Vibrating Screen Motor: Single and Twin Motor Selection for Screening Plants

"Vibrating screen motor" can mean two different things: on classic eccentric-shaft screens a standard three-phase motor placed beside the screen box turns the vibrating shaft through V-belts; on vibrator-motor screens two special vibration motors with unbalanced weights on their shaft ends are bolted directly to the screen box and create the vibration themselves. The first type is common on large quarry screens; models on the market show 11–45 kW on single-motor screens and 18.5–37 kW per motor on large twin-motor screens [1][2]. On small vibrator-motor screens a few kW per motor is enough [4].

Below are the difference between the two drive types, how deck count and screen size change motor power, a screen speed calculation from the pulley ratio and the DRG equivalents. For other motors in a crushing and screening plant see Stone Crushing Plant Motors; for prices of standard motors see Buy Electric Motors Online.

What is a vibrating screen and where does it sit in a crushing line?

A vibrating screen separates mixed-size crushed rock into fractions by passing it through stacked screen decks: e.g. 0–5 mm sand and 5–12, 12–22 and 22+ mm chippings. The screen box sits on springs; the drive shakes it dozens of times per second, and as the rock travels over the wire or polyurethane media the small particles fall through. The screen follows the secondary and tertiary crushers; oversize from the top deck usually returns to a crusher on a conveyor, so the line works in closed circuit.

There are two main types. Inclined screens sit at around 15–20 degrees and work with circular motion; material flows down the slope. Horizontal screens sit at 0–10 degrees and push material forward with oval or linear motion; they are chosen where a lower installation height is needed. Whichever type is chosen, screen selection and motion settings are the screen manufacturer's job; the motor supplier provides a motor matching the given power, speed and mounting.

Eccentric-shaft screen versus vibrator-motor screen

Before selecting a motor, establish how the screen is driven, because the two types need entirely different motors.

Eccentric-shaft (mechanical) screen: A shaft running through the screen box carries unbalanced weights or eccentric bearings. The motor sits on a base fixed to the ground and turns this shaft through V-belts. One manufacturer uses a V-belt drive and a self-adjusting motor base on its inclined screens [1]; another lists motor sheave and screen sheave sizes in the catalogue of its horizontal screens [3]. Because the motor stays outside the vibrating box, it is a standard IEC three-phase motor.

Vibrator-motor screen: Two vibration motors turn in opposite directions; the forces of their weights add up in one direction and cancel in the other, so the box moves linearly. One manufacturer states that the electrical unbalanced motors on such screens self-synchronise [4]. These motors are special products built for continuous vibration; a standard motor cannot do this job. DRG's vibration motor range is 0.12–15 kW and is described on the Vibration Motors page; for the operating principle see our article on how vibration motors work. Vibration motors are not sold in the online store; ask for a quotation for the right model and current price: contact or WhatsApp.

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How many kW for a vibrating screen motor? Single and total power

A) Motor power seen on screens on the market

In this machine group, motor options of about 4.5–45 kW per motor are seen depending on the manufacturer's model and screen size [4][1]. On standard-motor eccentric screens a single motor is 11–45 kW; on large twin-motor screens each motor is 18.5–37 kW, 37–74 kW in total [1][2]. Plant total power is not in this table; crushers, feeders and conveyors of the same plant are added separately.

How do deck count and screen size change power?

The screen motor does not carry the material; its real job is to shake the spring-mounted box, the screen media and the rock load on it at a given amplitude and speed. As the box grows and decks are added, the vibrating mass rises and so does the motor. Manufacturer catalogues show this clearly:

• On the same 2.0×5.0 m box, 1- and 2-deck screens have 15 kW, 3- and 4-deck screens 22 kW [4].
• On a 1880×6105 mm box, 2- and 3-deck screens have 18.5 kW, the 4-deck screen 22 kW [1].
• When the box reaches 2184 mm width and 3 decks, 2 × 18.5 kW is used instead of a single motor [1].

So power is largely set by box size and deck count; hourly tonnage selects the screen size and thus enlarges the motor indirectly. Wet screening, sticky material and heavy media such as thick polyurethane panels increase the vibrating mass and the power.

B) Matching motors in the DRG range

The 11–45 kW single motors of eccentric-shaft screens and the 18.5–37 kW motors of twin-motor screens fall within DRG's 0.55–355 kW cast iron range; 1000 and 1500 rpm options are chosen by pulley ratio. The motors of vibrator-motor screens are not standard IEC motors; they are covered on quotation from the DRG vibration motor range (0.12–15 kW). Large mining screens driven directly through gearboxes without belts and requiring 750 rpm motors are outside the DRG range.

Screen speed and motor choice from the pulley ratio: example

One maker's 3-deck, 1930×6096 mm horizontal screen comes with a 37 kW motor; the catalogue lists a Ø620 mm screen sheave, a Ø306–365 mm motor sheave and a screen speed of 730–870 rpm with a 1500 rpm motor [3]. If DRG-225S-4 is chosen (37 kW, 1485 rpm, 66.1 A at 400 V, rated torque 237.9 Nm):

• Screen speed with the smallest motor sheave: 1485 × 306 / 620 ≈ 733 rpm.
• With the largest motor sheave: 1485 × 365 / 620 ≈ 874 rpm. The result matches the catalogue range of 730–870 rpm.
• Torque at the screen shaft, ignoring belt losses, is 237.9 × 620 / 306 ≈ 482 Nm with the smallest sheave.

If a 6-pole 980 rpm motor were fitted with the same sheaves, screen speed would fall to 980 × 306 / 620 ≈ 484 rpm. Since vibrating force varies with the square of speed, (484 / 733)² ≈ 0.44: the box would be shaken with less than half of the required force, the media would blind and separation would suffer. That is why speed is kept when a screen motor is replaced. You can run the pulley calculation with your own values in the pulley-belt calculator.

Motor selection checklist, mounting and starting

• Drive type: belt-driven eccentric, cardan shaft or vibrator motors?
• Number of motors and the nameplate of each: kW, speed, frame, voltage.
• Screen size (width × length), number of decks, inclined or horizontal.
• Pulley diameters and number of grooves; tensioning base or spring-loaded motor base.
• Dry or wet screening: in wet screening the motor is near the water sprays.
• Starting: direct, star-delta, soft starter; do screen and crusher start at the same time?

On belt-driven screens the motor is usually B3 foot-mounted on a tensioning base or a spring-loaded motor base; the exact type and base dimensions come from the screen manufacturer's drawing. On twin-motor eccentric screens each mechanism has its own motor and the two motors must have the same power and speed. At start-up the box shakes with large amplitude for a short time as it passes through the resonance zone; the same happens when stopping. The screen is therefore stopped only after the feed is cut and the decks are empty. In our range, motors of 4 kW and above have 400/690 V windings, so star-delta starting on a 400 V supply is possible. Panel wiring must be done by a qualified electrician.

DRG motors for eccentric-shaft screens

DRG Motor is a manufacturer, supplier and seller of electric motors. Our standard IEC motors are built from 0.25 to 11 kW in aluminium and from 0.55 to 355 kW in cast iron; synchronous speeds are 1000, 1500 and 3000 rpm, three-phase, wound for 230/400 V or 400/690 V; B3, B5, B14 or B35 mounting is noted when ordering. Example models for belt-driven eccentric screens:

DRG MOTOR motors are guaranteed against material and manufacturing defects for 2 years from the delivery date (warranty certificate). For vibrator-motor screens, quotations are prepared from the range on the Vibration Motors page.

Motors in this power range:

• DRG-160L-4 – 15 kW – 1465 rpm – 160L cast iron
• DRG-180M-4 – 18.5 kW – 1470 rpm – 180M cast iron
• DRG-180L-4 – 22 kW – 1470 rpm – 180L cast iron
• DRG-200L-4 – 30 kW – 1475 rpm – 200L cast iron
• DRG-225S-4 – 37 kW – 1485 rpm – 225S cast iron
• DRG-225M-4 – 45 kW – 1485 rpm – 225M cast iron

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Vibrating screen motor: frequently asked questions

Can a vibration motor replace a screen drive motor?

No, the two drives are different designs. A belt-driven eccentric screen works through its mechanism, a vibrator-motor screen through motors bolted to the box. Changing the drive type is a job for the screen manufacturer.

What speed should a screen motor have?

On belt-driven screens the motor is mostly 1500 rpm and screen speed is set by the pulley ratio. Keep the old motor's speed when replacing.

Why must the motors of a twin-motor screen be identical?

Each motor turns one mechanism; a difference in power or speed upsets the balance of the box. Order both motors as the same model.

Why does the screen motor throw belts or run hot?

A slack belt slips and heats up; an over-tight belt overloads the motor bearing. Blinded media and very wet material also raise current; check belt tension and the screen surface first.

Send us the screen size, number of decks, the old motor's nameplate and the pulley diameters, and we will select the right DRG model together. Phone +90 (542) 666 11 11, e-mail [email protected], contact page. Current prices of standard motors: Buy Electric Motors Online.

Sources

1. Weir Minerals – Screening brochure (Trio TIO / TTH, Enduron) – TIO inclined screens with V-belt drive and self-adjusting motor base; 1575×4280 mm 2-deck 11 kW … 2494×7325 mm 3-deck 30×2 kW; TIOSP largest 37×2 kW; TTH horizontal 18.5–45 kW; vibrator motors or exciters on larger screens.
2. Sandvik – Stationary screening brochure – SA1854 15 kW, SJ2462 22 kW, SL3063 2×30 kW; screen speed 730–1,100 rpm.
3. MEKA – MHS Series Horizontal Screens (katalog) – 2–3 deck horizontal screens 30–37 kW; screen sheave Ø620 mm, motor sheave Ø306–365 mm; screen speed 730–870 rpm with a 1500 rpm motor.
4. Metso – Opti-Flo screens & feeders range (Toromont Cat kopyası) – CVB inclined screens 1–4 decks 11–30 kW; DF screens with electrical unbalanced motors, 2×4.5 and 2×6.6 kW, self-synchronised linear motion.