MOOG Dual PWM Amplifier G123-814

Application Notes

Scope

These application notes are a guide to applying the G123-814 Dual PWM Amplifier. They show you how to install, connect and adjust the PWM amplifier.

They do not cover how to select a proportional valve or how to design a closed-loop system.

Instructions

The G123-814 Dual PWM Amplifier is used to drive two coils of a three position 24V solenoid proportional valve.

It is designed for low-end closed-loop applications. It allows the use of very low cost proportional valves where much more expensive servo valves would normally be required.

Using it with the companion servo amplifier G122-824 and a proportional valve produces an economical closed loop solution.

Applicability

The G123-814-001 has a closed loop configuration and is used with Hydrolux WP series proportional valves.

Important specifications considered include 24V @ 800mA coil and 12% spool overlap.

Output current is 25% higher than rated to ensure that maximum flow is not unduly affected by valve production tolerances and spool Bernoulli forces.

Deadband compensation circuitry to eliminate spool overlap has been optimised for flow bench and field applications. Deadband compensation is not user adjustable. Applying this amplifier

Apply this amplifier to other valves with the same specifications to obtain the same performance as Hydrolux valves.

The G12-814 is not suitable for conventional open-loop proportional valve applications. A zero flow condition is highly unlikely as the deadband compensation circuit cancels out spool overlap.

Zero flow conditions are unlikely with zero coil current as the deadband compensation circuit cancels out spool overlap.

Mounting

Installation consists of mounting a horizontal DIN rail to the vertical rear surface of an industrial steel enclosure.

The rail release clips on the G123-814 should face downward to allow front panel and terminal markings to be clearly readable and to allow cooling airflow to the internal electronics.

An important consideration for module placement is electromagnetic interference (EMI) from other equipment in the enclosure.

For example, VFs and AC servo drives generate high levels of EMI. be sure to check other equipment for EMC compliance before placing it near the G123-814.

Cooling

Vents at the top and bottom of the G123-814 chassis provide cooling for internal electronic equipment. These vents should be kept clear.

It is important to ensure that the equipment below does not generate hot exhaust gases that could heat the G123-814.

Wiring

It is recommended that crimped "guide lace sleeves" be used as screw terminals. Allow sufficient length of cable

so that the wires remain connected when the circuit card is removed from the housing. This allows the circuitry to be checked while the circuit card is still connected and operational.

For cables connected to the outside of the housing as well as for cables connected to the adjacent DIN rail unit, an additional 100 mm is sufficient.

The cable to the valve coil carries 1 Amp and should be sized accordingly.

Cables with a conductor size of 0.2 mm2 are normally rated at 1 Amp and are suitable for cable lengths up to 5 metres.

Electromagnetic compatibility

The G123-814 emits emissions well below the levels required for CE marking testing.

However, the cable connecting the valve coil should be shielded to ensure that no interfering radiation is emitted.

Connect both ends of the shielded cable to chassis earth. Use terminals 10 and 14 on G123-814.

Immunity to external interference radiation depends on careful wiring techniques. The recognised method is to use shielded cables for all connections, the

The accepted method is to use shielded cable for all connections and to radially terminate the cable shield with a suitable grounded cable gland where it enters the industrial steel enclosure.

If this is not possible, chassis ground screw terminals are available on the G123-814.

The length of bare wire should be minimised. Connect the shield at each end of the cable to chassis ground.