Download TECHNICAL DESCRIPTION

TECHNICAL DESCRIPTION
PULSE WIDTH MODULATED
4-QUADRANT SERVO-CONTROLLER
TYPE
TRA
IMPORTANT!
* It is of vital importance that you read the technical description before starting-up
* Protect the unit from aggressive and electrically conductive media. They could
cause malfunction and/or destroy the unit!
* Do not touch any life parts. Danger to life!
* Installation, connection and starting-up may only be carried out by an expert subject
to all relevant safety regulations.
* Assured properties and functions of the unit are only guaranteed when expertly
handled.
* Tamperings and modifications that have not been expressly authorized by us, as well
as any non-authorized use result in the exclusion of any guarantee and liability.
* Basis for any legal business with us are our "Allgemeine Gesch‰ftsbedingungen "
(General Terms of Business).
* All documentations, drawings, diagrams etc. are subject to copyright terms. Any use,
duplication, forwarding, processing and alteration without our explicit consent is
prohibited.
Table of Contents
Page
1. Technical Description
1.1 General introduction
1.2 Model overview
1.3 Technical data
1.4 Control principle
1.5 Description of function
1.6 Block diagram
1.7 Overview setting possibilities / displays
1.8 Front view
4
4
4
5
6
7
9
10
11
2. Connecting the Unit
2.1 Plug wiring
2.2 Explanation of plug wiring
2.3 Proper polarity of motor and tachometer
2.4 Input monitoring circuit
2.5 Connection diagram (proposal)
2.6 Running of wires
12
12
13
14
15
16
17
3. Starting-up
3.1 Presettings
3.2 Setting of pulse and effective current
3.3 Tachometer adaptation
3.4 EMK and IxR compensation
3.5 Offset-rectification
17
17
18
18
18
19
4. Optimizing the control behaviour
4.1 Amplification of alternating voltage
4.2 Amplification of direct voltage
4.3 Tachometer screening
4.4 Integral part of speed controller
19
19
19
19
20
Appendix: Line-up diagrams
Basic printed circuit board TRA
Speed control module TRA-D
1.
Technical Description
1.1
General Introduction
4-Quadrant Servo-Controller for 2 motor axes
The units of the TRA-construction series consist of 2 independent servo-controllers for
permanently energized DC motors which are operated on the same intermediate circuit.
Both controllers as well as the mutual grid system part and a combinational circuit part
for the supply of the electronic for both axes are on a double Europe card. This way
very economic solutions in view of expense, space and energy requirements are
possible. The application possibilities comprise mainly those in need of two or more
axles, that means e.g. X-Y-drives or coiling automatons. The unit can be supplied only
as a current controller, or by adding a plug module also as a speed controller with tacho
return circuit and/or EMK / IxR-control. The use of SMD-technique and powerMOSFETs guarantees good efficiency and a compact construction. The installation
width is only 8 TE.
The units dispose of a short-circuit and earth fault protection as well as of all standard
control, protection and supervision possibilities. Nominal voltages of 60 V and 120 V
each and nominal currents of 6A and 12A can be realized. For acceleration and braking
purposes, the 2.5-fold pulse current is for about 3 seconds at disposal.
1.2
Model overview
Designation
of unit
TRAS60/6DD
TRA60/12DD
TRA120/5DD
TRA120/10DD
TRAB48/12DD
nominal output
voltage
60V
60V
120V
120V
48V
nominal
current
6A
12A
5A
10A
12A
pulse
current
15A
30A
10A
20A
30A
minimum load fuses
inductivity
0,8 mH
16A
0,4 mH
25A
1,6 mH
16A
0,8 mH
25A
0,4 mH
25A
All units can also be obtained as current controllers only. Then the designation changes
from TRA...DD to TRA...DS. The first "D" stands for double controller, the second for
speed controller and/or with "S" for current controller.
Recommended transformer voltages for nominal operation:
(effective values under consideration of + 5% no-load/full load and +10 % mains overvoltage)
TRA60/6D..
TA60/12D..
TRA120/5D..
TRA120/10D..
52 V, 3~AC/ 9 A
52 V, 3~AC/ 18 A
95 V, 3~AC/ 7,5 A
95 V, 3~AC/ 15 A
1.3
Technical Data
* minimum intermediate circuit voltage
* maximum intermediate circuit voltage
* stroke frequency of output stage
* frequency of current ripples
* frequency-range of subordinated current controller
* maximum input drift
* minimum load inductivity
* over-all efficiency appr.
* output current shaping factor
(30) 60
(85) 170
9
18
1
± 21
see model survey
93
Error!
Bookmark
not defined.
1,001
VDC
VDC
KHz
KHz
KHz
µV/∞C
%
(with min. load inductivity with nominal current and voltage)
* voltage range of differential input
* internal resistance of rated value input
* input attenuation via resistor RE
* voltage range of tachometer inputs
± 10
20
0-100
V
KOhm
%
14,5 - 86
7,25 - 43
3,4 - 20,2
/ 50
/100
/ 50
= 10
V
V
V
mA
mA
mA
%
(with Usoll = ±10 V and nominal speed)
with RE = 20 KOhm
with RE = 10 KOhm
with RE = 3,3 KOhm
* auxiliary voltage for add. external circuits
* ready-for-operation pilot relay
* I2T message (open-collector-output)
* anchor current monitor (output)
±15 V
max.100V
± 15 V
1V
(of the unit specific pulse current)
* enable (input) active at
Available Options
* Front plate
* ballast circuit
* bus PCBs
* current control
12 V - 35
V
1.4
Control Principle
Servo-controllers TRA operate on the principle of speed control with a subordinated
current control circuit. The signal flow chart of this control principle is illustrated in the
following diagram:
The current control circuit consists of a current controller and of the amplifier output
stage. The respective actual current value is determined at the output of the output
stage and fed back to the point of summation. The speed controller supplies the
nominal current value. (*) Nominal and actual values are compared and the difference
is fed to the current controller.
The superordinated speed control circuit consists of a speed controller, a current
control circuit and a motor/tachometer combination. The nominal speed value is
externally preset by the user, like e.g. by potentiometer, NC-control. The actual speed
value is determined directly on the motor shaft, e.g. by a tacho alternator, and is
compared on the first point of summation with the nominal speed value. The difference
getting known this way is the input regulated quantity of the speed controller. It shapes
from the control difference the required nominal current value.
The advantage of this control principle is that a very stable control behaviour is
achieved as the subordinated current controller can react quickly to disturbance
variables and relieves such the speed controller. In addition, current limitations required
for the protection of motor and amplifier, can be realized in a simple way only by limiting
the output voltage of the speed controller (nominal current value).
(*) In some applications a superordinated position control circuit already takes care of the
speed control. Therefore the TRA can be modified in such a way that it works only as current
controller - please consult our technicians in case of demand.
1.5
Description of Functions with Block Diagram
a. Voltage supply
The functions of the amplifier are explained by way of a block circuit diagram (see page
9). The first block concerns rectification and screening. In this part of the circuit, the
required direct voltage UCC (intermediate circuit voltage) which is required for operating
the unit, is generated from the alternating voltage supply.
With this voltage the output stage is supplied and it is used at the same time for
generating the auxiliary voltage Error! Bookmark not defined. 15 V by means of the
circuit power supply required for the supply of the control part.
b. Control part
The nominal speed value is fed to the differential input and can be preset by means of
RE (see page 22) in different areas. For obtaining the actual speed value there are two
possibilities:
1. with the aid of a tacho-alternator
The output voltage of the tacho-alternator is conducted to a RC-member (smoothing of
tachometer voltage). With the fixed resistor RE tacho-alternators of different EMK are
adapted to the control.
2. with the "EMK"- and IxR-compensation
In this case a part of the armature voltage of the motor which is measured with the UAmeasuring circuit, is used as actual speed value. In addition, with the IxR-compensation
the current proportional voltage drop on the internal resistance of the motor can be
balanced.
By means of the two soldering bridges tacho/IxR (right and left below the plug module
TRA-D) must be chosen how the actual speed value is entered. In the factory the
corresponding soldering bridges are set to tacho operation (see page 22).
At summation point SP1 nominal and actual speed values are compared. The control
difference is amplified from the PI-speed controller with the related counter-coupling
power supply and the control deviation is balanced to O. The starting regulated quantity
of the speed controller is the nominal current value (SP 2). Here engage also all current
limitations:
- effective current limitation
The actual armature current value is fed to this circuit, quadrated there and filtered with
a subsequent low-pass, with the time constant T = 8,2 s. The actual effective current
value obtained this way is compared with an adjustable nominal value. If the two values
are approaching, the circuit reduces the nominal current value required from the control
so far that there is no further rise of the actual effective current value.
- internal limitation of nominal current value with P1a (P1b)
This current limitation is subsequently added to all limitations. That means that the
pulse current set on P1 can on no account be exceeded.
The limited nominal current value is fed to summation point SP3. The actual current
value still missing for a nominal/actual-comparison is measured by the armature current
measuring circuit and fed to summation point SP3 as well.
The current controller generates from the comparison of nominal and actual current
value the regulated quantity for the 4-quadrant output stage. The current controller is a
PI-controller with a proportional amplification K p = 3,12 and a resetting time of TN =
1ms. As this is an impulse generated controller, the continuous regulated quantity must
be transformed to a pulse width modulated signal. This occurs in the pulse width
modulator in which the regulated quantity is modulated with a triangle voltage of the
frequency 9 KHz, and out of which the signals for the driver stage are shaped.
By a special modulation principle one obtains a doubling of the current flow frequency
(18 KHz) which ensures a low noise operation.
Because transistors switch on faster than they switch off, it is necessary to delay the
switch-on-signals a little in order to prevent that two quadrants of the output stage are
conducting at the same time. This signal delay is realized in the dead time formation.
c. Driver and Output Stage
The driver stage amplifies the signals coming from the pulse width modulator. It is
designed for an optimum approach of the output stage. This ensures for any kind of
operation a loss-free and safe operation of the output stage, its MOSFET-switch
transforming the signals which are placed at disposal from the driver stage, into power.
1.6
Blockdiagram TRA
1.7
Survey of Displays and Setting Possibilities
LED 1 (green) :
Indicates operating condition of unit. Shines also when amplifier is
switched to "Disable".
LED 2 (red):
Shines in case of trouble (overvoltage, excess current and/or
excess temperature); after this LED has started shining the
amplifier can only be reactivated by switching it off and then on
again.
LED 3 (yellow):
Effective current limitation (I2 t), amplifier A, shines after expiration
of the pulse current phase.
LED 4 (yellow):
Same function as LED 3, but for amplifier B.
Amplifier A:
Potentiometer 1A:
Potentiometer 2A:
Potentiometer 5A:
Potentiometer 6A:
Potentiometer 7A:
Potentiometer 8A:
Pulse current limitation setting range 10-100% of the unit specific
pulse current
effective current limit value, setting range 0 - 100% of the unit
specific effective current
voltage divider for tachometer input
offset balance of speed controller
alternating voltage amplifier of speed controller
EMK-potentiometer, control by means of fed back motor voltage
(setting range 1: 4,3)
Amplifier B:
The potentiometers of amplifier "B" have the same functions as
amplifier "A". In addition they bear the letter "B".
Please note:
The potentiometers P5A-P8A and P5B-P8B are on the plug
module "TRA-D" (speed control). When the unit is used as a
current controller these potentiometers do not exist.
1.8
Front View
2.
Connecting the Unit
2.1
Plug Wiring
ST2 Signal Plug DIN 41612-D32
------------------------------------------------------
2a
2c
4 a,c
6a
6c
8a
8c
10 a
10 c
12 a
12 c
14 a
14 c
16 a
16 c
18 a
18 c
20 a
20 c
22 a
22 c
24 a,c
26 a
26 c
28 a
28 c
30 a,c
32 a
input A (+)
input A (-)
0V
IA - monitor A
UA - monitor A
0V
I2t-message A
tacho A (+)
tacho A (-)
0V
+ 15 V
0V
- 15 V
tacho B (+)
tacho B (-)
+ 15 V
enable A
+ 15 V
enable B
input B (+)
input B (-)
0V
IA-monitor B
UA-monitor B
0V
I2t-message B
NC (not occupied)
ready for operation (potentialfree reed contact)
32c
ready for operation (for both
axles together)
ST1 Power Plug H15 DIN 41612
--------------------------------------------
4
6
8
10
motor B (+)
motor B (-)
motor A (+)
motor A (-)
12
14 0 Volt mass
16
18
20 AC-supply
22 AC-supply (with three-phase
24 current only)
26
28 AC-supply
30
32 + UCC
2.2. Explanation of Plug Wiring
References for amplifier B are in square brackets.
Mass: = 0 V reference potential.
ST2 Signal Plug D32
Auxiliary voltage Error! Bookmark not defined.15 V (12 c - 14 c)
At clamp 12c an auxiliary voltage of + 15 V and on clamp 14 c of -15 V for external
consumers with a power input of max. 50 mA are at disposal.
Nominal Value Input (2a - 2c) [22a - 22 c]
Input of differential amplifiers for presetting the nominal speed value. The maximum
differential voltage may be Ò 10 V. Clamp 2a [22a] acts positively towards clamp 2c
[22c].
Tacho Input (10a - 10c) [16a - 16c])
Input for connecting DC-tacho alternators for return message of speed. For nominal
speed with a nominal value of 10 V the tacho voltage should be at least 3,5 V and not
more than 86 V. The ranges must be determined with the fixed resistor RE (see page
18).
Enable (Release of Output Stage) (18c) [20c]
For standard operation this connection must be connected with a voltage between 12
and 35 V. With a voltage below 4 V and with an open input this output stage is
"disabled" and the motor is not energized. The range between 4 V and 12 V is not
defined.
Anchor Current Monitor (6a) [26a]
These outputs dispose of a current proportional analogous signal which can be
externally evaluated. The maximum voltage with a unit specific pulse current is Ò 10 V.
Anchor Voltage Monitor 6 c [26c]
These outputs supply a voltage proportional to the anchor voltage of the motor. The 60
V-units have a monitor with standard 6 V at 60 V EMK. The monitor of 120V-units
supplies 10 V at 120 V EMK.
Relay contact "Ready for Operation" (32a - 32c)
Potential-free relay contact indicating that the unit is ready for operation. This contact is
closed when the unit is ready for operation and is not influenced by the enable-function.
In case of trouble (LED 2 shines), the contact is open. This function exists only one
time, that means it is controlled by both axles together.
ST1 Power Plug H15
Motor connections (8 and 10) [4 and 6]
These are the output clamps of the output stages to which the motors are connected.
Trafo Connections (18/20 - 22/24 - 26/28)
The secondary connections of the transformer are connected to these contacts. These
connections must be secured externally. When using a single-phase transformer,
connections 18/20 and 26/28 must be used. Attention must be paid that the transformer
connections are connected to the respective two contacts.
When using an extremely low-resistance transformer (e.g. with parallel connection of
several axles) a cutting-in current limiter might be necessary in order not the destroy the
rectifier diodes.
Connections UCC (30,32)
O Volt (12,14,16)
These connections are either used for an external ballast circuit (available as option) or
if a direct voltage supply is requested.
2.3 Proper Polarity of Motor and Tachometer
If one turns - while the unit is switched off - the motor shaft by hand in the direction
defined as positive, then on clamps 8 [4] a positive voltage must be measurable
compared with clamps 10 [6].
Further the tacho voltage on clamp 10 a [16a] must be positive compared with clamp 10
c [16c]. If the polarity of motor or tachometer is not correct, the corresponding
connection lines must be interchanged.
2.4
Input Monitoring Circuit
2.5
Connection Diagram (Proposal)
2.6
Running of Wires
In order to prevent function trouble or subsequent damage in case of mass or ground
leaks, motor housing and the cores of possibly existing external storage coils must be
ground lowly resistive against the power mass (ST1/12,14,16).
When not observing this regulation, there can be heavy damage on all amplifier
construction groups and on the control in case of mass leaks on the output, if this is
operating on earth potential.
Control and servo-amplifier must lie on the same potential (mostly earth potential). If the
control (e.g. a simple battery box) is not self-ground, the screening of the control cable
for the potential balance may be used; the screen is then connected to the servoamplifier and to the control box. With ground control, the screen of the control line must
only be connected to the control and not to the amplifier.
The lines of an input (+ and -) must both be conducted in the same cable right up to the
control. Referring one of the two control input lines to the 0 V potential on the servoamplifier, nullifies the advantages of the differential input and can lead to trouble. The
screen of the tacho-line must only be ground to the amplifier. The tacho-alternator itself
must only be connected or ground to the provided input clamps and nowhere else.
Long motor lines must consist of a 2-wired separate cable for each motor. For special
requirements concerning immunity from interference, a screened cable can be used;
the screen must be connected to the minus pole of the DC-intermediate circuit. If the
motor housing has no further earth connection, the screen can be used instead of a
separate earth circuit. The result is a construction with an especially low interference
rate.
3.
Starting up
3.1
Presetting
Please check the wiring carefully and compare all connections according to the plug
wiring on page 12. All units have of course been tested and have been preset with the
nominal data before leaving our works.
If you might not be able to totally exclude wiring faults, we recommend to proceed as
following in order to prevent damage on motor and machine:
* Set rated value input to 0, or short-circuit the input
* set tacho poti P5A [P5B] to left-hand stop
* set amplifier poti P7A [P7B] to left-hand-stop
* pulse-current poti P1A [P1B] to about 1/3 from left-hand stop
* effective current poti P2A [P2B] to about 1/3 from left-hand stop
Are the soldering bridges set to the requested mode of operation? (see page 22). When
you now switch on the motor it must develop a holding torque and may drift just a little.
If the motor runs off uncontrolled please switch it off immediately and check again the
tacho-circuit in view of wrong polarity, short-circuit or line interruption.
If now small rated values are preset, the motor must follow them.
3.2
Setting of Pulse and Effective Current
For a precise setting of the pulse current, either the nominal value O V can be preset
and the motor manually turned out of the zero position, or the motor blocks and a
constant nominal value can be preset. Then the potentiometer P1A [P1B] must be set
to the requested pulse current. If the I2t-current limit actuates, the Enable-input must be
opened for about 20 seconds for the unit to regenerate; after closing it again, the
setting can be continued.
After the expiration of the pulse current phase, the current is automatically reduced to
the effective current, which can be set on P2A [P2B]. When setting the P2A [P2B]
always proceed in portions and without hesitation. After a short time of adaptation in
which the current is either O or IIMP, the new permanent current is flowing.
Please note:
For measuring the set current, the motor can be replaced by an ammeter with suitable
measuring range. The required minimum load inductivity (see table page 4) must
however be ensured, if necessary by coils.
3.3
Tachometer Adaptation
In the factory the units are equipped with a tachometer supplying 6 V / 1000 r.p.m. and
adjusted to a motor speed of 3.000 r.p.m.
For setting the maximum speed, a nominal value of 10 V, or a certain percentage of
this, is put on the nominal value input. With the tacho poti P5A [P5B] then the
requested final speed, or the same percentage like with the nominal value is adjusted. If
the speed cannot be adjusted in the requested range this way, then another tacho
voltage range must be selected by changing the resistor RE. The line-up place of the
RE can be found on page 22.
Tacho voltage range
14,5 - 86 V
7,25 - 43 V
3,4 - 20 V
values for RE
20 KOhm
10 KOhm
4,7 KOhm
If the speed is too high, RE must be reduced and reversed. From the manufacturer a
value of 20 KOhm has been soldered into the RE.
3.4
EMK and IxR-Compensation
If there is no tacho-alternator for speed control at disposal, then the soldering bridge
"Tacho/EMK" (see page 22) must be resoldered to "EMK" as shown in the diagram. In
this case it is possible to set the requested maximum speed with a nominal value
presetting of 10 V with the EMK-potentiometer P8A [P8B].
If additionally an IxR-compensation is requested, then this can be carried out by
soldering-in a respective resistance RxA [RxB] (see page 22). The IxR-compensation
effects an increase of the output voltage, which compensates proportionally to the
current input the voltage drop on the internal motor resistance and thus counteracts to
the speed drop with increasing load. The size of the resistance RX to be soldered in
depends on the internal resistance of the motor, but also on the ratio of nominal motor
voltage and nominal amplifier voltage.
For an optimum setting of the IxR-compensation start/stop-impulses are preset and the
braking behaviour of the motor is observed. The correct value for RxA [RxB] is easiest
determined by connecting a resistance decade which is clamped to the RXconnections. One starts with a low-resistance setting, e.g. 1 KÍ and increases the
resistance value for so long until the requested step function response is achieved.
When braking, the motor should reach the new nominal speed value after overshooting
once or twice. If no overshooting can be detected, RX must be increased. If the
overshooting lasts too long or is too strong, RX must be reduced.
3.5
Offset-Rectification
After all preceding settings have been carried out, there is still the offset-rectification to
be performed. For this purpose, again the rated value 0 Volt is preset and any possible
drifting off of the motor shaft is prevented with P2.
For a more precise setting of the offset, the tachometer voltage can be measured on
clamps 10a [16a] and 10c [16c] with a voltmeter (switch to smallest measuring range)
and balanced to 0 Volt.
4.
Optimizing the Control Behaviour
4.1
Amplification of Alternating Voltage
In most applications an optimizing is limited to setting the alternating voltage amplifier
(gain) on potentiometer P7A [P7B]. For this purpose couple the motor to the load and
preset a rated value of 0 V. Turn potentiometer P7A [P7B] to the right until the
oscillation starts and then turn immediately to the left until you find the point where it
stops again.
4.2
Amplification of Direct Voltage
Especially with a superordinated position control circuit, a precisely defined static rigidity
is often requested. For changing this rigidity, the resistance RP-A [RP-B] (appr. 330
Ohm) is provided (see page 22). The rigidity lessens with increasing resistance. The
static rigidity must not be confused with the dynamic rigidity which can be set on P7A
[P7B] (amplification of alternating voltage).
4.3
Tachometer Screening
For filtering the tachometer signal, the capacitor CT-A [CT-B] has been provided with
appr. 47 n F (see page 22). This capacitor must additionally limit the control range in
such a way that there is no oscillation by torsion resonances. If the motor causes
howling sounds which cannot be removed by means of the amplifier potentiometer P7,
then such an oscillation by torsion resonance is the case. For its suppression the
capacitor CT must be increased stepwise until the motor is running quietly. Increasing it
above that point, unnecessarily worsens the dynamic control behaviour (overshooting).
4.4
Integral Part of Speed Controller
For the integral part of the speed controller, the capacitor CI-A [CI-B] with appr. 100 nF
is competent (see page 22).
The requirements in view of the dynamic of the amplifiers clearly differ when operating
them as speed controllers from those required when there is a superordinated position
controller at hand.
In the first case, the rigidity must be produced by the speed controller, which is why its
integral amplification must be as big as possible (CI must be small), whereby a brief
overshooting is mostly permitted. Contrary to this, in an operation with a superordinated
position controller the rigidity is produced by the controller. The important factor here is
the biggest possible bandwidth of the servo-amplifier, whereby the integral amplification
can be much lower than in the first case. The capacitor CI must be enlarged for this.
The overshooting of the amplifier without position control gets less this way, the braking
time until standstill of the motor takes, however, a little longer.
Basic Printed Circuit Board PC-TRA
Speed Control Module TRA-D