English
Français
Türkçe
Español
Русский
The electric motor of a cone crusher usually drives the crusher's countershaft (pinion shaft) by V-belt; the compatibility of a spare motor is therefore checked starting from this belt arrangement, the direction of rotation and the lubrication interlock. Power and speed are set according to the crusher manufacturer's data; when the spare motor has the same power, the same number of poles and the same frame as the old one, the pulley, slide rails and control panel remain unchanged. This article explains the drive arrangement of a cone crusher and the points to check when choosing a spare motor.
How is power transmitted in a cone crusher?
In a cone crusher, crushing takes place between the mantle (inner cone), which gyrates with an eccentric motion, and the fixed outer liner (concave). The motor does not produce this eccentric motion directly; power is transmitted in this order:
- Motor and motor pulley: The motor sits next to the crusher on slide rails or an adjustable base.
- V-belt set: A multi-groove belt carries power to the crusher's countershaft pulley.
- Countershaft and bevel gear: The countershaft turns the eccentric bushing through a bevel gear pair.
- Eccentric and main shaft: The eccentric sets the mantle into gyration; the material is crushed by this motion.
In some plants the motor is also connected to the countershaft with a flexible coupling. However, the most common arrangement on site is belt-driven; the belt partly damps the shocks in the crusher before they reach the motor, and the crusher speed can be adjusted with the pulley ratio.
Crusher speed and pulley ratio
In a cone crusher, countershaft speed directly affects product size and capacity; that is why the crusher manufacturer specifies a given speed range. Countershaft speed comes from the motor speed and the ratio of the pulley diameters: countershaft speed = motor speed × motor pulley diameter ÷ crusher pulley diameter.
For this reason, the spare motor must have the same number of poles as the old one. Crushers most often use 4-pole (1,500 rpm class) motors; some plants prefer 6-pole motors. If the number of poles changes, the crusher speed also changes with the same pulleys; product size shifts and gears and bearings run outside their design speed. If a speed change is needed, it must be done with the crusher manufacturer's approval and by changing pulleys.
A hypothetical check
The values are only meant to show the method. With a 4-pole motor (rated 1,486 rpm), a 315 mm motor pulley and a 900 mm crusher pulley, the countershaft turns at about 1,486 × 315 ÷ 900 ≈ 520 rpm. If the spare motor's rated speed differs by a few rpm, the countershaft speed practically does not change. But if a 6-pole motor (about 985 rpm) is fitted to the same arrangement, the countershaft drops to about 345 rpm; this may fall outside the crusher's operating range.
Direction of rotation and lubrication interlock
On most cone crushers the direction of rotation of the countershaft is set by the manufacturer and shown by an arrow on the crusher body. Running in the wrong direction can lead to mechanical problems such as the nut that holds the mantle working loose. After the spare motor is connected, a short jog should be made without the belts fitted and the direction compared with the arrow. If the direction is wrong, two phases are swapped.
Cone crushers usually have a separate lubrication unit. The control panel does not allow the main motor to run until oil pressure and temperature are suitable. This interlock works together with the main motor's connection in the panel; when replacing the motor, the interlock circuit must not be touched, and during commissioning it must be confirmed that the lubrication unit starts first. The lubrication pump motor is a separate small motor; it is also assessed separately according to its nameplate.
Starting and load: starting with a full crusher
In normal operation a cone crusher starts empty and the feed is opened afterwards. However, after a power cut or an emergency stop, the crushing chamber may remain full of material. In that case the motor has to turn the full crusher and the heavy flywheel together; the start takes longer and the current stays high for a long time.
- Star-delta: Common for empty starts; because starting torque drops, it may be insufficient for a full crusher.
- Soft starter: Reduces starting shock and current; if a full start is required, its settings must be made accordingly.
- Frequency inverter: Provides a controlled start and speed adjustment; some plants use it to set the crusher speed according to the product.
In plants where a full start is possible, not attempting a start without emptying the chamber is the safest operating practice. This article covers starting in general terms; the real question affecting motor selection is which method the old motor ran with. For star-delta starting on a 400 V supply, the motor nameplate must read 400/690 V (Δ/Y); the models of 4 kW and above on sale are offered with this rating.
