Product Description

Neptune is a high performance closed loop servo drive controller suitable for DC brushed, voice coils and brushless motors.

Its compact design (40 mm x 40 mm) includes CANopen/EtherCAT, RS-232 and USB communication ports, enabling thus a wide choice of interfacing methods. Its extended nominal voltage range from 9 V to 48 V with a single supply and current up to 2.5 A continuous allows its use in several applications, and the small footprint and the needless of an external heatsink allow the controller to be a valid OEM for critical-size applications.

The Neptune Digital Servo Drive has been designed with efficiency in mind. It incorporates cutting-edge MOSFET technology as well as optimized control algorithms to provide the perfect trade-off between EMIs and efficiency. In addition its ultra-low PWM deadtime (<10 ns) provides great control stability in velocity and position applications.

Neptune Servo Drive is provided with several 24V tolerant general purpose inputs and outputs with 5V TTL levels. They are fully protected against short circuits and overvoltage and can be interfaced in industrial environments. By using these inputs and outputs it is possible to implement alarm signals, connect digital sensors, activate external devices (motor brake, LEDs, actuators, solenoids, etc.). Some of the digital and analog inputs can also be used as command / target sources.

Neptune includes many passive and active protections to ensure its safe operation and easy integration.

Neptune part numbering

Neptune part numbering

Ordering part number

Status

Image

NEP-2/48-C-S

ACTIVE

NEP-2/48-C-P

ON DEMAND

-

NEP-2/48-E-S

ACTIVE

Specifications

Electrical and power specifications
Part number NEP-2/48-y-SNEP-2/48-y-P

Nominal power supply voltage

9 VDC to 48 VDC

Maximum continuous power supply voltage50 VDC
Transient peak voltage60 VDC @ 100 ms
Logic supply voltageNot needed, supplied from Power supply voltage
Internal DC bus capacitance22 µF
Minimum motor inductance100 µH

Nominal phase continuous current

2.5 ARMS (50ºC air temperature, no heatsink)

Maximum phase peak current

5 ARMS (2 s)

Current sense range± 6.3 A
Current sense resolution12.28 mA/count
Shunt braking transistor No
Cold plateNo
Power connectorsPluggable terminal block 2.54 mm pitchPin header 2.54 mm pitch, 5.84 mm length
Standby power consumption1 W (max). 2 W EtherCAT version (NEP-2/48-E-z)
Efficiency> 95% at the rated power and current
Motion control specifications
Motion control coreIngenia E-Core with EMCL2.

Supported motor types

  • Rotary brushless (trapezoidal and sinusoidal)
  • Linear brushless (trapezoidal and sinusoidal)
  • DC brushed
  • Rotary voice coil
  • Linear voice coil

Power stage PWM frequency

40 kHz (default)

80 kHz (alternative PWM frequency, configurable)

Current sensing

On phases A and B (phase C generated internally).

Accuracy is ± 1% full scale.

10 bit ADC resolution.

Hall sensor current measurement. Neptune is not suitable for environments with high magnetic fields such as close to a motor. Current noise will be observed.

Sensors for commutation (brushless motors)

  • Digital Halls (Trapezoidal)
  • Analog Halls (Sinusoidal / Trapezoidal)
  • Quad. Incremental encoder (Sinusoidal / Trapezoidal)
  • PWM encoder (Sinusoidal / Trapezoidal)
  • Analog potentiometer (Sinusoidal / Trapezoidal)
Sensors supported for servo loops
  • Digital halls 
  • Analog halls 
  • Quad. Incremental encoder
  • PWM encoder 
  • Analog potentiometer 
  • DC tachometer

Supported target sources

  • Network communication – USB 
  • Network communication – CANopen
  • Network communication – RS-232
  • Network communication – EtherCAT
  • Standalone (execution from Internal EEPROM memory)
  • Analog input (±10 V or 0 to 5 V)
  • Step and Direction (Pulse and direction)
  • PWM command
  • Encoder follower / Electronic Gearing
Inputs/outputs and protections
Inputs and Outputs
  • 2 x non isolated single ended digital inputs. GPI1, GPI2 (5 V TTL logic, 24V tolerant).
  • 2 x non isolated high speed differential digital inputs. HS_GPI1 Pulse, HS_GPI2 Direction (5V logic, 24V tolerant).
  • 1 x (±10 V) differential analog input (12 bits). AN_IN2. (24 V tolerant).
  • 1 x 0 V... 5 V single ended analog input (12 bits). AN_IN1. (24 V tolerant).
  • 2 x Open open drain digital outputs with a weak pull-up to 5 V. (24V tolerant and 1 A short-circuit and overcurrent rugged).
  • 1 x 5 V output supply for powering external circuitry (up to 200 mA).

Protections

  • User configurable:
    • Bus over-voltage
    • Bus under-voltage
    • Over-temperature
    • Under-temperature
    • Over-current
    • Overload (I2t)
  • Short-circuit protections: 
    • Phase-GND
    • Phase-DC bus
    • Phase-phase
  • Mechanical limits for homing functions.
  • Hall sequence/combination error.
  • ESD protections in all inputs, outputs, feedbacks and communications.
  • EMI protections (noise filters) in all feedbacks and motor connections.
  • Inverse polarity supply protection: A P-Channel MOSFET provides protection against polarity inversion.
  • High power transient voltage suppressor for short braking (600 W peak TVS diode).
Motor brakeMotor brake output through GPO1 or GPO2. Up to 24 V and 1 A.
Communications
USBµUSB (2.0) connector. The board can be supplied from USB for configuration purposes but will not power the motor.
SerialRS-232 non-isolated.
CANopen

Available. Non-isolated. 120Ω termination not included on board.
CiA-301, CiA-305 and CiA-402 compliant.

EtherCATAvailable.
Environmental and mechanical specifications

Ambient air temperature

  • -25 ºC to +50 ºC full current (operating).
  • +50 ºC to +100 ºC current derating (operating).
  • -40 ºC to +125 ºC (storage).

Maximum humidity

5% - 85% (non-condensing)

Dimensions

40 mm x 40 mm x 15 mm

Weight (exc. mating connectors)

20 g


Hardware revisions

Hardware revision*Description and changes
1.0.0BFirst product demo.
1.0.1R

First product release. Changes from previous version:

  • Minor manufacturing improvements.
  • Increased minimum absolute system voltage to 8 V to ensure integrated power supply performance at all ranges.
  • Assembly slots slightly redefined to improve assembly.
  • Increased default PWM frequency to 80 kHz to target low inductance motors.
  • Increased over-current range.

Identifying the hardware revision

Hardware revision is screen printed on the board. 

Power and current ratings

Neptune is capable of providing the nominal current from -40ºC to 50ºC ambient air temperature without the need of any additional heatsink or forced cooling system. From 50ºC to 100ºC of ambient temperature a current derating is needed.

Excessive power losses lead to over temperature that will be detected and cause the drive to turn off. The system temperature is available in E-Core registers and is measured on the power stage. The temperature parameter that can be accessed from USB 2.0, CAN or RS232 interface does not indicate the air temperature. Above 110ºC the Neptune automatically turns off the power stage and stay in fault state avoiding any damage to the drive. A Fault LED will be activated and cannot be reset unless temperature decreases.

Drive safety is always ensured by its protections. However, power losses and temperature limit the allowable motor current.

Some parts of the Neptune exceed 100ºC when operating, especially at high load levels.
Do not touch the Neptune when operating and wait at least 5 minutes after turn off to allow a safe cool down.

Following figure shows the basic power flow and losses in a servo drive system.

NeptunePowerGraphic

Current ratings

The Neptune Servo Drive has no cold plate, so the board itself is the heatsink. Power losses cause the drive to increase its temperature according to:

T_P \approx T_A + P_{LOSS} · Z_{θ PA}

Power losses have a positive correlation with the motor RMS current. For this reason, when the ambient temperature rises above 50 ºC, the output current must be limited to avoid an excessive drive temperature (TP< 100ºC).

Current derating

The current derating graph is only indicative and is based on thermal tests performed in a climatic room where there was enough room for natural air convection. Each application may reach different ratings depending on the installation, ventilation or housing. Current derating is only a recommendation and is not performed automatically by the drive.

Dynamic application (non-constant current)

The Neptune has a great thermal inertia that allows storing heat during short power pulses (exceeding nominal current) without overpassing the maximum temperature. This allows achieving high peak current ratings without need of additional heatsink.

For most systems where the cycle time is shorter than 3 τ (thermal time constant) the equivalent current can be calculated as the quadratic mean of the current during the full cycle. The load cycle can be simplified as different constant currents during some times: 

I_{eq} = \sqrt{ \frac{t_1·I_1^2+t_2·I_2^2+ \cdots +t_n·I_n^2}{t_1+t_2+ \cdots +t_n}}

T = t_1+t_2+ \cdots +t_n

Where:

is the full cycle period.

I1 is the current during t1

I2 is the current during t

In is the current during tn

System temperature

Next thermal image shows an example of the heat distribution in a the Neptune. The test has been performed at maximum load and air temperature with a 3 phase application.

NeptuneThermalImage

The drive is getting hot even at 0 current!

This is normal. Neptune power stage includes high power MOSFET transistors which have parasitic capacitances. Switching them fast means charging and discharging those capacitors thousands of times per second which results in power losses and temperature increase even at 0 current!

Recommendation: when motor is off, exit motor enable mode which will switch off the power stage.

Improving heat dissipation with a heatsink

The Neptune uses the whole PCB as a heatsink by providing preferential heat path from the power stage to the whole board ground planes. 

However in some cases, to improve the heat dissipation, a small heatsink can be attached to the power stage block. Also it is possible to mount it on a cooling plate.

In order to do that:

  • Provide thermal dissipation in the area indicated on the figure below.
  • Use a thermal interface material between the heatsink and the power stage (to ensure good contact and minimize mechanical stress to the package). Double sided heat transfer tapes are recommended. Like Bergquist Bond-Ply 100 BP100-0.005-00-1112.
  • Avoid touching any live part such as capacitors with the heatsink.
  • This a delicate process, do it with the drive totally unpowered and contact Ingenia engineers for further assistance.

  Neptune power stage dissipation area

Following are a small heatsink and a recommended thermal interface material for the Neptune.

ManufacturerPNDatasheetPicture
 Wakefield Solutions651-BDimensions
BergquistBP100-0.005-00-1112Application guide

Assembly recommendations for best heat dissipation

  • Always allow natural air convection by ensuring ≥ 10 mm air space around the drive.
  • Place the Neptune in vertical position.
  • If housed, use a good thermal conductivity material such as black anodized aluminum. Placing the drive in a small plastic package will definitively reduce its temperature range.
  • Temperature range can be increased by providing forced cooling with a fan or by placing a thermal gap pad on top of the board. Always ensure electrical isolation between live parts and the heatsink.

Architecture

Following figure shows a simplified hardware architecture of the Neptune.

NeptuneHWarchitecture