What Is a Blade Fuse Base? NH Sizes and Selection Criteria
A blade fuse base is a fuse carrier that grips an NH blade fuse link with its spring contacts, secures it to the panel and connects it to the line.
A blade fuse base (NH fuse base) is a carrier that grips the blades of an NH fuse link with its spring contacts, secures the fuse link to the panel and connects it to the line. It is used in distribution and power factor correction panels on incoming and outgoing lines protected by NH fuses. A fuse base is not a switching device: the fuse link is not removed under load. Where switching on and off under load is required, a fused load break switch is used.
NH sizes and fuse bases in the catalog
The base must be the same size as the fuse link fitted to it; its rated current corresponds to the largest fuse link of that size. The Blade Fuse Bases category has 6 active products: Siemens 5, Sigma 1. The 3NH6430 and 3NH3530 are priced on request.
| NH size | Rated current | Product |
|---|---|---|
| 000 / 00 | 160 A | Siemens `3NH6030` |
| 00 | Not stated in the name | Sigma `SNB00` |
| 1 | 250 A | Siemens `3NH6230` |
| 2 | 400 A | Siemens `3NH6330` |
| 3 | 630 A | Siemens `3NH6430` |
| 4 | 1250 A | Siemens `3NH3530` |
Selection criteria
- Size and current: The fuse link is chosen first, from the line current and cable cross-section; the base is taken in the same size and rated at least for the fuse link's current. Blade and body dimensions differ between sizes.
- Number of poles: The Siemens 3NH bases in the catalog are single-pole; a three-phase outgoing line needs three bases.
- Voltage and breaking capacity: The Siemens 3NH6030 and 3NH3530 datasheets give a rated voltage of 690 V AC and a short-circuit rating of 120 kA AC together with the fuse link; the fuse link, not the base, interrupts the current.
- Connection: The 3NH6030 and 3NH3530 have flat terminals and are connected with a cable lug or a busbar; the 3NH6030 takes conductors of 6–95 mm². Take the lug hole size and tightening torque from the datasheet.
- Mounting distance: When bases are mounted side by side without phase barriers, leave the minimum distance given in the datasheet; 25 mm for the 3NH3530.
Common mistakes
- Pulling the fuse link under load: This causes an arc. Disconnect the load first and remove the fuse link with an insulated NH fuse puller.
- Choosing a base smaller than the fuse link: A 250 A fuse link does not fit a 160 A base; check size and current together.
- Tightening connections by feel: A loose flat connection heats up; apply the tightening torque in the datasheet.
Standards
- IEC 60269-1: Low-voltage fuses, general requirements. The Siemens 3NH3530 datasheet gives its NH4 fuse system according to EN 60269-1.
- IEC 60269-2: Fuses for use by authorized persons; the NH fuse system is defined in this part.
NH fuse links and Siemens 3NP fused load break switches are in the Blade Fuses category; horizontal and vertical load break switches are in Load Break Switches.
Frequently asked questions
What does a blade fuse base do?
It secures the NH fuse link to the panel and connects it to the line. When the fuse blows, the base stays in place and only the fuse link is replaced.
Can an NH1 fuse be fitted to an NH00 base?
No. The fuse link and the base must be the same size; an NH1 fuse link needs an NH1 base, for example the 250 A Siemens 3NH6230.
Should I choose a fuse base or a fused load break switch?
If the line will be switched on and off under load, choose a fused load break switch. A base suits outgoing lines where the fuse is needed only for protection and is rarely replaced.