Which encoder is used on a lift traction motor?

Usually a rotary encoder on the motor shaft giving commutation and speed, often with a digital interface such as EnDat. HEIDENHAIN lists an incremental encoder as its standard lift motor encoder, with absolute encoders for more demanding machines and for digital shaft copying, where the car's absolute position survives a power cut. Gearless machines need high resolution because the motor turns slowly.

What does EN 81-20 require from a lift door drive?

The landing and car door, with their rigidly connected parts, must not exceed 10 J kinetic energy at average closing speed, falling to 4 J with an audible signal if the protective device has failed. The protective device must cover 25 to 1,600 mm above the sill and detect obstacles of at least 50 mm. The drive and controller have to deliver that reliably across door sizes and masses.

How do I size a hoist gearbox?

Work out drum torque from rope pull and drum radius, and drum speed from rope speed and drum diameter, then choose the ratio from motor speed. Next, find the ISO 4301 mechanism class from average daily running time and load spectrum, and apply the service factor the gearbox maker gives for that class. Check radial load at the output and the braking torque reflected through the ratio.

What slip ring does a tower crane need?

A slip ring at the slew centre carrying the main power to the jib, trolley and hoist motors plus control and sensor circuits. Published tower crane units carry several hundred amps; one example is quoted at 900 A and 380 V on six rings. Specify all circuits with spares, the bus for anti-collision or monitoring systems, outdoor sealing and an earth ring.

What speed limit applies to a wheelchair platform lift?

EN 81-41 covers powered vertical lifting platforms fixed to a building for people with impaired mobility, and limits rated speed to 0.15 m/s, with the guided path no more than 15° from vertical. It excludes platforms mainly for goods and those with fully enclosed carriers. Size the actuator or drive so that speed cannot be exceeded at any load.

How often must lifting equipment be examined in the UK?

Under LOLER, equipment and accessories used to lift people, and all lifting accessories, need a thorough examination every 6 months, and other lifting equipment every 12 months, unless an examination scheme sets different intervals. Examinations are also required before first use in most cases, after assembly at a new site, and after damage or major changes.

Lift encoders, crane slip rings and hoist gearboxes

Specify Motion technical library · Updated 30 October 2026 · How we prepare our content

In short:Lifts, cranes and hoists move people and heavy loads, so their motion components are chosen around safety rules first: EN 81-20 for lift doors and car movement, EN 81-41 for platform lifts, ISO 4301 duty classes for crane mechanisms, and LOLER examinations in service. The core parts are encoders on the motor, brake and shaft, door drives, slip rings for slewing and cable reels, and hoist gearboxes sized for the duty class.

Typical requirements

Lift door kinetic energy (EN 81-20)	≤10 J at average closing speed; ≤4 J if the protective device fails
Lift door detection zone (EN 81-20)	25–1,600 mm above the sill; obstacles ≥50 mm
Platform lift speed (EN 81-41)	≤0.15 m/s; path within 15° of vertical
Crane mechanism class (ISO 4301-1)	M1–M8, from utilisation T1–T8 (400–50,000 h) and load spectrum L1–L4
Gearless lift machine (published example)	3.5–11 kW, S3 40% duty, IP54, EnDat encoder
Tower crane power slip ring (published example)	900 A, 380 V, 6 rings
LOLER thorough examination (UK)	6-monthly for people-lifting equipment and accessories; 12-monthly otherwise

Machinery we specify motion for

Traction lift main motors
Lift door operators
Lift brake monitoring
Lift shaft position systems
Escalators
Tower, mobile and loader cranes
Marine and offshore cranes
Hoists and winches
Wheelchair platform and ramp lifts
Hose and cable reels

What lifts, cranes and hoists demand from motion components

Lifting equipment carries people and heavy loads over people, so every motion component is chosen against a safety rule before it is chosen on performance. A lift door drive is limited by how much energy the door may carry. A hoist gearbox is sized by how many hours it will spend at what fraction of full load. A crane slew encoder feeds the device that stops the crane overturning. And in the UK, the finished equipment is examined in service under LOLER: every 6 months for people-lifting equipment and lifting accessories, every 12 months for other lifting equipment, unless an examination scheme says otherwise.

The duty is also long. A lift or crane mechanism may run for decades, often outdoors or in a shaft that is hard to reach, so ease of inspection and diagnostic data matter as much as the headline rating.

Where each component sits: lifts, cranes and hoists

Machine	Motion component	What it does
Traction lift machine	Motor encoder; frameless or geared motor	Commutation and speed control at low sheave speed
Lift brake	Brake monitoring sensor	Confirms release, engagement and wear
Lift shaft	Absolute encoder or tape system	Car position, kept through a power cut
Lift door operator	Brushless motor, encoder, drive	Speed-profiled doors within EN 81-20 energy limits
Tower, mobile and port cranes	Slip ring, slew encoder, slew gearbox	Power and data across the slew; absolute slew angle
Hoists and winches	Motor, gearbox, brake, drum encoder	Lifting at the duty class; rope position
Cable and hose reels	Slip ring, reel drive	Power and data to travelling equipment
Platform and ramp lifts	Linear actuator or geared motor	Low-speed lifting, ramp deployment

Lift motors, brakes and shaft position

HEIDENHAIN splits lift feedback into four jobs: motor control, brake monitoring, shaft position and door motors. It names an incremental encoder as its standard lift motor encoder, an inductive encoder that detects brake stroke and temperature without extra microswitches (tied to unintended car movement monitoring), absolute encoders for digital shaft copying so the car can go straight to its destination after a power cut, and compact door-motor encoders under 40 mm diameter. One shaft encoder option carries up to 150 N axial and 350 N radial load.

Gearless machines run slowly. A published WEG gearless machine covers 3.5–11 kW, S3 40% duty, IP54, with an integrated brake and an EnDat encoder. Low speed means the encoder needs high resolution for smooth control near zero speed. For OEM-built machines, frameless kits such as the ADR-P (110–360 mm, up to 365 Nm continuous) or the in-runner TI Series can be built around the sheave. See frameless torque motors.

Lift door operators

Under EN 81-20, the door and its rigidly connected parts must stay at or below 10 J kinetic energy at average closing speed, and 4 J with an audible warning if the protective device has failed. The detection device must cover 25 to 1,600 mm above the sill and detect a 50 mm obstacle. That is why door operators have moved to brushless motors with encoders and a positioning controller: the drive must shape the speed profile to the door’s mass. maxon’s door drive developed with Schindler uses a 90 mm brushless flat motor with an on-board encoder and a controller that calibrates door size and weight, moving doors up to 400 kg in its belt-drive version.

Cranes, slewing and cable reels

rotarX lists the slew connection on mobile cranes, cable reels on gantry and harbour cranes, tower cranes, pillar jib cranes and attachments such as grabs as slip ring uses. Power levels are high: one published tower crane slip ring is quoted at 900 A and 380 V on six rings. Our pages on slip rings for cranes and slewing and slip rings for cable reels go into circuit design. For high currents, start from the carbon-brush BHR Series; for slew and reel units with data channels, the RF Integrated / Cable Reel Slip Ring range.

Mobile cranes rely on a rated capacity limiter, and rated capacity indicator systems such as Trimble’s take inputs from angle, length and slew sensors to warn the operator as the crane nears its rated capacity. The EN 13000 amendment reported by KHL limits operating speed to 15% when the limiter is overridden. A slew encoder that fails or slips therefore affects a safety function, not just a display. Choose one with diagnostics, mount it so the gear mesh cannot jump a tooth, and give the control system a way to detect a frozen or implausible reading.

Escalators and hose reels

Escalators use the same building blocks as lifts: a main drive motor and brake, with speed feedback to the control and safety system. Hose and cable reels on fire appliances, process plant and travelling cranes need a slip ring or rotary union on the reel axis and a reel drive that keeps tension without overrunning. Where a reel carries both fluid and power, a combined unit saves space; see rotary unions.

How to size a hoist: worked example

A wire rope hoist lifts 1,000 kg at 8 m/min on two-fall reeving with a 200 mm drum, running about 2 hours a day at a medium load spectrum.

Rope pull: 1,000 × 9.81 / 2 falls = about 4,900 N.
Drum torque: 4,900 N × 0.1 m = 490 Nm.
Drum speed: rope speed is 16 m/min with two falls; 16 / (π × 0.2) = about 25 rpm.
Ratio: with a 1,500 rpm motor, about 59:1.
Power: 1,000 × 9.81 × (8/60) = 1.31 kW at the hook; at an assumed 85% drivetrain efficiency, about 1.5 kW at the motor. Add acceleration torque.
Duty class: under ISO 4301-1, 1–2 hours of daily running is utilisation class T4 (3,200 h design life) and 2–4 hours is T5 (6,300 h). Combine the class with the load spectrum (L1–L4) to get the mechanism group, M1–M8, and apply the gearbox maker’s service factor for that group.
Brake: the brake on the motor must hold the load with margin; check the gearbox can carry that braking torque at its output.
Feedback: a multi-turn absolute encoder on the drum, such as the VLM, keeps hook position through a power cut.

Platform lifts and ramps

EN 81-41 covers powered vertical lifting platforms for people with impaired mobility: rated speed no more than 0.15 m/s and a path within 15° of vertical. At those speeds a 12/24 V screw actuator such as the GT44 (6,000 N push) or a geared motor and screw is a common drive. Check duty cycle, manual lowering on power loss and outdoor sealing. See how to size a linear actuator.

Typical pitfalls

Sizing a hoist gearbox on peak load only and ignoring the mechanism class and running hours.
No spare slip ring circuits. Cameras, anti-collision systems and wind sensors get added later.
Incremental slew or drum feedback that needs re-homing after a power cut with a load on the hook.
Door drives tuned for one door mass. EN 81-20 energy limits must hold across the whole range.
Forgetting the examination regime. Make brakes, slip rings and encoders easy to inspect.

Send us the load, speeds, duty class, supply and environment, and our specialist engineering and supply partners will propose matched encoders, slip rings, motors, gearboxes and drives.

Slip rings for cranes, slewing rings and cable reels

Tower, mobile and port cranes carry power, control and data across the slewing ring, and cable reels feed travelling cranes and hoists. Specify every power circuit's current and voltage, the signal and fieldbus channels (CAN, Profinet, Ethernet), rotation speed, bore for hydraulic swivels, and sealing for outdoor or marine use. Carbon-brush rings handle hundreds of amps but need planned maintenance; gold or silver contacts suit signals. Include spare circuits, an earthing ring and anti-condensation measures, because a crane slip ring is costly to reach once the crane is built.

Tower cranes: power and control across the slew
Mobile and loader cranes: power and sensor signals to the superstructure
Port and gantry cranes: cable reel power and data
Offshore cranes: sealed, corrosion-resistant slew slip rings