1176 — Single-Anode Mercury-Vapour and Gas-Filled Rectifying Valve

The 1176 is an industrial, single-anode, mercury-vapour and gas-filled rectifying valve designed for high-current applications. It is primarily utilized in industrial rectifiers, such as those configured for charging up to 110 lead-acid (Pb) accumulator cells. The valve features a directly heated, oxide-coated filament and incorporates an auxiliary ignition electrode to facilitate reliable starting.

Mechanical Construction and Physical Dimensions

The 1176 is constructed with a heavy glass envelope designed to withstand the thermal and electrical demands of industrial service. It must be operated strictly in a vertical position with the base down.

The physical dimensions and mechanical connections of the valve are as follows:

• Maximum Bulb Diameter: 92 mm
• Maximum Overall Height: 301 mm
• Anode Connection: Located at the top of the bulb, featuring an M8 screw terminal.
• Base Connections: Two heavy filament terminals (f, f) spaced 125 mm apart, with a total base width of 145 mm.
• Auxiliary Ignition Connection: An auxiliary ignition electrode (ah) terminal with an M4 screw thread located at the base.
• Weight: Net weight of approximately 600 g, with a shipping weight of 1190 g.

Filament and Heating Requirements

The valve utilizes a directly heated, oxide-coated filament. Because the tube contains mercury vapour and gas, the filament must be preheated to its proper operating temperature before anode voltage is applied. This preheating time ($T_w$) is critical to prevent damage to the cathode surface from ion bombardment.

• Filament Voltage ($V_f$): 1.9 V
• Filament Current ($I_f$): 28 A
• Heating Supply: Direct by A.C.

Filament Power Calculation

Using the nominal filament voltage and current, the electrical power consumed by the filament is calculated as: $\text{Power} = V_f \times I_f = 1.9\text{ V} \times 28\text{ A} = 53.2\text{ W}$

Preheating Time ($T_w$) Requirements

• Recommended Preheating Time: 2 minutes under normal operating conditions.
• Minimum Preheating Time: May be reduced to 1 minute in urgent situations.
• Extended Preheating Time: A delay of 5 minutes is required after transport or after a long interruption of service to ensure proper mercury distribution.
• Control: A time-delay switch, such as type 4152, is recommended to automate and enforce this delay.

Typical and Operating Characteristics

The 1176 exhibits a low internal voltage drop during conduction, which is typical of gas and mercury-vapour rectifiers.

Ignition and Arc Characteristics

• Arc Voltage ($V_{\text{arc}}$): 12 V (typical)
• Ignition Voltage ($V_{\text{ign}}$): 22 V (typical)

To achieve the typical ignition voltage of 22 V, an auxiliary D.C. supply unit delivering a minimum of 40 V and 10 mA must be connected via a current-limiting resistor between the auxiliary ignition electrode ($ah$, positive) and the cathode (negative). The Philips Auxiliary Ignition Unit type 1289 is recommended for this purpose.

Rectifier Circuit Configurations

The valve can be operated in several standard rectifier circuit configurations (designated a through g). These configurations yield different output voltages ($V_o$) and currents ($I_o$) from specified transformer secondary voltages ($V_{\text{tr}}$):

Limiting Values (Absolute Limits)

The absolute maximum ratings of the 1176 are highly dependent on the operating temperature of both the ambient air ($t_{\text{amb}}$) and the condensed mercury ($t_{\text{Hg}}$). The manufacturer defines two distinct sets of absolute limits based on these temperature ranges:

These limits demonstrate that operating the valve at a slightly lower maximum ambient temperature (up to 45 °C instead of 50 °C) allows it to withstand a higher peak inverse voltage of 850 V, though the maximum peak anode current is conversely restricted to 75 A.

Technical Summary

The 1176 is a heavy-duty, single-anode, mercury-vapour and gas-filled rectifying valve designed for industrial power applications. It features a directly heated 1.9 V / 28 A filament requiring a calculated 53.2 W of heating power. To protect the oxide-coated cathode, a preheating delay of 2 minutes (or 5 minutes following transport) must be observed. The valve operates with a typical arc drop of 12 V and utilizes an auxiliary ignition electrode to initiate conduction at 22 V. Depending on the operating temperature, the 1176 supports peak inverse voltages up to 850 V and average anode currents up to 15 A, making it highly suitable for high-current industrial battery charging and rectification systems.