Siemens 6RA70, SIMOREG CM Faq

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A&D LD CS 31 October 2007

FAQ for 6RA70 DC MASTER and SIMOREG CM

Question:

How can I manually record the field characteristic?

Answer:

The automatic optimization run P051 = 27 supports recording of the field characteristic. If this routine cannot be used, the field characteristic needs to be recorded manually as described below. A field characteristic is required for motors which will also operate in the field-weakening range. It must not be recorded for motors which will operate up to rated speed only.

Relationships: The magnetic flux Φ is determined by the excitation current of the motor. When the excitation current increases (up to its rated value), however, the flux Φ does not increase linearly because the stator core becomes saturated. The relationship between the excitation current and the flux is not linear and is represented by the field characteristic (magnetization characteristic). The induced motor voltage is the EMF of the motor. EMF[V] = k * Φ * n[RPM]; the EMF reaches its rated value when the motor is operating at rated speed. To prevent the motor EMF from reaching excessive values at speeds above the motor rated speed, the flux Φ is reduced in this range and the EMF is regulated to a constant value, i.e. the rated EMF value. The following relation applies in steady-state motor operation: Ud – Id * Ra = EMF Ud: Motor armature voltage, Id: Motor armature current, Ra: Armature resistance of motor

The maximum speed adjustment must be made before the field characteristic is recorded. P741 for an analog tachometer or P143 for a pulse encoder. The maximum speed adjustment must be made at a speed lower than rated speed. The current controller and speed controller must then be optimized (Section 7.5 of Operating Instructions). The field characteristic can then be recorded.

Recording of a motor field characteristic (magnetization characteristic):

To record the field characteristic, the magnetization characteristic is measured. This is done by setting the field current setpoint

the motor

65.0 %, 60.5 %, 56.5 %, 53.0 %, 50.0 %, 47.0 %, 44.0 %, 41.0 %, 38.0 %, 35.0 %, 32.0 %,

29.0 %, 26.0 %, 23.0 %, 20.0 %, 17.0 %, 14.0 %, 11.0 %, 8.0 %.

At a given speed, therefore, a specific actual EMF value

value of the field current. The actual speed value

not decisive, but it is important that the speed is maintained at a constant value for each single measuring point.

The EMF value

speed value is displayed in parameter r025.

, e.g. in the following increments: 91.0 %, 83.0 %, 76.0 %, 70.0 %,

motorratedfield

EMF for each measuring point is displayed in parameter r037. The actual

act

I , starting at 100.0 % of the rated excitation current of

fset

EMF is measured at each actual

act

n at the individual measuring points is

act

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The flux values

setpoints

I are determined according to the formula defined below from the actual EMF

fset

normalized to rated flux which are reached at specific field current

)(

IΦ

fset

and speed values calculated and measured respectively and entered in a table of flux values.

I ∗∗=Φ %100)(

EMF EMF

fset

act

EMF

act

... measured values in field-weakening range at specified

act

fieldrated

... measured values with rated field (100.0 % rated excitation current)

fieldrated

act

EMF

fieldrated

... in field-weakening range at specified

fieldrated

fset

Settings: P102: Rated excitation current motor

Set P103 = 0, minimum excitation current motor P613.01 = 401, parameter P401 specifies the factor for the excitation current setpoint (x 0 – 100%). P433.01 = 402, parameter P402 specifies the speed setpoint. The speed setpoint must be set to a value lower than the rated speed of the motor. Start recording at approximately 80% of the rated motor EMF. Procedure: Maintaining a constant speed for the various settings of P401 (starting at 100%), enter r037 and r025 in the table and calculate Φ (I

fset

I in % of

fset

(rated field)

motorratedfield

P401

100.0 %

91.0 %

83.0 %

76.0 %

70.0 %

65.0 %

60.5 %

56.5 %

53.0 %

50.0 %

47.0 %

44.0 %

41.0 %

38.0 %

35.0 %

32.0 %

29.0 %

26.0 %

23.0 %

20.0 %

17.0 %

14.0 %

11.0 %

8.0 %

act

r037

fieldrated

act

r025

fieldrated

acc. to formula

100.00 %

)

EMF

EMF )

fset

above

)(

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The field characteristic can be plotted on the basis of the field currents and calculated normalized flux values entered in the table.

The field current values corresponding to linearly graduated

(in increments of 5%) flux values can then be read off this plot and stored in the field characteristic parameters P121 (field current at 5% flux) to P139 (field current at 95% machine flux)

(see Figure 1 below for an

example of a field characteristic plot).

Machine flux as % of rated flux

Figure 1. Example of a field characteristic – in this diagram, the field current as a % of the rated excitation current of the motor is plotted along the x axis.

Field current as % of P102

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Parameter P118 (rated value of EMF)

∗

is calculated from the rated armature voltage of the motor minus the voltage drop across the armature circuit resistance at the rated armature current of the motor. P118 = P101 – P100 * P110.

The associated value of parameter P119 (rated speed)

is calculated as follows and specifies

the "cut-out" speed:

nEMFratedP

speedratedP

)(119

EMF

fieldratedatact

)(118

fieldratedatact

Further settings

P117 = 1

P081 = 1

(field characteristic parameters P118 to P139 are valid)

P613.01 = 1 Suppress influence of P401 on the field current setpoint

P433.01 =

P103 = xx

Set connector number for the speed setpoint

The minimum field current must be set slightly lower than required for maximum

speed.

Run the motor through the entire speed range and check whether a stable actual speed value can be obtained. Re-optimize the speed controller / current controller if necessary.

EMF-dependent field-weakening using the EMF controller without recording of the field characteristic:

For applications which do not require a high dynamic response to speed changes in the fieldweakening range, there is no need to record the field characteristic. In these cases, fieldweakening can be implemented solely via the EMF controller.

Settings:

P081 = 1

P117 = 1

P273.01 = 0

The motor rating plate:

SIEMENS

DC - Motor

No. N R7 1145783 010 001 / 2004

Wärmekl./Th.Cl. H

20 ... 420

420

A 985 990

1GG6286-0NG40-1VV1-Z

IP23 / IC 06 IM B3

1/min

10 ... 1410

1410 ... 1620

2,76 ... 390

EN 60034

Gew./Wt. 1,56 t

390

Rated speed of the motor 1410 [RPM]

Fremderr./Separate excit.: 310 ... 210 V, 14,5 ... 11,5 A

Fremdkühlung/Separate cooling: 0,75 m

B6C, 400 V, 50 Hz

MADE IN GERMANY

Luftrichtung/ Dir. of Ventilation NDE-DE

Maximum field-weakening speed of the motor 1620 [RPM]

Rated excitation current of the motor 14.5 [A]