Emerson 400518-01 installation manual Transformer Sizing, Single Phase Power Supply Connections

Safety Information	Product Overview	Installation	Diagnostics	Options and	Specification
				Accessories
DISTRIBUTION PANEL		3 Ø Isolation Step Down Transformer
				L3
				L2
> 140 Vac					To Fusing and
					Drive Terminals
				L1
				N
EARTH				PE
GROUND				(Protective Earth)

Figure 12: Grounded WYE Distribution >140 Vac Phase to Neutral. Recommend Using Step Down Transformer so Line to Line is 240 Vac or less.

Fuse

L1

To Drive

Terminals

L2

Fuse

L1

To Drive

Terminals

L2

Fuse

Figure 13: Single Phase Power Supply Connections

Transformer Sizing

If your application requires a transformer, use the following table for sizing the KVA rating. The values in the table are based on “worst case” power usage and can be considered a conservative recommendation. You can down-size the values only if the maximum power usage is less than the transformer continuous power rating. Other factors that may influence the required KVA rating are high transformer ambient temperatures (>40° C or >104° F) and drive operation near the maximum speeds.

Transformer output voltage drop may become a limiting factor at motor speeds and loads near maximum ratings. Typically, higher KVA transformers have lower voltage drop due to lower impedance.

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