Siemens MICROMASTER 420 User manual

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MICROMASTER 420 Reference Manual
ii Issue A1
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MICROMASTER 420 Reference Manual
Issue A1 iii
Valid for A1 Release
Inverter Type Control Version
MICROMASTER 420 MM4
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MICROMASTER 420 Reference Manual
iv Issue A1
Further information is available on the Internet under:
http://www.siemens.de/micromaster
Approved Siemens Quality for Software and Training
is to DIN ISO 9001, Reg. No. 2160-01
The reproduction, transmission or use of this document, or its
contents is not permitted unless authorized in writing.
Offenders will be liable for damages. All rights including rights
created by patent grant or registration of a utility model or
design are reserved.
© Siemens AG 2000. All Rights Reserved.
MICROMASTER® is a registered trademark of Siemens.
Other functions not described in this document may be
available. However, this fact shall not constitute an obligation
to supply such functions with a new control, or when
servicing.
We have checked that the contents of this document
correspond to the hardware and software described. There
may be discrepancies nevertheless, and no guarantee can be
given that they are completely identical. The information
contained in this document is reviewed regularly and any
necessary changes will be included in the next edition. We
welcome suggestions for improvement.
Siemens handbooks are printed on chlorine-free paper that
has been produced from managed sustainable forests. No
solvents have been used in the printing or binding process.
Document subject to change without prior notice.
Printed in the United Kingdom Siemens-Aktiengesellschaft.

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MICROMASTER 420 Reference Manual
Issue A1 v
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1.1 Purpose of this Manual..............................................................................................2
1.2 Compatibilty...............................................................................................................2
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2.1 Current Limit and Overload Operation ......................................................................8
2.2 Fast Current Limit......................................................................................................9
2.3 Positive Temperature Coefficient Resistor Use.......................................................10
2.4 I2t Performance........................................................................................................10
2.5 Internal Overtemperature ........................................................................................10
2.6 Overvoltage and Trip Levels....................................................................................11
2.7 Boost........................................................................................................................11
2.8 Proportional and Integral Control (PI)......................................................................12
2.9 Braking.....................................................................................................................20
2.10 Derating Factors......................................................................................................22
2.11 Cubicle Calculations................................................................................................26
2.12 Thermal Protection and Automatic De-rating..........................................................26
2.13 Operation from Unearthed Supplies........................................................................27
2.14 Multi-Motor Connection ...........................................................................................27
2.15 Control Modes (P1300) ...........................................................................................27
2.16 Working with Binary Connectors (BiCo)..................................................................28
2.17 Acoustic Noise.........................................................................................................35
2.18 Harmonic Currents ..................................................................................................36
2.19 Power Losses..........................................................................................................38

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MICROMASTER 420 Reference Manual
vi Issue A1
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3.1 Using the Serial Interface........................................................................................41
3.2 Working with Serial Communications......................................................................41
3.3 Using the Universal Serial Interface Protocol..........................................................43
3.4 PROFIBUS ..............................................................................................................60
3.5 PROFIBUS Module .................................................................................................61
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4.1 Introduction..............................................................................................................66
4.2 Variant Dependent Options.....................................................................................66
4.3 Variant Independent Options...................................................................................73
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5.1 Troubleshooting with Status Display Panel.............................................................76
5.2 MICROMASTER 420 Fault Codes..........................................................................76
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6.1 Maintenance............................................................................................................78
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MICROMASTER 420 Reference Manual
Issue A1 vii
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Figure 2-1 Current Limit Interaction.........................................................................................................8
Figure 2-2 PTC Resistor Connections..................................................................................................10
Figure 2-3 Boost Level...........................................................................................................................11
Figure 2-4 Quick response with overshoot: P2280 = 0.30; P2285 = 0.03 s..........................................14
Figure 2-5 Quick response with overshoot, but instability: P2280 = 0.55; P2285 = 0.03 s ....................15
Figure 2-6 Damped response: P2280 = 0.20; P2285 = 0.15 s...............................................................15
Figure 2-7 Response to 5 Hz step: L = 100 ms .....................................................................................16
Figure 2-8 Response to 5 Hz step: T = 700 ms .....................................................................................17
Figure 2-9 Step Response in PI control with P2280 = 9.84 and P2285 = 0.30......................................17
Figure 2-10 PI Basic Block Diagram........................................................................................................19
Figure 2-11 Frequency Ramp Down........................................................................................................20
Figure 2-12 DC Braking...........................................................................................................................20
Figure 2-13 Compound Braking...............................................................................................................21
Figure 2-14 Derating with Temperature...................................................................................................22
Figure 2-15 Derating with Altitude............................................................................................................24
Figure 2-16 Power Losses.......................................................................................................................38
Figure 3-1 Typical RS485 Multidrop Interface........................................................................................42
Figure 3-2 Telegram Structure...............................................................................................................43
Figure 3-3 Address (ADR) Bit Numbers.................................................................................................44
Figure 3-4 Useful Data Characters........................................................................................................44
Figure 4-1 Inverter with Filter.................................................................................................................66
Figure 4-2 Inverter with Input Choke......................................................................................................67
Figure 4-3 Inverter with Output Choke...................................................................................................68
Figure 6-1 Fan Removal........................................................................................................................78

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MICROMASTER 420 Reference Manual
viii Issue A1
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Table 2-1 Current Limit and Overload.....................................................................................................8
Table 2-2 Measured Current Monitoring Accuracy.................................................................................9
Table 2-3 Trip Levels............................................................................................................................11
Table 2-4 Maximum Cable Lengths......................................................................................................23
Table 2-5 Derating with Switching Frequencies....................................................................................25
Table 2-6 Cubicle Calculations.............................................................................................................26
Table 2-7 BiCo Connections (r0019 to r0054)......................................................................................31
Table 2-8 BiCo Connections (r0055 to r1119)......................................................................................32
Table 2-9 BiCo Connections (r1170 to r2050)......................................................................................33
Table 2-10 BiCo connections (r2053 to r2294).......................................................................................34
Table 2-11 Acoustic Test Results...........................................................................................................35
Table 2-12 Single Phase 230V Connection............................................................................................36
Table 2-13 Three Phase 230V Connection.............................................................................................36
Table 2-14 Three Phase 400V Connection.............................................................................................37
Table 3-1 Defined Task ID....................................................................................................................47
Table 3-2 Defined Reply ID ..................................................................................................................47
Table 3-3 Defined Error Values for Reply ID = Task cannot be executed ............................................48
Table 3-4 PZD Area Structure..............................................................................................................51
Table 3-5 Inverter Control Word (STW)................................................................................................52
Table 3-6 Inverter Status Word (PZD)..................................................................................................53
Table 3-7 Practical Examples...............................................................................................................54
Table 3-8 Comparison Table (MICROMASTER 420/Earlier MICROMASTER)....................................58
Table 3-9 Assignment of the PROFIBUS SUB-D socket connector .....................................................63
Table 3-10 Maximum Cable Lengths for Data Transfer Rates................................................................63
Table 3-11 Order Numbers for Connectors and Cables .........................................................................63
Table 3-12 Technical data......................................................................................................................64
Table 3-13 PROFIBUS Ordering information..........................................................................................64
Table 4-1 Recommended Fuses (230 V Single-phase)........................................................................69
Table 4-2 Recommended Fuses (230 V Three-phase) ........................................................................69
Table 4-3 Recommended Fuses (380 V – 480 V) ................................................................................70
Table 4-4 Recommended Circuit Breakers (230 V Single-phase)........................................................71
Table 4-5 Recommended Circuit Breakers (230 V Three-phase).........................................................71
Table 4-6 Recommended Circuit Breakers 380 V – 480 V)..................................................................72
Table 5-1 Inverter conditions indicated by the LEDs on the SDP.........................................................76

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MICROMASTER 420 Reference Manual
Issue A1 1
1Introduction
This Chapter contains an introduction to the contents of the manual with a brief
description of each chapter.
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1.1 Purpose of this Manual..............................................................................................2
1.2 Compatibilty...............................................................................................................2

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MICROMASTER 420 Reference Manual
2Issue A1
1.1Purpose of this Manual
The purpose of this manual is to familiarize the user with the benefits and
properties of the MICROMASTER 420 and to expand on information found in
related documentation.
Chapter 2 contains engineering information designed to assist the user in operating
the inverter in the most efficient way and provides detailed information on derating
factors and protection characteristics.
The MICROMASTER 420 has extensive communications and control capabilities.
Chapter 3 explains the various methods and communications protocols, giving
working examples to aid understanding.
Several options and accessories are available for use with the inverter. Chapter 4
contains a brief explanation of each option with references to more detailed
information.
Chapter 5 provides troubleshooting advice and fault code particulars.
Service information and an illustration showing fan removal are contained in
Chapter 6.
Appendix A gives a brief description of the standards referenced in the design and
production of the MICROMASTER 420 and you can obtain more information from
the documentation products listed in Appendix B.
An index is provided at the back of this manual.
1.2Compatibilty
If you have experience of the MM3, the following notes will help you get to know
the MICROMASTER 420.
The MICROMASTER 420 (6SE64) is designed to replace the MM3 6SE92 and
offers many new features and functions.
1. The MICROMASTER 420 is footprint compatible, and uses the same mounting
positions. Frame Size A is about 8mm deeper than MM3 FSA.. In some cases, the
fan housing is deeper, but you should ensure that the surrounding area is free.
2. The terminal marking and numbering are the same with the terminals mounted at
the front of the unit for easier connection. An analogue output and RS485 are
provided via new terminals 12, 13, 14 and 15.
3. The MICROMASTER 420 is supplied with a Status Display Panel (SDP).
Parameters cannot be changed unless a Basic Operator Panel (BOP) or an
Advanced Operator Panel (AOP) is fitted. The MICROMASTER 420 is, therefore,
supplied with the parameters set for simple control using Digital and Analogue
inputs:
a. Digital input 1 (terminal 5) – Run Right / Stop (OFF1).
b. Digital input 2 (terminal 6) – Reverse.
c. Digital input 3 (terminal 7) – Fault reset.
d. Analogue input 0 to 10 V = 0 to 50 Hz (Frequency Setpoint).
e. Analogue Output 0 to 20 mA = 0 to 50 Hz output frequency.
f. Relay output: (Fault) Relay de-energized when inverter fault active.

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MICROMASTER 420 Reference Manual
Issue A1 3
4. A Dual In-line Package (DIP) switch is used to select North American Defaults.
DIP switch 2 located under the SDP selects North American defaults when set to
‘on’ (up). Next switch ‘on’ will set 60 Hz etc. P0100, settings 0 and 1 will be
overwritten by DIP switch 2.
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Do not change DIP switch 1 from ‘off’.
5. The BOP has an additional button to MM3, a function button (Fn). This has several
functions:
a. If a fault occurs and the drive trips, pressing the Fn button will reset the
fault.
b. After reading or accessing a parameter (e.g. P1210), pressing the Fn
button will return the display to r0000, saving scrolling time.
c. If the output frequency is displayed and Fn pressed for approximately one
second, the DC link voltage is displayed. Short presses toggle though
output current, output voltage, output frequency. A long press returns to
original display.
d. When changing parameter values, pressing the Fn button and using the
arrows will allow individual digits to be accessed for easy setting of least
significant digits.
6. The parameter structure is completely different. Parameters are logically grouped;
e.g. P0700 to P0799 are control I/O functions.
a. Parameter access levels are controlled by parameter P0003; e.g. Level 2
gives access to a similar number of parameters as MM3.
b. Parameter P0004 allows access to parameter groups; e.g. P0004 = 3
allows motor data parameters to be accessed and changed.
c. Setting parameter P0010 = 1 enters a ‘quick commissioning’ mode which
enables key parameters to be set and motor data automatically calculated.
(See the Getting Started Guide for detailed information on ‘Quick
Commissioning’).
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With P0010 = 1, the drive will not run.
d. Some parameters (P0100, Motor parameters etc.) can only be changed
when P0010 =1.
e. Setting Parameter P0010 = 30 and then P0970 = 1 resets factory
parameters to default (except North American defaults).
f. Parameter P0100 = 0 or 1 allows the DIP switch (see above ) to be read.
g. Parameter P1910 and P3900 calculate the motor parameters, like P088 on
MM3. This is important on MICROMASTER 420 and is part of the quick
commissioning. If the Binary Connectors (BiCo) settings of the digital
inputs are enabled by setting P0701, 2 or 3 to 99, the only way to clear
them is to reset all parameters using P0970. (BiCo details are contained in
Chapter 2, Engineering Information)
7. There are important differences in the implementation of the USS protocol. It will
be necessary to change the control messages used to control the
MICROMASTER 420. (See Chapter 3, Communications).

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MICROMASTER 420 Reference Manual
4Issue A1

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MICROMASTER 420 Reference Manual
Issue A1 5
2Engineering Information
This chapter contains Information to assist the user in using the
MICROMASTER 420 in the most efficient way.
Topics include connection details, derating factors and methods of protecting the
motor and inverter.
Examples are given to illustrate the use of the parameter list.
&RQWHQWV
2.1 Current Limit and Overload Operation ......................................................................8
2.1.1 Current Monitoring Accuracy.....................................................................................9
2.2 Fast Current Limit......................................................................................................9
2.3 Positive Temperature Coefficient Resistor Use.......................................................10
2.4 I2t Performance........................................................................................................10
2.5 Internal Overtemperature ........................................................................................10
2.6 Overvoltage and Trip Levels....................................................................................11
2.7 Boost........................................................................................................................11
2.8 Proportional and Integral Control (PI)......................................................................12
2.8.1 What is Closed Loop control?..................................................................................12
2.8.2 Implementation on MICROMASTER 420................................................................12
2.8.3 Setting up the PI controller ......................................................................................12
2.8.4 PI Setpoint ramp times............................................................................................14
2.8.5 PI Controller Proportional and Integral terms..........................................................14
2.8.6 Ziegler-Nichols method of Optimisation ..................................................................16
2.8.7 PI output limits.........................................................................................................18
2.8.8 Further features.......................................................................................................18
2.9 Braking.....................................................................................................................20
2.9.1 Normal Braking........................................................................................................20
2.9.2 DC Braking ..............................................................................................................20
2.9.3 Vdc Max Controller..................................................................................................21
2.9.4 Compound Braking..................................................................................................21
2.10 Derating Factors......................................................................................................22
2.10.1 Derating with Temperature......................................................................................22
2.10.2 Operation with Long Cables....................................................................................22
2.10.3 Derating with Altitude...............................................................................................24
2.10.4 Derating with Switching Frequency.........................................................................24
2.10.5 Derating for Sideways Installation...........................................................................25

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MICROMASTER 420 Reference Manual
6Issue A1
2.10.6 Derating with Single-Phase Input............................................................................25
2.11 Cubicle Calculations................................................................................................26
2.12 Thermal Protection and Automatic De-rating..........................................................26
2.13 Operation from Unearthed Supplies........................................................................27
2.14 Multi-Motor Connection ...........................................................................................27
2.15 Control Modes (P1300) ...........................................................................................27
2.15.1 Linear V/f Control.....................................................................................................27
2.15.2 Flux Current Control (FCC) .....................................................................................27
2.15.3 Quadratic V/f Control...............................................................................................27
2.15.4 Multi-point V/f Control..............................................................................................27
2.16 Working with Binary Connectors (BiCo)..................................................................28
2.16.1 Introduction..............................................................................................................28
2.16.2 How does BiCo work?.............................................................................................28
2.16.3 Using Control and Status Words with BiCo.............................................................30
2.16.4 BiCo Connections....................................................................................................31
2.17 Acoustic Noise.........................................................................................................35
2.18 Harmonic Currents ..................................................................................................36
2.19 Power Losses..........................................................................................................38

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MICROMASTER 420 Reference Manual
Issue A1 7
)LJXUHV
Figure 2-1 Current Limit Interaction.........................................................................................................8
Figure 2-2 PTC Resistor Connections..................................................................................................10
Figure 2-3 Boost Level...........................................................................................................................11
Figure 2-4 Quick response with overshoot: P2280 = 0.30; P2285 = 0.03 s..........................................14
Figure 2-5 Quick response with overshoot, but instability: P2280 = 0.55; P2285 = 0.03 s ....................15
Figure 2-6 Damped response: P2280 = 0.20; P2285 = 0.15 s...............................................................15
Figure 2-7 Response to 5 Hz step: L = 100 ms .....................................................................................16
Figure 2-8 Response to 5 Hz step: T = 700 ms .....................................................................................17
Figure 2-9 Step Response in PI control with P2280 = 9.84 and P2285 = 0.30......................................17
Figure 2-10 PI Basic Block Diagram........................................................................................................19
Figure 2-11 Frequency Ramp Down........................................................................................................20
Figure 2-12 DC Braking...........................................................................................................................20
Figure 2-13 Compound Braking...............................................................................................................21
Figure 2-14 Derating with Temperature...................................................................................................22
Figure 2-15 Derating with Altitude............................................................................................................24
Figure 2-16 Power Losses.......................................................................................................................38
7DEOHV
Table 2-1 Current Limit and Overload.....................................................................................................8
Table 2-2 Measured Current Monitoring Accuracy.................................................................................9
Table 2-3 Trip Levels............................................................................................................................11
Table 2-4 Maximum Cable Lengths......................................................................................................23
Table 2-5 Derating with Switching Frequencies....................................................................................25
Table 2-6 Cubicle Calculations.............................................................................................................26
Table 2-7 BiCo Connections (r0019 to r0054)......................................................................................31
Table 2-8 BiCo Connections (r0055 to r1119)......................................................................................32
Table 2-9 BiCo Connections (r1170 to r2050)......................................................................................33
Table 2-10 BiCo connections (r2053 to r2294).......................................................................................34
Table 2-11 Acoustic Test Results...........................................................................................................35
Table 2-12 Single Phase 230V Connection............................................................................................36
Table 2-13 Three Phase 230V Connection.............................................................................................36
Table 2-14 Three Phase 400V Connection.............................................................................................37

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MICROMASTER 420 Reference Manual
8Issue A1
2.1Current Limit and Overload Operation
The inverter will always protect itself, the motor and the system from possible
damage. Where a short circuit exists on the output of the inverter, the unit will trip
almost instantaneously to protect itself. In the event of short and/or long term
overload conditions, current limit facilities now operate very rapidly to reduce the
current and prevent a trip occurring. Table 2-1 describes the facilities available.
Table 2-1 Current Limit and Overload
(OHFWURQLF7ULS This is a very fast current limit, which operates if
there is a short circuit (line to line or line to earth) on
the output. It is a fixed level trip and operates within
a few microseconds.
2YHUORDG/LPLW This is a very fast limit, which operates within a few
microseconds and removes some of the output
pulses to limit the current and protect the inverter. If
this pulse dropping occurs during overload, the
operating condition will usually recover and the
motor will continue to run without tripping.
/RQJ7HUP2YHUORDG/LPLW This is a slower limit which allows an overload of at
least 60 seconds where the current lies above the
motor limit but below the Electronic Trip and
Overload Limit.
&RQWLQXRXV/LPLW This is the level set as the maximum continuous
motor current. The inverter will control the current to
this level after other overloads have timed out.
Figure 2-1 illustrates the interaction of the parameters associated with current limit.
The Read Only parameters r0027, r0034, r0037 and r0067 will help with fault
diagnosis.
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MICROMASTER 420 Reference Manual
Issue A1 9
2.1.1Current Monitoring Accuracy
The current display accuracy is typically +/- 2% of the measured current, but could
vary up to +/- 5%. Table 2-2 shows the sample results comparing the current
measured with a current scope, and the current displayed on the inverter, using
measurements taken from a variety of inverters at various switching frequencies,
current loads, frequency setpoints and cable lengths.
Table 2-2 Measured Current Monitoring Accuracy
Inverter FSA 230 V
750 W FSB 230 V 2.2 kW FSC 230 V 5.5 kW
Switching frequency 8 kHz 16 kHz 2 kHz
Load on inverter min. load 1.5 A max. load 12 A max. load 25 A
Frequency setpoint 45 Hz 25 Hz 10 Hz
Scope current (long cable) 1.5 A 12 A 23.0 A
Drive current (long cable) 1.6 A 11.9 A 23.3 A
% difference (inverter/scope) -2.3% 0.8% -1.2%
Scope current (short cable) 1.5 A 12 A 25 A
Drive current (short cable) 1.5 A 11.9 A 25.5 A
% difference (inverter/scope) 0.0% 0.8% -2.0%
2.2Fast Current Limit
Fast Current Limit (FCL) is a cycle by cycle hardware current limit built into the
inverter. The current is rapidly reduced by pulse dropping, that is by turning off the
Insulated Gate Bipolar Transistors (IGBTs) on a pulse by pulse (cycle by cycle)
basis. The normal current limit operation then takes over.
The FCL threshold is set slightly below the software overcurrent trip threshold and
reacts much quicker (i.e. in milliseconds), thus preventing spurious and unwanted
trips when sudden loads are applied or fast accelerations requested.
FCL is especially useful when working in open loop control to override unwanted
currents.

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MICROMASTER 420 Reference Manual
10 Issue A1
2.3Positive Temperature Coefficient Resistor Use
Many motors are available with a Positive Temperature Coefficient (PTC) resistor
built into the windings. The resistance of the resistor rises rapidly at a particular
temperature and this change can be detected by the inverter. If the resistor is
connected to the inverter terminals as shown in Figure 2-2, and the PTC input
enabled by setting parameter P087=001, then if the resistance rises above 2 kΩ,
the inverter will trip and Fault Code F004 displayed.
Most Motor Protection PTC resistors have a resistance of 2-300 ohms when cold
and this value rises rapidly at the ‘knee point’ to typically 10 kΩand greater. The
PTC input is set so that it will operate at 1 kΩminimum, 1.5 kΩnominal, and 2 kΩ
maximum. The input has considerable filtering because the PTC connection
usually carries considerable Electro Magnetic Interference (EMI). On this basis two
or three PTCs may be connected in series when a motor has more than one PTC
built in, or if two or three motors are connected to the inverter output and require
individual protection.
Inverter Control Terminals
Motor PTC 1 KΩ
8 5, 6 or 7 9
Figure 2-2 PTC Resistor Connections
2.4I2t Performance
When the motor is running at low speed and high load, the built-in cooling fan may
not provide enough cooling and the motor may overheat. Parameter P074 allows a
frequency dependent I2t limit to be enabled to protect the motor.
When the inverter is operating in the region above the selected curve (i.e. at low
frequency and high current), a timer is started, and after some time, (based on the
current, the motor size and previous operating history), the inverter will trip or
reduce output frequency. Trip or reduction of output frequency will depend on the
parameter setting.
2.5Internal Overtemperature
Under normal circumstances, the inverter will not overheat. A heatsink and fan
combine to maintain the inverter at normal operating temperature. Careful
consideration when mounting the inverter will ensure adequate ventilation and
reduce the likelihood of overheating. Check to see whether other units may restrict
airflow.
The heatsink temperature is monitored using a PTC resistor and the inverter will
trip if the maximum temperature is exceeded. If the inverter persistently trips, you
should check for high ambient temperature, a faulty fan, or blocked airflow.
You can verify the heatsink temperature by displaying Parameter r0037. Units are
given in degrees Celsius (oC). Removing a faulty fan is described in Chapter 6,
Maintenance.

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MICROMASTER 420 Reference Manual
Issue A1 11
2.6Overvoltage and Trip Levels
The inverter will protect itself from both supply overvoltage and undervoltage. Trip
levels are shown in Table 2-3. Internal overvoltage can occur during braking
where internal voltages are forced high by energy from an external load.
Table 2-3 Trip Levels
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1/3 Phase 230 V 205 V 410 V
3 Phase 400 V 410 V 820 V
When output pulses are disabled from the inverter an undervoltage trip will not
occur. An overvoltage trip will occur at any time when the overvoltage threshold is
exceeded.
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Check to ensure you have matched the input supply to the inverter. If the supply
voltage is too high, you may damage the inverter even if it trips.
2.7Boost
Boost is used to increase the output voltage in order to overcome losses and non-
linearity at low frequencies. If the correct amount of boost is applied, the current
and torque will be increased at low frequencies. However, if too much boost is
applied, the motor may overheat if run at low frequencies for a long time and
excessive boost may also saturate the motor, leading to loss of torque.
The I2t function helps protect the motor under these circumstances. Boost is
calculated such that 100% boost is the voltage given by:
Stator resistance (P0350) multiplied by rated motor current (P0305).
Which means that changing the value of these parameters will affect the boost
level.
Voltage
Frequency
Boost Increases
voltage here
Figure 2-3 Boost Level

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MICROMASTER 420 Reference Manual
12 Issue A1
3 This parameter sets the% boost applied at 0 Hz. The boost level is then
reduced with increasing frequency to a minimum value, set by P1316,
typically around about 10 Hz.
3 This parameter sets a boost voltage, as P1310, except that the boost is
applied only during acceleration, either following a start command or from
set point changes.
3 This parameter allows a constant linear boost, again as P1310, to be
applied following a start command only to improve ‘first time’ starting.
The maximum values of P1310, 1311,and 1312 are 250%, but the overall
maximum boost is limited by P0640, the motor overload setting. The boost voltage
will also be limited by the operation of the I2t function, so boost may be reduced
further if the motor is in danger of overheating. The progress of the I2t function can
be monitored by parameter r0034.
The default settings (P1310 = 50, P1311 and P1312 = 0) allow satisfactory
operation with most loads. Increasing the boost up to say 200% (note that P0640
setting will limit) on smaller motors and 100% on larger motors will often give
improved torque at low frequencies. Use P1311 and P1312 to limit this to
accelerating boost only (e.g. P1310 = 100, P1312 = 100), to reduce the possibility
of overheating.
2.8Proportional and Integral Control (PI)
2.8.1What is Closed Loop control?
Closed loop control is widely used in industrial applications to control a wide variety
of processes. Control engineering is a complex subject, but a simple closed loop
control uses a feedback signal from the process (such as temperature, pressure,
speed) a desired value or setpoint (often set manually) and a control system that
compares the two and derives an error signal. The error signal is then processed
and used to control the inverter and motor (in this case) to try to reduce the error.
The error signal processing can be very complex because of delays in the system.
The error signal is usually processed using a Proportional and Integral (PI)
controller whose parameters can be adjusted to optimize the performance and
stability of the system. Once a system is set up and stable, very efficient and
accurate control can be achieved. See Figure 2-10. Page 19.
2.8.2Implementation on MICROMASTER 420
The MICROMASTER 420 has a built in PI controller that can be enabled by the
user to allow closed loop control. Once the PI controller is enabled (using P2200),
the PI controller internally generates the motor frequency necessary to minimize
the error between the PI setpoint and the PI feedback. It does this by continuously
comparing the feedback signal with the setpoint and uses the PI controller to
determine the necessary motor frequency. The normal frequency setpoint (P1000
setting) and ramp times (P1120 & P1121) are automatically disabled but the
minimum and maximum output frequency settings (P1080 and P1082) remain
active.
2.8.3Setting up the PI controller
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The PI parameters are in the range between P2200 and P2294. For most
applications, the level 2 parameters are sufficient for setting up the PI controller.