Knowledge Base

Valid for UL and CSA regions.

Power Supply

¹ time-delay fuse for the line protection (overload protection)
²combination of line protection fuse and semiconducter fuse for line and device protection

Hints for cross section change from mains supply to motor can be found on page UL cross section

Fuses

You must use fuse classes RK5, CC, J or T with a 600VAC voltage rating and 200kArms interrupting rating. The fuse must be UL and CSA listed, UR recognized is not sufficient.

Automatic Circuit Breakers

There is no UL approved automatic circuit breaker for fuse classes RK5, CC, J or T. If automatic circuit breakers mare used in a system, which will be operated in UL / cUL regions, then the system must be inspected.

Note: If you select a circuit breaker, in the AC feed, a GFI breaker cannot be utilized due to leakage currents.

Fuse Holder

in addition to the standard fuse blocks there are finger safe fuse holder according to IEC 60529.

Examples:
Bussmann: CH Series Modular Fuse Holders, fuse size 0 to 30A class J, 3 poles: CH30J3
Ferraz: Ultrasafe Fuse holders, fuse size 0 to 30A class J, 3 poles: US3J3I

24V Supply

The description below delivers just examples for 24V fuse applications. It shows some possible applications only.

The required current values and the allowed wire cross sections for 24Vdc supply are described in the servo amplifier's instructions manuals. The 24V supply inputs are secures internally with 4A fuses. Therefore the external fuses only protect the lines.

Fuses

Micro fuse 6,3x32mm
Fuse holders integrated to series terminal blocks (35 mm standard rail),
e.g. from company Phoenix Contact: 4ST-HESI (6.3x32mm)

Automatic Circuit Breakers

ABB delivers special automatic circuit breakers for 60Vdc according to UL489 for Branch Circuit Protection:
Families S201 DC-k and S201 DC-Z with or without integrated auxiliary contact. These automatic circuit breakers for Branch Circuit Protection are developed especially for switching power supplies with short circuit limitations for selective protection.

Important: observe the manufacturer's application notes sales information!!!
If switching power supplies are used for the 24V supply, you must consider, that these power supplies with short circuit limitation may be react as fast to a short circuit (typical <100ms), that fuses and automatic circuit breakers may not react and therefore selective protection isn't ensured anymore.

Over Current Protection

Electronic over current protection devices for 24Vdc supply voltage are developed especially for selectively protection for use with switching power supplies with short circuit limitation.
Examples are:
Electronic over current protection ESX10-T from company E-T-A
and the SITOP-select series of SIEMENS AG.

Brake Resistor

Minimum wire cross section of the connection between servo amplifier, fuse and external brake resistor must be ensured, see table below:

Fuse Type

Bussmann:
up to 50A: FWP-xxA14F, Size 14x51mm with 800Vdc UL approval
up to 100A: FWP-zzzA22F, Size 22x58mm with 500Vdc UL approval

The fuses do not protect the brake resistor from thermal overload. this supervision is done by the amplifier's software if the parameterizing is correct. The fuses shall protect from short circuit and earth short circuit!

Fuse Holder

Bussmann: CH142D, CH222B

Intermediate Circuit (DC Bus)

Fuse type

Bussmann: FWP-50A14F, Size 14x51mm with 800Vdc UL approval

Fuse holder

Bussmann: CH142D