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hydraulics · motor-control

Hydraulic power unit control circuit

This diagram captures the electrical controls around a small hydraulic power unit. The fused 24 V control supply reaches a start button, a normally closed stop button, and the pump motor contactor. An auxiliary contact provides the seal-in path that keeps the contactor active after the operator releases Start. A pressure switch is shown separately with a low-pressure pilot lamp so the operator has a simple status indication. It is a useful starting point for documenting a hydraulic lift, press, or fixture power pack. Add the motor power circuit, overload relay, emergency stop, and the hydraulic fluid circuit as separate drawings where the machine requires them.

Type Circuit schematicStandard IEEE Std 315 / ANSI Y32.2Engine schematex-circuitUpdated 9/24/2026
Hydraulic power-unit control
Drawing preview
The request

“Draw a 24 V hydraulic power-unit control circuit with a fuse, start and stop pushbuttons, a pump motor contactor with a seal-in contact, and a pressure switch that operates a low-pressure lamp.”

Then tryAdd an emergency-stop pushbutton before the start button.Change the low-pressure lamp to an audible buzzer.
What is in this drawing

Read the decisions behind it.

01Start/stop station

Momentary start and normally closed stop commands control the contactor.

02Seal-in contact

The auxiliary contact keeps the motor contactor energized after start is released.

03Pressure indication

A pressure-switch input drives a visible low-pressure warning.

Use for a basic power-pack control concept before adding overload protection, a motor starter, and plant safety interlocks.

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FAQ

Common questions

What is a hydraulic power unit?

It is the pump, motor, reservoir, and related controls that supply pressurized fluid to a hydraulic machine.

What is a seal-in contact?

It is an auxiliary contact that keeps a relay or contactor energized after a momentary start button is released.

Why use a pressure switch?

It changes state at a set fluid pressure and can provide an alarm, permissive, or control signal.