Brecon external vibrators range from low frequency vibrators with 1000, 1500, 3000 vibrations per minute at a power frequency of 50 Hz to high frequency vibrators with 6000, or 12000 vibrations per minute at a power frequency of 200 Hz. The selection of external vibrators depends on the area of application (compacting, loosening, conveying), on the vibration equipment (rigidity, weight), and on the material is worked with (properties, weight). A basic rule applies, that a vibrator at same centrifugal force with smaller vibration frequency creates a larger vibration amplitude and at the same centrifugal force with higher vibration frequency creates a smaller vibration amplitude. External vibrators with 1000 and 1500 vibrations per minute because of their comparative large vibration amplitude for example are used for sieving and for conveying of coarse-grained materials.

Types of motors	Electrical frequency	Number of pole pairs	Speed	Mechanical frequency
High frequency external vibrator (HF)	200 Hz 200 Hz	1 2	12000l/min 6000l/min	200 Hz 100 Hz
Low frequency external vibrator (LF)	50 Hz 50 Hz 50 Hz	1 2 3	3000l/min 1500l/min 1000l/min	50 Hz 25 Hz 16,66 Hz
Number of pole pairs x 2 = Number of poles

Table 1: Important vibrator performance characteristics

External vibrators with 3000 vibrations/minute deliver optimal performance at loosening and breaking up of fine-grained bulk materials. High frequency external vibrators with 6000 and 12000 vibrations per minute are excellent at compacting of fine-grained materials since their high frequency and small amplitude particularly strong activate micro-grained material. High frequency vibrators find most application at concrete compacting. External vibrators with 6000 vibrations/minute have a better depth effect and make less noise than vibrators with 12000 vibrations per minute.