker Q1 on each UPS,

External maintenance bypass
	Q3BP
Modular UPS 1
Q4S	static switch
Q4S
mains 2
rectifier-	inverter
charger	inverter
Q1	Q5N
mains 1
QF1
	battery
Modular UPS 2	load
	load
	Q5N
Q4S	static switch
Q4S
mains 2
rectifier-	inverter
charger	inverter
Q1	Q5N
mains 1
QF1
	battery

Fig. 31

	◗ start all the inverters (press the	Note. It is strongly advised to call on
	◗ start all the inverters (press the	our after-sales support department for
	"inverter on" button 6 ).	our after-sales support department for
	"inverter on" button 6 ).	these operations.
	The UPSs all come on line at the same	these operations.
	time if they are sufficient in number to
	supply the load.