Siemens 420 manual Hz characteristic, Star / delta circuit configurations

Issue 07/04 3 Functions

1 I1

U12

2

3

U1N

Z

1	I1
I1N

Z	U12	Z	Z
N		I12
	2
Z
			Z
	3

I

= I

= I

I1,∆

= 1

I1,Y

I12

=

I23

=

I31

= 1

⋅

I1

1

2

3

3

3

U12 = U23 = U31

= 3 ⋅ U

U12,∆

=

1

U12,Y

U

= U

= U

1Ν

3

12

23

31

U12 = 2 ⋅ Z

Z12,∆ =

Z12,Y

U12 =

2

⋅ Z

3

3

I1

I1

Fig. 3-19 Star / delta circuit configurations

87 Hz characteristic

When a motor with a delta circuit configuration (e. g. VN∆ , motor = 230 V) is fed from a frequency inverter, where the rated voltage corresponds to the star circuit configuration (e.g. 400 V frequency inverter), then it is important to proceed as follows and observe the following:

The motor must have the appropriate voltage strength.

Above the rated motor frequency, the iron losses in the motor increase over- proportionally. This is the reason that above this frequency, the thermal motor torque should be reduced.

For the quick commissioning, the rating plate data for the delta circuit configuration should be entered or the rating plate must be appropriately converted.

The drive inverter must be designed for the higher current (delta circuit configuration).

The 87 Hz characteristic is independent of the control type.

When using the 87 Hz characteristic, the mechanical motor limits must be taken into account (refer to Catalog M11).

For the 87 Hz characteristic, the ratio between the voltage and frequency (V/f characteristic) remain constant. This is the reason that the following relationships apply:

U		PN1 = UN1 ⋅ PN∆
									P = power
UN1				UN∆					f = frequency
(400 V)		fN1	=	UN1 ⋅	fN∆				n = speed
UN∆				UN∆					p = pole pair No.
(230 V)					s 
			=	60 		−		) +
		nN1		 min  (			fN∆		n∆
				p	fN1
		f
	fN∆	fN1
	(50 Hz)	(87 Hz)
Fig. 3-20	V/f characteristic

MICROMASTER 420	Operating Instructions
6SE6400-5AA00-0BP0	67