APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
1
BFI Applications Support Library
Application Note
AN-BEI-P2-050
Title
Open Loop Permanent Magnet Motor Control
Related Products
Beijer Frequency Inverter P2
Level
4
1 – Fundamental - No previous experience necessary
2 – Basic – Some Basic drives knowledge recommended
3 – Advanced – Some Basic drives knowledge required
4 – Expert – Good experience in topic of subject matter recommended
Overview:
This document provides an overview of the operation of the Beijer Frequency Inverter P2 when used for open-loop
permanent magnet (PM) motor control. Beijer Frequency Inverter P2 continues the design philosophy of ‘easy to set-
up’ and ‘high levels of performance’ into PM motor applications through simplification of the parameter set and
intelligent and accurate auto-tuning functions.
Applications:
PM motor control is provided as standard on the Beijer Frequency Inverter P2. In order to simplify the user manual
PM motor parameters have been excluded and this application note is provided as the addendum for this function.
The objective of using a PM motor in combination with Beijer Frequency Inverter P2 is to realize the high efficiency
and savings, in combination with smooth and responsive performance, and smaller motor frame sizes, which can be
achieved.
Beijer Frequency Inverter P2 provides open loop PM motor control, there is no facility for operation of PM motors in
closed loop or for any internal positioning functionality.
The Beijer Frequency Inverter P2 PM Control algorithm is suitable for both Surface mounted (SPM) and rotor inbuilt
(IPM) permanent magnet motors. Brushless DC motor control is realizable but it is important to first consult
technical support for additional data and advice.
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
2
Par.
Description
Range
Units
Default
Explanation
P1-14
Extended menu
access
Code 0 to 30000
--- 0 Set to ‘201’ for access to PM motor control parameters.
PM motor selection setting (in P4-01) and menu 7 are
not visible when other value (than 201) is set.
P4-01
Control Mode
0, 1, 2: See Std Guide
3: PM Motor Control
--- 2 Selects the motor control method.
Set to ‘3’ for Sensor-less PM motor control
P7-01
Stator
Resistance
0.000 – 50.000
ohm
2.8
Motor Stator Resistance (phase –phase).
Measure with ‘auto-tune’ or enter manually.
P7-03
Lsd Phase
Inductance
0.0000 – 1.0000
Henry
0.13
Inductance Per Phase.
‘d’ component of armature winding inductance from
the d-q linear model.
Measure with ‘auto-tune’ or enter manually.
P7-06
Lsq Phase
Inductance
0.0000 – 1.0000
Henry
0.13
Inductance Per Phase.
‘q’ component of armature winding inductance from
the d-q linear model.
Measure with ‘auto-tune’ or enter manually.
P7-10
Inertia Ratio
0 - 100
%
10
System Load Inertia to Motor Inertia Ratio. Entered into
P7-10 as:
P7-10 = (J
Tot
/ J
Mot
) . 10
P7-12
Current
magnetising
time
0 - 2000
mS
45
Motor magnetising time at start.
Time following drive enable to establish magnetising
flux in motor windings in order to accurately phase
motor shaft.
P7-14
Boost Current
Level
0 - 100 % 0
Boost current applied at start-up, as % of motor rated
current (P1-08)
P7-15
Boost
Frequency
0 – 50 % 0
Frequency range for applied boost current (P7-14) as %
of motor rated speed (P1-10)
Firmware Overview – Additional Parameters and Settings:
Additional Parameter information to that provided in the standard Beijer Frequency Inverter P2 manual is as
follows:-
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
3
Par.
Description
Range
Units
Default
Explanation
P1-03
Acceleration
ramp time
0 – 3000.0
Sec
5.0
Acceleration ramp time from 0 to base speed (P1-09) in
seconds
P1-04
Deceleration
ramp time
0 – 3000.0
Sec
5.0
Deceleration ramp time from base speed (P1-09) to
standstill in seconds
P1-07
Nominal back
emf
0 – 250 / 500
Volts
(rms)
8
Phase – Phase voltage imposed by magnets while
motor rotating at motor rated speed (P1-10)
P1-08
Motor rated
current
25 – 100% of drive
rated current
Amps
(rms)
0.13
Rated (nominal) phase current of the motor (used for
over-current protection)
P1-09
Motor rated
frequency
25 – 500
Hz
0.13
Rated (nominal) frequency of the motor.
P1-10
Motor rated
speed
0 – 60,000
Rpm
0
Rated (nominal) speed of the motor.
P2-24
Switching
frequency
4 - 32
kHz
Model
Based
Value
Effective Power Stage switching frequency. Higher
frequencies give smoother operation but care must be
taken to apply necessary de-rate factors.
P4-02
Motor
parameter
auto-tune
0: Disable
1: Enable
--- 0 When set to 1 the drive will perform an auto-tune
immediately of exiting the parameter. Values will be
written automatically to parameters P7-01, P7-03, &
P7-06.
P4-03
Speed
Controller
proportional
Gain
0.0 – 400.0
%
25.0
Sets the proportional gain value for the speed
controller. Higher values provide better output
frequency regulation and response. Too high a
value can cause instability or even over current
trips. For applications requiring best possible
performance, the value should be adjusted to suit
the connected load.
P4-04
Speed
Controller
integral time
constant
0.000 – 1.000
s
0.500
Sets the integral time for the speed controller.
Smaller values provide a faster response in
reaction to motor load changes, at the risk of
introducing instability. For best dynamic
performance, the value should be adjusted to suit
the connected load.
P4-07
Maximum
motoring
Torque limit
P4-08 – 200
%
200
When P4-01 is set to 3, sets the maximum torque limit.
P4-09
Maximum
generating
Torque limit
0.0 - 200
%
200
Sets the maximum regenerating torque limit permitted
by the drive.
Firmware Overview – Standard Parameters for PM motor set-up:
The following parameters are taken from the main Beijer Frequency Inverter P2 user manual but are required for
set-up / configuration of a PM motor. Parameters highlighted in ‘Blue’ are essential for successful PM motor control
with the Beijer Frequency Inverter P2. They are not configured during the auto-tune function and must be entered
manually:-
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
4
Set-up Procedure – Permanent magnet motors:
The following procedure should be followed to ensure correct parameterisation of the Beijer Frequency Inverter P2
P-2 and optimum performance from the permanent magnet motor.
Step 1: Entering basic motor parameters.
Note: Accurate entry of data for parameters P1-07 thru P1-10 is very important for optimum performance.
P1-07: Nominal back emf
Voltage imposed by the magnets when the motor is spun at rated speed and often referred to as motor nominal
voltage (UN). Its value can be found from the motor manufacturer, from the motor technical data sheet, or taken
from the motor data plate. Value entered must be phase to phase voltage. Phase voltages (phase – neutral) must be
multiplied by √3 (1.732) and the resultant value entered into P1-07
P1-08: Motor rated current
Rated phase current of the motor often referred to as the motor nominal current (IN). Its value can be found from
the motor manufacturer, from the motor technical data sheet, or taken from the motor data plate. Values given in
motor data are generally provided as current per phase and thus can be entered directly into P1-08.
P1-09: Motor rated frequency
Rated operating frequency of the motor often referred to as the motor nominal frequency (fN). Its value can be
found from the motor manufacturer, from the motor technical data sheet, or taken from the motor data plate.
P1-10: Motor rated speed
Rated output speed of the motor shaft often referred to as the motor nominal speed (nN). Its value can be found
from the motor manufacturer, from the motor technical data sheet, or taken from the motor data plate.
Step 2: Entering security code for Permanent Magnet parameter access.
In order to select PM motor control method and enter associated parameters a dedicated access code must be
entered into parameter P1-14. The dedicated code for PM motor set up is ‘201’. Once this value is set parameter
P4-01 will allow selection of PM motor control method and parameter group 7 will be available (visible). Security
Code ‘201’ also provides access to any menus accessible through the standard security password (default 101).
Step 3: Setting Beijer Frequency Inverter P2 effective output switching frequency.
Note: For smooth operation and consistent performance the minimum recommended switching frequency for PM
motor control is 16 kHz.
Setting of the drive output switching frequency is a compromise between smoothest possible operation and
minimisation of drive losses (and the potential need to de-rate the drive). Some testing may be required to
establish the lowest switching frequency (minimum 16kHz) that can be selected whilst maintaining the required
level of performance. When increasing switching frequency setting always consult the appropriate de-rating data
and configure parameter P1-08, Motor rated current, appropriately.
Step 4: Selecting PM motor control.
Set parameter P4-01, Beijer Frequency Inverter P2 control method, to a value of 3 to enable PM motor control. If
P1-14 has not been set with the correct security code then P4-01 will be locked at a maximum value ‘2’ (refer to
set-up Step 2).
Step 5: Beijer Frequency Inverter P2 Auto-tune for PM motor control.
Motor inductance and resistance values, programmed into Beijer Frequency Inverter P2 menu 7, can be configured
manually or derived by the Beijer Frequency Inverter P2 software using the auto-tune function.
If motor values for parameter menu 7 are know then step 5 can be omitted and the values entered manually,
however it is generally recommended for optimum performance and ease of set-up that the auto-tune procedure
is completed.
To activate auto-tune function set parameter P4-02 to value ‘1’ and exit the parameter. Auto-tune begins
immediately on exiting the parameter. During autoreturning to its normal condition once auto-tune is complete.
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
5
Auto-tune is a non-rotational function although some minor rotation of the motor shaft may occur. It is not
necessary to disconnect the motor from the driven load for this function to be completed successfully but the rotor
should not be locked such that motion is prevented.
Step 6: Setting baseline values for speed loop gains.
The Default gains values for the speed controller are generally suited to standard induction motor control. PM
motors generally permit high gains values and faster response / improved performance. The recommended
starting values for PM motor control are: P4-03: Speed Controller proportional Gain, Set to Value 50 (%).
P4-04: Speed Controller Integral Time Constant, Set to Value 100 (ms).
These values may need to be adjusted at the end of the process when system performance can be monitored for
effective tuning and improvement.
Step 7: Enter or check of menu 7 motor values.
If auto-tune function (P4-02) was completed then the following values will be measured and entered automatically
by the Beijer Frequency Inverter P2. The measured values can be viewed in the listed parameters for reference.
The motor values can be entered manually direct to the parameters listed below (taken from the manufacturer
data) if required: P7-01: Stator Resistance, Phase to Phase – measured between motor terminals.
P7-03: Lsd Phase Inductance, ‘d’ component of armature winding inductance.
P7-04: Lsq Phase Inductance, ‘q’ component of armature winding inductance.
It is generally recommended for optimum performance and ease of set-up that the auto-tune procedure is used to
complete these values.
Step 8: Setting Motor magnetising time.
Parameter P7-12, motor magnetising time, is used to set a time delay between drive output enable and the drive
output being ramped to the set-point speed. This delay is used by the drive to establish magnetising current in the
motor windings and to align orientation of the rotor to a known position. Magnetising current applied is 50% of the
value contained in parameter P1-08.
This function creates a start-up delay, however if insufficient time is provided to magnetise and orientate the rotor
position then start up and operational performance could be affected. Set to minimum value where the rotor can
be seen to successfully align prior to start up: P7-12: Motor Magnetising Time.
Step 9: Low Speed Boost Phase.
Low speed operation of a PM motor, below the speed range of approximately 20:1, should generally be avoided.
Low output voltage from the drive at low speeds (caused by V/f ratio and proportional to designed nominal motor
voltage) can create instabilities in the motor control model as the known phase angle of the rotor becomes
gradually more difficult to predict.
Beijer Frequency Inverter P2 provides a boost function that can inject some current into the motor at low speed to
help ensure the rotor alignment is maintained and to allow effective operation of the motor at lower speeds.
To implement some low speed boost run the drive at the effective lowest frequency required by the application
and increase boost levels to provide both required torque and smooth operation.
Boost current is set as a percentage of motor nominal current setting (P1-08). Boost frequency (P7-15) sets the
frequency cut off point above which boost current is no longer applied to the motor. Boost frequency is set as a
percentage of nominal motor frequency (P1-09).
Care should be taken not to cause motor over-heating issues through sustained low speed / high current boost
operation.
Below are some recommended settings: Default Boost Setting: P7-14: Boost Current = 0%. P7-15: Boost Frequency = 0%
Low Boost Setting: P7-14: Boost Current = 25%. P7-15: Boost Frequency = 10%
High Boost Setting: P7-14: Boost Current = 50%. P7-15: Boost Frequency = 20%
Beijer Frequency Inverter P2 PM motor configuration is now complete.
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
6
Optimisation for Permanent magnet motors:
Once the basic set-up procedure is complete for the Beijer Frequency Inverter P2 with PM motor the following
parameters can be adjusted to improve or optimise performance.
Changing Speed Controller Ramp Rates
Acceleration Ramp Rate:
Parameter P1-03 sets acceleration ramp rate. If adjusting speed controller gains (P4-03 & P4-04) always set
required ramps rates prior to tuning these values. Ensure ramp rate setting and acceleration / deceleration cycle
does not result in the drive operating excessively in the over-current (>100%) region such that nuisance tripping
might occur.
Deceleration Ramp Rate:
Parameter P1-04 sets deceleration ramp rate. If adjusting speed controller gains (P4-03 & P4-04) always set
required ramps rates prior to tuning these values. Ensure deceleration ramp rate setting does not result in
excessively braking energy being returned to the drive such that an over-voltage nuisance trip occurs.
Changing Beijer Frequency Inverter P2 Output Switching Frequency
Parameter P2-24 sets the drive effective output switching frequency. If adjusting speed controller gains (P4-03 &
P4-04) always set required switching frequency prior to tuning these values.
Higher values result in smoother motor operation but are less efficient and may require some de-rating of the
drive. Set for optimised performance, or optimised efficiency or combination thereof.
Note: For smooth operation and consistent performance the minimum recommended switching frequency for
PM motor control is 16 kHz.
Entering Motor / Load Inertia Ratio
Parameter P7-10 allows the inertia ratio between the motor and connected load to be entered into the Beijer
Frequency Inverter P2. This value can normally be left at the default value (10); however it is used by the Beijer
Frequency Inverter P2 control algorithm as a feed forward term in order to provide optimum torque / current to
accelerate the load. Hence accurate setting of the inertia ratio will produce better system response and dynamics.
If value is unknown then leave value set to default (10).
The value entered into P7-10 is given as; P7-10 = (J
Where; J
J
is Total Inertia (including motor, load, and any coupling)
Tot
is Motor Inertia
Mot
Motor inertia will be given by the motor manufacturer as part of their standard motor data.
Total inertia must either be known from the system design or measured.
Tuning Speed Controller Responses
Changes to the speed controller tuning parameters should be made very gradually with close observation of the
resulting effect on system response.
P4-03: Speed Controller proportional Gain
The proportional gain is used to change the output to the motor as a proportional of the error in the speed loop
controller (difference between commanded and actual speed). The proportional response of the drive is adjusted
by multiplying the error by a constant called the proportional gain that is set in parameter P4-03. Increasing the
value in parameter 4.03 decreases drive response times / improves system dynamics.
If proportional gain is set too low the system response will be poor (slow) however if set too high the system could
oscillate and could grow unstable.
P4-04: Speed Controller integral time constant
The integral gain is an ‘accumulated’ gain based on both the magnitude of the error in the speed controller and the
time the error has existed, essentially working to eliminate prolonged and steady state error in the system.
Tot
/ J
Mot
) . 10
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
7
Symptom
Solution / Advice
Cannot set P4-01 for PM motor Control
PM motor access code not entered in P1-14. Value ‘201’ required.
Delay seen after drive enable
There is an in-built delay after enable to magnetise and orientate the motor
shaft immediately after enable. Delay time is controlled by parameter P7-12.
See drive optimisation setting for optimal set-up.
Auto-tune failure
See standard Beijer Frequency Inverter P2 P-2 user guide
Poor Torque Performance at low speed
Some low speed current boost required. See Low speed boost phase in set
up section.
Too much current causing motor to heat up
Check parameter P1-07, motor nominal voltage is set correctly
Check parameter P1-08, motor nominal current is set correctly
If operating for sustained time period at low speed check levels of boost
current applied (P7-14, and P7-15)
Motor Stalled
Check motor connection
Check values entered into motor parameters (P1-07 to P1-10)
Check Auto-tune performed
Reduce the load
Increase acceleration / deceleration time
Increase drive / motor rating
Unstable motor speed
Check switching frequency hasn’t been adjusted below recommended
minimum (16 kHz)
Check values entered into motor parameters (P1-07 to P1-10)
Check Auto-tune performed
Check appropriate tuning of speed loop controller, reduce gains as required
Poor motor dynamics, slow response times
Check values entered into motor parameters (P1-07 to P1-10)
Check Auto-tune performed
Check appropriate tuning of speed loop controller, increase gains as
required
Parameter P4-04 is set as a time (in ms). The smaller the time (integration time) the more responsive the drive
output, at the possible expensive of instability.
Small amounts of integral gain can have a significant effect on reaction times and stability of the speed controller.
General practice with tuning a PI system is to set the integral value (P4-04) to its highest possible setting (1.0 sec)
and tune the proportional value (P4-03) for optimum performance. When proportional gain has been set /
optimized then the integral gain (P4-04) can then be adjusted to eliminate steady state speed errors.
Changing Beijer Frequency Inverter P2 Torque Limits
Drive torque limits (proportionally related to current limits) are adjusted by parameters P4-07 (for drive motoring
torque), and P4-09 (for drive generating torque) respectively.
Generally PM motors have a significantly higher peak torque rating in relation to nominal torque (>200% of
nominal torque), such that these values do not normally need to be adjusted. Peak torque values are available
from the motor technical data sheet and if less that 200% of nominal torque these parameters can be adjusted to
provide peak torque to the motor.
PM Motor Troubleshooting:
Trip codes and fault diagnostic information is provided in the standard Beijer Frequency Inverter P2 manual. Below
is further troubleshooting information specific to PM motor control.
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
8
1
2
3
4
5
6
7
P1-12 = 0
P1-13 = 1
Input 1:
O: Stop (Disable)
C: Run (Enable)
Input 3:
Enable
Imput 2:
+24V Output
+10V Output
0V
Analog Speed Ref
12
13
Safe Torque Off Input
Safe Torque Off 0V
Permanent magnet motors quick set-up:
The quick start is intended as a basic first step to successfully running the motor. For Optimum performance the
full programming and optimisation procedure should be followed.
Quick Step 1: Setting of the required parameters
Set the following parameters in the sequence they are listed.
P1-07: Nominal back emf (rms Phase-Phase) - = Motor Dependant
P1-08: Motor rated current (rms Phase) - - = Motor Dependant
P1-09: Motor rated frequency (Hz) - - = Motor Dependant
P1-10: Motor rated speed (rpm) - - - = Motor Dependant
P1-14: Parameter access code - - - = 201
P2-24: Switching frequency (kHz) - - = 16
P4-01: Control Mode - - - - = 3
P4-03: Speed Controller proportional Gain (%) - = 50
P4-04: Speed Controller integral time constant (ms) = 100
Quick Step 2: Complete Auto-tune function
Note: Safe Torque Off input (terminal 12 and 13) needs to be connected in order to enable the safe torque off
function and allow auto-tune and motor control. See connection diagram below.
Set the following parameter. Drive will perform auto-tune on exit of parameter entry.
P4-02: Auto-tune Function - - = 1
Wait for completion of auto-tune.
Quick Step 3: Check motor operation
Apply enable and speed set-point inputs to the Beijer
Frequency Inverter P2 P-2 Default configuration is shown right.
Vary speed set-point and check smooth operation of the motor.
Optional:
To set Beijer Frequency Inverter P2 in keypad mode set
parameter P12 = 1 Beijer Frequency Inverter P2 can now be
controlled direct from the keypad.
Quick Step 4: Set Current magnetising time
Set the following parameter to adjust Current magnetising time.
P7-12: Current magnetising time
Adjust upward if the rotor cannot be seen to orientate on start
up.
Adjust downward if a significant delay follows the orientation
of the rotor on start up.
Quick Step 5: Set Low speed boost parameters
Check low speed operation of the motor. If torque performance
at low speed needs adjustment set the following values.
P7-14: Boost Current Level - - = 25%
P7-14: Boost Frequency - - = 10%
Values should be optimised following on from the quick start procedure.
APPLICATION NOTE AN-BEI-P2-050
Date: 15/02/12
AN-BEI-P2-050 Open Loop Permanent Magnet Motor Control
9
Revision History
Version
Comments
Author
Date
1.00
New Application Note Created
JP
15/02/12
Appendix:
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