Crusher & Stone Crushing Plant Electric Motor Selection

In a stone crushing plant, an electric motor failure means not only an hourly loss of production but also that the deadline commitments given to ready-mixed concrete and asphalt customers come under threat. When the motor beneath the jaw crusher stops, the entire plant stops; and a motor chosen at the wrong power or the wrong speed reveals itself in the very first months with a burnt winding, bearing damage and constant thermal tripping. This guide gathers into a single article all the commercial and technical questions that businesses building or renewing a crusher and stone crushing-screening plant ask when selecting a motor. As an electric motor manufacturer producing in Turkey since 1979, HEM Motor knows the harsh operating conditions of the crushing sector closely; it delivers cast iron body motors in the IE3 and IE4 efficiency classes, from 0.55 kW up to 355 kW, quickly from its strong stocks. At the end of the article you will also find the contact details through which you can request a quote directly.

Why Is Motor Selection in a Crusher Plant Different from Standard Industrial Applications?

Stone crushing plants are one of the most demanding application groups in the field for electric motors. There are three main reasons for this. First, the load character: in jaw and impact crushers the material is fed irregularly from the hopper, and the motor passes in an instant from no-load running to full load, and even to short-term overload. Second, the starting conditions: large-flywheel jaw crushers have a high moment of inertia and cause the motor to draw high current for a long time during start-up. Third, the ambient conditions: heavy stone dust, vibration, and out in the open field sun, rain and frost in winter constantly strain the motor's body, bearings and insulation.

For this reason, the motor to be used in a crusher must have a cast iron body, at least IP55 protection class, class F insulation and a design suitable for heavy starting. HEM Motor's stone crushing plant electric motors are produced precisely for these conditions: with reinforced bearing housings, sealing elements resistant to dusty environments and a rotor design offering high starting torque, long service life is targeted on the crusher site.

The Right Power and Speed Selection for Every Piece of Equipment in the Plant

Jaw Crusher (Primary Crusher) Motors

The jaw crusher is the plant's largest power consumer. Depending on the crusher's mouth size and capacity, motors generally between 75 kW and 200 kW are used; on large primary crushers, powers of 250 kW and above are reached. On the speed side, because jaw crushers are driven by belt and pulley, motors of mostly 1500 rpm (4-pole) or 1000 rpm (6-pole) are preferred. Because the flywheel's inertia is high, the motor's starting torque and its heating capacity during start-up are of critical importance; at this point, be sure to ask your manufacturer whether the motor's rotor design is suitable for heavy starting.

Impact and Cone Crusher (Secondary/Tertiary) Motors

In secondary impact crushers the 90–250 kW range is common and the speed is generally chosen as 1500 rpm. Cone crushers draw a more regular load but, in cases of jamming (tramp metal entering), sudden torque shocks occur; for this reason the motor's short-term overload capability is important. In tertiary sand machines, the high speed requirement is solved by the pulley ratio, and on the motor side 1500 rpm is again standard.

Screen (Vibrating Screen) Motors

Vibrating screens are driven in the 7.5–37 kW range, mostly by 1500 rpm motors. Because the screen's continuous vibration is transmitted directly to the motor bearings, in this application bearing quality and body rigidity are decisive. A cast iron body provides a serious advantage in vibration damping over an aluminium body.

Belt Conveyor Motors

A medium-sized plant has 8–15 belt conveyors, and each requires a motor between 4–30 kW. Because the belts are driven through a gearbox, the motor speed is chosen as 1500 rpm; on long and loaded belts, the use of a soft starter is common to reduce the tension shock at the moment of start-up. Because belt motors form the most numerous motor group in the plant by count, standardising on the same type and brand makes spare parts management considerably easier.

Summary Power and Speed Table

Body, Protection Class and Mounting Type: The Details That Make the Difference in the Field

On a crusher site, the three headings that come after power and speed in motor selection directly determine the motor's life. The first is the body material: in this application, where stone dust and vibration are intense, a cast iron body is standard; its impact resistance and heat dissipation capacity are markedly superior to aluminium. The second is the protection class: IP55 protection provides full protection against dust and resistance to water jets from all directions; this is the minimum requirement for all crusher motors working in the open field. The third is the insulation class: class F insulation protects the thermal life of the windings at site temperatures exceeding 40 degrees in the shade in summer and in frequent-start operation.

On mounting type, the great majority of crusher equipment requires B3 (foot-mounted) mounting; on belt drives directly coupled to a gearbox, B5 (flange) or B35 (foot + flange) motors are used. Confirming the mounting type of each piece of equipment from the chassis before ordering prevents costly work losses in the field such as base welding and adapter flanges. In HEM Motor's IE4 electric motors category, B3, B5, B14 and B35 mounting options are offered from stock.

IE3 or IE4? The Commercial Meaning of the Efficiency Class in Crushing

Crusher plant motors run 2,500–5,000 hours a year, most of the time close to full load. This operating profile means the efficiency class is directly reflected in the electricity bill. An IE4 class motor runs with one to two percent less loss than IE3, depending on power; on a 160 kW crusher motor this difference means thousands of kilowatt-hours of saving per year. Considering that a plant has dozens of motors, the advantage in the energy expense of a plant set up with IE4 typically pays back the price difference between the motors within two to three years; while the economic life of the motor exceeds 15 years. On newly built plants we recommend IE4, and on overhauls at least IE3. Moreover, because high-efficiency motors run at a lower temperature, the insulation and bearing life are also extended; this is reflected as a second saving item in the maintenance budget.

The Cost of Wrong Motor Selection to the Plant

The most frequent mistake we encounter in the field is choosing a small power for the crusher motor on the grounds that "it is belt-driven anyway." An underpowered motor runs constantly at the tipping limit during the heavy feeding from the hopper; the current rises, the thermal trips, the winding temperature strains the class F limits and the motor goes for rewinding within a season or two. Just as a rewinding cost reaches a significant part of the price of a new motor, the real loss is the 3–7 days of plant downtime: in a plant crushing a thousand tonnes a day, this is a turnover loss that is hard to recover.

The opposite mistake, selecting an oversized motor, is not innocent either: it creates a chain of unnecessary investment cost, a fall in efficiency and power factor due to underloading, the risk of a compensation penalty and the need for a larger starter. The third group of mistakes is mechanical incompatibility: the wrong shaft diameter, the wrong mounting type or the wrong frame size comes back as a pulley change and chassis modification in the field. The correct selection is made by validating the power and speed values given by the crusher manufacturer together with the motor manufacturer; HEM Motor's engineering team performs this validation free of charge at the quotation stage.

A Realistic Scenario: The Motor List of a 200 Tonne/Hour Plant

To make it concrete, let us take a typical fixed plant with a capacity of 200 tonnes per hour, with a jaw + impact combination. Under the hopper, the vibrating feeder has an 11 kW 1000 rpm motor, the primary jaw crusher a 132 kW 1500 rpm motor suitable for heavy starting, the secondary impact crusher a 160 kW 1500 rpm motor, the two-deck main screen 2x22 kW, the return and product screens 15–18.5 kW motors, and the ten belt conveyors a total of around 120 kW of belt motors ranging from 5.5 to 22 kW. The plant's total installed motor power reaches the order of 500 kW.

On mobile plants the picture remains similar, but when generator supply comes into play the motors' starting current directly affects the generator sizing; in this case, starting the large motors with a soft starter and staggering the starting sequence through automation is standard practice. If you share the generator-site information at the quotation stage, we shape the motor and starting recommendation accordingly.

The striking point in this list is this: the two large crusher motors make up 60 percent of the plant in terms of power, but only 10 percent by count. The purchasing strategy should be built accordingly: focus on technical validation and heavy-duty design on the crusher motors; while on the screen and belt motors, standardise on a single brand and keep one spare of each power. HEM Motor can deliver all the powers in this scenario from a single source, with a manufacturer's warranty, and the great majority of them from stock.

A 10-Item Checklist Before Purchasing

Clarifying the following information before requesting a quote ensures both that you get the right price and that the delivery is made correctly the first time. This list has been compiled from the information our sales team — which has been supplying motors to the crusher sector for more than twenty years — most often finds missing in the field.

• Equipment and capacity: The type of equipment the motor will connect to (jaw crusher, screen, belt) and its hourly capacity.
• Power and speed: The kW value recommended by the equipment manufacturer and the motor speed (1500, 1000 or 750 rpm).
• Mounting type: Is it B3 foot-mounted or B5/B35 flange; if an existing motor is being replaced, a nameplate photo.
• Frame size and shaft diameter: Critical for compatibility with existing pulleys and couplings.
• Mains voltage: Is 380/660 V standard, is there generator operation.
• Starting method: Direct, star-delta, soft starter or drive.
• Duty cycle: Daily operating hours and number of starts per hour.
• Ambient conditions: If the altitude exceeds 1000 metres and the summer temperature is high, a power derating is required.
• Efficiency preference: IE3 or IE4; we recommend IE4 for a new investment.
• Spare requirement: Whether a spare of the critical motors will be kept on site.

If you do not have all of this information, that is no problem: we can complete the selection together with the existing motor's nameplate photo and the equipment information. What matters is that all uncertainties are closed before ordering, and that the motor starts working the day it lands on site.

Stock and Delivery: The Crusher Operator's Real Question

For a crusher operator, the second issue as critical as the motor's technical specification is the supply time. Waiting for an importer to supply a 160 kW motor that has burnt out mid-season can take weeks; every day of waiting is a loss of production. The field meaning of HEM Motor being a manufacturer emerges precisely here: motors in common powers and speeds wait ready in factory stocks in Turkey, and after ordering, shipment is made the same day or the next day on most items. Special configurations not in stock, on the other hand, are planned on our own production line, far below import supply times. Furthermore, buying from the manufacturer means a solution under warranty instead of rewinding, the supply of a like-for-like spare motor, and the guarantee of finding an equivalent in the same frame size even years later.

If a gearbox is also to be renewed along with the motor in your plant, we recommend taking a look at our article on the factors affecting worm gear reducer prices, which explains the cost items of the reducers used in belt drives; and if you also have an investment on the ready-mixed concrete side, at our concrete batching plant electric motor supply guide.

Frequently Asked Questions

Should I use star-delta or a soft starter on crusher motors?

On crusher and screen motors above 30 kW, direct starting strains the mains and the mechanical components. Because the starting time is long on flywheel jaw crushers, a soft starter or a properly adjusted star-delta is used; on belts that start and stop frequently, a soft starter noticeably extends belt life. If you state the starting method when ordering the motor, the winding and rotor design are validated accordingly.

Which powers can I receive from stock, and how long does a special motor take?

In standard powers from 0.55 kW up to 355 kW, at speeds of 3000/1500/1000/750 rpm and in B3/B5/B14/B35 mounting types, the great majority of our motors are delivered from stock. For configurations such as a special shaft, special winding voltage or dual speed, the production plan is finalised at the moment of ordering and a written delivery date is given to you.

Can I replace a foreign-brand motor in my old plant on a like-for-like basis with HEM Motor?

Yes. Because our motors are produced in standard frame dimensions, in place of any brand of the same frame size, the shaft diameter, shaft height and mounting dimensions are installed in fully compatible fashion. It is enough to send us the nameplate details; we carry out the compatibility check together with the quote.

Get a Quote

Send us the motor list for your crusher or stone crushing-screening plant; let us validate the powers, speeds and mounting types free of charge and convey a manufacturer's price the same day along with the stock status and delivery time. You can reach us on +90 (532) 345 49 86 or send your request in writing via our contact us page. HEM Motor, with its manufacturer's assurance and Turkey stocks since 1979, is on your site so that your plant does not stop.