Traditionally overload relays, when combined with contactors, provided the necessary motor protection for most electrical applications. But within the past few decades manual motor starters (MMS's), also referred to as manual motor protectors (MMP's) or motor starter protectors (MSP's), have created their own niche in the motor protection realm. Simply put, manual motor starters offer an economical solution for applications that require the manual starting and stopping of motors in one small unit.
While manual motor protectors are often used without the addition of a contactor and as a standalone unit, they must have short circuit protection in the form of a fuses or circuit breaker upstream of this unit. But when combined in a group motor installation, only one set of fuses or a circuit breaker is required for all the manual starters within that same group, providing a cost savings and a reduction in wiring saving time and expense.
Motor starter protectors share many of the same similarities and features of overload relays and essentially function in the same manner. All manual motor starters are suited for 3 phase applications and offer phase loss protection along with Class 10 or Class 20 tripping times. In addition, when combined with a 3 pole contactor, these units function as a UL 508 Type E self-protected manual combination starter/motor controller. This offers protection in four ways: motor overload protection, short circuit
protection, disconnect and motor controller.
There are seemingly endless accessories for these units that can be added to accommodate any application regardless of complexity. The list includes but is not restricted to front and side mounted auxiliary contacts, plastic and metal enclosures, under voltage trip mechanisms, shunt trips, along with line and load side adapters, just to name a few.
If you need assistance to determine which motor protection unit is right for you, please give us a call at 800.222.5129 and we can discuss your situation and determine which would bet suit your needs.