Category Archives: Control Techniques

AC or DC Drives Comparison: Which is best for you?

AC or DC Drives Comparison: Which is best for you?

AC Drives:

An AC drive stands for Alternating Current, but could also be referred to as an adjustable speed drive, adjustable frequency drive, variable frequency drive, variable speed drive, frequency converter, inverters and a power converter. Typically, they are used to control the speed of an electric motor in order to enhance the operation of numerous applications relying on electric motors, minimize mechanical stress on motor control applications, generate energy as efficiently as possible, cut down on energy usage and, lastly, optimize process control.

Also known as adjustable speed drives, inverters and power converters, adjustable frequency drives, and variable speed drives, AC drives are similar to  DC drives because an AC input is regulated to DC by simple bridge rectifiers, commonly referred to as SCRs. Because AC drives use a capacitor bank to stabilize and smooth this DC voltage, the DC output would be half cycle according to AC input phase frequency. Then, power is supplied to the motor in the output section of the drive by means of 6 output transistor or IGBT modules. Essentially, the AC input current is converted by the drive to DC and, again, converted back to AC in order to supply the motor. The current is converted twice by the drive because the AC input is either 50 or 60-hertz cycles. When the DC voltage is converted to AC again by the drive, it uses a carrier frequency of at least 2 KHZ to 100 KHZ in more complex drives. Therefore, the output current is able to be raised tens or hundreds of times without burning up the motor coil.

The AC motor is also able to rapidly switch speeds with zero problems because of this function. AC drives typically have numerous types of feedbacks from simple, 2-line incremental encoders, to resolvers or absolute encoders with a significant resolution that facilitates the drive to calculate motor shaft speed and angle as spot-on as possible. There is a third circuit called regeneration on a handful of larger, more powerful drives. This circuit converts the inertia of the load and motor to AC power and transfers it back to the input lines when the motor transitions from a significantly high speed to a low one, which, in the long run, would conserve on power and increase energy efficiency.

AC or DC Drives Comparison


AC drives serve many different industrial and commercial applications.

DC Drives:

Essentially, a DC drive converts an AC drive into direct current, otherwise known as DC to operate a DC motor. The majority of DC drives use a handful of thyristors (also known as SCR’s) to craft a half cycle of DC output from a single phase AC input, also known as the half-bridge method. The more complex ones use up to 6 SCR’s to power a DC output from a 3 phase AC input, which is known as the full-bridge. Therefore, in the full-bridge method, we have 2 SCR’s for every input phase. The aspects of a DC drive are as follows: compact in size, outstanding speed regulation, broad speed range, cost-effective for medium and high HP applications, and speed changes that are derived from by increasing or decreasing the amount of DC voltage the drive feeds the motor.

Controlled by the gate input, an SCR switch is similar to a one direction switch and turns on by applying a low voltage to the gates. The drive can control the motor speed by applying the voltage to the gate at a contrasting angle of the input phase. To authenticate the motor speed and compensate if necessary, the majority of DC drives require the motor to have a tachometer as means of feedback. A tachometer is essentially a mini permanent magnet DC motor accompanied by the main motor’s shaft.

Because higher motor speed generates more voltage in the tachometer, the drive references this voltage to ensure the motor is operating at a correct speed per-user settings. More compact DC motors have a permanent magnet field while larger DC motors have a separate coil inside the motor, also known as a field, which eliminates the need for a permanent magnet in the motor. DC drives with field output typically have a more compact circuit to supply the field coil. DC drives are best used in when a DC motor exists in a safe and dry atmosphere and the use of DPG, DPG-FV, TENV, or TEFC motor enclosures is required, motor speeds are able to reach 2500 RPM, application requirements are medium or large, and starting torque is either unpredictable or greater than 150%.


AC or DC Drives Comparison:


DC drives are commonly considered problematic, despite their prestige for having simple circuits, providing high start-up torque, and being ideal for applications with constant speed due to the requirement of commutators and brush assemblies in their motors. These motors can become worn over time, have operational issues, and will likely require labor to preserve.

On the opposite side of the spectrum, AC drives are considered more energy-friendly and are able to endure rapid speed changes more efficiently due to their running induction motors. Often times, they have hundreds of numerous programmable parameters for secure protection. Although, because of these factors, the AC drive is more complex, modernized software is simplifying their overall use.

In previous years, DC drives were regularly utilized due to their simplicity, the majority of machine manufacturers prefer to use AC drives as of late. The complexity of an AC drive has been repeatedly simplified and fine-tuned, resulting in a plethora of advantages.

Though in the past DC drives were often utilized due to their simplicity, most machine manufacturers now prefer to use AC drives (especially for servo applications). The intricacy of an AC drive has been simplified over time and has many upper hands.

MRO Electric and Supply has new and refurbished Control Techniques parts available now, and also offers repair pricing. For more information, please call 800-691-8511 or email


Control Techniques Commander CDE Trips: Troubleshooting


Control Techniques Commander CDE Trips: Troubleshooting

MRO Electric and Supply has new and refurbished Control Techniques parts available now, and also offers repair pricing. For more information, please call 800-691-8511 or email



Control Techniques Commander CDE Trips: Troubleshooting

When a failure occurs with the CDE drive the display will flash a series of segment characters for the trip.

Example: tr iP OU

Commander CDE series stores the past ten failure codes in parameters #10.14 – 10.23 in trip number form. A numeric value trip code is a basic form of the symptom for the technician to work with. These past trips can be accessed via the keypad by entering the value of 149 in the keypad at parameter 00.

Scroll to menu 10, for parameter #10.14 to see a trip number.

Example: 6

Symptom explanations provide an avenue on how to analyze the drive for particular problems.

To make the troubleshooting process easier a chart was created to link the type of trip with the symptom.


TRIP Display | TRIP Number | Symptom

cL 114-20m Loop of current loop 1
Et2External trip contact has opened
I . t3Overload lxt- Sustained Overcurrent
Oh4Heatsink over temperature- Fan Failure ???
OI AC5Instantaneous AC over current trip
OU6DC bus over voltage-Braking Resistor Problem
Ph7AC Supply phase loss
PS8Internal power supply fault
th9Motor thermistor trip-Hot Motor
OI dC10Instantaneous DC over current trip
EPS11External power supply fault +24vdc short?
th512Motor thermistor short circuit
UU13DC bus under voltage
SCL14Serial comms. Loss-Keypad loose/failure
POdL15Loss of Control keypad
cL2164-20mA Loop Loss of current loop 2
cL3174-20mA Loop Loss of current loop 3
Prc219Processor 2 fault
OA20Ambient over temperature
rS21Stator resistance measurement failure
OUSP22Overspeed Trip
hFPP26-39Hardware Fault
PhPC100AC Supply phase loss from a drive module
OtPC101Over temperature trip in a Drive module
OtPn102-109Over temperature trip in Drive Module #n
PSPn110-117Over voltage trip in Drive Module #n
I OPn118-125Instantaneous Over current in Drive #n
OuPn126-133Over voltage trip in Drive Module #n
dcPn134-141Instantaneous DC current trip in Drive #n
FtYP142Spurious Unidentified trip
ConF143Module Address switches incorrect x t trip Warning flashing dots





Emerson Industrial Automation: Unidrive SP Troubleshooting

Emerson Industrial Automation: Unidrive SP Troubleshooting


The Unidrive SP can be enabled to run in several ways. The drive can use digital inputs, keypad, or a field buss networks to give the OK to run. The drive will display inh, rdy, or run depending on the given commands. The drive can be programmed to use positive or negative logic. The logic type is set up at #8.29 in the Unidrive SP. The Unidrive SP defaults to positive logic. When the drive is in positive logic you will need to inject +24VDC to activate the digital inputs. The +24VDC can be supplied by the drive or externally.

The Unidrive SP can be enabled to run in numerous ways.

When the drive is in the terminal mode the following sequence occurs under default conditions:

Unidrive SP:

Inh = Drive disabled = Connect pins 22-31 drive should go to rdy
Rdy = Drive enabled = Connect pins 22-26 drive should go to run
Run = Drive is enabled and ready to run when a speed reference is applied

Parameter #0.05 sets up the Reference Select. This will tell the drive where to search for run commands and speed references. You will only need to close the enable signal if it is set to pad. Then, the keypad can be used to control the drive and to set the speed reference. The speed reference will come in on an analog input if you choose a terminal code. The digital inputs will select the enable, run, and preset selections. The drive should operate as seen above if the digital inputs are activated correctly.


When the drive is not running, there are several additional parameters in menu 6 that can assess the issue. The digital inputs may be configured wrong or inactive if the parameters are not going to a 1 with the corresponding commands. Check the following parameters:

#6.15 = 1 = Drive enabled

#6.43 = 1 = Control word disabled, Set to 1 for Field Buss Control

#6.29 = 1 = Hardware Enable (Pin 31 is activated)

#6.30 = 1 = Run Forward #6.31 = 1 = Jog

#6.32 = 1 = Run Reverse

#6.33 = 1 = Forward/Reverse

#6.34 = 1 = Run

#6.37 = 1 = Jog Reverse

#6.39 = 1 = Not Stop


Unidrive SP

The voltage on the corresponding digital inputs should be measured if the parameters in menu 6 aren’t changing state accordingly. The DC voltage should change between 0VDC and 24VDC when a command is given. Check the digital input configuration in menu 8 if menu 6 isn’t changing and the voltage is.


To control the start/stop functions, the drive does not have to use the digital inputs. When #6.43 = 1 the control word is enabled. The drive will now accept a decimal value from 0 to 32767 at #6.42. This decimal value can be converted to a binary value.To see the function that will be carried out, you can reference the binary value to the chart below.

Unidrive SP

Speed Reference

The drive still may not run if the digital inputs and the drive sequencer are each working properly. There could be an issue with the speed reference to the drive if the display shows Run but the motor isn’t turning. The speed reference is able to be applied in several methods. An analog input can be used (current or voltage), preset speeds, and a field buss reference. The example is a 0-10VDC signal on analog input #1.

The final speed of the demand is parameter #3.01. The speed reference should be displayed here if the digital inputs and the drive sequencer are failing to operate properly. Check menu 1 and 2 to determine where it is stopping if the reference is not getting to this point.

If the drive is running in torque mode, the torque reference will come on parameter #4.08 under default conditions. #4.08 is able to be linked to an analog input or be written to via a filed buss network.


Unidrive SP


#7.01 should be inspected to determine if it changes with the change in reference at terminal 5 once the signal has been confirmed. #7.01 goes from +/- 0% – 100%. Check the destination of the speed reference at #7.10 if everything looks good. Follow it to the destination and confirm the speed reference value is arriving there and then through #3.01.


Unidrive SP


Contact the America’s Service Center if the drive will still not run after the Speed Reference, Digital Inputs and Drive Sequencer have all been confirmed.

MRO Electric and Supply has new and refurbished Control Techniques Unidrives available now, and also offers repair pricing. For more information, please call 800-691-8511 or email



Emerson Industrial Automation: Unidrive Classic HF Trip Codes

Emerson Industrial Automation: Unidrive Classic HF Trip Codes
This document is pertinent to all Unidrive Classic models
MRO Electric and Supply has new and refurbished Control Techniques Unidrives  available now, and also offers repair pricing. For more information, please call 800-691-8511 or email
Emerson Industrial Automation: Unidrive Classic HF Trip Codes

HF81 Software Error (odd address word)

Unidrive Fault Code DiagnosticsHF81 HF82 HF83 HF84 HF85 HF86 HF87 HF88 HF89 HF90 HF91 HF92 HF93 HF94 HF95 HF96 HF97 HF98 HF99

HF82 Large Option Module Missing

HF83 Power Board Code Failure

HF84 Current Offset Trim Failure

HF85 A to D failure (ES-CC step)

HF86 Interrupt Watchdog failure

HF87 Internal ROM check error

HF88 Watchdog Failure

HF89 Unused Interrupts (nmi as source)

HF90 Stack Overflow

HF91 Stack Underflow

HF92 Software Error (undefined op code)

HF93 Software Error (protection fault)

HF94 Software Error (odd address word)

HF95 Software Error (odd address instruction)

HF96 Software Error (illegal ext bus)

HF97 Level 1 Noise

HF98 Interrupt Crash

HF99 Level 1 Crash


HF Faults are not recorded in the Drive Historical Fault Log

All of the above HF trips in BLUE are typically a result of some sort of hardware failure on the UD90A control PCB. This control board is common to all Unidrive Classics.

For the HF codes in RED refer to the following page

HF82 Large option module missing

If one of the UD7x large option modules is removed, the trip may be expected. There is an issue with either the large option module or the UD90A control PCB if this trip occurs at any other time than the case above.

HF83 Power Board Code Failure

Because the UD90A control PCB was unable to recognize the power rating of the power PCB it is connected to, this trip occurred.

The trip is likely due to the power PCB in the Drive or a problem with the UD90A control PCB on Unidrive Sizes 1 to 4 (which includes UNI1401, UNI1402, UNI1403, UNI1404, UNI1405, UNI2401, UNI2402, UNI2403, UNI3401, UNI3402, UNI3403, UNI3404, UINI3405, UNI4401, UNI4402, UNI4403, and UNI4404).

UD99 PCB or the UD90A PCB cause the trip on a Unidrive Size 5. The interconnects between the PCBs should also be checked, as they could also cause a trip.

HF84 Current Offset Trim Failure

Due to an issue with the current feedback on the drive, this trip occurs. The trip is likely due to the power PCB in the Drive on Unidrive Sizes 1 to 4. An issue with the UD90A control PCB may also cause this trip.

The UD99 PCB or the UD90A PCB cause the trip on a Unidrive Size 5, along with the interconnects between the PCBs.

HF88 Watchdog Failure

This trip can result from a faulty UD7x Co-Processor. With power off, remove Co-Processor and re-apply power.

HF82 Large option module missing

If one of the UD7x larger option modules is removed while the Drive is powered up, this trip is likely to occur. There is an issue with either the UD90A control PCB or the large option module if this trip were to occur at any other time.

HF83 Power Board Code Failure

The UD90A control PCB was unable to recognize the power rating of the power PCB it is connected to, which is what caused the trip.

The trip is likely due to the power PCB in the Drive on Unidrive Sizes 1 to 4, however, an issue with the UD90A control PCB is also able to cause this trip.

The trip is caused by the UD90A PCB, the UD99 PCB, or the interconnects between the PCBs on a Unidrive Size 5.


HF84 Current Offset Trim Failure

If there is an issue with the current feedback on the Drive, this trip will occur. The trip is likely due to the power PCB in the Drive, but an issue with the UD90A control PCB could also result in a trip on Unidrive Sizes 1 to 4.

On a Unidrive Size 5, the trip is cause by either UD99 PCB or the UD90A PCB. The interconnects between the PCBs could also cause this trip and should be checked.

A trip could be caused by either UD99 PCB, UD90A PCB, or the interconnects between the PCBs on a Unidrive Size 5.

HF88 Watchdog Failure

A faulty UD7x Co-Processor and large option module, ( includes UD70, UD71, UD73, UD74, UD75, and UD76) can cause this trip. Remove Co-Processor and re-apply power with power off.

Unidrive Fault Code DiagnosticsHF81 HF82 HF83 HF84 HF85 HF86 HF87 HF88 HF89 HF90 HF91 HF92 HF93 HF94 HF95 HF96 HF97 HF98 HF99

UD55 Small Option Module for Control Techniques Unidrives

The UD55 Cloning Small Option Module can store up to eight parameters-sets which contain all the read–write parameters for a Drive, and include those in Menus 16 & 20, when applicable. These parameter sets can be individually recalled for loading onto the same or another drive.

The cloning of drives can only be performed when the operating mode (Open-loop, Closed-loop Vector, Servo or Regen) of the destination drive is the same as that of the source drive. The UD55 must be fitted in the small option module bay of the Unidrive. All connections to the drive are made by a multi-way connector. Connections from external equipment are made to a plug-in 16-way screw-terminal block on the option module. Some parameters have a profound effect on the operation of the Unidrive. They must not be altered without careful consideration of the impact on the controlled system. Measures must be taken to prevent unwanted changes due to error or tampering.

UD55 Installation

1. Disconnect the AC supply from the Drive.
2. Check that the exterior of the UD55 is not damaged, and that the multi-way connector is free from dirt and debris. Do not fit a damaged or dirty UD55 in a Unidrive.
3. Remove the terminal cover from the Drive.
4. If a small option module is already fitted in the Unidrive, grip the recesses at the ends of the module and pull the module out of the Drive. Keep the module for re-fitting.
5. Position the multi-way connector on the rear of the UD55 over the connector in the Drive (see figure below), and press on the thumb pad to push the UD55 into place.

UD55 Installation
UD55 Installation

Saving Parameters

If the Drive trips and a trip code is displayed while this procedure is being followed, ensure that all the required parameters have been set up in the source Drive and that new parameter values have been saved.
If a small option module was fitted in the Drive, its associated Menu 16 parameters will be copied to the UD55 in addition to the parameters in the other menus.
1. Insert the UD55 in the source Drive (refer to Chapter 3, Inserting theUD55 in a Drive).
2. Ensure terminal 30 of the Drive Signal connector is open-circuit so that the Drive does not become enabled when powered-up.
3. On the UD55 connector, connect terminal 40 directly to terminal 41 to enable the save function (see Figure 2).
4. Re-fit the terminal cover to the Drive.
5. Connect the AC supply to the Drive.
6. Decide which parameter-set number is to be used in the UD55. If a parameter-set already contains parameter values, these will be over-written without warning. It is recommended that a record is made of at least the following for each parameter-set number:
• A means of identifying the configuration of the source Drive
• The model size of the source Drive
• The type(s) of option module(s) fitted
• Motor ratings
7. Set parameter .00 (in any menu) at 300X, where X is the required parameter-set number (1 to 8).
8. Press . The parameter values are now copied (saved) to the UD55.
Saving takes approximately 5 seconds. When it has finished, parameter .00 returns to zero.
9. It is recommended that parameter 11.38 is set at the number of the parameter-set (value of X in step 7) and the value of parameter 11.40 UD55 full parameter check sum noted, as a means of identifying the parameter-set at a later date.
10. Disconnect the AC supply from the Drive.
11. Remove the terminal cover.
12. Disconnect the link between terminals 40 and 41 on the UD55 connector.
13. Remove the UD55 from the Drive.
14. If a small option module was previously fitted in the Drive, re-fit the module.
15. Replace the terminal cover.
16. The Drive can now be used.

MRO Electric provides sales and support for Control Techniques Unidrives and their Option Modules. To request a quote or for more information, visit our UD55 Product Page or call 800-691-8511.

UNI3404: Beyond the User Manual

The UNI3404 is available with a number of option modules, which increase its flexibility and make it suitable for a very wide range of applications. These modules are briefly described in the following paragraphs. For full details refer to UNI3404 manual that is supplied with each of them. The modules are in two physical formats and are known as Large Option Modules (LOM) and Small Option Modules (SOM). Each Undrive may be fitted with one LOM and one SOM.

Unidrive UNI3404 Large Option Modules
  1. UD78 High Precision Analog Input Module. (LOM):
    • This module provides the following features: a) Infinite resolution analog input for precision speed and position control. Large Option Module Small Option Module 1. Introduction 11 b) RS485 communication port. c) Back up supply connector (requires user provided 24VDC) to maintain power to the drive control circuits and encoder feedback when the 3 phase input to the drive is disconnected.
  2. UD70 Co-Processor Module (LOM)
    • The UD70 is an Intel 960 based co processor module that allows the user to write programs in both IEC1131 ladder / Function Block Diagram and Drive Programming Language (DPL) to provide 1.5 axis motion control and sequence control. This is accomplished using the SyPT programming tool on a PC. The module is fitted with an RS232 programming port for this purpose. It also has an RS485 port for general use and this supports the ANSI protocol as a slave or master controller and ModBus RTU as a slave only.
  3. UD71 Serial Communications Module (LOM)
    • The UD71 provides simple serial communication and has both RS232 and RS485 ports.
  4. UD73 Profibus Interface Module (LOM)
    • The UD73 provides full UD70 co-processor functionality and additionally allows the drive to be connected to a Profibus DP network running at speeds up to 1.5 Mbaud.
  5. UD74 Interbus-S Interface Module (LOM)
    • The UD74 provides full UD70 co-processor functionality and additionally allows the drive to be connected to an Interbus-S network at a fixed data rate of 500 Kbaud.
  6. UD75 CTNet Interface Module (LOM)
    • The UD75 provides full UD70 co-processor functionality and additionally allows connection to a CTNet nework. CTNet is Control Techniques fully de-centralized peer to peer fieldbus. This allows implementation of a fully distributed control system with no central PLC controller required.
  7. UD76 Modbus Plus Interface Module (LOM)
    • The UD76 provides full UD70 co-processor functionality and additionally allows connection to a Modbus Plus network.
  8. UD77 DeviceNet interface module (LOM)
    • The UD77 provides full UD70 co-processor functionality and additionally allows connection to a DeviceNet network.
  9. CAN interface module
    • This is based on the UD77 hardware but has different firmware to allow the user to communicate through the CAN physical layer but using his own protocol written using the SyPT toolkit.
  10. CanOpen interface module
    • This is based on the UD77 hardware but the firmware is changed so that the network uses the CanOpen protocol.
Unidrive UNI3404 Small Option Modules
  1. UD50 Extended I/O module
    • This module provides the following additional I/O capability:
      • a) qty. 3, 24VDC digital inputs.
      • b) qty. 3, dual function (user selectable) 24VDC digital inputs / outputs. Rated at 30mA when configured as outputs.
      • c) qty. 2, 10 bit plus sign analog inputs +10 to –10VDC
      • d) qty. 1, analog output +10 to –10VDC.
  2. UD51
    • Second encoder module In servo mode this provides the drive with the following additional capabilities:
      • a) Allows use of a second incremental encoder as a master reference input for digital lock, Electronic Gear box and camming functions.
      • b) Alternatively the UD51 may be configured for frequency and direction input to be used as the drive speed reference.
  3. UD52 Sin/Cos encoder module
    • The UD52 allows a servomotor fitted with a sin/cos encoder to be used. This provides an interpolated resolution of up to 1,048,576 ppr when used with a 512 pulse sin cos encoder and also allows use of an optional 4096 revolution absolute encoder. The Unimotor is available with these encoders fitted as a standard option.
  4. UD53 Resolver Module
    • The UD53 allows use with a servomotor having resolver feedback. This is much more rugged than an encoder and therefore suitable for use in harsh environments. The UD53 can operate with resolver having either 2:1 or 3:1 turns ratio (primary : secondary)
  5. UD55 Cloning Module
    • The cloning module is intended to make it possible to copy up to 8 different parameter sets and subsequently load any of these onto another drive. It is useful in a production environment when many drives have to be set up with the same parameters. Unlike the other small option modules it is not normally left permanently installed in a drive.


Contact us today for an instant quote on any Control Techniques Unidrive, small option module, or large option module at 1-800-691-8511 or at


UNI3405 Configuration and Setup

You can check out our previous blog post on the Control Techniques UNI3405 manual here for more information.

Since capacitance in the motor cable causes loading on the output of the UNI3405 Drive, ensure the cable length does not exceed 660 ft. (400 volts) or 410 ft. (480 volts).
Cable lengths in excess of the specified values may be used in the UNI3405 configuration only when special techniques are adopted; refer to the supplier of the Drive.

The maximum cable length  for the Unidrive UNI3405 configuration is reduced from that shown above under the following conditions:

  • PWM switching frequency exceeding 3kHz in model sizes 3 and 4 — The maximum cable length is reduced in proportion to the increase in PWM switching frequency, eg. at 9kHz, the maximum length is 1/3 of that shown.
  • High-capacitance cables – Most cables have an insulating jacket between the cores and the armour or shield; these cables have a low capacitance and are recommended. Cables that do not have an insulating jacket tend to have high capacitance; if a cable of this type is used, the maximum cable length is half that quoted in the table.
The Drive has two forms of thermal protection for the power output stage (IGBT bridge), as follows:
  1. A thermistor mounted on the heatsink monitors the heatsink temperature. If this exceeds 95 °C (203 °F), the thermistor will cause the Drive to trip. The display will indicate Oh2
  2. Intelligent thermal modelling estimates (by calculation) the junction temperature of the IGBTs. There are two temperature thresholds which cause the following to occur:
    • If the first threshold is reached, the PWM switching frequency is halved in order to reduce dissipation in the IGBTs. (When the frequency is halved, the value of parameter 0.41 PWM switching frequency remains at the value set by the user; if the frequency is 3kHz or 4.5kHz, no halving occurs). Then at one second intervals, the Drive will attempt to restore the original PWM switching frequency. This will be successful if the estimated temperature has reduced sufficiently.
    • If the estimated temperature has continued to rise and reaches a second threshold, the Drive will trip. The display will indicate Oh1.

You can get price and availability by emailing or calling 1-800-691-8511.

Control Techniques uni3405

UD73 Configuration and Setup

You can check out our previous blog post on the UD73 here for additional setup and configuration info.

For UD73 configuration, most common parameters are arranged in one concise menu. Hundreds of user-configurable functions separated into 20 logical menus provide quick setup for advanced application. For positioning, ratio control, camming and multi-axis systems, plug-in option modules easily extend the Unidrive’s capabilities. High horsepower Unidrives cover the range from 200 to 1600 HP. The 300 amp power module and control pod (the “brain”) are available as components. They are also available as a packaged drive solution that includes fusing and a disconnect. (See our Packaged Drive Section, pages 120-123 and 128-133.) With the UD73’s extensive selection of communication, application, feedback and I/O modules, you can easily upgrade the performance of your drive. Yet, it is simple to configure by using the drive keypad, a remote keypad (CTKP), or UniSoft, the UD73 Windows based drive set-up tool. You can tailor each Unidrive to be the drive you want when you want it.
  • Digital AC Drive
  • 1 to 30 HP, 3 Phase, 208-230 VAC
  • 1 to 1600 HP, 3 Phase, 380-460 VAC
  • Five operating modes
    • V/Hz
    • Open loop vector
    • Closed loop vector
    • Brushless AC servo
    • Regenerative
  • UniSoft Windows based configuration tool
  • Configurable analog and digital I/O
  • Complete Motor Solutions


The UD73 configuration is suited for use with AC brushless servo motors. Servo control is ideal for applications requiring load transfer to and from any position, at any speed. The UD73 is designed for both stand-alone and multi-axis system applications.
In regen mode, two standard UD73’s operate together to provide full four-quadrant control of an AC motor. The system consists of two basic sub-systems, one being a Unidrive operating in any of its standard operating modes (open loop, vector or servo), and the other is a Unidrive operating in its regenerative mode. The link between the two sub-systems is simply the DC bus connections. In this mode, the UD73 is capable
of either supplying power to the DC bus of the Unidrive controlling the motor or removing power from the DC bus of the Unidrive controlling the motor and returning it back to the power line.
If you would like to order a module or get more info you can email or call 1-800-691-8511.

UNI2403 Configuration and Setup

The UNI2403 and UNI2403-r configuration process is a relatively simple setup process that should be able to get you back up and running with minimal downtime.

With some simple UNI2403 11kw configuration the drive can be used as an AC Regenerative Unit, also known as a Regen Drive. In the case of a drive operating in Regen mode, the IGBT bridge is used as a sinusoidal rectifier, which converts the AC supply to a controlled DC voltage. This DC voltage can then be used to supply one or more Unidrives which control motors, commonly known as motoring drives.

A regen drive produces PWM output voltage which has a sinusoidal fundamental at an amplitude and phase which are almost the same as those of the AC supply voltage. The difference between the drive PWM line voltage and the supply voltage occurs across the Regen drive’s inductors.

There are a number of possible options available when designing a Unidrive Regen system depending on the user requirements and the nature of the AC supply. Non standard systems can be created where favourable supply conditions exist, allowing cost and space savings to be achieved by reducing the number of components.

A Unidrive can be used as a sinusoidal input current power unit to supply one or more Unidrives via their DC buses. When this mode is selected as the drive type, menu 15 appears. This menu is used to set up the Unidrive. At the same time, menu 0 defaults to showing Pr 15.01 to Pr 15.13 as Pr0.11 to Pr 0.28.

You can check out our previous blog post on the UNI2403 manual and UNI2403-r manual here with additional setup info. To get a UNI2403 price quote or for ordering info you can call 1-800-691-8511 or email

UNI2403 Configuration
UNI2403 Configuration

UNI3405: Beyond the User Manual Parameters

The UNI3405 Unidrive is part of the Classic Unidrive series. Control Techniques introduced the Unidrive Classic around 1993 in Europe and approximately 1995 in the Americas. Because the Unidrive Classic ran simple Open Loop, Closed Loop Vector, and Servo motor applications as well as offering a Regen mode, the UNI3405 found its way into a great many industrial applications, from simple to quote complex.

Due to its status as a legacy product, the UNI3405 is becoming available only in limited quantities.

The UNI3405 contains approximately 500-600 parameters that help machine manufacturers achieve the desired functionality for a certain machine requirement. Some applications may require 20-30 or more parameters to be changed from the drives factory default settings. Should drive replacement become necessary, one must have a complete and accurate list of these parameters so that the original functionality can be restored. If you do not have a list of the required parameters, one could copy down these parameters manual. This is assuming that the drive still works enough to power the display, and even then the manual copying of parameters is tedious and error prone.

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