Woodward EM-80/EM-300 Actuator system

Woodward EM-80/EM-300 Actuator system

The EM-80 and EM-300 are all-electric actuator systems that provide a nominal

40° of actuator output rotation. Each system consists of a three-phase brushless

ac motor which drives a high-precision planetary reduction gear box. A dedicated

driver controls the actuator position.

A complete system consists of:

 an actuator (Woodward-supplied) (Chapter 4)

 a driver (Woodward-supplied) (Chapter 5)

 a resolver cable (Woodward-supplied)

 shielded power cable

 shielded motor drive cable

 an EMI filter (Woodward-supplied) (Chapter 6)

 metal cabinet enclosure

 15- and 25-pin filter pin D-sub connector adapters (Woodward-supplied)

 protected 24 Vdc power source

The actuator is available in two versions, offering two work output levels, EM-80

and EM-300 (see the specifications in Chapter 9). Both versions use the same

three-phase brushless AC motor.

The difference in output is achieved by the use of two different gearboxes. The

EM-80 uses a single-stage planetary 1:7 gear ratio, while the EM-300 uses a

two-stage planetary 1:20 gear ratio.

The motor–gearbox combination comes assembled on a mounting bracket with a

fixed hole pattern. Although the EM-300 is longer than the EM-80, both use the

same mounting hole pattern, allowing the actuators to be interchangeable.

The output flange provides an easy mounting surface for a variety of lever

configurations, and is equipped with a rugged pointer and scale for quick output

position reference while working on the prime mover. A breakaway extension and

two stop pins form a simple means of detecting whether the actuator has been

driven outside its operating boundaries.

Electrical connections are made in a standard, shielded, three-phase terminal

box mounted on the motor, and will accommodate standard cable. The resolver

cable has a 1 m (39”) flying lead that removes the connector from the high

vibration environment of the prime mover. The use of the specified resolver cable

and connector will help ensure correct connections to the driver.

The EM-80 and EM-300 actuators have different position-sensing systems. Both

systems use the same hollow shaft resolver, producing a sine and cosine wave

output with an overall accuracy of 12 arc-minutes. This resolver is mounted at the

rear of the motor and looks at the relative position of the motor shaft.

The EM-80 uses only the resolver since the 1:7 gear ratio within the gearbox

allows full stroke of the actuator output flange with less than one full revolution of

the motor shaft.

The EM-300 has a 1:20 gearbox ratio to achieve the required torque output.

Because of this, the motor shaft rotates more than one full revolution to achieve

full stroke. To ensure proper position indication over the full range, a 10-turn

potentiometer is added behind the resolver to supply a coarse position signal

from which the correct rotor revolution is deduced. The same resolver as used on

the EM-80 gives the accurate position within that revolution.

Motor Controller Module Description

The motor controller module is a digital closed loop motor control, which works

with a position loop at 62.5 μs. For position feedback, it receives a resolver signal

form the motor shaft. The motor controller configuration is divided into several

functional modules. The main modules are the:

 Positioning/encoder module

 Position control module

 Speed control module

 Torque/current control module

 PLC logic module

The positioning/encoder module manages the resolver feedback signal and the

“engine” controller position command signal. The module receives both setpoint

and actual and generates an output to the position control module. The position

control module generates an output to the speed controller module. It signals the

speed control module which direction to rotate and how fast. These three

modules determine the dynamic behavior of the actuator system.

The speed control module generates an output to the torque/current control

module. The torque/current control module controls the excitation of the proper

motor phase with the proper current level. The current is limited to limit the

torque.

The PLC logic module is programmed to convert the “engine” controller position