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Table of Contents
Related Manuals for Elmo SSA Series
Summary of Contents for Elmo SSA Series
- Page 1 Rev 6/98 SSA - Rev 6/98...
- Page 2 Any interruption of the protective earth conductors inside the instrument, is likely to make the instrument dangerous. Components which are important for the safety of the instrument, may only be renewed by components obtained through Elmo service organization. Before switching...
- Page 3 How to use this manual - Flow Chart The SSA amplifier is designed for OEM applications. It enables the user to adjust the amplifier for various types of motors and to save valuable adjusting time in repetitive applications. Use the following flow chart in order to determine the chapters that you should read.
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Page 4: Table Of Contents
TABLE OF CONTENTS 1. DESCRIPTION.......................... 7 2. TYPE DESIGNATION ....................... 8 3. TECHNICAL SPECIFICATIONS....................8 4. OPERATION OF THE SERVO CONTROL................10 4.1 Inputs ....................................10 4.2 Velocity mode..................................11 4.2.1 Velocity control using armature voltage feedback.......................12 4.3 Current mode..................................12 4.4 Current loop..................................12 4.5 Current limits .................................12 4.5.1 Time dependent peak current limit..........................13 4.6 Protective functions.................................14... - Page 5 6.3 Load inductance................................21 6.4 DC power supply ................................21 6.5 Wiring diagrams................................23 7. START - UP PROCEDURES ....................28 7.1 Common procedures for all amplifiers types ......................... 28 7.1.1 Inhibit logic ................................28 7.1.2 Velocity mode................................30 7.1.3 Current mode................................30 7.1.4 Static current limits ..............................
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Page 6: Description
The SSA is a miniature PWM servo amplifier designed for DC servo motors. It utilizes power MOSFETs which contribute to its high efficiency and compact design. The SSA is constructed from two PCBs mounted on a heat sink plate. The lower board contains the power switching transistors which drive the motor, terminals for the power stage, the switch mode power supply and the protection logic. -
Page 7: Type Designation
SIB-SSA The SIB-SSA is an interface board for the SSA that is used to convert the SSA flat ribbon connector to spring type Phoenix terminals. This board has the same size as the SSA board and it can be assembled as an add-on card on top of any SSA amplifier or as a separate panel mount unit. - Page 8 * Outputs voltages of +13V, (15mA each) for external use. * Efficiency at rated current - 97%. * Drift: 10µV/° C (referred to input) * Operating temperature: 0-50 ° C. * Storage temperature: -10 - +70 ° C. SSA - Rev 6/98...
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Page 9: Operation Of The Servo Control
The SSA has 2 inputs: A single ended input (no.1) at terminal 1 and a differential input (no.2) at terminals 3,4. The current gain of input 1 (current mode) is given by: 66 x Ic Gc = ----------- (Amp/Volt), R1 in Kohm 100 + R1 Ic - amplifier rated continuous current The current gain of the differential input for R6=R7 (current mode) is given by:... -
Page 10: Velocity Mode
In this mode op amp U1/2 is employed as a high gain error amplifier. The amplifier sums velocity command and the tachogenerator feedback signal, and provides the necessary servo compensation and gain adjustments, resulting in stable, optimum servo operation. This op amp is configured with two feedback paths: One, in the form of a resistive T network, controls the DC gain of this amplifier. -
Page 11: Velocity Control Using Armature Voltage Feedback
The feedback element must be connected for negative feedback. The polarity of the SSA servo amplifiers is such that a positive input signal results in a negative voltage at terminal M1 with respect to terminal M2. Using the differential input amplifier to adjust its value, the armature voltage can be used as velocity feedback in all cases when low regulation ratio and low speed accuracy are acceptable. -
Page 12: Time Dependent Peak Current Limit
Each amplifier is factory calibrated to have this shape of voltage-current operating area with rated values of continuous and peak current limits. To adjust other values current limits, user calculate insert resistors (one for the continuous limit and one for the peak limit). In addition to these "static"... -
Page 13: Protective Functions
All the protective functions activate internal inhibit. If the cause of the inhibit disappears, amplifier will restart automatically. user monitor this function by checking terminal 12. The short circuit protection uses the capability of the power MOSFET to tolerate high energy peaks for short periods of time. This protection is realized by sensing current in the DC line. - Page 14 100K .01MF 100K 100K 4700PF 1000PF 100K 4700PF CONVERTER .01MF 100K CURRENT FEEDBACK POWER CURRENT LIMITS STAGE .01MF EXTERNAL IC LIMIT CONTROL (ECL IC) EXTERNAL IP LIMIT CONTROL (ECL IP) CURRENT MONITOR INHIBIT OUTPUT EXT. INH. LED PROTECTIONS EXT. Ic LED +13V -13V INHIBIT INPUT...
- Page 15 INH. SSA -CONTROL BOARD SSA - Rev 6/98...
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Page 16: Terminal Description
Power Stage Terminal Function Remark Power input positive Armature This output will be negative when a positive signal is output fed to one of the inputs. Armature This output will be positive when a positive signal is output fed to one of the inputs. Power input common... - Page 17 Control stage - Cont. Terminal Function Remark CCW disable Low level input voltage will disable half of the power bridge and rotation in one direction. Inhibit input level input voltage* will disable power bridge. See 7.1.1 for details Circuit common Inhibit indication Whenever the amplifier is inhibited, whether...
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Page 18: Terminals For Sib-Ssa
The numbering of the SIB-SSA terminals (1-16) is identical to the numbering of the SSA control board connector. CONNECTORS SSA WITH SIB-SSA CARD SSA - Rev 6/98... -
Page 19: Installation Procedures
Protection requirements in accordance with the most recent version of standard EN60204-1. The SSA series dissipates its heat by natural convection up to loads of 400W. For higher output load the amplifier should be mounted on an additional heatsink or cooled by fan. -
Page 20: Load Inductance
After wiring completed, carefully inspect conditions ensure tightness, good solder joints etc. A reliable connection with the spring type connectors (on the SIB-SSA) is achieved with wires of 0.5mm 2 (AWG 20) stripped to a length of 11mm (.043"). The total load inductance must be sufficient to keep the current ripple within the limits (10%-20% of rated current is recommended). - Page 21 1.2V dcmin < Vdc < 0.9V dcmax V dcmin - Minimum DC bus in the table of chapter 3 V dcmax - Maximum DC bus in the table of chapter 3 Recommended minimum power supply capacitance for single phase connection: 5600 µF For SSA-12/55 3300 µF...
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Page 22: Wiring Diagrams
Motor Chassis Minimum acceptance ============================================================= Power wires twisted together Motor Chassis Acceptable for most applications ============================================================ Power wires twisted and shielded Motor Chassis Optimum wiring, minimum RFI SSA - Rev 6/98... - Page 23 Isolating transformer PS/S DC power common is internally connected to control common * Heat sink Heatsink Guide lines for connecting a non isolated amplifier with an isolating power transformer Ground: DC power common Motor chassis Amplifier's heat sink Do not ground: Control common - It is internally connected to the power common.
- Page 24 PS/S DC power common Control common Heatsink DC power common To additional SSAs Control common Heatsink CONNECTING MORE THAN ONE SSA All rules about supply connections described in the previous page are also valid for multi-SSA connection. SSA - Rev 6/98...
- Page 25 Tacho Motor command External continuous current limit External peak current limit Current monitor CW disable CCW disable Twisted and shielded pair Inhibit input Inhibit output -13V +13V SSA CONTROL CONNECTIONS TACHOGENERATOR FEEDBACK SSA - Rev 6/98...
- Page 26 Motor command ARMATURE FEEDBACK External continuous current limit External peak current limit Current monitor CW disable CCW disable Twisted and shielded pair Inhibit input Inhibit output -13V +13V SSA CONTROL CONNECTIONS ARMATURE VOLTAGE FEEDBACK SSA - Rev 6/98...
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Page 27: Start - Up Procedures
All the operations of this chapter do not require to power on the unit. The steps of paragraph 7.1 must be performed before proceeding to the appropriate feedback sensor. Select the desired Inhibit logic you need: a) Disable by Low Inhibit function will be activated by connecting its input (terminal 10) to a low level signal. - Page 28 The power of Rex is given by: P = ----- (Watt) +13V INHIBIT INPUT Rex=1.2K, 0.25W INHIBIT INPUT Signal from external source SSA ENABLED BY ACTIVE HIGH OR CLOSED CONTACT SSA - Rev 6/98...
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Page 29: Velocity Mode
To operate in velocity mode the velocity loop should be enabled by converting the error amplifier to a high gain PI amplifier. Make sure that R11 (30 ohm),R12 (475Kohm) and C3 (0.022µF) are installed on the board (in solderless terminals). a) Converting the amplifier into current mode To operate in current mode the velocity loop should be disabled by converting the error amplifier to a low gain proportional amplifier. -
Page 30: Static Current Limits
The amplifiers' current limits can be adjusted statically (without load) by inserting fix resistors on the logic board. The current limits are factory adjusted to the amplifier's rated values. Reducing the nominal limits is performed as follows: a) Continuous current limit adjustment R40 should be calculated and inserted as follows: Ic(new) Q = ---------... -
Page 31: Velocity Control Using Tachogenerator Feedback
When using tacho feedback, it is recommended to use the single ended input for the tacho signal and to use the differential input for the reference signal in order to reduce common mode noises. For tacho voltage at maximum application speed higher than 5V: R1 = 20xVtm - 100 (Kohm) (R1 >... - Page 32 The velocity loop is closed by connecting the following terminals: Terminal M1 to terminal 4. Terminal M2 to terminal 3. The reference signal is fed to input 1 and R1 should be calculated as follows: K = ----- Vam - armature voltage at maximum application speed R1 = 20xV1mxK - 100 (Kohm) V1m - maximum reference voltage at input 1.
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Page 33: Amplifier Adjustment And Diagnostics
Important remarks: A. If all the previous steps were accomplished you may now turn the power on and continue with the following adjustments. You may skip the step for current mode or velocity mode according to your application. B. In some applications, especially those where the motor electrical parameters (total inductance and resistance in the armature circuit) are much smaller or larger than normally encountered, the current loop response should be optimized before proceeding with the following steps - See Appendix A. -
Page 34: External Current Limit (Ecl) Adjustment
If you do not use this feature, skip this chapter. The amplifiers' static current limits can be scaled down dynamically by two external voltage signals. a) ECL function on continuous current limit: V5 x Ic(nom) Ic = --------------- V5 - voltage applied at terminal 5. Voltages between 0 to 3V will control continuous current limit from zero to Ic(nom) or Ic(new) as set in the static adjustment. -
Page 35: Response Adjustment (Velocity Mode Only)
In most applications optimum response is achieved by adjusting the compensation (COMP) trimmer. Adjustment procedure is as follows: - Provide the amplifier with a low frequency, bi-directional square wave velocity command (A 0.5Hz, ±2V waveform is often employed). - Apply power to the amplifier, and while monitoring the tachometer signal, gradually adjust the COMP trimmer from the CCW toward the CW position. - Page 36 - If the previous step does not yield satisfactory results, if unacceptable overshooting has been noted, substitute a larger value than 0.033 µF; or, if the response is overdamped substitute a smaller value than 0.033 µF. Repetition of this procedure should yield an optimum choice for C3. Reference input signal Overdamped: T1 too far CW Critically damped: T1 optimum...
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Page 37: Tables And Summaries
Two trimmers are installed on the upper board of the amplifier with the following functions: T1 (compensation) - see 8.5. T2 (balance) - See 8.1. Three LEDs are installed on the upper board of the amplifier with the following designations: Ic, In, Vs. Under normal operation only Vs should illuminate (Vs indicates the existence of supply voltages). -
Page 38: Appendix A - Response Adjustment - Current Loop
In most applications it is not necessary to adjust the current loop to achieve optimum response. When there extreme electrical parameters armature circuit (inductance and resistance) the standard components values of 0.01µF for C11 and 100Kohm for R20 may not yield with the optimum response. The current loop should be optimized as follows: - Turn the amplifier to a current amplifier by removing R11 and R12. - Page 39 Reference input signal C11 too large / R20 too small Critically damped C11 too small / R20 too large Fig. A-1 Typical current response waveforms SSA - Rev 6/98...
- Page 40 SSA - Rev 6/98...
- Page 41 TOP VIEW SIDE VIEW 2.7 x 4 CONTROL CONNECTOR POWER CONNECTOR 93.5 CONTROL CONNECTOR 24.5 POWER 34.5 CONNECTOR ALL DIMENSIONS ARE IN mm. SSA - Rev 6/98...
- Page 42 2.7 x 4 SIB OPTION SSA WITH SIB-SSA CARD SIB OPTION 80.2 3 x 2 SSA WITH RIGHT ANGLE MOUNTING LEGS SSA - Rev 6/98...
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Page 43: Service Centers And Warranty
If any term or condition in this warranty performance shall be at variance or inconsistent with any provision or condition (whether special or general) contained or referred to in the Terms and Conditions of Sales set out at the back of Elmo's Standard Acknowledge Form, than the later shall prevail and be effective.
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