When selecting high-voltage slip-ring motors for crushers, maximum torque ratio (Tmax/Tn) is one of the most critical performance indicators. Crushers, especially jaw crushers, cone crushers and impact crushers, feature highly fluctuating loads, potential heavy starting conditions, and occasional overloads due to uncrushable materials or hard stone feeding.
In actual industrial applications, the standard maximum torque multiplier for high-voltage slip-ring motors driving crushers is usually in the range of 2.8 to 3.5 times the rated torque.
Motors with a maximum torque below 2.5 times are generally not recommended, as they may stall or trip under sudden load shocks. A value above 3.5 is rarely necessary for most crushing applications and will increase motor size, cost and power system requirements.
This torque level ensures reliable start-up with full load, stable operation under cyclic impact loads, and sufficient overload capacity to handle short-term peak stresses without damage. It also matches well with typical starting and speed-control equipment used with slip-ring motors.
When issuing quotations or technical proposals, it is essential to specify a minimum guaranteed maximum torque ratio of no less than 2.8 times, and for heavy-duty crushing conditions, 3.0 to 3.3 times is the most widely accepted and cost-effective design.