3Com VFD-D D manual Capacity Formulas, When one AC motor drive operates one motor

Appendix B How to Select AC Motor Drive DD Series

B-1 Capacity Formulas

1. When one AC motor drive operates one motor

The starting capacity should be less than 1.5x rated capacity of AC motor drive The starting capacity=

k ⋅ N	⎛	GD2
	⎜
	⎜TL +	375
973 ⋅η ⋅ cosϕ ⎝

N⎞

⋅⎟ ≤ 1.5 ⋅ the _ capacity _ of _ AC _ motor _ drive(kVA) tA ⎟⎠

2.When one AC motor drive operates more than one motor

2.1The starting capacity should be less than the rated capacity of AC motor drive

„Acceleration time ≦60 seconds

The starting capacity=

k ⋅ N	⎡		ns	⎤
	[nT + ns(ks − 1)] = PC1⎢⎢1	+		(ks − 1)⎥⎥	≤ 1.5 ⋅ the _ capacity _ of _ AC _ motor _ drive(kVA)
η ⋅ cos ϕ			nT
	⎣			⎦
	⎢			⎥

„Acceleration time ≧60 seconds

The starting capacity=

k ⋅ N	⎡		ns	⎤
	[nT + ns(ks − 1)] = PC1⎢⎢1	+		(ks − 1)⎥⎥	≤ the _ capacity _ of _ AC _ motor _ drive(kVA)
η ⋅ cosϕ			nT
	⎣			⎦
	⎢			⎥

2.2The current should be less than the rated current of AC motor drive(A)

„Acceleration time ≦60 seconds

⎡	nS ⎛	⎞⎤	≤ 1.5 ⋅ the _ rated _ current_ of _ AC _ motor _ drive( A)
nT + IM ⎢1+	⎜ kS −1⎟⎥
⎣	nT ⎝	⎠⎦

„Acceleration time ≧60 seconds

⎡	nS ⎛	⎞⎤	≤ the _ rated _ current _ of _ AC _ motor _ drive( A)
nT + IM ⎢1+	⎜ kS −1⎟⎥
⎣	nT ⎝	⎠⎦

2.3When it is running continuously

„The requirement of load capacity should be less than the capacity of AC motor drive(kVA) The requirement of load capacity=

k ⋅ PM	≤ the _ capacity _ of _ AC _ motor _ drive(kVA)
η ⋅ cosϕ

„ The motor capacity should be less than the capacity of AC motor drive

k ⋅ 3 ⋅VM ⋅ IM ⋅10−3 ≤ the_ capacity_ of _ AC _ motor _ drive(kVA)

„The current should be less than the rated current of AC motor drive(A)

k ⋅ IM ≤ the _ rated _ current _ of _ AC _ motor _ drive( A)

B-2