Component 29: Motor

Specifications

Line connections
1	Electrical power
2	Shaft power
3	Control inlet for efficiency (as H)

General User Input Values Characteristic Lines Physics Used Displays Example

General

The default values and characteristic lines have been updated in Release 10.

Implementing a load-independent mechanical loss (QLOSSM) (see Release-Notes for Release 12)

The sequence in which the proportional and the constant fraction are considered depends on the direction of the flow of energy.

If both a mechanical efficiency ETAMN and a constant loss QLOSSM are specified, the two are combined as follows:

Q_gross =( Q_net + QLOSSM) / ETAMN

The result value QLOSS comprises the entire (load-independent and load-dependent) loss

QLOSS = Q_gross – Q_net

The result value ETAM contains both fractions (as in the case of component 6), as ETAM is defined by

ETAM = Q_net / Q_gross

If a QLOSSM > 0 is specified, ETAM thus no longer equals ETAMN but is accordingly smaller (by QLOSSM/heat supply).

Efficiency specification via logic line

In the motor, the nominal value of the electrical efficiency can also be specified as enthalpy on the logic inlet (Pin 3) instead of in the specification value ETAEN, so that
this value can also be controlled. The flag FETAEN serves to define which specification is to be used.

Result value ETATOT

Besides the electrical and the mechanical efficiency, the total efficiency is output as result value ETATOT as well.

Default values

The previous default value for the electrical efficiency ETAEN = 0.85 is too low for big motors. The value has therefore been increased to 0.95. In the case of rated powers below 20 kW, however, a warning is output to suggest that the value should be adjusted.

Calculation of the rotational speed

The relationship between the rotational speed F2 on the mechanical shaft and the mains frequency F1 of the electric wire is considered. In the case of synchronous motors, the ratio is fixed by the (integer) number of pole pairs PP:

F2 = F1 / PP

In the case of asynchronous motors, the rotational speed is decreased by a load-dependent slippage SLIP:

F2 = (1-SLIP) * F1 / PP

The load dependence can be represented in Ebsilon via a Kernel expression. However, you can also specify the value directly. This is controlled via the flag FSLIP:

FSLIP = 0: use SLIP = 1 (synchronous motor)

FSLIP = 1: use specification value SLIP

FSLIP = 2: use value from Kernel expression ESLIP

FSLIP =-1: Shaft speed given externally, SLIP calculated (identification mode)

Since Ebsilon has not yet calculated the shaft speed on the motor, use FSLIP = -1 for compatibility with loading a circuit created with an older version of Ebsilon.
For newer models, the default setting is FSLIP=0.

Display Formats :

Generator: Graphical symbols can be displayed instead of or in addition to the letter “M”. (see Component Displays).

User Input Values

FMODE	Flag for calculation mode Like in Parent Profile (Sub Profile option only) Expression = 0: GLOBAL = 1: Local off-design =-1: Local design
FETAEN	Specification of electric efficiency Like in Parent Profile (Sub Profile option only) Expression = 0: By specification value ETAEN = 2: By enthalpy on control inlet
ETAEN	Electrical efficiency (nominal)
ETAMN	Mechanical efficiency (nominal)
QLOSSM	Mechanical loss (constant fraction)
PP	Number of pole pairs
FSLIP	Method for slip definition Like in Parent Profile (Sub Profile option only) Expression = 0: No Slip (synchronous motor) = 1: Slip given specification value SLIP = 2: Slip given by Kernel Expression ESLIP =-1: Shaft speed given externally, slip calculated
SLIP	Slip
ESLIP	Slip function function evalexpr:REAL; begin // $._1.m : net frequency [1/min] // $._1.p : voltage [V] // $._1.h : inlet power [kW] // $._1.phel : phase difference between voltage and current // $._1.cosp = cos($._1.phel) : power factor // $._2.m : motor speed [1/min] // $._2.h : outlet power [kW] // (30000/PI)*$._2.h$._2.m : torque [Nm] evalexpr:=0.0; end;
Q1N	Nominal power

The parameters marked in blue are reference quantities for the off-design mode. The actual off-design values refer to these quantities in the equations used.

Generally, all inputs that are visible are required. But, often default values are provided.

For more information on colour of the input fields and their descriptions see Edit Component\Specification values

For more information on design vs. off-design and nominal values see General\Accept Nominal values

Characteristic Lines

Characteristic line 1: Electrical efficiency ETAE/ETAEN = f (Q1/Q1N)

     X-axis          1         Q1/Q1N                      1^st point
                        2          Q1/Q1N                     2^nd point
                        .
                      N         Q1/Q1N                     last point

     Y-axis        1          ETAE/ETAEN            1^st point
                        2          ETAE/ETAEN             2^nd point
                        .
                        N         ETAE/ETAEN            last point

KCharacteristic line 2: Mechanical efficiency ETAM/ETAMN = f (Q1/Q1N)

    X-axis         1          Q1/Q1N                     1^st point
                        2          Q1/Q1N                     2^nd point
                        .
                      N         Q1/Q1N                     last point

     Y-axis        1          ETAM/ETAMN           1^st point
                        2          ETAM/ETAMN           2^nd point
                        .
                        N         ETAM/ETAMN           last point